Mt^ Pork §?tatt College of Agriculture at Cornell ©ntbetsitp Hihtat^ Cornell University Library QD 251.B57 1896 A text-book of organic chemistry .. 3 1924 003 072 612 Cornell University Library The original of tliis book is in tlie Cornell University Library. There are no known copyright restrictions in the United States on the use of the text. http://www.archive.org/details/cu31924003072612 ORGANIC CHEMISTRY A TEXT-BOOK or ORGANIC CHEMISTRY BY a: BERNTHSEN, Ph.D. Director of tho Scieutific Departmeut ia the Chief Lahoiutory of the Baden Aniline and Alkali Manufactory, Ludwigshafen-am-Rhein; fonnerly Professor of Chemistry in the University of Heidelherg TRANSLATED BY GEORGE M'GOWAN, Ph.D. FOURTH ENGLISH EDITION LONDON; BLACKIE & SON, Limited NEW YORK: D. VAN NOSTRAND COMPANY PRINTED AT THE VILLAFIELD PRESS GLASQOW TRANSLATOR'S PREFACE TO THE SECOND ENGLISH EDITION. A second edition of this book, which has taken its place as a text- book in this country and America, as well as in Germany, was called for some time ago, but its publication has been delayed for about six months, owing to lack of time on my part. The present work is virtually a translation of the fourth German edition, which was published last autumn, with one or two further additions and alter- ations. It will be seen, on comparing it with the first English edition, that no part of the book has escaped revision, while certain chapters have been more or less rewritten; this latter remark applies especially to the sections referred to by the author in his preface to the fourth German edition, and also to those which deal with the determination of molecular weights by physical methods, ketonic acids, di-ketones, etc., the uric acid group, azoles, certain naphthalene derivatives, and the quinoline and acridine groups. In his preface to the second German edition, the author expresses his indebtedness to Professors Briihl, B. Fischer, "W. Kuhne, and O. Wallach for their kind revision of the sections dealing with subjects of which tiiey themselves have made a special study, viz., Physical Chemistry, the Sugars, the Albumens, and the Terpenes. In conclusion, I should like to thank the friends and correspon- dents who have assisted me by their criticism and advice, and by calling my attention to printers' errors, etc. GEORGE M'GOWAN. June, 1894- NOTE TO THIRD EDITION. The second English edition being now exhausted, I have taken the opportunity of this reprint to correct various printers' errors, etc., to which my attention has been kindly called by different corre- spondents. G. M. October, 1896. AUTHOR'S PREFACE TO THE FOtTETH GERMAN EDITION. This book has been so cordially received, both by our academic youth and professors of chemistry, that the fourth edition is called for within the space of six years, and this notwithstanding the fact that the number of copies issued in the third edition was greater than that in the first or second. It has also been translated into English and Eussian. This of itself furnishes a sufiicient reason for not deviating in the coming edition from the original plan of treatment. Emphasis is again chiefly laid upon the discussion of the properties peculiar to each class of compounds. The abundant chemical literature of the last few years is referred to only so far as is thought to be absolutely necessary for the educational purpose of the book, the size of which has not been materially increased. But, although this fourth edition follows closely on the lines of those preceding it, various chapters have been recast in accordance with our present knowledge of the subject, and this applies particularly to the sections which deal with: — stereo-chemical isoiiierism; aldoximes and ketoximes; carbo- hydrates; special benzene formulae; aromatic compounds of phosphorus, etc.; hydrogenized phthalic acids; dyes of the diphenylene-methane oxide-, phenazine-, oxazine, and thi- azine groups; alkaloids, especially the derivatives of tropine; and, finally, the terpenes and camphors. I am much indebted to Professor Wallach for his kindness in revising the last- AUTHORS PREFACE. VU named section. The system of International Nomenclature agreed upon at the recent conference of chemists at Geneva has also beeoi duly taken into account, both in the text of the methane derivatives and in the index, the "official name" being generally added in brackets to that hitherto in use. Dr. Edward Buchner, of the University of Munich, has co- operated with me in bringing out this edition, and it is my pleasant duty to thank him here for the resource and care of which he has given proof throughout the work. I should also like to express my obligations to the many friends and col- leagues who have shown their interest in the book by corre- spondence and by pointing out errors in the text, etc. A. BEENTHSEN. Mannheim, June, 1893. AUTHOR'S PREFACE TO THE FIRST GEEMAN EDITION. In lecturing upon Organic Chemistry in the University of Heidelberg, I have felt more and more each session the desira- bility of being able to place in the hands of my students a small text-book, which, while not exceeding some thirty sheets in size, and of which the descriptive portion was condensed as far as practicable, should yet be of a strictly scientific charac- ter ; a book which, beginning with homologous series, should lay especial emphasis upon summarizing the characteristics of each class of compounds, and, wherever possible, upon the inductive development of the theoretical relations existing between them. The following text-book of Organic Chemistry is an attempt to fulfil these requirements. Excepting in a few cases, where another arrangement appeared to be more suitable, there is given here for each class (after a short general description) a concise statement of the occurrence, general modes of forma- tion, constitution and isomerides, and behaviour of the com- pounds in question. The choice of the compounds described has been practically determined by the requirements of teach- ing. A number of tables are incorporated, which I have already found useful in my lectures, and which are of service for summarizing. The treatment of the theoretical matter is, especially in the first half of the book, purely inductive; the isomeric relations of the paraffins, for instance, are first referred to under butane, AUTHORS PREFACE. ix and no constitutional formula of any important compound is given without the grounds for it being indicated. The induc- tive method is also retained even where, as in the case of the theory of the benzene derivatives, the historical development has run on other lines. In accordance with this the class definitions are based not on theoretical but on actual relations. Type of two sizes has been employed in the book, in order that the matter which is of the greatest importance, either in itself or for the purposes of a general review, may be readily distinguished. I have deemed it advisable to give a number of references with regard to points which have a particular historical value, and also to some of the more important recent researches, especially where space did not allow of these being treated in detail. Special pains have been taken to make the index complete. I trust, therefore, that the book will be found useful, not only to the student of chemistry proper on his entering upon the study of Organic Chemistry, but also to students of medi- cine and pharmacy, whose requirements have been carefuUy borne in mind. It should also prove of service to chemists engaged in technical work, who may wish to obtain a short survey of the present state of our science. I should feel greatly obliged if my readers would kindly draw attention to any inaccuracies of statement or errors of print which may have crept into the work. (Signed) A. BERNTHSEN. HeideIiBBRG, April, 1887. AUTHOR'S PREFACE TO THE FIKST ENGLISH EDITION. The translation of this book has been carried out by Dr. M'Gowan, who has reproduced the meaning of it so thoroughly that I feel myself bound to acknowledge in an especial manner the accuracy of the work, and to express my warm thanks to him for the same. The large amount of new and important matter in the domain of Organic Chemistry, which has appeared since the German edition of this book was published, has been specially gone over for this edition, and at the same time the original text has been carefully revised. (Signed) A B. Manitheim, March, 1889. TRANSLATOR'S PREFACE TO THE FIRST ENGLISH EDITION. In introducing the English edition of this text-book, almost nothing remains to be added to what Professor Bernthsen has said in his prefaces. The proof slips had the great advantage of being carefully revised by himself after my own corrections had been made, which should ensure the accuracy of the work. The book has been very well received in Germany, and will, I trust, be found equally acceptable here. GEORGE M'GOWAN. Univeesitt College op N. Wales, Bangor, May, 1889. TABLE OF CONTENTS. INTKODUCTION. Page Qualitative Analysis, - .... 2 Quantitative Analysis, .... 4 Calculation of the Formula, - ... 7 Determination of Molecular Weight, - 8 Modes of determining Vapour Density, - - 12 Polymerism and Isomerism, - • 14 Chemical Theories, - - 14 Explanation of Isomerism ; determination of the Constitution of Organic Compounds, - - ■ 17 The nature of Carbon, ... - 20 Stereo-chemical Isomerism, - - - - - 21 Rational Formulae, ... . ... 26 Homology, - - - 27 International Chemical Nomenclature, - • - - 28 Radicles, - - 29 Classification of Organic Compounds, 30 Physical Properties of Organic Compounds, 31 Class I.— METHANE DEPJVATIVES. I. Hydbooarbons, - - . 42 A. Saturated Hydrocarbons, C„H2„+2, - - 42 Isomerism, Nomenclature, Constitution, - 49 B. Olefines, C.Hj., - - . 54 Hydrocarbons, CaHa,, vf ith closed chain, 54 0. Acetylene Series, C„H2„_j, ... D. Hydrocarbons, C„Hai_4 and C„Ha,_6, n. Haloid Substitution Products of the Htdrooabbons, 67 A. Of the Saturated Hydrocarbons, .... 67 B. Of the Unsaturated Hydrocarbons, . - - - 78 ni. MoNATOMio Alcohols, - ..... 79 A. Monatomic Saturated Alcohols, C„H2„+iOH, - 80 Constitution and Isomers; Classification of the Alcohols, 82 62 66 CU CONTENTS. Page B. Monatomio Unsaturated Alcohols, OnH2„_iOH, - - 95 0. Monatomio Unsaturated Alcohols, C„H2„_sOH. - - ■ 97 IV. Deeivatives of the Alcohols, 97 A. Ethers (Alcoholic), - - 97 B. Thio-alcohols and -ethers, - - - 102 u. Ethers (Esters) of the Alcohols with Inorganic Acids, and their Isomers, 107 1. Ethers of Nitric Acid, - - - - 109 2. Derivatives of Nitrous Acid: c. Ethers, - - - 110 /3. Nitro-derivatives of the Hydrocarbons, - 110 3. Derivatives of Hyponitrous Acid, - IIS 4. Ethers of the Chlorine Acids, - - - 113 5. Ethers of Sulphuric Acid, - - - - 113 6. Derivatives of Sulphurous Acid : .*. Ethers, . . 114 /S. Sulphonic Acids, - - 115 7. Ethers of Tri- and Polybasio Acids, - - 116 8. Alcoholic Derivatives of Hydrocyanic Acid: a. Nitriles, . . - 117 j3. Iso-nitriles, - . 119 D. Nitrogen Bases of. the Alcohol Radicles, - - 120 Appendix : Hydroxylamines, Hydrazines, - 128 E. Compounds of Phosphorus, Arsenic, etc., with Alcohol Radicles : 1. Phosphorus Compounds, . 130 2. Arsenic Compounds, I33 3. Antimony, Boron and Silicon Compounds, - 136 F. Metallic Compounds of the Alcohol Radicles, - . 137 V. Aldekydes and Ketones, - . 139 A. Aldehydes, - - . . Aldoximes, .... a. Ketones, - - .... Ketoximes, VI. Monobasic Eatty Acids, .... A. Saturated Acids, CoHa,02, B. Unsaturated Acids, CoHj^.jOj, - 140 150 151 158 160 160 178 CONTENTS. xiii Page o. Propiolio Acid Series, C„H2„_,0j, 181 D. Substitution Products of the Monobasic Acids, - - 182 viL Acid Deeivatives, - .... 187 A. Ethers of the Fatty Acids (Esters), - . .188 B. Chlorides of the Acid Radicles, 190 0. Acid Anhydrides, . 192 D. Thio-aoids and Thio-anhydrides, . . 193 E. Amides, 194 p. Amido- and Imido-chlorides, - . - - 198 G. Thiamides and Imido-thio-ethers, .... 199 B. Amidines, . . 200 Amidoximes, - . 201 VIII. POLYATOMIO ALCOHOLS, . . . . 202 A. Glycols, - - . . . 202 Derivatives, - . . 207 Amines of the Diatomic Alcohols, ■ 208 B. Triatomic Alcohols, 213 0. Tetra-, Penta- and Hexatomio Alcohols, 217 Oxidation Products of the Polyatomic Alcohols, - - 219 IX. Polyatomic Monobasic Acids, - - 221 A. Diatomic Monobasic Acids, - ... 221 Amido-acids, - - 227 Lactic Acids, ■ - 229 Appendix: Lactones, - - - 233 B. Tri- and Polyatomic Monobasic- Acids, - 234 c. Aldehyde-alcohols, - - -, 237 D. Ketone-alcohols, - - 237 E. Diatomic Aldehydes, - 238 F. Diatomic Ketones, 238 G. Oxy-methylene-ketonea and Ketoue-aldehydes, 239 H. Monobasic Aldehyde- and Oxy-methylene-acids, - . 239 1. Monobasic Ketonic Acids, - . - 240 X. Dibasic Acids, - a. Saturated Diatomic Dibasic Acids, B. Unsaturated Diatomic Dibasic Acids, 0. Triatomic Dibasic Acids, 246 247 255 257 CONTENTS. D. Tetratomie Dibasic Acids, - ■ - 259 Isomerism of the Tartaric Acids, ... - 260 E. Penta- and Hexatomio Dibasic Acids, - - 264 F. Dibasic Ketonic Acids, - - 264 XI. Tri- to Hexabasio Acids, - 266 A. Triatomio Tribasie Saturated Acids, - - 266 B. Unsaturated Acids, 267 o. Tetratomie Tribasie Acids, - - - 267 D. Pentatomio Tribasie Acids, - 268 B. Tetra-, Penta- and Hexabasic Acids, - - 268 XII. OiANOGEN Compounds, - - 269 A. Cyanogen and Hydrocyanic Acid, - 272 B, Halogen Compounds of Cyanogen, - 278 0. Cyanic and Cyauuric Acids, - . - 278 D. Thiocyanic Acid and its Derivatives, - - 282 E. Cyanamide and its Derivatives, . - 285 r. Appendix: Theoretical Considerations as to Isomerism in the Cyanogen Group, - - 286 XIII. Cabbonio Acid Dbeivativbs, A. Ethers of Carbonic Acid, B. Chlorides of Carbonic Acid, - o. Amides of Carbonic Acid, Ureides, d. Sulphur Derivatives of Carbonic Acid, E. Amidines of Carbonic Acid, F. Uric Acid Group, XIV. Cakeohtdbates, - A. Pentoses, B. The Grape Sugar Group, 0. The Cane Sugar Group, D. The Cellulose Group, - XV. Tbansition to the Abomatio Compounds, A. Tri-, Tetra- and Penta-methylenes, &o., B. JTurfurane, Thiophene and Pyrrol, 0. Azoles, Pyrazoles and Thiazoles, 287 . 288 - 289 - 290 293 and 300 295 - 298 300 307 308 309 317 320 323 324 326 - 332 CONTENTS. XV Class II.— BENZENE DERIVATIVEa Page IVI. SUMMABT, ... . . 335 Differences between the Benzene and Fatty Hydrocarbons, 338 Isomeric Belations, - - 339 ' Proof of the Equal "Value of the Six Hydrogen Atoms, 339 Proofs, that for every H-atom (a), two other pairs of symmetrically linked H-atoms exist, - - • 340 Constitution of Benzene, - • 343 Determination of Position, ... . 345 Special Benzene Formulae, ... 348 Laws Governing Substitution, - - • 350 Further Isomerism, - - - 351 Occurrence of the Benzene Derivatives, - 352 Modes of Formation of the Benzene Derivatives, 353 XVII. Benzene Hydeooabbons, A. Saturated Hydrocarbons, B. ITnsaturated Hydrocarbons, - XVIII. Haloid Substitution Peoduots, XIX. Nitro-substitution Peoduots, Nitroso-derivatives, XX. Amido-deeivatives, A. Primary Monamines, - B. Secondary Monamines, 0. Tertiary Monamines, - d. Quaternary Bases, E. Diamines, Triamines, etc., Aniline, Substitution Products of Aniline, Alkylated Anilines, Di- and Tri-phenylamines, Indamines and Indophenols, Anilides, Homologues of Aniline, Diamines, Triamines, etc., 356 356 365 366 370 373 374 376 380 382 382 383 384 386 387 389 389 391 392 XVI CONTENTS. XXI. DiAZO- AND AZO-OOMPOUNDS : HYDRAZINES, A. Diazo-compouuds, B. Diazo-amido-compouuds, Nitrosamines of Aromatic bases, o. Azo-oompounds, 1. Azoxy-compounds, 2. Hydrazo-compounds, 3. Azo-oompounds, 4. Amido-azo- and Oxy-azo-compounds, D. Hydrazines, XXII. Akomatio Sulphonio Aoids, XXIII. Phenols, A. Monatomio Phenols, - - - Phenol, Derivatives of Phenol, ... Homologues of Phenol, B. Diatomic Phenols, .... 0. Triatomio Phenols, ... D. Tetra-, Penta- and Hexatomio Phenols, B. Quinones, - - - - F. Quinone-aniles and Anilido-quinones, • a. Quinone Chlor-imides, xxrv. Akomatio Alcohols, Aldehydes and Ketones, A. Aromatic Alcohols, ..... B. Aromatic Aldehydes, .... 0. Aromatic Ketones, D. Oxy-alcohols and -aldehydes; Ketone-alcohols, XXV. Aeomatio Acids, A. Monobasic Aromatic Acids, 1. Monatomio Saturated Acids, Benzoic Acid, 2. Monatomio Unsaturated Acids, 3. Diatomic Saturated Phenolic Acids, 4. Alcohol-, Ketone- and Aldehyde- Acids, 5. Tri- and Polyatomic Phenolic Aoids, 6. XJnaaturated Phenolic Acids, ... Page 394 394 398 400 400 401 401 401 402 406 408 411 413 416 417 422 423 426 427 427 430 430 431 431 433 43.5 436 437 445 448 448 453 455 458 461 463 CONTENTS. XVii Page B. Dibasic Acids, - - ... 464 Hydro-phthalio Acids, 465 0. Tri- to Hexabasio Acids, - ... 468 XXVI. Indigo (ob Indole) Gboup, . - ■" 469 Indigo, 469 Derivatives of Indigo, - 471 Indole, 474 Appendix: Cumarone and Indazole G-roup, - see p. 567 xxvn. DiPHENTL GBonp, 476 Diphenyl, ... 476 Diphenyl Derivatives, • 477 XXVm. DiPHENTL-METHANB GeOUP, - - - 480 Diphenyl-methane, - 480 Benzoplienone, . . - 482 Homologues of Diphenyl-methane; Fluorene, - 483 XXIX. Tbiphbntl-mbthanb Geoup, . - ... 485 Triphenyl-methane, .... 485 Triphenyl-methane Dyes, - 486 1. Amido- and Diamido-triphenyl-methane Group, 487 2. Rosaniline Group, - - - 488 3. Trioxy-triphenyl-methane Group, . 493 4. Triphenyl-methane-carboxylic Acid (the Eosin Group), 494 XXX. DlBENZTL Gboup, ... . 496 Appendix: Diphenyl-diacetylene, . - 498 COMPOUNDS WITH CONDENSED BENZENE NUCLEI. XXXI. Naphthalene Group, - - - 499 Naphthalene, - - 499 Derivatives of Naphthalene, - - - 502 Homologues; Carboxylic Acids, - . 507 Appendix: Indene; Thiophtene, ... 507 xxxn. Anthkacenb and Phbnantheenb Gboups, - . 608 A. Anthracene, ..... 608 Derivatives of Anthracene, ..... 510 Alizarin, - • - - 513 xvin CONTENTS. B. Phenanthrene, - . . . . o. Hydrocarbons of more Complex Nature: — Fluorantheue; Pyrene; Chrysene; Eetene, Page 615 516 PYRIDINE DERIVATIVES, ALKALOIDS AND COMPOUNDS RELATED TO THEM. General Characters; Summary, .... 517 ixxin. Ptbidine Gkoup, Pyridine, . . - Homologues of Pyridine, ■ Pyridine-carboxylic Acids, Hydro-derivatives, 520 - 524 525 526 527 Appendix: Pyrone;Pyrazine;Pyrimidine;Morpholine,&c., 529 XXXIT. QniNOLINE AND AOEIDINB GkOUPS; AzINES, A. Quinoline Group, Quinoline, Homologues; Condensed Quinolines, Quinoline-carboxylic Acids, Bases related to Quinoline, B. Acridine Group, Appendix: Diphenylene-methune Oxide Group, 0. Azines, Oxazines and Thiazines, 1. Azines, Phenazine, .... Toluylene Red, Safranines, Indulines, - ... 2. Oxazines, .... 3. Thiazines (Thionine dyes), XXXV. Alkaloids of Complex Constitution, - A. The Tropine Group, B. Opium Bases, o. Cinchona Bases, - D. Strychnine Bases, E. Solanine Bases, - F. Further Alkaloids, 530 530 684 535 536 536 537 638 538 589 539 540 541 641 542 543 543 543 544 545 546 546 547 CONTENTS. XIX age XXXVI. Tekpenes and Camphoks, 548 A. Terpeuea, - 548 B. Camphors, - ....... 555 Appendix: Olefinic Camphors, ... 558 XXXVII. Kesins; Glucosides; Vegetable Substances (of Un- known Constitdtion), - - - 558 A. Resins, - .... 658 B. Glucosides, - - - - 559 0. Vegetable Substances of Unknown Constitution, 560 xxxvui. Albuminous Substances; Animal Chemistet, - 561 A. Albumens, - 562 B. Albumenoids, - - 565 0. Substances produced during Metabolic Processes, - 566 Appendix to p. 475: Gumarone and Indazole Groups, 567 INDEX, . 669 ABBREVIATIONS. A. =Liebig's Annalen der Chemie. Ann. Chim. Ph ys. = Annales de Chimie et de Physique. Arch. f. Phys. = Archiv fur Phj'siologie. B. = Berichte der Deutschen Chemischen Gesellschaft. Bull. Soc. Chim. = Bulletin de la Sooi^t^ Chimique, Paris. Ch. Soc. J. — Journal of the Chemical Society. Chem. News = Chemical News. Chem. Ztg. = Chemiker-Zeitung, Cothen. J. pr. Ch.:= Journal fiir Praktische Chemie. Monats. f . Chemie = Monatshefte fiir Chemie und verwandte Theile anderer Wissenschaften. Proc. Chem. Soo. = Proceedings of the Chemical Society. Hec. Tr. Ch. =Eeceuil des Travaux Chimiques des Pays Bas. Z. Anal. Ch. = Zeitschrif t f tir Analy tische Chemie. Z. phys. Chem. — Zeitschrif t fiir physikalisehe Chemie. Z. physiolog. Chem. = Zeitschrif t f Ur physiologische Chemie. "0. N." = OfEoial Name (agreed upon by International Congress), n. or N. = Normal. ( °) or B. Pt. = Boiling Point. [ °] or M. Pt. = Melting Point. 20 OEGANIC CHEMISTRY, INTRODUCTION. Organic Chemistry is the Chemistry of the Carbon Com- pounds. Formerly those compounds which occur in the organic, i.e. the animal and vegetable, worlds were classed under Organic, and those which occur in the mineral world under Inorganic Chemistry, the first to adopt this arrangement having been Limiry in his Cours de Chimie (1675). After the recognition of the fact that all organic substances contain car- bon, it was thought that the difference between organic and inorganic compounds could be explained by saying that the latter were capable of preparation in the laboratory, but the former only in the organism, under the influence of a particular force, the life force — vis vitalis — (Berzelius). But this assump- tion was rendered untenable when Wohler in 1828 synthetically prepared urea, C0N2H^, a typical secretion of the animal organism, from cyanic acid and ammonia, two compounds which were at that time held to be inorganic; and when, shortly afterwards, the synthesis of acetic acid, by the use of carbon, sulphur, chlorine, water and zinc, was effected. Since then so many syntheses of this kind have been achieved as to prove beyond doubt that the same chemical forces act both in the organic and inorganic worlds. The separation of the two branches, Organic and Inorganic Chemistry, from each other is, however, still retained for con- venience sake, although the original reasons for this separation, which at the time was more or less a matter of necessity, have since been found to be erroneous. In consequence of the great capability for combination which carbon possesses, the number of organic compounds is extraordinarily large, and in order to (506) 1 A 2 INTRODUCTION. be in a position to study them, it is necessary to have a know- ledge of the other elements, including the metals. The carbon compounds, many of the most important of which contain only carbon and hydrogen, or carbon, hydrogen, and oxygen, also stand in a closer relationship to each other than do the com- pounds of the other elements. Partly upon grounds of con- venience, carbon itself and some of its principal compounds, such as carbonic acid, which is so widely distributed in the mineral kingdom, are treated of under Inorganic Chemistry. One must not confound the terms "organic" and "organized" bodies; the latter, e.g. leaves, nerves and muscles, and also the life-processes which go on in the interior of the organism, are treated of under Physiology and Physiological Chemistry. Constituents of the Carbon Compounds. Many organic substances are made up of carbon and hydro- gen alone, such being termed hydrocarbons, for instance, ethyl- ene, benzine, petroleum, benzene, naphthalene, and oil of tur- pentine; a vast number consist of carbon, hydrogen, and oxy- gen, for instance, wood spirit, alcohol, glycerine, aldehyde, oil of bitter almonds, formic acid, acetic acid, stearic acid, tartaric acid, benzoic acid, carbolic acid, tannic acid, and alizarin; many (chiefly basic) compounds contain carbon, hydrogen, and nitrogen, for instance, prussic acid, aniline, and conine; as examples of compounds containing carbon, hydrogen, nitrogen, and oxygen, may be taken urea, uric acid, indigo, morphine, and quinine. In addition to these, sulphur, chlorine, bromine, iodine, phosphorus, and, generally speaking, the larger number of the more important elements, are also frequent constituents of the carbon compounds. Qualitative Analysis of Organic Compounds. The presence of Carbon in a compound is often proved by the "carbonization'' of the latter, e.g. starch, sugar, &c., when heated in a glass tube, or when concentrated sulphuric acid is poured over it. Those compounds which boil without decom- QUALITATIVE ANALYSIS. 3 position deposit carbon when their vapours are led through a red-hot tube. But the best proof of the presence of carbon is obtained by completely oxidizing the organic compound by either heating it with copper oxide (see below), or by leading its vapour over the glowing oxide. The carbon present is thus converted into carbon dioxide, and the Hydrogen into water. Nitrogen in organic compounds is recognized — (a) Frequently by a smell resembling that of burnt hair, upon heating; (b) Frequently by the presence of red fumes, or by explosion, upon heating (nitro- and diazo-compounds) ; (c) In most cases by the liberation of ammonia upon heating with soda-lime (Wbhier); (d) In all cases by heating with potassium (and in most cases with sodium), and testing the metallic cyanide formed — (see Cyanogen Compounds) — by dissolving the melted mass in water, adding alkali and a few drops of ferrous sulphate and ferric chloride solutions, boiling, and saturating with hydro- chloric acid (formation of Prussian Blue); or by converting the cyanide into thiocyanate, and proving the presence of the latter by means of the blood-red coloration with ferric chloride. [See tests for hydrocyanic acid (Lassaigne).] If sulphur be likewise present, iron filings must be added. Testing for the Halogens. Direct addition of nitrate of silvfer is usually not practicable; thus, no chlorine can be detected in chloroform even upon boiling it with AgNOg. The halogens are therefore tested for : (a) By heating the substance on a platinum wire with cupric oxide in the Bwnsen flame, or by causing the vapour of the compound to pass over glowing copper gauze; in this way chlorine gives first a blue and then a green flame coloration, and iodine a green (Beilstein); (6) By heatiag the substance strongly with pure lime, and testing the haloid calcium salt produced with silver nitrate, (c) By heating in a sealed tube with fuming nitric acid and nitrate of silver, when the haloid silver salt is produced {Garius). 4 INTRODUCTION. Testing for Sulphur: (a) In many cases, upon boiling with an alkaline solution of lead oxide, brown sulphide of lead is formed (e.g. white of egg); (6) By heating with sodium, and testing the resulting sodium sulphide with water upon a silver coin (black stain); or by means of sodium nitroprusside (purple -violet coloration) (Schonn) ; (c) By complete oxidation in the dry way, by fusing with potassium hydrate and nitre, or by heating with mercuric oxide and sodic carbonate; or in the wet way, by fuming nitric acid (Carius), and testing the sulphuric acid produced, by chloride of barium. In like manner Phosphorus is converted by complete oxida- tion into phosphoric acid; or, upon heating with powdered magnesia, and moistening the resulting mass with water, the presence of phosphuretted hydrogen can be recognized (Schonn). AU the other Elements are tested for, after complete oxida- tion of the compound (preferably by Carius' method), in the usual way. Quantitative Organic or Elementary Analysis. A. Estimation of Carbon and Hydrogen (Combustion). The substance is oxidized by heating it to redness with cupric oxide (Liebig), or with other substances which readily give up oxygen, such as lead chromate, platinum asbestos and oxygen (Kopfer), &c., in a tube of difficultly fusible glass, which is open either at one or at both ends. The carbon dioxide, thus produced by the oxidation of the carbon, is absorbed by a moderately concentrated solution of caustic potash contained in specially shaped bulbs (Liebig, Mohr, Mitscherlich, Winkler, Delisle, &c.), and the water, produced by the oxidation of the hydrogen, in a U-shaped chloride of calcium tube, both tubes being weighed before and after the combustion. If the substance — (0-2 to 0-3 grm.) — is solid, it is either mixed with fine copper oxide (Liebig, Bunsen), or placed in a porcelain ELEMENTARY ANALYSIS. 6 or platinum boat and burnt in a stream of air or oxygen (open tube). Liquids are ■weighed out in small thin sealed glass bulbs. When nitrogen is present, a spiral of copper-foil is placed in the front part of the combustion tube and heated to redness, in order to reduce any oxides of nitrogen which may be formed in the subsequent combustion. In the presence of sulphur or of the halogens, lead chromate, which has been fused and then powdered, is used instead of copper oxide, so as to convert any CI, SOg, &c., into Pb Clj, Pb SO^, &c., and so to prevent them from passing into the potash solution. When only halogens, without sulphur, are present, the combustion is carried out with copper oxide, a copper, or still better a silver spiral, which is kept cool, being placed in the fore-part of the tube to retain the halogens. In the presence of alkalies or alkaline earths (which would retain carbon dioxide), lead chromate mixed with y^yth of its weight of potassic bichromate is usedj the chromic acid then expels all the carbonic acid. Explosive compounds must be burnt in a vacuum. Prom the weights of carbon dioxide and water found, the percentages of and H are readily calculated : C = T^C0,;H = ^H20. B. Estimation of Nitrogen. This estimation is either rela- tive or absolute. In the former case the proportion between the nitrogen and the carbonic acid evolved is determined {lAehig, Bunsen); in the latter the nitrogen is either estimated as such volumetrically, or as ammonia. The conversion into Ammonia is effected by heating the substance strongly with soda -lime {Will, Farrentrapp), or by treating it with strong sulphuric acid and permanganate of pot- ash{Kjeldahl; Z. Anal. Ch. 22. 366; also B. 19, E. 852; 24, 3241). The ammonia is then either titrated directly, or transformed into the double chloride of ammonium and platinum, (NH^C1)2 PtCl^, which is then weighed, or else ignited, and the weight of the residual metallic platinum noted. 6 INTRODUCTION. In the Volumetric Estimation of Nitrogen the substance is mixed with copper oxide, a copper spiral being also used, and the combustion is carried out in the usual way, but in a stream of carbonic acid; the COj is either generated from magnesite in the tube itself, or led through it. The nitrogen is collected over mercury and aqueous caustic potash {Dumas), or directly over potash (Zulhowsky, Schwarz, Schiff, &c.). Its percentage is got from the formula — 273 b-w 100 N (per cent.) = V • 3^3^^ • -^ • 0-001256 • — where V = the volume of the nitrogen, b = the barometric pressure t — the temperature, w = the tension of the water vapour, 0-001256 = the weight of a normal cubic centimeter of nitrogen, and g = the weight of the substance taken. The volumetric method is available in every case, but the other (ammonia) method not always; not, for instance, in the case of nitro-compounds, of many organic bases, &c., the nitro- gen of these not being completely transformed into ammonia upon heating with soda-lime. !For the simultaneous determination of carbon, hydrogen, and nitrogen, the combustion must be carried on in a stream of pure oxygen, the mixture of gases escaping from the potash bulbs being collected over a solution of chromous chloride, which absorbs the oxygen but not the nitrogen (A. 233, 375). C. Estimation of Sulphur and Phosphorus, The Sulphur is estimated as sulphuric acid, being converted into this — (a) in the wet way, by heating the substance with fuming nitric acid to 150°-300° in a sealed tube (Carim), or ip a com- bustion tube in a mixed stream of nitric oxide and oxygen (Claesson), or nitric acid vapour (Klason). (J) in the dry way — (and this method is only available in the case of the less volatile compounds) — by fusing the sub- stance with potassic hydrate and nitre, or with soda and CALCULATION OF FORMULAE. 7 chlorate or chromate of potash, also by heating with soda and mercuric oxide, or with Ume in a stream of oxygen, and so on; (c) by burning in a stream of oxygen and collecting the SOj formed in hydroohlorio acid containing bromine (Sauer; of. Z. Anal. Ch. 12, 32, 178). Phosphorus is estimated by analogous methods. D. Estimation of the Halogens. Here also the organic sub- stance is completely decomposed — (a) after Carius, as above, in a sealed tube, with addition of silver nitrate, by which means the halogen is converted into its silver salt; (J) by heating the compound strongly with pure lime in a hard glass tube, or in two crucibles, one of which is inverted in the other, or with sodic carbonate and nitre in a tube. The chloride formed is precipitated with silver nitrate in the usual way; (c) by the action of nascent hydrogen (sodium amalgam), the halogen in the organic substance can frequently be converted into its hydrogen compound {KehuU). E. Inorganic Bases and Acids, contained in organic salts, can often be estimated directly by the usual methods. F. Oxygen is almost InTariably determined by difference ; direct methods of estimation have been proposed by Bavmhwuer, Ladenburg, Stromeyer, and others. The limit of error in an estimation of carbon is about 0'05 to 0"1 p.c, in one of hydrogen + O'l to 0-2 p.c, while in the volumetric estimation of nitrogen several tenths p.c. too much are easily found. The Calculation of the Formula. The same principle applies here as in the case of inorganic compounds, i.e. the percentage numbers found are divided by the atomic weights of the respective elements, the relative pro- portions of the quotients obtained being expressed in whole numbers. For instance, acetic acid being found to contain 40-11 p.c. carbon, 6'80 p.c. hydrogen, and, consequently, 53"09 8 INTRODUCTION. p.c. oxygen, the quotients are to each other as 3'34 : 6'80 ; 3'32 = 1:2:1. The simplest analysis-formula of acetic acid would therefore be CHjO. Sometimes figures are obtained which correspond with equal nearness to different formulae, between which it is therefore impossible, without further data, to choose. For instance, a sample of naphthalene yields on analysis 93*70 p.o. carbon and 6"30 p.c. hydrogen; the quotient proportion here is 7"81 to 6'30 = 1'239 : 1, which corresponds equally well with the numbers 5 : 4 or 11 :9. The formula CsH, requires 9375 p.c. carbon and 6"25 p.c. hydrogen, and the formula C11H9, 93'62 p.c carbon and 6'38 p.c. hydrogen, the deviations from the actual numbers found being in both cases within the limits of experimental error. Therefore other considerations must be taken into account here, in order to decide between the two formulae. Even in simple cases, such as that of acetic acid, the formula found (CHjO) is not to be taken as the molecular formula without further proof j it only expresses the atomic number proportions. The molecular formula has to be determined according to special principles. Determination of Molecular Weight. 1. By Cheuical Methods. Our chemical formulae {e.g. CHjO) express not merely a percentage relation, but at the same time the smallest quantity of the compound which is capable of existing as such, i.e. a molecule of it. This molecule is ideally no longer divisible by mechanical means, but only by chemical, and then into its con- stituent atoms. If the formula CHjO were the correct one for acetic acid, then the amount of oxygen (or carbon) contained in a molecule would be indivisible, and that of hydrogen divisible only by 2. Since, however, it has been observed that one-fourth of the total hydrogen in acetic acid is replaceable, e.g. by a metal, with the formation of a salt, it is obvious that the quan- tity of hydrogen in the molecule must be divisible by 4, and so the formula must contain at least 4 atoms of hydrogen, and must therefore be O^H^Oj, or some multiple of it. This is, in fact, the case. Acetate of silver contains 64-67 p.c. sUver and therefore 35-33 p.c. of the acetic acid radicle; or, to 1 atom of silver = 108 parts by weight, there are 59 parts by weight of the acid radicle. This 59, together with 1 atom of hydrogen = 1 DETERMINATION OF MOLECULAR WEIGHT. 9 makes the molecular weight of acetic acid 60, = 2 x 30, = 2 X CH2O, = OjH^Og. This is a determination of molecular 'weight by chemical means. Such determinations are carried out in the case of acids generally by means of their silver salts, which are usually constituted normally, are easy to purify, are almost always free from water of crystallization, and are readily analysed. One only requires to know here whether the acid is mono- or polybasic. In the case of a di-, tri-, &c., basic acid, the above calculation must be made with reference to 2, 3, &c., atoms of sUver, whereas acetic acid — being monobasic — contains only one replaceable atom of hydrogen, which is therefore exchanged for one atom of silver. Consequently, its formula cannot be a multiple of CjH^Oj. In the determination of the molecular weight of Bases, their platinum salts are similarly made use of, these being almost always constituted on the type of platinum-ammonium chloride : (NH^C1)2, PtCl^: i.e. they contain two molecules of hydro- chloric acid and one molecule platinic chloride to every two molecules of a mono-acid, or to one molecule of a di-acid base. To determine the molecular weight of Indifferent Com- pounds, derivatives must be prepared and examined for the proportion of the total hydrogen which is replaceable, e.g., by chlorine. For example, by the action of chlorine upon naph- thalene, there is first formed the substance mono-chloro-naph- thalene, which contains 73'8 per cent. C, 4-3 per cent. H, and 21-9 per cent. 01, these numbers giving the formula CiqHjCI. In the same way benzene yields the compound CgHjCl. In both these cases the halogen acts by replacing hydrogen, and at least one atom of the latter in the molecule must be replaced, since fractions of an atom are necessarily out of the question. If, then, the compound obtained has the formula CjgHyCl, it follows that ^th of the H present has been replaced by 01, and there must consequently be 8, 8 x 2, or 8 x 3, &c., atoms of hydrogen in the compound, and likewise 10 atoms, or some multiple of 10, of carbon. But a multiple of 8 or 10 may be rejected, since no compounds have been observed which would 10 INTRODUCTION. indicate the replacement of j-\th of the total hydrogen. This leads to the formula Cj(,Hg for naphthalene, the other possible formula got by analysis, viz., OuHg (see p. 8), being now untenable. In a similar way the formula of benzene is found to be CgHg. 2. By Physical Methods. a. By Estimating the Vapour Density. According to the law oiAvogadro (1811), a,n6L Amphre (1814), all gases under similar conditions, i.e. in the perfectly gaseous state and under the same temperature and pressure, contain in equal volumes equal numbers of molecules. It follows from this that the weights of equal volumes of different gases are proportional to the weights of equal numbers of their con- stituent molecules, in other words, the molecular weight is proportional to the specific gravity of the gas. Thus, if M^ be the molecular weight of any given substance required, Mg that of hydrogen, S the specific gravity of the former as com- pared with air, and 0-06926 the corresponding specific gravity of the latter, then M,:Mh = S: 0-06926. And since Mh = 2, To determine, therefore, the molecular weight of a gas, one has only to find its specific gravity, (air = l), and to multiply this by 28-87. To- take an example, the specific gravity of acetic acid vapour being found to be 2-078, then M = 2-078x 28-87 = 60, and the molecular formula is C^H^Oj = 60. In like manner, the specific gravity of naphthalene vapour is 4-33 and the molecular weight 128 = CjoH8; the specific gravity of benzene vapour 2-702 and the molecular weight 78 = C5Hg. It is essential to the application of this method that the temperature of the vapour shall be so high above the boiling DETERMINATION OF MOLECULAR WEIGHT. 11 temperature of the substance that the latter is in the perfectly gaseous state, remaining at the same time undecomposed. Up to a few years ago, the determination of molecular weight by physical means was restricted to the (different modifications of the) method which has just been described, and consequently it could only be carried out with substances which were either already gaseous, or which could be rendered so without decom- position. The recent important researches of van H Hoff, Raoult, Ar- rhenius, Ostwald and others, upon the nature of solution — in particular, the proof that the laws of Boyle, Gay-Lussac and Avogadro are applicable to solutions as well as to gases — now permit, however, of the ready determination of the molecular weight of substances in solution, and therefore of compounds which could not be volatilized without decomposition. This is accom- plished as follows: — b. By Measuring the Depression of the Freezing Tempera- ture of Solutions. According to Raoult (Ann. Chim. Phys., 1883 efseq.), the law holds that " Equimolecular solutions have the same point of solidifi- cation." By equimolecular solutions are meant such as contain, in equal quantities of the solvent, quantities of the dissolved substances proportional to their molecular weights. If n molecular weights in grammes of a substance are dissolved in g grammes of a solvent, and if the depression of the freezing point of that solvent is represented by A, then A ™ 9 r being a constant, dependent upon the nature of the solvent alone. This latter constant is first ascertained by dissolving compounds of known molecular weight in the solvent, and noting the depression produced. This gives— _^ »•=- In order now to determine the (unknown) molecular weight m of another compound, p grammes of the latter are dissolved in g grammes of the sol- vent, and the freezing temperature of this solution is observed. We then have: — «=.£.; and, consequently, A = -*-, or m = — ". m.g Lg Glacial acetic acid is of especial use as a solvent, but other substances are also employed, e.g. benzene, naphthalene, etc. Cf. Y. Meyer, B. 31, 536 et seq.; also, for the apparatus employed, JBeclc- mann, Z. Phys. Chem. 2, 638 and 715; 7, 323; 8, 223; cf. also B. 25, Kef. 265. The method can also be employed in many cases to study the course of a reaction (B. 25, 1347). 12 INTRODUCTION. c. By Measurement of the Osmotic Pressure. According to van 't Hoff{Z. Phys. Chem. I. 481), all solutions which con- tain substances dissolved in the proportions of their molecular weights {i.e. in " equimoleoular quantities") exert the same osmotic pressure, equality of temperature being assumed here. From this it follows, by reasoning ana- logous to that in section (b), that the molecular weight of a compound can be ascertained by measuring the osmotic pressure of its solution. (Of. Ladenlurg, B. 23, 1225; M. Plcmck, Z. Phys. Chem. VI. 187.) d. By Measurement of the Lowering of the Vapour Pressure. According to Raoult, it molecular quantities of any given substances are dissolved in the same solvent, they give rise to an equal and constant lowering of the vapour pressure. This law can be deduced theoretically from the preceding one (c), and it also stands in theoretical continuity with that of (b). For its application to the determination of molecular weights, of. Z. Phys. Chem. 2, 353, 602; 3, 603; 4, 532; 6, 437; B. 22, 1084. In the journal last quoted the literature on the subject is given. e. By Measuring the Decrease in Solubility. {Nernst, B. 23, Kef. 619.) Appendix: Determination of the Specific Gravity of Gases and Vapours. (Vapour Density.) A, By estimating the weight of a given volume of the gas or vapour. 1. Bunsen's method. Three glass balloons of equal size and weight are used, the first being pumped empty of air, and the second and third filled respectively with air and with the gas in question in a thermostat at a constant temperature. The respective weights of the balloons being ^i, pi, and Pa, the specific gravity = ^°~^' 2. Dumas' method. 10 to 20 grm. of the substance are heated to boiling in a round glass balloon with a narrow neck, immersed, e.g., in an oil-bath. After the temperature has remained constant for a, con- siderable time, the point of the neck is closed by the blowpipe, and the balloon weighed ; it is then opened over mercury and weighed again. Both of the above methods require a large quantity of material and, further, if the substance be not absolutely pure, the last-mentioned method will be liable to the error caused by the vapour of the more difficultly volatile constituent remaining in large quantity in the balloon. Troost and HautefeuilU have modified the method for higher tempera- tures, using a porcelain balloon. B. By estimating the volume of vapour from a given weight of substance. DETERMINATION OP VAPOUR DENSITY. 13 1* . Qay Lussac's method. The substance, weighed in a small bulb, is introduced into a glass cylinder filled with mercury. This cylinder is surrounded by a glass mantle, the lower end of which also dips into mercury, and which is filled with a hot liquid, such as water, aniline, etc. The whole apparatus is warmed and, after the substance in question has been completely vaporized, its volume at the temperature t" is determined. l^ A. W. Hofmann's method. The substance is introduced into a barometer tube surrounded by a wider cylinder, through which the vapour of a suitable heating liquid (water, aniline, diphenylamine, etc.) is led. The cylinder can itself act as a reflux condenser. One advantage of this method is that, by the use of a partial or even complete vacuum, the boiling point of the substance in question is lowered, and thus the vapour density of compounds which decompose on being gasified under the ordinary atmospheric pressure can be determined. There are various modifications of this most accurate method. 2. V. Meyer's air -displacement method. The small tube containing the substance is dropped into a vertical glass tube, the lower and wider part of which is cylindrically shaped and sealed. This is kept warm at a constant temperature, being surrounded by a long glass mantle in which a suitable liquid boils, the upper part of the mantle itself serving for the condensation of the vapour. The displaced air alone escapes, and is collected over water and measured. No determination, therefore, of the temperature of the vapour of the substance in question is required. Both of the above methods require only up to O'l grm. substance. In all cases where g = the weight of the vapour, and v = the weight of an equal volume of air. Thus by the air-displacement method S=- 9 Vb-w) 273 1 760 273-l-i 773 where m = the number of cubic centimetres of displaced air, 1 o.c. of air at 0° C. and 760 m.m. pressure weighing y|^ of a gramme. The other figures have the same meaning as on p. 6. If, instead of having the apparatus filled with air, hydrogen is employed, the greater molecular velocity of the latter allows of the conversion of sub- stances into vapour at 30°-40° below their ordinary boiling temperatures (F. Meyer and Demuth, B. 23, 311) 14 INTRODUCTION. Polymerism and Isomerism. The determination of molecular weight is of the first im- portance, because different substances very frequently have the same percentage composition and therefore the same empirical analysis-formula, and yet are totally distinct from one another. This difference is often found to arise from difference in the size of the molecule. Thus formic aldehyde, CHgO, acetic acid, C2H4O2, lactic acid, CgHgOg, and grape sugar, CgH^jOg, have all the same percentage composition, as have also ethy- lene, CgH^, propylene, OgHg, and butylene, C^Hg. Compounds standing in such relation to each other are termed polymers. Very frequently, however, substances which are totally dis- tinct from each other possess both the same percentage com- position and the same molecular weight ; that is to say, these compounds are made up not only of the same atoms, but also of an equal number of these atoms j such substances are termed isomers or metamers. (See Ethers.) Thus, for instance, common alcohol and methyl ether, the latter of which is obtained by heating methyl alcohol with sulphuric acid, have one and the same molecular formula, OgHgO. The striking phenomenon of isomerism is only explicable on the assumption that the grouping of the constituent atoms of the molecule is different in the two cases. This difference in grouping may be considered as being due to a difference in the linking powers of the atoms, as is indicated by the dissimilar chemical behaviour of isomers, and explained by the theory of valency. See p. 17. Chemical Theories ; the Theory of Valency. After the fall of the Electro-Chemical theory, unitary formulae in contradistinction to the earlier dualistic formulae — were much used • thus alcohol had the formula CiHjOa (using the old equivalent weights). The necessity for comparing substances of complicated composition with simpler ones, taken as " Types," had already repeatedly led to the pro- pounding of new theories for representing the constitution of organic compounds, e.g. the older Type theory {Dumas), and the Nucleus theory {Laurent), gerhardt's theory of types. 15 These obtained a firmer basis through Gerhardt's Theory of Types, which received support more especially from the discovery of ethylamine and other ammonia bases [Wurts (1849) and Hofmann (1849, 1850)], the proper interpretation of the formulae of the ethers \Williamson (1850)> and the discovery of the acid anhydrides [Oerhardt (1851)]. All com- pounds, inorganic as well as organic, vfere in this way compared with simpler inorganic substances taken as " Types," of which Oerhardt named four, viz. — g) S} }° iJN The first two of these really belong to the same type, lowing formulae, for example, were arrived at — Potassium chloride. Ethyl chloride. Thus the fol- Potassium hydrate. Nitric acid. Potassium oxide. Nitric anhydride. CoH, H Alcohol, }» CI / Acetyl chloride. C2H3OI ;}» }" CaH, Ether. C2H5 H H N ©0 Acetic acid. CaHgOXj-, C,HsO;" Acetic anhydride. CjHgO 1 H \ Ethylamine. Aoetamide. etc., etc. Organic compounds could thus, like inorganic, be referred to inorganic types by assuming in them the presence of Radicles {e.g. ethyl, C2H5; acetyl, CjHjO, etc.), i.e. of groups of atoms which play a part analogous to that of an element, and which can be transferred by double decomposition from one compound to another. Thus ethyl chloride, CjHjCl, alcohol, CjHjO, ethylamine, CgHyN, ether, C4H10O, etc., received the same radicle C2H5, ethyl, this showing the close relationship existing between these compounds, a relationship which now found in this way expression in writing. Sulphuric acid, H2SO4, was derived from the double water type, thus — Halo (SO,)"\q . and chloroform, CECI3, and glycerin, CsHgOs, from the triple hydro- chloric acid and water types — H,1 (CH)"'\ . Hj-1 (CsBb)"'-1 o . CI3I CI3 I' nj^» H3 r" the assumption being made that the radicles (C2H5)', (SOj)", (CH)'", and 1 6 INTRODUCTION. (OsHs)'" could replace a number of hydrogen atoma corresponding to the number of accents (') marked upon them, i.e. that they were monatomic, diatomic, etc. To the above three types KekuU afterwards added a fourth, of especial importance as regards the carbon compounds, viz. — H) ■n- > C, Marsh gas. h) It was then found that many compounds could be referred equally well to one or another of these types, methylamine, for instance, either to CH4 or to NHj, thus — „ yc or H fN. H ) ^ ' The assumption, already mentioned, of the atomic groups (radicles) which in these types replaced hydrogen, led further to more exact investigations of the chemical value, i.e. the replaceable value,of those groups as compared with that of hydrogen. In this way chemists learnt to distinguish between mono-, di-, tri-, etc., valent groups, and, generally speaking, to pay more attention to equivalent proportions. As the outcome of his researches upon organo-metallio compounds, Frank- land formulated in 1852 (A. 85, 368) the law that the elements nitrogen, phosphorus, arsenic and antimony tend to form compounds which contain three or five equivalents of other elements. KekuU then, in 1857-8 (A. 104, 129; 106, 129), proceeded to show that a more profound idea (the " Type idea ") lay at the root of the types them- selves, viz., that there are mono-, di-, tri-, and tetravalent, etc., elements, which possess a corresponding replacing or combining value as regards hydrogen ; and that hydrogen is therefore monovalent, oxygen divalent, nitrogen trivalent, carbon tetravalent, and so on. The principles of the theory of Valency or theory of Chemical Values are in this book assumed to have been already learnt from inorganic chemistry. With the setting up of the type CHi by KekuU, and the knowledge of the tetravalent nature of carbon accompanying this, were connected the endea- vours of Kolbe to derive the constitution of organic compounds from carbonic acid (according to Kolbe C2O4, C = 6, = 8), by the exchange of oxygen for organic radicles (A. 113, 293); see also, for further details, Kopp's " Entwickelung der Ghemie in der ueueren Zeit" (Oldenbourg, Munich, 1873), and M. V. Meyer's " History of Chemistry " (Macmillan, 1891). The question of the valency of elements, a point which it is often difficult to decide in inorganic chemistry, is infinitely easier of determination in the case of the carbon compounds, because carbon shows itself tetravalent towards hydrogen as well as towards chlorine and oxygen. Since now hydrogen as the unit of valency is monovalent, and, further, since the divalence of oxygen cannot reasonably be doubted, the valency of the three " organic " elements hydrogen, oxygen and carbon may be considered as resting upon a sure basis, as may also the (606) EXPLANATION OF ISOMERISM. 17 conclusions drawn therefrom, and this all the more since the most important carbon compounds are made up of those three elements. Explanation of Isomerism; Determination of the Constitution of Organic Compounds. The theory of valency makes the phenomenon of Isomerism easy to understand. That this depends upon the different grouping or combination of the atoms in the molecule follows from the fact that isomeric bodies, upon chemical transforma- tion, break up into or exchange perfectly different atomic groups or atoms. We now arrive at the task of determining the different modes of combination of the atoms in the molecule, i.e. the chemical constitution of the carbon compounds. This is in every case only possible and admissible for com- pounds whose chemical behaviour in the most dissimilar directions is known. In considering this, let us fix our attention, in the first instance, upon the mode of linking of atoms in a molecule which can be subjected to the test of actual experiment, leaving aside the further point as to how far a difference in the grouping of atoms in space may come into question here. With regard to this latter, see p. 21 ei seq. The points of view which determine this can best be explained by giving an example. When an ethereal solution of methyl iodide, CH3I, is treated with sodium, there is first formed the group CH3, methyl, which — from carbon being tetravalent — must have a " free affinity " (*) — /H *— C-H \H The determination of the molecular weight of the gaseous compound ethane, formerly called methyl, which is thus pro- duced, shows however that it has the formula C2H5, ( = 2CH3). The two methyl groups have therefore combined together, and it cannot well be doubted that this combination is effected by their free affinities. Ethane therefore receives the constitu- tional formula — HqC — CHq:= } C=H3 J MS) 8 18 INTRODUCTION. or, more shortly, CH, This ethane can also be prepared from common alcohol. By the action of a halogen-hydride upon alcohol, one atom of oxygen and one of hydrogen together are exchanged for an atom of the halogen with formation, for example, of CgHjCl, ethyl chloride ; then nascent hydrogen, acting upon this chloride, replaces the halogen, thus, CjHgO + HCl = C2H5CI + HgO ; C2H5C1+H2 = C2H6 + HC1. Conversely, by treating ethane with chlorine, ethyl chloride, CgHjCl, can be formed, and from this latter compound, alcohol. (See Special Part.) Thus, one atom of oxygen and one of hydrogen have here replaced one atom of chlorine, from which it follows that the two first-named together form the monovalent residue — (0 — H), hydroxyl. It is also evident from this reaction that one atom of hydrogen in alcohol behaves differently to the other five, and must con- sequently be difi'erently bound. Thus it is, for instance, re- placeable by metals, acid radicles, etc., and, when the oxygen is removed from the compound, it is removed also, whereas the other five hydrogen atoms are not affected. It is especially to be noted that the relation of the two carbon atoms to one another is not altered by the removal of the oxygen. All these facts lead to the constitutional formula for alcohol : C=H3 CH3— CHjOH or /H. 0— H \0— H In methyl ether, CjHgO, which is isomeric with this alcohol, no one of the six hydrogen atoms shows any difference to the others ; and, further, when its oxygen is removed, say by the action of hydriodic acid, the connection between its two carbon atoms is broken, with the formation of products which contain DETERMINATION OF CONSTITUTION. 19 only one atom of carbon in the molecule, these products being, according to the conditions, — either one molecule methyl iodide and one molecule methyl alcohol or two molecules methyl iodide, thus — C,HeO + HI =CH,0 + CH3l, or, CjHeO + 2HI = 2CH3I + H^O. From this it is to be concluded that in methyl ether the two carbon atoms are not bound directly to one another, but only by interposition of the oxygen ; so that when the source of this connection is removed, the carbon atoms separate from one another. These conditions find expression in the following constitutional (or structural) formula — CH3— 0— CH3; or i G-^K,. In a precisely analogous manner we obtain for acetic acid the constitutional formula — C-H. H O I ^O ; or H— 0— C 1 ^\0H I I H 6— H The grounds for this formula will be explained later on. It corresponds perfectly with the chemical behaviour of acetic acid and explains the following facts: — (a) that one of the hydrogen atoms of the acid possesses properties different to those of the three others, the first-named being easily replace- able by metals; (b) that the two oxygen atoms behave differ- ently, not being exchangeable with equal ease for other elements or atomic groups; (c) that different functions appertain to the two carbon atoms, so that one of them — being already joined to two atoms of oxygen — easily gives rise to carbonic acid, while the other — connected as it is with three atoms of hy- drogen— -readily passes into methane or methyl compounds. On account of the innumerable cases of isomerism which have been observed, empirical formulae alone are in most cases 20 INTEODUCTION. insufficient for the discrimination of organic compounds; it generally requires the constitutional formulae to give a clear idea of their behaviour and of their relations to other substances. Careful study has made it possible vi^ithin the last few de- cades to find out the mode in which the atoms are combined in the molecule of most organic compounds, and from this' to deduce new methods for their preparation. The constitutional formulae thus arrived at are sometimes very simple, sometimes, however, very complicated, as, for instance, in the cases of citric acid and grape sugar (which see). THE NATURE OF CARBON. The theoretical views and the knowledge thereby gained of the nature of carbon may be expressed somewhat as follows : — 1. Carbon is tetravalent. 2. Its four valencies are all equal; there is only one mono- substitution product of methane. 3. The atoms or atomic groups which are held bound by these four valencies cannot directly exchange places with each other (the Le Bel-van 't Eoff law, 1874). Proof : there are in every case two physically different tetra-substitution products, C, a, b, c, d of methane (see p. 22). 4. Several carbon atoms can be connected together by efither one, two, or three valencies (see p. 30): — C, O^C, C^C- ; 5. Similarly, three or more carbon atoms may be united, forining in this way the so-called " carbon chains " (see p. 29), thus — C_C— C— C; C— C— C=C— C— C; C=C\p, p, (./C— C. The number of the atoms so linked together may be a very large one, e.g. much above 30. 6. Those compounds form either open or ring-shaped closed chains., -Open chains are those which have separate constituent atoms at either end, as in- (5). In closed chains 6v atomic rings, op the contrary, the first and last constituent atoms are linked NATURE OF CARBON. 21 together (although there may at the same time be subsidiary branches from them), thus — C- C 7. Other elements, with the exception, of course, of mono- valent ones, may likewise take part in the formation of such chains, both open and closed; for example: — C— Ov c— C. /C— 0. N; I >S; G^ >K c-c/ c— 0^ \C— c^ The above figures (the hexagon, etc.), which are made use of to represent such chains or rings, are merely meant to be pictorial {schemaiisch) and not geometrical; the question of the spacial arrangement of atoms in compounds will be treated of later. 8. When a carbon atom is linked to four other atoms or atomic groups similar to each other, its four affinities apparently act uniformly and equally, as may be pictured in a regular tetra- hedron whose central point is joined to each corner by straight lines. We .may thus imagine the system (spacially) as a regular tetrahedron, the centre of which is occupied by the carbon atom, and in whose corners the centres of gravity of the four other atoms (etc.) are to be found. If the four atoms (etc.) which are linked to the carbon atom be dissimilar, then the affinity-directions {Affinitdtsrichtungen)wi\\ undergo corresponding diversions, the distances of the centres of gravity of the four atoms from the carbon atom will be different, and the whole system will give a picture of a less regular tetra- hedron. (For further details, see under " Stereo-chemical Isomerism "). 9. For the spacial distribution of valencies, and for an attempt to explain tension phenomena when carbon atoms are linked together by two or more bonds, cf. Baeyer, B. 18, 2277. ; STEREO-CHEMICAL ISOMERISM. ' In the course of .the investigation of the constitution of organic compounds, a variety of cases have gradually come to aa INTKODTJCTION. light in which the same constitutional formula must he given to two or mxyre compounds, seeing that they show a perfectly similar chemical behaviour, or at least a behaviour similar in many respects. Substances of this kind also frequently agree or closely resemble one another in their physical properties, and the one modification can usually be transformed into the other by very simple means, e.g. by raising the temperature (i.e. a "molecular transformation" is brought about). It is the development of the above assumptions with respect to the spacial configuration of the carbon compounds which has led to a conception of the cause of such cases of fine isomerism. This latter is to be sought for in the relative spacial arrange- ment of the individual atoms within the molecule, i.e. in the configuration of the molecule; it is therefore termed Stereo-chemical Isomerism, or, less frequently, Allo-isomerism. The above views were first published by van 't Hoff, and they have been developed, more particularly, by J. Wisli- cenus. Cf. van 't Hoff, "Dix Annies dans I'histoire d'une Theorie;" Kotter- dam, 1887 (English translation by J. B. Marsh, Clarendon Press, 1891); /. WisUcenus, "Kaumliohe Anordnung der Atome," Leipzig (Hirzel), 1887; ibid., B. 20, Eef. 448; A. 248, 281 et seq.; Baeyer, B. 18, 2277; A. 245, 103; Auwers and Victor Meyer, B. 21, 784, 946; V. Meyer, B. 21, 265, 288, etc. Shortly stated, they are somewhat as follows: — 1. If one carbon atom is linked to four other atoms or atomic groups which differ from one another, i.e. if the carbon atom is " asymmetric," then only one constitutional formula is possible; an isomerism in virtue of different constitution is not conceiv- able. Nevertheless, two physically different tetra-substitution products of this kind may exist [see p. 20 (3)]. Thus, if we picture them as tetrahedra projected on the surface of this paper, the centre of each being occupied by the carbon atom, we shall get the two following configurations. (The carbon atom in the centre is not shown in the drawing; the linked atoms or atomic groups are designated by the letters A, B, and D.) STEREO-CHEMICAL ISOMERISM. 25 The two figures below are not congruent, the one being the mirror image of the other. The succession of B, C and D is. in the first case, in the same direction as the motion of the hands of a watch, while in the second it is just the opposite. If, therefore, any physical property be dependent upon the spacial arrangement of these atoms or atomic groups, B, C and D, e.g. the power of optical rotation (see p. 38), then this pro- perty will be exercised in opposite directions in the two cases; if the compound which corresponds to fig. (I.) be dextro-rotatory, then the other will be laevo-rotatory ; and so on. A simple explanation is thus afforded of the existence of isomeric compounds which differ from one another in their optical properties alone. For further details on this point, see under lactic acid. 2. If two carbon atoms are linked together by one affinity of each, and if they are at the same time asymmetric, the con- ditions which have just been described under (1) may repeat themselves in a variety of ways (see under tartaric acid). Two carbon atoms, bound together by one affinity of each, may be thus represented: — more simply: — C BymbolioaUy:— C 24 INTRODUCTION. In general we have to assume in this case that the two atoms can rotate about their common axis independently of one another. At the same time the atoms which are linked to the one carbon atom will exert a discriminating {orientirende) action upon those which are linked to the other, according to the measure of their mutual attraction, in consequence of which they will take up a so-called " favoured " position. Supposing the groups H, 01 and COaH to be severally linked to both the carbon atoms, as is the case in dichloro- succinio acid, COjH-CHOl-CHCl-COaH ; then, taking the order of succes- sion of the substituents as that just given (apart from intermediate posi- tions), three configurations are possible, viz. : — ■CQaH iU COaH COiH f^l^^^^^j^^^^^^^^^^^f-Q^ H<^^_^^_^^;^;^^Ci co^i<^,:^jj^^^^:.zi^^K n CO3H a The strong affinity between hydrogen and chlorine, however, makes the first of those configurations the "favoured" one, and therefore the one which must recur most frequently. It is further possible that the directive influences of these last-mentioned forces of attraction may even entirely arrest free rotation in certain cases. But no instances of this nature are as yet known with certainty. 3. If two carbon atoms are linked together by two affinities of each, then the system no longer possesses freedom of motion. Supposing that to each-of the carbon atoms two different atoms or atomic groups, a and b, are united, then — with the same linking chemically — two isomers may exist, from the different distribution of a and b, thus (in the first and third figures the edges of the tetrahedra are merely indicated by dotted lines, the full lines showing the affinity-directions) : — a^i" - ^^^b ar- ^h a^^- ^b a,; ^b more \ X. / '» A;\ / more (L) X'- vK ^™P'^'~ V" V (n.) %-■■%' simply:- a.*^--- '^b a. h b*^- -^a b'^ ^a STEREOCHEMICAL ISOMERISM. 25 or, abbreviated: — (L) 0—0—6 (11.) 0—0— J II II a—G—b h—G—a In fig. I. aa stand in a "corresponding" or " piano -symmetric" ("r cis") position to one another; in fig. II. in a "centrical- symmetric" or " axial-symmetric" (" r cistrans"). (I.) is there- fore designated the "cis" form, seeing that in it both of the atoms or atomic groups aa are on one side of the plane which is formed by the affinity -directions of the double linking; (II.), on the other hand, is the "trans" form, oo being on opposite sides here. It is easy to imagine that in the one case the atoms or groups, a and i, would exert a stronger mutual attraction than in the other. Stereo- isomers of this kind show greater differences both chemically and physically than the compounds whose stereo-chemical isomerism has been treated of under (1) and (2) (see p. 22). The one isomer, in contradistinction to the other, is often characterized by a definite intra-moleoular reaction, e.g. the formation of an anhydride, this being induced by the spacial approximation of the reacting atoms or atomic groups towards one another, in consequence of the configuration. The interesting isomerism of fumaric and maleic acids — to give an in- stance — has been clearly explained by the above theory, the value of which has been enhanced by the fact that this explanation has led to the discovery of other cases of isomerism in unsaturated compounds (chloro-propylenej chloro-crotonio acid, etc.). 4. A nitrogen atom may also give rise to isomerism in this way, if its three affinities do not act in one and the same plane, but in a similar direc- tion, as from one comer of a tetrahedron to the three others. Thus, of the compound — "^C = N c the two following modes of spacial arrangement of the atoms are conceiv- able (the affinity-directions are here represented by straight lines, and the edges of the carbon-atom tetrahedra by dotted ones): — ■C or, abbreviated: — a— 0—5 0—0— J II and II N—e e—N 26 INTRODUCTION. What has just been said under (3) applies here also, viz. that it is easy to conceive that the groups or atoms, a and o, would exert a stronger mutual influence in the one case than in the other, and would thus give rise to outward differences in the two substances represented by the above formulae. This conception is of especial value for the explanation of the observed cases of isomerism among the ketoximes (which see). Cf. Hantzsch and Werner, B. 83, 1 ; 24, 3511 ; 25, 2164; V. Meyer, B. 23, 567. 5. While the nitrogen-isomerism, which has Just been de- scribed, corresponds in many respects with the carbon-isomerism treated of under paragraph (3), a nitrogen-isomerism among compounds containing pentavalent nitrogen [cf. nitrogen bases, behaviour of, paragraph (7)] has been met with, which resem- bles the carbon-isomerism spoken of under paragraph (1). {Le Bel, B. 24, Eef. 441.) 6. The above cases of isomerism must not be confounded with dimorphism, which exists among many inorganic, as well as among certain organic, compounds. On the other hand, there are also numerous cases known in which two different constitutional formulae may be ascribed with equal correctness to one a,nd the same substance, according to its behaviour in different reactions. Such formulae are termed tautomeric. — For further particulars see the Cyanogen Compounds, Section F. Rational Formulae. Great latitude is permissible as regards the mode of writing constitutional formulae, according to the particular points which it is desired to emphasize. A formula on paper is not as a rule intended to represent the symmetrical or other arrange- ment of the atoms in a compound. A shortened constitutional formula, which indicates more chemical relations than an empirical one does, is called a rational formula; e.g. CgH^OH, alcohol; (0113)20, methyl ether. HOMOLOGY. 27 For acetic acid, instead of the constitutional formula already given on page 19, the following rational formulae may be used — CH3— CC CH— CHg— CH3: Ethyl-isopropyL g|3>CH-0Hc'H, Tri-methylene (" O.N." Cyclo-propane). Hexa-methylene (" O.N." Cyelo-hemme). These latter hydrocarbons are more or less related to the benzene derivatives, and will be treated of partly along with these, and partly in a separate section (XV.), as compounds midway between those of the fatty and the aromatic series. The naphtbenes, mentioned on p. 54, belong to them. Summary, M. Pt. B. Pt. M.Pt. B.Pt Ethylene, O^H, -160° -103° Dodeoylene, C12H24 -31° {96°+ Propylene, CsHe Gas Trideoylene, O13H26 233° (a -5° Tetradeoylene, CnHjs -12° {127° Butylene (3), CiH, \ P -1-r Pentadeeylene, CifiHao 247° (7 -6° Hexadeoylene, \ (Cetene), J n. Tr„ + 4° f 274° I {155° {179° Amylene (5), C5H10* + 35° ^iG^^sa Hexylene, OeHia 68° Ootadeoylene, OisHss 18° Heptylene, C,H„ 98° Eicosylene, CjoH«i Octylene, OsHiB 124° Carotene, CajHa 68° Nonylene, C»Hi8 153° Melene, OaoHeo 62° Decylene, O10H20 172° TJndeoylene, OnHiB 195° A Methylene, CHg = , does not exist. * The melting and boiling points given from CsHjo on, are those of the normal hydrocarbons. + { Signifies boiling point under 15 m.m. pressure. 56 I. HYDROCARBONS. The members of this second series of hydrocarbons differ from the paraffins by containing two atoms of hydrogen less than these. In their physical properties they resemble the methane homologues very closely. OgH^, CgH,., and C^Hg are gases, CjHjo a volatile liquid, the higher members liquids with rising boiling point and diminishing mobility, while the highest are solid and similar to paraffins. The boiling points of members of both series containing the same number of carbon atoms, and whose constitutions are comparable, lie very close together, but the melting points of the olefines are somewhat the lower of the two ; e.g. CigHg^, M. Pt. 21°, B. Pt. {157°, and CigHg^, M. Pt. 4°, B. Pt. {155°.* Most of the olefines are easily soluble in alcohol and ether, but insoluble in water, only the lower members dissolving slightly in the latter. The specific gravities of the normal olefines, measured at the melting points, rise from about 63 upwards, and approach with increasing carbon to a definite limit, viz., about 079. In their chemical relations, the olefines differ materially from the paraffins : (a) By additive reactions. They combine readily with nascent hydrogen, with hydrochloric, hydrobromic, and hydri- odic acids, with chlorine, bromine, iodine, fuming sulphuric acid, hypochlorous acid, nitrous acid, and, generally speaking, with two monad atoms or monovalent groups, whereby members of the methane series or their derivatives ensue; hence their name of " Unsaturated Hydrocarbons." C^H. + H, = C,H,. C,H, + Cl2 = C,H,Cl2. C^H. + HI = CgHjI. C2H, + H2SO,= C^H.CSO.H). Combination with hydrogen is sometimes effected, e.g. in the case of ethylene, by the aid of platinum black at the ordinary temperature, or by raising to a red heat, or by heating the olefines or their di-chlor-, etc. , addition products with fum i i ; " hydriodic acid and phosphorus. (Of. modes of formation of the saturated hydrocarbons B 1 and 5.) * See note, p. 4i THE OLEFINES. 57 Ethylene chloride, CjH^Cla, obtained by the combination of ethylene with chlorine, was formerly called the oil of the Dutch chemists, hence the name of " defines" for the whole class of hydrocarbons C^Han (Guthrie). Chlorine adds itself on more easily than iodine, but hydro- chloric acid with more difficulty than hydriodic, bromine and hydrobromic acid standing mid-way. When a halogen hydride is used, the halogen attaches itself to that carbon atom which is combined with the least hydrogen. (Of. Substitution Products.) Particular olefines, e.g. isobutylene, also combine slowly with water to alcohols under the influence of dilute acids. Ethylene combines with fuming sulphuric acid at the ordin- ary temperature, and with the English acid at 160°-170°. Amylene forms with nitrogen tetroxide, N2O4, amylene nitrosate (A. 248, 161); nitrogen trioxide and nitrosyl chloride also unite directly with the olefines. (b) By their capability of polymerizing, especially in presence of sulphuric acid or zinc chloride. In this way are formed from amylene, C5H10, in presence of sulphuric acid, the polymers CioHjo, CisHao, and C2oHio; and from tertiary butyl alcohol, warmed with acid of a definite strength, di-isobutylene. The poly- merization is brought about through the junction of the atomic groups in question, by means of a new carbon -linking (see A. 189, 44). (c) By their behaviour upon oxidation. They are easily oxidized by KMnO^ or CrOg, but not by cold HNO3. By this reaction, either oxidation products — (acids) — containing less car- bon are formed, by the breaking up of the double carbon bond (see p. 59, also A. 197, 243) ; or, when KMnOi is employed, no carbon atoms are separated, but two hydroxyls are introduced, with formation of a diatomic alcohol. (See p. 202; cf. B. 21, 1230, etc.) The "official name" (p. 28) of the olefines is formed by replacing the last syllable "ane" of the paraffins by "ene." The position of the double bond is denoted by the number of the carbon atom from which it proceeds. In a branching chain the numbering is the same as in the case of the corre- sponding saturated hydrocarbons ; in a normal chain it begins at the end carbon atom which is nearest to the double bond. Modes of Formation, (a) Together with paraffins by the destructive distillation of many substances, such as wood, lignite and coal, and also by the distillation of the paraffins 58 I. HYDEOCAKBONS. (cf. pp. 45 and 52); illuminating gas consequently contains the defines CgH^ CjHg, C^Hg, etc. (b) By abstraction of water from the alcohols, CnHjn+iOH, by heating them with sulphuric acid, phosphorus pentoxide, zinc chloride, etc. When sulphuric acid is used, an alkyl-sulphuric acid, e.g. ethyl-sulphuric acid, OgHjSO^H, is first formed, and this decomposes upon further warming into alkylene and sul- phuric acid. This method is especially applicable in the case of the lower homologues. Many alcohols split up into olefine and water, even when only strongly heated alone, e.g. secondary butyl alcohol at 240°. A convenient method of obtaining the higher olefines is to distil the palmitic ethers of the higher alcohols under somewhat diminished pressure, when the corresponding olefines and palmitic acid are produced. (c) By heating the halogen compounds C^Hjn+jX with alco- holic potash, or by passing their vapour over red-hot lime or hot oxide of lead, etc. ; sometimes by distillation alone : CjHuI -1- KOH = C5H10 -^ KI + H2O. The bromine compounds are particularly suited for this. (d) Sometimes from the haloid compounds CaHsnXa by abstraction of the halogen, e.g. ethylene from ethylene bromide by treatment with zinc, or zinc dust and alcohol: CzHiBrj -f Zn = OaH, + ZnBra. (e) By the 'electrolysis of dibasic acids of the succinic acid series ; thus succinic acid itself yields ethylene : C2H,(COOH)2 = C2H4 -h 2 CO2 -I- H2. Other modes of formation correspond with these under D. 1 and 2 for the parafSns. Constitution of the Olefines. For ethylene, produced by the abstraction of two atoms of hydrogen from ethane, the following formulae may be given: CH3 CH2- CH„ LI IL I III. II CH= CH2— CH2 ■In the formulae I. and II., two free carbon aflSnities are assumed in the ethylene molecule. Formula III. follows from the assumption that the affinity which becomes free at each of CONSTITUTION OF THE OLEFINES. 59 the two carbon atoms, upon abstraction of the hydrogen, is employed in creating a " double bond " between them. Upon the taking up again of two atoms of hydrogen or halogen, the two free affinities in I. and II. would become bound by them, while in III. the double bond would be changed into a single one, and the free aflSnity of either carbon atom would be employed in binding the two new hydrogen (or other) atoms. Now the ethylene bromide which is formed by the addition of bromine to ethylene has, for reasons which will be given under that compound, the constitution CHjBr — CHjBr, and likewise the compound obtained by the addition of ClOH, i.e. 01 and OH, viz. glycol chlorhydrin, the constitution CHjCl — CHjOH; consequently formula I, according to which these substances would have the constitutions CHg — CHBrg and CH3— CHCl(OH), is excluded. Formula III. is more probable than formula II.: — (a) On account of methylene, CH2^, being incapable of existence ; all attempts to isolate it have only yielded ethylene, C2H4 (see p. 60), so that free affinities probably cannot exist in the carbon atom. (b) Because one would otherwise expect to have two isomeric ethylenes, but all endeavours to prepare an isomer have proved fruitless {Tollens and L. Meyer); and further, because more isomers of the next higher homologues, propylene and butylene, should exist than can actually be prepared. (c) Because the free affinities to be assumed according to II. are never found singly (which should in that case be possible), but invariably in pairs only, and indeed only on neighbouring carbon atoms. This is proved from the constitution of the compounds obtained by the addition, for instance, of" Bfj. It is therefore to be concluded that in ethylene and its homologues a double carbon bond, corresponding to formula III., exists. By this term " double bond " is not, however, to be understood a closer or more intimate combination. The olefines, on the contrary, are more readily oxidized than the paraffins, being thereby attacked at the point of 60 L HYDROCARBONS. the double bond. Other properties, especially physical ones, also give indications that a double bond between two carbon atoms is looser, and therefore more easily broken than a single one. (Of. Brilhl, A. 211, 162.) 1. A Methylene (Methene), CHj, does not exist, as already mentioned on p. 59. Numerous attempts at preparing it, e.g. by the withdrawal of hydro- gen and chlorine from methyl chloride, have invariably yielded ethylene, thus :— 2 CHs 01 - 2 H CI = O2H4. Here the two resulting CHj-residues have united together, in the same way as the two methyl-groups coalesced to ethane (p. 46). 2. Ethylene (Ethene), elayl, oil-forming Gas, CjH^, = CH2=CH2. This compound was discovered in 1795 by four Dutch chemists. Its formula was established by JDaZton. Formation — see above. Illuminating gas generally contains 4 to 5 p.c. of ethylene. The latter is usually prepared by heat- ing alcohol with excess of concentrated sulphuric acid, with addition of sand, a mixture of equal portions of the two liquids being subsequently dropped into the evolution flask. Sulphur dioxide, etc., are produced at the same time by secondary reactions. Small quantities can be conveniently prepared from ethylene bromide and zinc. It is further formed (instead of its hypothetical isomer indicated above) by heating ethylidene chloride, CHg — CHCI2, with sodium. Liquid at 0° under 44 atmos. pressure. B. Pt. - 103°; M. Pt. -160°- Very slightly soluble in water and alcohol. Burns with a luminous flame, and forms an explosive mixture with oxygen. When rapidly mixed with two volumes of chlorine and set fire to, it burns with a dark red flame, with formation of hydrochloric acid and deposition of much soot. It is con- verted at a red heat into methane, CH4, ethane, CjHj, acetyl- ene, CgHg, etc., with separation of carbon. (See p. 48.) It combines with hydrogen in presence of spongy platinum to ethane, CjHg. 3. Propylene (Propene), CgHg, = CH2=CH— CHg. Only one propylene belonging to the olefine group is theoretically pos- sible and only one is known, viz. a methylated ethylene (see p. 54). (On the assumption of two free afiinities instead of a double bond, four isomeric propylenes would be possible.) It BUTYLENE, AMYLENE, ETC. 61 can be prepared from isopropyl iodide and caustic potash, or by heating glycerine with zinc dust. It is still a gas at - 40°. Is isomeric with tri-methylene (see Section XV.) 4. Butylene, OiHa. Three butylenes are possible according to theory, and three are known. All of them are gaseous, their boiling, points lying between —6° and +3°. Butylene and pseudo-butylene are derived from normal butane, while isobutylene comes from isobutane, since they severally combine with Hj to form these hydrocarbons. The first, a-butylene, is prepared from normal; the second, ;8-butylene, from secondary; and the third, 7-butylene, from tertiary butyl iodide, by the action of caustic potash upon these; the last can also be got from isobutyl alcohol and sulphuric acid. The isomerism of the two butylenes derived from normal butane is explained by the assumption of a double bond at different points, thus: CH2=CH — CII2 — OMs CHa — OH=CH — CH3 o-Butylene {1-Butene). /3-Butylene (2-£utene). Isobutylene has the formula (CH8)2=C=CH2 {2-methyl-2-propene). The behaviour of these isomers upon oxidation is in accordance with the above formulae, the oxidation always taking place at the point of the double bond. The butylenes are isomeric with tetra-methylene {cydo-butane, p. 323). 5. Amylene, C^H-^q. A large number of isomeric amylenes are known, among them being Amylene (B. Pt. 35°), which is obtained together with an isomer, Iso-amylene, by heating ordinary amyl alcohol with chloride of zinc. For it the con- stitutional formula (CHg)20=CH — CH3 ( = trimethyl-ethylene) is assumed. This is known in the pure form under the name of "pentaL" Another isomer is penta-methylene {eyclo-pentane, p. 323). 6. Sl-isobatylene, CsHm. Formation, see above, B. Pt. 102°. The higher defines of normal constitution, with 12, 14, 16 and 18 atoms of carbon, have been prepared by Krafft accord- ing to method b. Carotene and Melene (M. Pt. 62°) are obtained by the dis- tillation of Chinese wax and bees' wax respectively. They are like paraffin in appearance, and are but slightly soluble in alcohol 62 L HYDROCARBONS. O. Hydrocarbons, C„Hita-2: Acetylene Series. ISv/rnmary. C3H4 C4H8 {Acetylene \ (Ethine),/ AUylene (Allene), {Crotonylene, 1 etc. (Butine),j {Valerylene, etc. 1 (Pentine), j Diallyl (Hexine), Heptine, etc., B. Pt. Gas. 18°* 51° /59° \.80° 108° ^13^22 C14H25 /Dodecylidene \ \ (norm.), / {Tetradecylidene \ (norm.), / fHexadeoylidene "| -j norm.) > y (Cetine), J /Octadecylidene \ \ (norm.), / I Eicosylidene ( (norm.). M. Pt. -9° + 6° 20° 30° liquid B. Pt. {105°+ {134° {l60° {l84° 314° • The boiling points from C4 on, are those of the normal compounds. + Boiling point under 15 m.m. pressure. The hydrocarbons of this series again differ from those of the preceding by containing two atoms of hydrogen less. In physical properties they closely resemble both the latter and those of the methane series; thus the lowest members up to C^Hg are gaseous, the middle ones liquid, and the highest solid, and in their melting and boiling points they do not differ to any extent from those of the other series with an equal number of carbon atoms. The specific gravities of the normal hydrocarbons Cjg, Oj4, Cjg and Cjg, at the melting point, gradually approach with increasing carbon to a definite limit (0*80), and are somewhat higher than those of the corre- sponding members of the ethylene series throughout. In their chemical relations the acetylenes stand nearer to the olefines than to the parafSns, in so far that they are un- saturated and therefore capable of forming addition products. 1. They combine either with two atoms of hydrogen or THE ACETYLENE SERIES. 63 halogen, or ■with one molecule of halogen hydride to olefines or their substitution products, thus: O2H2 + H2 = 02H^. C2H2 + HBr= O^HgEr (vinyl bromide); or with four atoms of hydrogen or halogen, or two molecules halogen hydride to paraffins or paraffin substitution products, thus: CjHg + 2H2 = C2H13 (in presence of platinum black). C2H2 + 2HBr = C2H,Br2. C2H2 + 2Br2 =C2H2Br,. Like many of the olefines, various members of this series combine with water under the influence of dilute acids, thus allylene, CsHi, gives acetone, CsHjO; and acetylene, CaHj, gives orotonic aldehyde, with intermediate formation of acetic aldehyde ; and, as in the case of the olefines, ether- sulphnric acids are to be assumed here as intermediate products. HgCl^ and other mercury salts also induce such hydration : CzHa + HjO^CaHiO (aldehyde). CsHi + HaO^CsHeO (acetone). 2. The capability of undergoing polymerization is also peculiar to several of the acetylene hydrocarbons; thus, acetylene is transformed into benzene upon being led through a red-hot glass tube. This is an important synthesis of benzene : 3C!2H2 = GgHj. At the same time the compounds CgHg, CjQHg, etc., are formed. Similarly allylene, C3H4, gives mesitylene, CgHjj, upon treatment with sulphuric acid and a little water. (See Benzene Derivatives.) 3. Acetylene and some of its homologues react even at the ordinary temperature, in a manner which is peculiar to them, with an ammoniacal solution of cuprous or argentic oxide, to form reddish-brown or yellow-white precipitates, e.g. C2CU2; CgAgj; CgHjAg, which are explosive, and which are decomposable by acids, such as HCl, with regeneration of the hydrocarbon. The hydrogen of acetylene can be replaced by potassium or sodium; thus, upon heating the former with sodium, the com- 64 I. HYDROCARBONS. pounds C2HNa and CjNaj are obtained. TheSe are decom- posable by water or acids with separation of acetylene. All the hydrocarbons G,^^_3 do not, however, give such metallic compounds, but only the true homologues of acetylene, i.e. those which contain a triple bond. (See below.) Constitution. Upon grounds similar to those which have already been explained under ethylene, the constitutional formula for acetylene, CjHj, is assumed to be CH^^^CH, according to which the carbon atoms are joined together by a triple bond. For a compound CgH^, there are therefore possible the two following constitutional formulae: CH=C— CHg (AUylene), and CH2=C=CH2 (AUene). As a matter of fact two hydrocarbons C3H4 do exist, only one of which, allylene, yields metallic compounds. It is therefore to be considered the true homologue of acetylene, containing a triple bond, according to the first of the two above formulae, while to allene the second formula, with the two double bonds, is to be ascribed. The constitution of the tetra-bromo-propanes, which are formed from these by the addition of Br4, agrees with this conception. The capability of yielding metallic compounds is therefore contingent upon the presence of the group — C^CH. If the group — 0^0 — is linked on both sides to carbon atoms, it contains no hydrogen atom which is directly bound to carbon, and thus cannot form metallic compounds. In the case of the higher homologues, isomerism may be due either to the difference in position of the triple carbon bond in the molecule, or to the presence and different positions of the two double bonds. The constitution of a compound is fixed by the formation or otherwise of metallic derivatives, and by its behaviour upon oxidatioii. (See Oxidation of the Butylenes, (p. 57.) The "O.N." (p. 28) of the acetylene homologues proper, with a triple carbon -linking, ends in "ine;" that of the hydrocarbons with a double carbon-linking, in " diene.'' Modes of formation. 1. Along with the hydrocarbons already described, by the distillation of wood, lignite, coal, etc.j thus illuminating gas contains acetylene, allylene, and crotonylene. FORMATION OF THE ACETYLENES. 65 2. By treating the haloid, preferably the bromine, compounds CnHjaXa and OttH2n_iX with alcoholic potash : CaH^Brg = CjHgBr + HBr. CgHgBr =C2H2 +HBr. Further, from the unsaturated alcohols, CnHj^O, by the separation of the elements of water from them. 3. By electrolysis of the aoids of the fumario aoid series (EeJcuU). Acetylene is further formed : 4. Certain acetylene hydrocarbons, R — C^C — CHg, when heated with sodium, pass into the sodium compounds of their isomers, E — CHj — C^CH; on the other hand, when the latter are warmed with alcoholic potash, the opposite reaction takes place (Faworsky, B. 20, Ref. 781; 25, Ref. 81; 25, 2244). 5. From its elements, when an electric arc is caused to pass between two carbon poles in an atmosphere of hydrogen (Berthelot). (Cf. B. 23, 1637.) 6. By decomposing CgCa or OjKj by water. 7. By the incomplete combustion of many carbon compounds, for instance, when the gas in a Bunsen lamp burns below. 8. Prom chloroform and sodium (or red-hot copper) : 2CHCl3 + 3Na2 = CH=CH + 6NaCl. 9. From ethane, ethylene and methane at a red heat, or by the action of the induction spark. (See pp. 48 and 60.) Acetylene (Ethine), C2H2. — Was first obtained impure by E. Davy from CaC2 in 1839, and pure by Berthelot in 1849. Illuminating gas contains 0-06 per cent. Is best prepared from ethylene bromide. It becomes liquid at 1° under a pressure of 48 atmospheres, burns with a luminous and very sooty flame, and has a peculiar disagreeable smell. Dissolves in its own volume of water and in six times its volume of alcohol. Is poisonous, combining with the haemoglobin of the blood. It is decomposed into its elements with detonation by ex- plosive fulminate of silver, and also by the electric spark. It combines with hydrogen to ethane, upon being heated with the latter in presence of platinum black, or to ethylene, upon treating its copper (606) E 66 I. HYDROCARBONS. compound with zinc and ammonia. A mixture of acetylene and oxygen explodes violently when a light is applied to it. Chromic acid oxidizes acetylene to acetic acid, and permanganate of potash to oxalic acid. It combines with nitrogen under the influence of the induction spark to hydrocyanic acid (see this), and detonates upon being mixed with chlorine, but additive products, e.g. C2H2CI2 can however be prepared. As little as ^^ milligramme of it can be detected by the formation of the dark-red copper compound CaCuj. This latter explodes when struck, or when heated to a little over 100°. AUylene (" O.N." Propine), O3H4, = CHj— O^CH, can be prepared from propylene bromide, CaHsBrj, := CHs — CHBr — CHaBr. It resembles acetylene. Aliens ("O.N." Propadiene), C8H4, = OH2=C=CH2, is obtained by the electrolysis of itaconic acid. It is gaseous, and does not yield metallic compounds. Crotonylene or Butine, 0H2=CH — CH=CH2, is contained in illumin- ating gas, and can be prepared by the action of hydriodic acid upon erythrite ; it is isomeric or identical with : — Pyrrolylene ("O.N." VZ— Butadiene), CiHo, = CH2=CH— CH=CH2, which can be prepared from pyrrolidine (see this; cf. also B. 18, 2077). Piperylene ("O.N." 1-i^Pentadiene), CsH8, = CH2=CH— CH2— CH= CH2, is a hydrocarbon obtained from piperidine. (B. 16, 2059.) Isopreue, Hemi-terpene, Valerylene, CsHj, probably CH2=C(CH3) — CH =CH2 (B. Pt. 37°), is closely related to the terpenes from which it results on heating, and into which it passes by polymerization. Di-allyl 01 Hexine, OsHu,, = CHj=CH— CHj— CH2— CH=CH2, is got from allyl iodide and metallic sodium; B. Pt. 69°. Has a penetrating ethereal and radish-like odour. Gives no metallic compounds. Conylene, CeHu (probably Iso-propyl-piperylene), B. Pt. 125°, is prepared from Conine. (B. 14, 710.) The higher hydrocarbons of this series, containing 12, 14, 16 and 18 atoms of carbon in the molecule, have been prepared by Krafft from the corresponding olefines, according to method 2. Isomeric with these hydrocarbons are certain hydro - derivatives of aromatic hydrocarbons, e.g. tetra-hydro-xylene, OsHu; deca-hydro-naph- thalene, CuHig. (See Aromatic Oompounds.) D. Hydrocarbons, C„Hai_4 and G^Q^,^ Among the hydrocarbons still poorer in hydrogen may be mentioned — a. CnHan_4: Pirylene, CsHe (from piperidine. B. IS, 1024). Tht homologues of this have received the termination " cue," e.g. Hexone. h. G^^_^: Di-acetylene ("O.N." Butadiine), C^R,_,=GK= — C^OH. This is prepared by heating the ammonia salt of II. HALOID SUBSTITUTION PRODUCTS. 67 di-acetylene-di-carboxylic acid (see this), with ammoniacal copper solution, whereby it is transformed into the Cu-com- pound of di-acetylene, and then warming this with potassium cyanide. It is a gas of a peculiar odour, which yields a violet- red copper compound and a yellow silver one, the latter ex- ploding upon being rubbed, even when moist. (Baeyer, B. 18, 2269.) Di-propargyl ("O.N." \-b - Hexadiine), C6He, = CH=C— CHj — CHj — C^^CH, is obtained by the addition of bromine, 2Br2, to di-allyl, CgHj,,, 4 molecules HBr separating; B. Pt. 85°. It gives copper and silver compounds, and takes up 8 atoms of bromine, etc. It possesses an especial interest from being isomeric with benzene. Likewise isomeric with the latter is the hydrocarbon CgHg ("O.N." 2-i:-Hemdime), CHg— C^C— C=C— CHg. (B. 20, E. 564.) Tropilidene, CrHj, B. Pt. 114°, from Tropine. (A. 217, 133.) II. HALOID SUBSTITUTION PRODUCTS OF THE HYDROCARBONS. (See Table, p. 69.) A. Halogen Derivatives of the ParaflOns. General Properties. — Only a few of these compounds, e.g. CH3CI, CgHgCl, and GHgBr are gaseous at the ordinary tem- perature, most of them being liquid, and those with a very large number of carbon atoms in the molecule solid. Such also as contain a large number of halogen atoms, e.g. G\, CoClg, are solid ; among these come first the iodine compounds which, under similar conditions, also possess considerably higher boiling points than the analogous bromine compounds, and these again higher than the chlorine ones ; for instance, CaHgl, B. Pt. 72°, C^HsBr, B. Pt. 39°, and G^ILfil, B. Pt. 12°. Under comparable conditions, the boiling points of the iodides lie, for each atom of halogen, about 50°, (40°-60°), and those of the bromides about 22°, (20°-24°), above those of the chlorides. The lowest members of the series have, in the liquid form, 68 II. HALOID SUBSTITUTION PRODUCTS. at first a higher specific gravity than water, e.g. CH3I, Sp. Gr. 2-2, CjHjBr, Sp. Gr. 1-47. With increasing carbon, however, they become more like the paraflBns, the infiuence of the halogen diminishing, and consequently lighter than water. The halogen substitution products of the hydrocarbons are almost or quite insoluble in water, but easily soluble in, and therefore miscible to any extent with alcohol and ether, afld also soluble in glacial acetic acid. They often possess a sweet ethereal odour, but this becomes less marked with diminishing volatility. Most of them are combustible ; thus methyl- and ethyl chloride burn with a green-bordered flame, while ethyl iodide and chloroform can only be set fire to with difficulty. Many members of the series containing 1 or 2 atoms of carbon produce insensibility and unconsciousness when inhaled, e.g. CHCI3, CgHgClg, C^HgEr, and C2HCI5. In all these compounds the halogen is more firmly bound than in inorganic salts, so that, for instance, when silver nitrate is added to an alcoholic solution of the chlorine com- pound, e.g. chloroform, it causes no precipitation of AgCl. Nevertheless, the halogen is in most cases easily exchangeable for other elements or groups, a circumstance of the utmost importance for many organic reactions. This is especially true for the iodine and bromine compounds, which react more readily than the chlorides, and, on account of their lesser volatility, are easier to work with ; thus CgH^Br reacts with AgNOg at the boiling temperature, and CgHjI in the cold even. In all halogen compounds, the halogen can be again replaced by hydrogen by backward substitution, e.g. by Na-amalgam, by zinc dust and hydrochloric or acetic acid, or by heating with hydriodic acid. (See p. 44, B, 1.) Of fluorine compounds, only a few are known as yet ; CH3F and CgHjF are gases. Modes of formation. — 1. By Substitution. Chlorine and bromine act for the most part as direct substituents, (see p. 43.) With the gaseous hydrocarbons their action even in the cold is an extremely energetic one, (e.g. chlorine mixed with methane easily causes an explosion, so that dilution with CO2 is necessary) ; the higher members require to be heated. II. HALOID SUBSTITUTION PKODUGTS. 69 o M < o o Pi fi a o o P3 ;?; o M H \=> 05 n O Kl 00 CO 5D CO O I— I m ^ « Wi Tj^ Ir- O lO 3,3 .-a .2:3 '3 ■! ■ 0-S Q a) ^ u !h 0) •a c3 cj 3 i a ^ 2 . o - g (D rt <» ° 0° d ^ E>a t" >a 5" o"'^ PM M H a CM S + a ,s3 rt H Q) >— t ►i — ' ? S ■ -a 00 o (M Til tH IMCOIM (N I ■* rt COI>- „- 6j>> PT o fl &i d 2 ^ §3 S o g S^ o • • - • OQ I— ( CM CO ^ ffl P-( •■-' ^ I a'g'^ 6 ■? CD WWW la 10 tc 000 70 II. HALOID SUBSTITUTION PRODUCTS. The first halogen atom enters most easily into the compound, the substitution becoming more difficult as the number of those atoms present increases. In the case of the higher hydrocarbons there usually result two isomeric mono-substitution products. The action of the halogens is further facilitated by sunlight, and by the presence of iodine, this latter acting as a carrier of chlorine by the alternate forma- tion of ICI3 and 101, thus: ICl3=:ICl + Cla. Antimony pentachloride and ferric chloride act in the same way (and also for brominating and iodating, — B. 18, 2017; A. 231, 195); iron wire is especially useful in brominating (B. 24, 4249). When it is wanted to chlorinate completely, the substance in question is repeatedly saturated with chlorine in presence of iodine, and heated in a tube to a high temperature. Prom methane are formed the whole series of substitution products up • to coil. Ethane first yields ethyl chloride, OaHjCl, then ethylene chloride, C2H4012 and so on up to C2CI5. From propane is first produced normal propyl chloride, CsHjCl, and finally OsOlg. The latter decomposes, upon vigorous chlorination, first into CaCle and COI4, and the perchloro-ethane subsequently into 2 molecules CCI4. On chlorinating butane and the higher hydrocarbons strongly, an analogous splitting up of the molecule is effected. Strong chlorination or bromination readUy gives rise at the same time to hexaohloro- or hexabromo- benzene. Iodine seldom acts as a direct substituent, since by this reaction hydriodic acid would be formed, which would then substitute backwards. (See p. 45.) To induce the action therefore, the HI formed must be removed by HlOg or HgO. The iodine substitution products of the hydrocarbons are usually prepared indirectly, (according to 2 or 3). 2. From Unsaturated Hydrocarbons. These combine readily with halogen or halogen hydride. (See p. 56.) It stands to reason that no methane derivatives can be formed in this way. Ethylene gives with hydrochloric, hydrobromic, and hydri- odic acids, ethyl chloride, etc., ie. mono-substitution products of ethane; with chlorine, etc., it gives di-substitution products. The compound C2H4CI2, obtained by the action of chlorine, is called ethylene chloride, and is isomeric with the ethylidene chloride got by the further chlorination of CgHgOl. (For an explanation of this isomerism, see p. 76.) Propylene combines with hydriodic acid to isopropyl MODES OF FORMATION. 71 iodide, CgH^I, which is reconverted into propylene oy separa- tion of HI. But the same propylene results from a compound isomeric with isopropyl iodide, viz., normal propyl iodide, (and also, of course, from the above-mentioned normal propyl chloride), by the splitting off of hydriodic (or hydrochloric) acid, so that by this reaction normal propyl iodide can be transformed into isopropyl iodide. (See p. 74.) From the three butylenes there result similarly two butyl iodides, viz., secondary and tertiary, which, as well as the two other exist- ing butyl iodides, yield these butylenes again with alcoholic potash ; in this way the two last-mentioned butyl iodides are convertible into their isomers, the two first, (see p. 75). A study of the constitution of the compounds formed, shows that in these addition reactions the halogen invariably aflSxes itself to that carbon atom with which are combined the smallest number of hydrogen atoms, e.g. CHg— CH=CH2 + HI = CH3— CHI— CH3, {not CH3— CHj— CHgl) ; from CgHjX onwards therefore, there result only " secondary " and " tertiary " * compounds. 3. From Compounds containing oxygen. {a) From the alcohols CnHa^+iOH. In these the OH is readily exchangeable for chlorine, bromine, or iodine by the action of halogen hydride, f thus : C2H5OH + HBr = CaHgBr -1- H^O. In the action of these acids a state of equilibrium is reached, since the above reaction can go on in exactly the opposite direction ; it is therefore necessary either to use a large excess of halogen hydride, (e.g. to saturate with the gas or to heat in a sealed tube), or to remove the water formed, by sulphuric acid, zinc chloride, etc. * The names " primary," " secondary,'' and " tertiary '' compounds are founded upon those of the alcohols — primary, secondary and tertiary — in question, from which they can be prepared according to method 3, o. t In such exchange the halogen takes the place of the hydroxy!, so that the constitution of the haloid product corresponds with that of the alcohol used. 72 IL HALOID SUBSTITUTION PEODUCTS. Methyl- and ethyl chlorides are easily prepared by distil- ling the corresponding alcohol with common salt and sulphuric acid, or by leading hydrochloric acid gas into the warmed alcohol containing half its weight of zinc chloride in solution, (Groves). The chlorides of phosphorus are also applicable for the sub- stitution of OH by CI, since they react in the same way with alcohols as with water, thus : PCI3 + 3HOH = P(0H)3 + 3HC1. PCI3 + 3O2H5OH = P(OH)g + 3C2H5Cl. Phosphorus pentachloride is most frequently used for this purpose, going as a rule into the oxychloride ; PClg + CaHjOH = O2H5CI + HCI + POCI3. Phosphorus oxychloride itself is also sometimes employed. Of especial importance here is the application of the halogen compounds of phosphorus in the production of bromine and iodine compounds. The former need not be prepared before- hand, the end being achieved by gradually bringing phosphorus and iodine or bromine together in presence of the alcohol : 3CH3OH -I- P -I- 31 = 3GH3I + H3PO3. (5) From the polyatomic alcohols, halogen substitution pro- ducts are also obtained, e.g. tri-chlorhydrin, C3H5GI3, from glycerine, G3H5(OH)3, and PClgj isopropyl iodide, CgHyl, or allyl iodide, C3H5I, from glycerine and HI, i.e. I and P, according to the conditions of the experiment (see p. 74); hexyl iodide, GgHijI, from mannite, GgHg(OH)g and HI, the latter acting here as a reducing agent also. (c) From aldehydes and ketones, (see these), di-ohloro-substitution prodacts result by the action of PCI5, e.g. ethylidene chloride, C2H4CI2, from aldehyde, CaHjO ; acetone chloride, CsHsCli!, from acetone CsHeO. {d) Halogen substitution products are also occasionally prepared from acids by the exchange of O and OH for three CI atoms. 4. Chlorine and bromine compounds are frequently formed from the corresponding iodine or bromine ones by driving out the weaker halogen from its combination by the stronger one, e.g. isopropyl bromide from the iodide, or methylene bromide from methylene iodide; (also by treatment with mercuric chlor- ide, stannic chloride, or fuming hydrochloric acid). Conversely METHYL AND ETHYL CHLORIDES, ETC. 73 the chlorine and bromine compounds may be transformed into the iodine ones by heating with sodium iodide (in alcohoUc solution, see B. 18, 519), potassium iodide, dry calcium iodide (B. 16, 392), or with fuming hydriodic acid. Fluorine compounds are obtained in a similar way from silver fluoride and carbon tetrachloride, chloroform, methylene chloride, or alkyl iodide. 6. Carbon Tetrafluoride, CF4, also results from the direct union of carbon and fluorine. 6. For special modes of formation, see the compounds OHsOl, CHCI3, and CHIj. Mono-substitution Products. Methyl chloride,* CH3CI (Dumas and Piligot, from CH^O, 1836). Prepared from methyl alcohol, ZnCl2, and HCl (see p. 71); also by distilling the "vinasse" of the sugar manu- factories, and heating the tri-methylamine hydrochlorate obtained to 260° {Vincent). Colourless gas with an ethereal odour. B. Pt. -22°. Slightly soluble in water (4 volumes in 1 volume water), but more easily in alcohol. Is used for the production of artificial cold, for extracting perfumes from flowers, and for methylating dyes in the colour industry. Burns with a green-bordered flame. Methyl bromide, CHgBr (Bunsen, from cacodyl compounds, 1844). Prepared from methyl alcohol, P and Br. B. Pt. -I- 4-5°; Sp. Gr. 1 -73 at 0°; has a pleasant ethereal odour similar to that of methyl chloride and of chloroform and a burning taste, and burns with difficulty, with a greenish-brown flame. Methyl iodide, CH3I {Dumas and Piligot). Prepared from methyl alcohol, P and I. B. Pt. 44°; Sp. Gr. 2-27 at 25°. Is not easily set fire to. When it is heated with 16 volumes of water to 100°, methyl alcohol and hydriodic acid are pro- duced. Ethyl chloride, CjHgClt {Basilius Valentinus: "Spiritus salis et vini," or " sweetened alcohol"). Prepared by the action of CI on CjHg {Scharlemmer; cf. pp. 48 and 70.) For Groves' method (1874), see p. 72. Is formed as a bye-product in the manufacture of chloral. Easily compressible gas; B. Pt. -l- 12°. • " O.N." Chloro-methane. t " O.N." Chloro-ethane. 74 IL HALOID SUBSTITUTION PRODUCTS. Burns with a green-bordered flame. Can be easily preserved in alcoholic solution (1 : 2). Ethyl bromide, G^H^Bt (Serullas, 1827). Prepared from alcohol with P and Br, or with KBr + HjSO^. Burns with a beautiful green smokeless flame, emitting bromine vapours. Ethyl iodide, CjHjI {Gay-Lussac, 1815). Is best prepared from 90 per cent, alcohol, P and I. Colourless liquid with a peculiar ethereal smell, somewhat resembling that of leeks. B. Pt. 72°; Sp. Gr. 1-94. Almost insoluble in water, but mis- cible with alcohol and ether, and difficult of ignition. Heated with water to 100°, it is converted, analogously to methyl iodide, into C2H5O and HI. Chlorine converts it into CjHjCl, and bromine into C2H5Br. When exposed to light, iodine separates with formation of G^Hjq. It is used for inhalation in cases of asthma. Ethyl riuoride, CiHsF. A gas of ethereal odour, which liquefies at - 48°; it bums with a blue flame, and does not attack glass. Of Propyl chloride, -bromide, and -iodide, C3H7X, two iso- mers each exist, the normal propyl and the isopropyl compounds, the former boiling at a somewhat higher temperature than the latter. To the normal compounds the constitutional formula CHg — CH2 — CHgX is ascribed, and to the iso-compounds the formula CHg — CHX — CHg, since they are derivable respec- tively from normal propyl alcohol and from isopropyl alcohol or acetone, substances whose constitution is easily arrived at According to theory only these two cases are possible, since propane contains but two kinds of hydrogen atoms, viz. : (1) six combined with the end carbon atoms, and (2) two combined with the middle ones. For the transformation of the normal into the iso-compounds, see p. 70. Normal propyl chloride, see p. 70, also table, p. 69. Normal propyl bromide only passes partially into isopropyl bromide at 280°, but when heated with AljBr^ the transfor- mation is direct, an intermediate Al-compound being formed {KekuM, Schrbtter). Isopropyl iodide* is prepared from glycerine, phosphorus and iodine (see p. 72); allyl iodide is formed as intermediate product, and at the same time some propylene : CgHsCOH), -h SHI - SH^O = C3H6I3 = CsHgl + 1^. CgHjI -H HI = CgHe + 12. C3H5I -I- 2HI = CaH^I -1- 1,. * "O.N." 2-Iodo-propane. BUTYL-HALOID COMPOUNDS. 75 Normal propyl iodide is got from the alcohol The Butyl-haloid compounds, C4HgX, are already known each in four isomeric forms, which in part differ materially from one another in boiling point (up to 30°). As a matter of faT)t four isomers are theoretically possible. Thus from normal butane are derived : (a) CHs— CHj— CHj— CHJ, and (6) CHs— CH^— CHI— CHs. Normal butyl iodide ("O.N." 1-Iodo-hutane). Secondary butyl iodide (Linnemann.) ("O.N." 2 -lodo- butane). In these hydrocarbons also there are two kinds of hydrogen atoms, (a) those connected with the end, and (6) those with the middle carbon atoms. From tri-methyl-methaue, 0H^(CHa)3, are similarly derived (o) ci^CH-CHJ, and (- 2. Crystallizes in the cold. Yields glycol, 02H4(OH)2, upon prolonged heating with excess of water to 100°, or with KgCOg. Ethylene iodide, C2H^l2, is solid and easily decomposable. These compounds yield acetylene with alcoholic potash, and are transformed into glycol by exchanging their halogen atoms for hydroxyl. Now, from the relation of the latter to glycol chlorhydrin and mono-chloracetic acid, it has the con- CH2— OH stitution • : consequently in ethylene chloride, etc., CH2 — OH the two halogen atoms are combined with different atoms of carbon. The following forms more special proof of the above statement : Ethylene chloride can, by exchange of CI for OH, be transformed into glycol chlorhydrin, (which is also formed from glycol and HCl), and this can then be oxidized to mono-chloracetio acid, CjH4(0H)Cl + Oj = H2O + OHjOl-COOH (see this). Since in the latter the OH and CI are bound to different carbon atoms, the same must be the case in glycol chlorhydrin, and also, for the 01 atoms, in ethylene chloride. The Ethylidene compounds are obtained from aldehyde, (para-aldehyde), by exchange of the oxygen for halogen by means of phosphorus chloride, etc. * " O.N " 1 2'I)ichIoro-ethane. i " O.K." 1-2-Dibromo-ethaue. ETHYLIDENE CHLORIDE— CHLOROFORM. 77 Ethylidene chloride, also called ethidene chloride,* is, however, most convaniently prepared with phosgene, COClg, thus: CH3-CHO + COCI2 = CH3— CHCI2 + CO2. It is also formed by the further chlorination of CjHjCl, and is a bye-product in the manufacture of chloral. Its boiling point (57°) is lower than that of ethylene chloride (84°). It is an anaesthetic. Propylene ohloride.t etc., OaHeClis, -Brj, - 12, are likewise known. They result partly upon the addition of halogen to propylene, and have then an uusymmetrioal constitution, e.g. propylene chloride, CHs — CHCl CHaCl. Isomeric with them are the symmetrically constituted Trimethylene de- rivatives, of which tri-methylene-bromide,t CHsBr— CHj— CHjBr, results from the addition of hydrobromio acid to aEyl bromide: CHs=CH— CHjBr + HBr = CHjBr— CHa— CHjBr. Tetramethylene bromide, OHjBr— CH2— CH2— CHaBr. B. Pt. 189°. Pentamethylene bromide, CHaBr— (CHjja— CHaBr. B. Pt. 205°. (Cf . B. 22, Kef. 489.) 3. Tri-substitution Products. Chloroform, CHCI3, (Liebig and Soubeiran, 1831 ; formula established by Dumas, 1835.) Formation. 1. From methane and methyl chloride, (see p. 70). 2. By heating alcohol with chloride of lime and water. 3. Along with alkaline formate by warming chloral or chloral hydrate with aqueous alkali : CClg— CHO + NaOH = CHCI3 + HCOaNa. This last method of formation is the best for the obtaining of pure chloroform. Its formation from alcohol and bleaching powder, i.e. by the action of chlorine upon alcohol, may be considered to rest upon the intermediate production of chloral. Properties. Colourless liquid of a peculiar ethereal odour and sweetish taste. Hardly soluble in water. Solid below -70°. B. Pt. 61-2°. Sp. Gr. 1-527. Dissolves fats, resins, caoutchouc, iodine, etc. Is a most valuable anaesthetic, {Simpson, Edinburgh, 1848). The carbamine reaction (see Iso-nitriles) furnishes a delicate test for the presence of chloroform. * "O.N." l-Dichloro-ethane. t "O.N." 1-2-DicMoro-propane. { "O.N." 1-3-Di- bromo-propane. 78 II. HALOID SUBSTITUTION PRODUCTS. Beactions. Alkaline chromate produces phosgene. Potassium amalgam induces the formation of acetylene. Potash decomposes it to formate and chloride, thus: CHOI, + 4K0H = HCO2K + 3KC1 + 2H2O. Ammonia at a red heat produces hydrocyanic and hydrochloric acids : CHCls + NHs = HON + 3HC1. Bromoform, CHBrj, is sometimes present in commercial bromine. Iodoform, CHI3 (Seridlas, 1822; formula established by Dumas), is prepared by warming alcohol with iodine and alkali or alkaline carbonate : C2H5OH + 4I2 + 6K0H = CHI3 + HCO2K + 5KI + 5H2O. It can also be got in the same way from acetone, aldehyde, lactic acid and, generally, from compounds which contain the group CH3— CHOH— C, or CH3-CO— (Lieben); also by the electrolysis of an alcoholic solution of iodine. Yellow hexagonal plates. M. Pt. 119°. Contains only 0-25 per cent. H, which at first caused the presence of the latter to be overlooked. Has a peculiar odour, and is volatile with steam. Important antiseptic. Fluoroform, CHFj- Gaseous (cf. p. 73). Methyl-chloroform,* CH3 — COls. This compound, the trichloride of acetic acid, also acts as an anaesthetic. Glyceryl chloride,! tri-chlorhydrin, C3H5CI3, is obtained from glycerine and PCI5 (p. 72). B. Pt. 158°. The corresponding bromine compound is also known, but not the iodine one, C3H5I3, which decomposes in the nascent state {i.e. when glycerine, phosphorus and iodine react together), into allyl iodide, C3H5I, and I^. (See pp. 72 and 74.) 4. Higher Substitution Products. Carhon tetra-chloride, CCl* Can be prepared from chloroform or carbon bisulphide and chlorine. Colourless liquid. B. Pt. 77°. Carbon tetra-hromide, CBrt. Plates. Boils without decomposition. Carbon tetra-iodide, CI,. Dark red octahedra. Decomposes upon heating. Carbon tetra-fluoride, CFi. Colourless gas, readily oondeusible; can be synthetized from lampblack and fluorine. Per-chloro-ethane, CjCIb. Khombic plates of camphor-like odour. Melts and boils at 185°. B.— Haloid Derivatives of the Unsaturated Hydrocarbons. These compounds are obtained either by partially withdraw- * "O.N." l-Trichloro-ethane. t "O.N." 1-2-8-TricMoro-propane. III. MONATOMIC ALCOHOLS. 79 ing halogen or halogen hydride from the halogen derivatives of the saturated hydrocarbons, or by incompletely saturating the hydrocarbons poorer in hydrogen with halogen or halogen hydride, e.g. CgH^Br^ - HBr = CaHgBr. C2H2 + HBr = C^HaBr. They are also got by treating the haloid addition products of unsaturated acids with potassium carbonate: — CjHeClaOa = C3H5CI + HOI + COj. Crotonio acid dichloride; a-Chloro-propylene. The allyl compounds, C3H5X, result from allyl alcohol and halogen hydride or halogen-phosphorus. These unsaturated products are very similar to the corre- sponding saturated ones, but they are of course capable of combining further with halogen or halogen hydride, and they exist in geometrically isomeric modifications. The following among them may be mentioned: — Bromo-ethylene, vinyl bromide, C2H3Br, = CH2=CHBr. Allyl-chloride, -bromide, and -iodide,* CH2=CH— CH^X. These are of importance on account of their relation to the allyl compounds found in nature, e.g. oil of mustard and oil of garlic. The iodide is prepared from glycerine, phosphorus and iodine, and from it, by means of HgClg, the chloride. Isomeric with these are the Propylene compounds, e.g. a-Chloro-propyl- ene ("O.N." 1-chloro-l-propene), CHC1=CH — CH3. In its formation, as given above, both of the stereo-chemical isomers, which are theoretically possible, result {Wislicenus, A. 248, 281), viz.: — H— C— 01 H— C— 01 II and II H — C — CHs OH3 — — H o-Chloro-propylene; Iso-o-Chloro-propylene. Per-cMoro-ethylene, OaClj. Odourless liquid. B. Pt. 121°. Mono-chlor-acetylene, O2HCI. Gas which catches fire spontaneously. Mono-brom-acetylene, CoHBr. Also a spontaneously inflammable gas, which bums with a purple-coloured and exceedingly sooty flame. Halogen compounds containing several different halogens are also known. III. MONATOMIO ALCOHOLS. As alcohols are designated those compounds containing oxygen and of neutral reaction, which, like bases, combine with acids with the elimination of water, to form other compounds analogous to salts in constitution, the latter being termed "esters," "ethers," or "compound ethers," thus: CaHsOH-f-NOjOH = G^'a,.(O.NO^) + Il,0. Alcohols are further easily transformable by oxidation into • " O.N." 3-Halogen-l-Propene. 80 III. MONATOMIC ALCOHOLS. compounds richer in oxygen or poorer in hydrogen, (aldehydes, ketones, and acids) ; they do not undergo substitution by the action of halogens, but oxidation, etc., etc. According to theory, the alcohols are derived from the hydrocarbons by the replacement of hydrogen by hydroxyl. (See pp. 27 and 82.) Just as we know mono- and poly-acid bases, so are there mono-, di-, tri-, etc., hydric or -atomic alcohols, according to the number of molecules of a monobasic acid which can react with one molecule of the alcohol to form an ether. The poly- atomic alcohols, e.g. glycol, C2H4(OH)2, glycerine, 63115(011)3, mannite, CeHg(OH)e, etc., will be treated of later on. The monatomic alcohols are likewise either saturated or unsaturated, according to the hydrocarbons from which they are derived. The unsaturated resemble the saturated closely, excepting in that they are capable of forming addition com- pounds. A. Monatomic Saturated Alcohols, C^Hs^+iOH (See Table, p. 81.) The lowest members of this series are colourless mobile liquids, the middle ones are more oily, and the highest — from dodecyl alcohol, CjgHjgOH, onwards — are solid and like paraffin in appearance at the ordinary temperature. Gaseous alcohols are unknown. With analogous constitution the boiling point rises with tolerable regularity ; in the case of the lower members by about 19°, and higher up in the series by a smaller number. The lowest members are miscible with water, but this solubility rapidly diminishes as the series ascends ; thus butyl alcohol requires 12 parts and amyl alcohol 40 parts of water for solution, while the higher members are no longer soluble in water. The former can be separated or "salted out" from their aqueous solution by the addition of salts, e.g. KgCOg and CaCL. The specific gravity is always <: 1 The highest members, (over C15), can only be distilled undecomposed in a vacuum ; at the ordinary pressure they break up into define and water. MONATOMIC SATURATED ALCOHOLS. 81 t* lO r-t CO in !>. oi - ^ « rH ,M (N {ll9°t {143° {l67° {189° >— ( IN ■ e 1 t~ rt) 00 05 eS CO ■* o> 03 U3 VO I- 00 W W W M o o o o S S E3 S 14 |X| |Ij |lj o" d- o" d" i4 kd Dl Ixl o o q o fl W^ W" f^. d" o" d* d" W M W W 03 'o « - * s 1 - - - t 1: 1. 1 w tS 1 1 ft P H M Ph iS k 1? t^ 00 OS CO f-t O Oi 00 1— 1 p— 1 00 !>• 00 ^ i-H i-H 43 PM o CO 1 + a til -Hrt (M ■* 00 CO 1 -H ^(N ■* QO * o * * * 1 . . 1 A y O O Q ^ WO O 06 l3J>>3Vo^s5c&3 pa-H- ej CO ^■ -a^ J-g ft-s •^1-;©; CO (S06) 82 HI. MONATOMIC ALCOHOLS. The lowest members possess an alcoholic odour, those over C5, an odour of fusel, and both have a burning taste, wMle the highest members are like paraffin in appearance and without either taste or smelL Constitution and Isomers; Classification of the Alcohols. From CgHgO on, many of the alcohols are known in different isomeric modifications, thus there are two propyl, four butyl, and seven amyl alcohols, etc. Of these, some only are oxidizable to acids, CnHjnOj, contain- ing an equal number of carbon atoms, an aldehyde, CnHajO, being formed as intermediate product. Such alcohols are termed primary alcohols, (primary propyl-, butyl-, and isobutyl alcohols, etc). Another class of alcohols is not oxidizable to acids with an equal number of atoms of carbon, but to ketones, CaHj^O, with separation of two atoms of hydrogen, e.g. isopropyl alcohol yields acetone, CgHgO. These are termed secondary, (secondary butyl alcohol). Upon further oxidation the ketones do indeed yield acids which, however, contain not an equal but always a lesser number of carbon atoms, the carbon chain having thus been broken up. Lastly, the third class of alcohols, the tertiary, yield upon oxidation neither aldehydes, ketones nor acids with an equal number of carbon atoms, but only ketones or acids containing fewer atoms of carbon. Constitution of the Alcohols. — In the monatomic alcohols one of the hydrogen atoms plays a part different to that of the others ; thus it is replaceable by metals, (K and Na), and by acid radicles, and, together with the oxygen atom, com- bines with the hydrogen of a halogen hydride to form water, while the other hydrogen atoms of the alcohol remain un- changed. This hydrogen atom, which has already been formulated under the Theory of Types apart from the others, is called the " typical " or " extrarradicle " hydrogen atom. It is not joined directly to the carbon atom but CLASSIFICATION OF THE ALCOHOLS. 83 through the oxygen one, which is apparent from the fact of the alcohols being capable of preparation from the monohaloid substitution products of the saturated hydrocarbons. (See p. 85.) This has been already gone into in some detail for ethyl alcohol (p. 18). The alcohols therefore contain a hydroxyl, OH, and their general constitutional formula is (CoHan+O-OH. According to theory, this hydroxyl can either replace an atom of hydrogen in a methyl group, in which case an alcohol containing the group CHgOH, (one carbon atom being joined to the other by a single bond), results, e.g. CHj— CHgOH. Or it can replace the hydrogen of a CHj = group in a hydro- carbon, so that the resulting compound contains the atomic group =CH.OH, the carbon atom being here joined to two other ones. Or, lastly, it is possible that in a hydrocarbon with branching carbon chain, the hydrogen of a methine group CH^ (p. 30) may be replaced by hydroxyl, when the result- ing compound consequently contains the group ^C. OH, in which one carbon atom is joined to other three. XT Now, it is easy to see that the group — C^q^tt can, by further oxidation, be transformed into this other, — C^n xj The latter, which is termed carboxyl, is contained in the acids GnHsnOj, = Cn_iH2„_iC00H, which result from the oxidation of the primary alcohols. Consequently it is the primary alcohols which contain the atomic group — GHg.OH. The group ==CH.OH can likewise be changed into =0=0, (i.e. C<^QTT - HgOY which is the characteristic atomic group of the ketones, by oxidation. A further introduction of or OH, whereby acids containing the group — CO.OH wouid ensue, is not possible in this case without a rupture of the carbon chain, since carbon is tetravalent. Since then it is the secondary alcohols which upon oxidation yield ketones, and not acids with an equal number of carbon atoms, the group =CH.OH is characteristic of these. 84 III. MONATOMIC ALCOHOLS. Finally, the atomic group ^C.OH already contains the maximum of oxygen which can be combined with a carbon atom already linked to three other atoms of carbon. A com- pound, therefore, in which this atomic group is present, cannot yield upon oxidation an aldehyde, acid, or ketone with an equal number of carbon atoms in the molecule, but the result of such oxidation must be the breaking of the carbon chain, and the formation of acids or ketones containing a lesser num- ber of carbon atoms in the molecule. This being the be- haviour of tertiary -alcohols, the group ^COH is peculiar to them. The existence of the three classes of alcohols finds in this way a thoroughly satisfactory explanation from theory. The secondary and tertiary alcohols were predicted by Kolbe in 1859 from theoretical considerations (A. 113, 301; 132, 102). Among the isomeric alcohols the primary possess the highest, and the tertiary the lowest boiling points, and the same holds good for their ethelrs. The tertiary have the highest melting points. Occurrence. — Different alcohols are found in nature combined with organic acids as ethers in ethereal oils and waxes; e.g. methyl-, ethyl-, butyl-, hexyl-, and octyl-alcohols, and also those with 16, 27, and 30 carbon atoms; ethyl alcohol also occurs in the free state. /. General Methods of Formation. — 1. By "saponification" or "hydrolysis" of their ethers, by boiling these with alkalies or acids, or by the action of superheated steam, thus: CHj^.OjHA + KOH = OH3OH + C7H5O2.OK Salicylic methyl ether. Potassium salicylate. Some ethers, e.g. ethyl-sulphuric acid, decompose when simply warmed with water: C2H5.O.SO3H-1-H2O = CsHj.OH-hSOiHj. 2. From the halogen compounds CnHjn+iX, and therefore indirectly from the parafBns and defines (pages 68 and 70), in which latter case secondary or tertiary alcohols, from O3 on, are obtained; this follows from the halogen of the olefine haloid compounds being linked to that carbon atom to which the fewest hydrogen atoms are attached. a. By warming these, especially the iodides, with excess of METHODS OF FORMATION. 85 water to 100° ; sometimes by simply allowing the mixture to stand, (tertiary iodides) : C2H5I + HOH = C2H5.OH + HI. When but little water is used, a state of equilibrium is reached (p. 71). These halogen compounds may also be termed the halogen-hydride ethers of the alcohols, so that, strictly speaking, the mode of formation 2 is included in 1. b. Frequently by digesting with moist silver oxide, (which acts here like the unknown hydroxide, AgOH), or by boiling with lead oxide and water : C2H5I + Ag.OH = C^Hg-OH + Agl. c. Upon warming with silver or potassium acetate, the acetic ether of the alcohol in question is formed, and this is then saponified, thus •, C,H,I + AgO.(0,H30) = C,H,.0.C,H30 + Agl. OaHjO.CjHgO + HOK = C2H5.OH + (02H30)OK. 3. From the paraffins and olefines, by first converting these into the halogen-compounds CnHj^^iX (see 2). Since the halogen-compounds obtained from tile oleiines contain the halogen linked to that carbon atom to which the smallest number of hydrogen atoms are joined (see p. 71), the alcohols prepared from these are — from Cg onwards— secondary or tertiary. 4. By the fermentation of the carbohydrates (e.g. grape sugar), the alcohols with 2, 3, 4, 5 and, under certain conditions, even 6 atoms of carbon are produced. (Yeast fermentation.) 4a. From glycerine (also from carbohydrates) by the schizomycetes fer- mentation, alcohols with 2, 3 and 4 carbon atoms are formed (Fitz). 5. On treating the primary amines with nitrous acid,* the nitrous ethers of the alcohols are got: C2H5NH2 -I- HONO = CjHs.OH -1- N2 -I- HjO. 6. From polyatomic alcohols by the partial action of halogen hydride and the backward substitution of the resulting com- pounds, e.g. : C„H5(OH)3 + 2HC1 = C3H5(OH)Cl2 -1- 2B.p. " . ' ^ . ' Glycerine. Di-ohlorhydrin. C3H5(OH)Cl2 -I- 2H2 = OgH^OH + 2HCL Isopropyl alcohol. II. Special Methods of Formation. — 1. Primary alcohols are obtained from aldehydes by reduction with sodium amalgam •For the sake of convenience, the formula of the hypothetical nitrous acid, NOjH, = NO.OH, is used instead of NjOa + H2O. 86 III. MONATOMIC ALCOHOLS. and very dilute sulphuric acid, {Wurtz) ; or with acetic acid and zinc dust, the acetic ethers of the alcohols resulting here : C,H,0 + H, = C,H«0. Similarly from acid anhydrides and nascent hydrogen, or from a mixture of anhydride and acid chloride (see these), when the acid ether of the alcohol is formed. In certain cases (see gluconic acid) acids can be directly reduced to alco- hols by sodium amalgam [E. Fischer). Since the acids can be synthetically prepared from alcohols containing one atom of carbon less than themselves, a means is thus given for convert- ing one alcohol into another higher in series (Lieben and Itoui). 2. Secondary alcohols are formed by the action of nascent hydrogen (sodium amalgam) on the ketones, 0„H2„0 : CHg— CO— CHj-i-Hj = CHg— CH.(OH)— CH3. Acetone. Isopropyl alcohol. Pinacones are obtained here as bye-products. (See Ketones.) 3. Secondary alcohols are further produced by the action of alde- hydes upon zinc-methyl or zinc-ethyl. 3(1. Also by the action of ziuc-alkyl upon ethyl formate. 4. Tertiary alcohols are formed by the prolonged action of zinc- methyl or -ethyl (2 mols. ) upon acid chlorides in the cold, and decom- position of the resulting product with water, (BuUerow). When the action is only a short one, ketones and not alcohols are got. 5. Secondary or tertiary alcohols sometimes ensue by the direct combination of an define with water, e.g. tertiary butyl alcohol, (CHjjjC.OH, from isobutylene. The Nomenclature of the alcohols, especially of the second- ary and tertiary, is based upon a comparison of them with methyl alcohol, also called carbinol. They are looked upon as carbinol, CH3. OH, in which the three hydrogen atoms are wholly or partially replaced by alcohol radicles, thus : tertiary butyl alcohol, (0113)30. OH, =tri-methyl carbinol; secondary butyl alcohol, OH3— CHj— CH(OH)— CH3, = CH(OH)(OH3)(C2H5), = methyl-ethyl carbinoL The "official name" of the alcohols terminates in "ol." Behaviour of the alcohols. 1. The typical hydrogen atom (p. 82) is replaceable by metals, e.g. directly by K or Na, with formation of compounds termed alcoholates : 2C2H5OH -f- Nag = 2C2HBONa -1- H^. Sodium ethylate. METHYL ALCOHOL. 87 These decompose again into alcohol and alkali on addition of water. (See p. 92.) Primary and secondarj'', but not tertiary, alcohols combine with baryta and lime to alcoholates at 130°. Crystalline com- pounds are formed with calcium chloride, so that this salt cannot be used for drying the alcohols ; these compounds are decomposed by water. 2. They enter into the composition of many compounds, as " alcohol of crystallization." (See pp. 88 and 92.) 3. They yield ethers with acids : C2H5OH + (C2H30)OH = C,Hs.0 . (CaH30 ) + Hfi. Acetic acid. Ethyl acetate. Of those, the benzoic ethers are specially suitable for the separation and recognition of alcohols. 4. Dehydrating agents convert them into defines. 5. With halogen hydride or halogen phosphorus, mono-substi- tution products of the hydrocarbons are produced. (See p. 71.) 6. For the behaviour of primary, secondary, and tertiary alcohols upon oxidation, see p. 83 et seq. The oxidation of methyl alcohol yields mostly carbonic instead of formic acid, on account of the easy oxidizability of the latter. 6a. The higher primary alcohols pass into the corresponding acids upon heating with soda-lime. 7. Halogens do not substitute but oxidize. (See above.) Certain haloid ethers of polyatomic alcohols may also be regarded aa substituted monatomic alcohols, e.g. ethylene ohlorhydrin (=Monochlor- ethyl alcohol), CHjCl— CH^OH, etc. 8. The primary, secondary and tertiary alcohols can also be distinguished from one another by the behaviour of their nitro-compounds, which are formed by the action of silver nitrate on the iodides ( V. Meyer). They vary also in the rate of rapidity with which etherification begins, and the point at which it ends, e.g. with acetic acid. Methyl alcohol,* Wood Spirit, CH3OH. Was discovered in wood tar by Boyle in 1661, and its difference from ordinary alcohol recognized in 1812 by Phillips Taylor. Its composition was established in 1834 by Dwmas and Peligot. Name derived from fiidv, wine, and tSAij, wood. Occwrence. As salicylic ether in GauUheria proewmbms (oil of winter green, Canada); as butyric ether in the unripe seeds of Heracleum giganteum. •"o.n." Methanol. 88 III. MONATOMIC ALCOHOLS. Formation. 1. By chlorinating methane, CH^, and saponi- fying the resulting methyl chloride, (Berthdot). 2. From methyl iodide and water. 3. By the destructive distillation of wood. By this distillation there are obtained — (a) Gases (CH4, CjHj, C2H4, CjHj, CjHj, C4H8, CO, CO2, Hj, etc.). (6) An aqueous distillate of " pyroligneous acid," containing methyl alcohol, acetic acid, acetone, methyl acetate, allyl alcohol, etc. (c) Wood-tar, containing paraffins, naphthalene, phenol, guaiacols, etc. {d) Wood charcoal. 4. Also by the dry distillation of vinasse. It is prepared in quantity from the crude pyroligneous acid by repeated distillation after neutralization, and is purified by formation of the OaOlg compound, which is stable at 1 00°, or, better, by transformation into the oxalic or benzoic ether, both of which are easy to purify and saponify. Properties. Colourless liquid. B. Pt. 66°. Sp. Gr. about O'B. The alcohol of commerce usually contains acetone. Burns with a non-luminous flame. Dissolves fats, oils, etc. Acts as an intoxicant like ethyl alcohol and, like the latter, enters into the composition of compounds as " alcohol of crystallization," e.g. BaO + 2CH40; MgClj-j-eOH^O ; CaClj + 4CH4O (six-sided plates). Is easily oxidized to formic aldehyde and formic acid, being also converted into the latter upon heating with sodaJime. Forms with metallic potassium the crystalline compound CHgOK + CHgOH. Potassium methylate, OH3OK, is a white crystalline powder. The anhydrous alcohol dissolves a small amount of de- hydrated cupric sulphate to a blue-green . solution. Distilled over heated zinc dust, it decomposes almost quantitatively into CO + 2H2. Uses. — For tar colours — (also as CH3I and CH3CI) ; as methyl ether in the manufacture of ice ; for polishes and varnishes ; as Wiggersheim's preservative liquid ; for methylating spirits of wine, etc. Ethyl alcohol,* Spirits of Wine, CjHjOH. Liquids con- taining spirits of wine have been known from very early times, and their concentration either by distillation or by dehydration with car- bonate of potash is also an old art. We read of it as " alcohol " in the 16th century. Lavoisier arrived at the qualitative, and de. Saussure in 1808 the quantitative composition of alcohol. * "O.N." Bthanoi. FORMATION OF ALCOHOL; FERMENTATIONS. 89 Occurrence. In the vegetable kingdom alcohol is only found occasionally, as butyric ether, but in the animal kingdom it occurs in various forms, e.g. in diabetic urine. It is also pre- sent in small quantity in coal tar, bone oil, wood spirit and bread, fresh English bread containing 0'3 per cent. Formation. 1. From OjHg by conversion into C2H5CI and saponification of the latter according to modes of formation 1 and 2. 2. From CjH^ and concentrated HgSO^. (See pp. 56 and 84.) This method was discovered by Faraday, and corroborated in 1855 by Berthelot. 3. From aldehyde, CgH^O, by reduction. {Wurtz, A. 123.) 4. Preparation hy the mnous fermentation of sugar. Directly from grape and fruit sugars, CgHjgOg, and indirectly from cane sugar, OjjHgjOj^, after previous hydration to 2 molecules CgHj^jOeJ *'^° from malt sugar (directly), from starch, etc. Fermentations are peculiar slow decomposition-processes of organic sub- stances which go on, as a rule, with liberation of gas and evolution of heat, and which are induced by micro-organisms. The vinous fermentation of sugar, i.e. the fermentation which produces spirit, is caused by the varieties of the genus saccharomyces, the yeast ferment, which forms small oval micro- scopic cells, multiplying by germination. As plants, these require for their sustenance inorganic salts, but, as non-assimilating fungi, no carbonic acid. In the vinous fermentation 94 to 95 per cent, of the sugar breaks up into alcohol and carbonic acid : CeHiA = 2C2H60 + 2CO, with 2-5 to 3-6 per cent, glycerine, OjHgOj, and 0'4 to 0-7 per cent, succinic acid, C4H5O4, as invariable bye-products. In addition to these, most of the higher homologues of ethyl alcohol are also formed — the so-called fusel oil — the latter resulting from the presence of foreign micro-organisms. The chief constituent of fusel oil is fermentation amyl alcohol (iso-butyl- carbinol), CsHnOH, but it has also been proved to contain the two propyl alcohols (chiefly iso-propyl), normal-, iso-, and tertiary-butyl alcohols, normal and active amyl (methyl-ethyl) alcohols, together with higher homologues and ethers. They can be separated by means of their hydro- bromio ethers. Conditions of fermentation. Fermentation can only go on 90 III. MONATOMIC ALCOHOLS. between the limits of 3° and 35°, the most favourable temperar ture being between 25° and 30°. The solution must not be too concentrated; the presence of air is not strictly necessary, but it has a favouring influence. Yeast loses its activity upon the addition of any reagents which destroy the cells, also when it is thoroughly dried, when heated to 60°, when treated with alcohol, acids and alkalies; the addition of small quantities of salicylic acid, phenol, corrosive sublimate, etc., also prevents fermentation. The following materials are used for the preparation of alcohol or of liquids containing alcohol: , (a) Grape sugar, fruit sugar, i.e. grapes and other ripe fruits, for wine, etc. ; (J) cane or beet sugar and molasses for brandy (see Sugar); (c) the starch of cereals for beer and corn brandy, and of potatoes for potato brandy. The starch is first con- verted into malt sugar and dextrine under the influence of diastase, or into grape sugar, potato sugar, and dextrine by boiling with dilute acids, and these sugars are then fermented. A wine of medium strength contains 8 J to 10 per cent, alcohol, port wine 15 per cent., sherry up to 21 per cent., champagne 8 to 9 percent., and beer an average of 2 to 6 per cent. The different varieties of brandy or spirits obtained by "burning," i.e. by distilling fermented liquids, contain 30 to 40 per cent, alcohol, and cognac even over 50 per cent. Pwification of alcohol. It is difiicult to separate alcohol completely from water by distillation, since their boiling points are only 22° apart from one another. Even after repeated rectification the distillates are found to contain water. The same reason applies to the difficulty of separating alcohol from its higher homologues (fusel oil). From an alcohol containing 30% of water the fusel oil can be extracted by chloroform. On the large scale this separation is excellently effected by the use of dephlegmators and rectifiers or column apparatus, which are based upon the principle of partial volatilization and partial cooling of the vapours (Adam and Berard; improved by SavaUe, Pistorius, Coffey and others.) In this way an alcohol containing 98 to 99 per cent, can be obtained. Aqueous alcohol can be deprived of the greater part of its water by the addition of strongly heated carbonate of potash or anhydrous copper sulphate, or by distillation over PROPERTIES OF ALCOHOL. 91 quick lime, and the last portions can be extracted by baryta, or by several additions of metallic sodium and repeated distil- lation. Alcohol containing water becomes turbid on being mixed with benzene, carbon bisulphide, or liquid parafiBn oil, and it gives a white precipitate of Ba(0H)2 on the addition of a solution of BaO in absolute alcohol. Alcohol free from water is termed absolute alcohol. Contraction takes place on mixing alcohol and water together, 53-9 volumes alcohol + 49-8 volumes water giving, not 103-7, but 100 volumes of the mixture. The percentage of alcohol in any spirit is determined either from its specific gravity by reference to a specially calculated table, or by areometers of particular construction, or by its vapour tension as estimated by Geissler's vaporimeter. Properties. Colourless mobile liquid with characteristic spirituous but not fusel smell. B. Pt. 78-3°, or 13° under 21 m.m. mercury pressure. Solidifies at - 1,30-5°. Sp. Gr. 0"79 at 15°. Burns with an almost non-luminous flame. Is exceedingly hygroscopic, and miscible with water and with ether in all proportions. Forms several cryo-hydrates with water (+ 12Aq., + 3Aq., +^Aq.). Is an excellent solvent for many organic substances such as resins and oils, and also dis- solves sulphur, phosphorus, etc., to some extent ; consequently it is much used in the laboratory. Gives with cone. H2SO4, according to the conditions, ethyl-sulphuric acid, ether, or ethylene. For its behaviour with HCl, etc., see p. 71. It diffuses through porous membranes into a dry atmosphere more slowly than water, and coagulates albumen, being therefore used for preserving anatomical preparations. It is very easily oxidized by the oxygen of the air, first to aldehyde and then to acetic acid, either in presence of finely- divided platinum or in dilute solutions containing nitrogenous matters ; thus, beer and wine become sour, but not the pure alcohol itself. KgCrgOy or Mn02-l-H2S04 oxidize it in the first instance to aldehyde ; fuming nitric acid attacks it violently with formation of nitrogen tri- and tetr-oxides, aldehyde, ethyl nitrite, and formic, oxalic and hydrocyanic 92 III. MONATOMIC ALCOHOLS. acids, but, by the action of colourless concentrated HNO3, ethyl nitrate can, without oxidation, be obtained ; in dilute solution glycoUic acid is formed. Alkalies also induce a gradual oxidation in the air ; thus, alcoholic potash or soda solutions quickly become brown with formation of aldehyde resin, this latter resulting from the action of the alkali upon the aldehyde first produced. Alcoholic potash therefore frequently acts as a reducing agent, e.g. upon aromatic nitro- compounds. (See these.) Chlorine and bromine first oxidize alcohol to aldehyde and then act as substituents. (See Chloral.) Chlorinated alcohols can therefore only be prepared indirectly (cf. Ethylene chlorhydrin). When the vapour of alcohol is led through a red-hot tube, H, CH4, C2H4, CgHj, CjHj, Cj^Hg, CO, CjH^O, C2H4O2, etc., are formed. Of the compounds containing alcohol of crystallization may be mentioned, KOH -1- 2C2HeO, LiCl + iCaHgO, CaClj-i- 4C2H6O, and MgCl, + eCjHgO. Sodium Ethylate, CgHjONa, is of special importance among the alcoholates. It is formed by the action of sodium upon absolute alcohol. The crystals of CgHj.ONa + 202HgO, at first obtained, lose their alcohol of crystallization at 200° and change into a white powder of CgHgONa. Sodium ethylate is of especial value for syntheses, and can frequently be employed in alcoholic solution. When taken in small quantity alcohol acts as a stimulant and an aid to digestion, in larger quantity as an intoxicant. Absolute alcohol is poisonous, and quickly causes death when injected into the veins. Detection of alcohol. 1. By the iodoform reaction (see Iodo- form), when 1 part in 2,000 of water can be recognized. 2. By means of benzoyl chloride, CeH5C0Cl, which yields with alcohol the characteristically-smelling benzoic ethyl ether. Propyl alcohols, CgHjOH. 1. Normal propyl alcohol,*e%Z carlm.ol,GR^ — CHj — CHjOH, (Chancel, 1853), is obtained from fusel oil by means of its hydro- bromic ether [Fiitig), or directly by fractionation. It has also been got from propionic aldehyde and propionic anhydride by reduction with sodium amalgam (Bossi). It is a liquid with a * I-Propanol. SECONDARY PROPYL ALCOHOL, ETC. 93 pleasant spirituous odour, and boils 19° higher than ethyl alcohol. Miscible with water in every proportion, and again separated out on addition of chloride of calcium. Gives pro- pionic acid upon oxidation. Its constitution follows from that of propionic acid, and from the preparation of the latter from ethyl alcohol. 2. Secondary propyl arlcohol,* isqprqpyZ alcohol, or dimethyl carbinol, (CH3)2^CH.OH, (Berthelot, 1855), was at first held to be primary. It is obtained from isopropyl iodide (from glycerine) by methods I. 2a and 25, also by the action of sodium amalgam on acetone by method II. 2, {Friedel, 1862). It also results unexpectedly, instead of the normal alcohol, from normal propylamine by method I. 4, on account of the intermediate formation of CgHg. Colourless liquid. Boils about 15° lower than its isomer, and like it can be "salted out" from aqueous solution. Gives acetone upon oxidation. The constitution of isopropyl alcohol follows from its formation from acetone, whose constitution is CHg — GO — CHg. Butyl alcohols, C^HgOH. The four isomers which are theoretically possible are known. 1. Normal butyl alcohol, t CHg— CHj— CHg— CHjOH. Present in fusel oil, being formed especially in the wine-yeast fermentation (by elliptical yeast). Is got rather easily from glycerine by the schizomycetes fermentation, (Fitz). Prepared from butyl aldehyde, butyric acid or butyryl chloride, accord- ing to II. 1 (lAeben and Bossi, 1869). Boils 19° higher than normal propyl alcohol. Has a peculiar odour, and gives rise to coughing when inhaled. Is not miscible with water in all pro- portions, 1 volume requiring 12 volumes water for solution at the ordinary temperature. Can be " salted out " from its solu- tion. Gives normal butyric acid, C^HgOj, on oxidation. Its constitution follows from its relation to the acid (see this), and from the preparation of the acid from normal propyl alcohol. 2. Secondary tutyl alcohol, J methyl-etliyl-carhinol, or hutyUne hyd/rate, g^8>CH0H, = CH3-CHj-CH(0H)-CHs. The hydriodic ether is formed from erythrite, C4He(OH)4, and HI (de Luynes], or from * 2-PropanoI. 1 1-Butanol. } 2ButanoL 94 III. MONATOMIC ALCOHOLS. normal butylene and HI, and is then saponified according to I. 2. The alcohol is also obtained from aldehyde and zinc ethyl, according to II. 3, and from formic ether according to II. 4, (Saytzeff). Strongly smelling liquid, boiling about 18° lower than the normal alcohol. Gives methyl-ethyl ketone upon oxidation, from which its constitution follows. 3. Isobutyl aXcdhctl* or fermentation butyl alcohol, (CH3),=CH— CH.OH, is the most important of the butyl alcohols. It is contained in fusel oil, (TVurtz, 1852), especially in potato fusel oil — (beer- yeast fermentation) — , and is best isolated from this as the iodide. Colourless liquid, with a spirituous fusel smell resembling that of wild jasmine. Boils about 8° lower than the normal alcohol. Yields isobutyric acid, C4H3O2, on oxidation, hence its constitution. 4. Trimethyl oarbluol,tor tertiary butyl alcohol, (CH3)3=O.OH, (Butlerow, 1863). Is contained in small quantity in fusel oil. Prepared, e.g. according to II. 5, but more simply by the action of 75 per cent. H2SO4 on isobutylene, from isobutyl alcohol. (See II. 5.) Rhombic prisms or tables. Smell spirituous and resembling that of camphor. M. Pt. 23-5°; B. Pt. 33° below that of the normal alcohol. Yields acetone, acetic acid and carbonic acid on oxidation. Its consti- tution follows, for instance, from method of formation II. 5, and also from the constitution of tertiary butyl iodide (pp. 51 and 75). Amyl alcohols, CjHuOH. Theoretically eight isomers are possible, four primary, three secondary and one tertiary, and all of these are known. 1. Normal primary amyl alcohol (l-Pentanol). CH3-CH2— CH2— CHg— CHa. OH, is contained in small quantity in fusel oil, and can be prepared from normal valeric aldehyde, (Lieben and Bossi), and from normal pentane, by formation of CgHuCl. 2. Isobutyl carbinol,1:(CH3)2=CH— CH2— CHjOH, (Brlen- meyer), forms the chief constituent of " fermentation amyl alcohol, "which was already known to Scheele, and is also found in nature in Roman camomile oil. It was prepared synthetically from isobutyl alcohol in 1876 by the Lieben-Rossi method. M. Pt.-134°; B. Pt. 131°. Has a fusel smell and burning taste, and is poisonous; causes the disagreeable toxic after- effects of intoxication by brandy, etc. * 2-M:ethyl-3-PropanoL f 2-Methyl-2-PropanoL J 2-MethyI-4-Bntanol MONATOMIC UNSATURATED ALCOHOLS. 95 3. Secondary Butyl-carbinol, *ac&eam2/ZaZco^^, ^^ ^CH— CHgOH (Pasteur, 1855), is also contained in fermentation amyl alcohol. It turns the plane of polarization of light to the left, its chloride, bromide, iodide, and the valeric acid resulting from its oxidation being also optically active (dextro-rotatory). The action upon polarized light is connected with the presence of an " asymmetric" carbon atom. (See p. 40.) A dextro-rotatory modification of this alcohol, obtained from it by fission-fungus fermentation (p. 39) exists, its iodide being laevo-rotatory. Amylene hydrate {2-Methyl-2-Butanol), tertiary amyl alcohol, q^'J^ C(OH) — CHj — CHa, results from the indirect union of amylene with water. It acts as a hypnotic. Hexyl alcoliols, Caproyl alcoJiols, CgH.j^.OK. Of these seventeen are possible, and eleven are already known. Normal primary hexyl alcohol, obtained from normal hexane and also from caproic acid, CgHuOj, is found in nature as butyric ether, e.g. in the essential oil of Heracleum sphondylium. Isomeric with it is primary fermentation hexyl alcohol from wine fusel oil. Heptyl alcohols, (Oenanthyl alcohol), C^HijOH. Thirty-eight are possible, and, up to now, thirteen or fourteen are known. Octyl alcohols, CgHj^OH. The normal octyl alcohol is found as acetic ether, together with hexyl alcohol, in varieties of Heracleum, etc. Normal Decyl alcohol, C10H21OH, Dodeoyl alcohol, CuHjjOH, Tetra- decyl alcohol, C14H29OH, Hexadecyl alcohol, C15H33OH, and Octadecyl alcohol, C1JH37OH, were prepared by Krafft in 1881, by reducing the corresponding acids with zinc dust and acetic acid. They are solid and like para£Sn in appearance. Normal Hexa-decyl-alcohol, also called Cetyl alcohol, or Ethal, forms as palmitic ether the chief constituent of sper- maceti. The cetyl alcohol of commerce contains, besides, a homologous alcohol, CigllggO. Ceryl alcohol, cerotin, G^'B.^fiB., forms as cerotio ether Chinese wax. Mellssic or Mlilcyl alcohol, CjoHjiOH or C31H83OH, is present as pal- mitic ether in bees' wax and in Carnauba wax, and is most conveniently prepared from the latter. The alcohols are obtained from all these ethers (wax varieties) by saponification with boiling alcoholic potash. B. Monatomic Unsaturated Alcohols, C^Hj^.iOH. These are very similar to the saturated alcohols both in physical properties and in general chemical behaviour, but are sharply distinguished from the latter by their capability of taking up 2 atoms of halogen or of hydrogen, or 1 molecule of * 2-MethyH-Butanol. 96 MONATOMIC ALCOHOLS. halogen hydride, and thereby forming saturated alcohols or their mono- or di-haloid substitution products. (These latter, as already mentioned at p. 87, cannot be prepared by direct substitution of the alcohols.) They thus behave in this respect like the olefines, OnHjn, and so the existence of a double carbon bond must be assumed in their case also. They are to be con- sidered as olefines in which an atom of hydrogen is replaced by hydroxyl. I"rom CsHs-OH onwards, they yield triatomic alcohols upon careful oxi- dation (B. 21, 3347). According to theory, the existence of alcohols which contain the oxy- methylene group, CH(OH), linked to a carbon atom by a double bond, might be predicted. To this class belongs Vinyl alcohol (EthenoL), CH2= (OH — OH), which occurs in commercial ether, but which has not yet been isolated (B. 22, 2863), although derivatives of it are known. By the re- actions in which one would expect it to be formed, its isomer aldehyde, CH3.CHO, results; in fact, the atomic group =C=CH.OH is for the most part unstable, passing as it does into the more stable one =CH — CHO, which is explicable upon the assumption that water, H.OH, is taken up and again split off. Similarly, instead of the group CH2=(C0H) — CHj, we always get the other, CHa — CO — GHa. AUyl alcohol {Propenol), C3H5.OH, = 0H2=CH— OH2OH (Cahours a,nd Hofmann, 1856). Present to the extent of Ol to 0'2 per cent, in wood spirit. Is formed (1) from allyl iodide; (2) by reduction of its aldehyde, acrolein (see this) ; (3) by heat- ing glycerine, C3H5(OH)3, with oxalic or formic acid and some ammonium chloride to 260°. This last reaction appears to be a reduction process, thus, CgHgOg - HgO - = CgHgO; as inter- mediate product, however, a formic ether of glycerine (see mono- formin) is obtained. Allyl alcohol is a mobile liquid of suffocating smell, having almost the same boiling point (97°) as N- propyl alcohol; like the latter it is miscible with water. It does not take up nascent hydrogen directly, but chlorine, bromine, cyanogen, hypochlorous acid, etc. If cautiously oxidized, it yields glycerine, but stronger oxidation converts it into its aldehyde, acrolein, and acid, acrylic acid, containing the same number of carbon atoms, and it is therefore a primary alcohol; hence the above constitutional formula. Mouobromo-allyl alcohol, CH2=CBr — OH2.OH, results from tribrom- hydrin, by successive treatment with potash and carbonate of potash. Liquid; B. Pt. 155°. Several higher homologues are known. UNSATURATED ALCOHOLS. 97 0. Monatomic Unsaturated Alcohols, C„H2,_8.0H, These alcohols are derivatives of acetylene and its homo- logues. In addition therefore to the general properties of the alcohols, and those common to the unsaturated alcohols of com- bining directly with 4 atoms of H, CI, Br, or 2 molecules HCl, HBr, etc., most of them possess the further peculiarity of form- ing explosive compounds with ammoniacal copper and silver solutions, e.g. OgHgAgOH, the former being coloured, e.g. yellow, and the latter white; acids decompose these com- pounds backwards again. Those of them which do not yield such metallic compounds contain, not a triple bond, but two double ones between the carbon atoms. The most important of the alcohols is Propargyl alcohol, or propinyl alcohol (Propinot), C3H3OH, = CH=0— CHoOH, a mobile liquid of agreeable odour, lighter than water, and boil- ing at 114°, i.e. somewhat higher than normal propyl alcohol. It is prepared by treating monobrom-allyl alcohol with potash ; can take up 4 atoms of bromine. IV. DERIVATIVES OP THE ALCOHOLS. These may be classed in the following divisions : — 1. Ethers of the alcohols, e.g. OgHj.O.CgHj, ethyl ether. 2. Thio-alcohols and ethers, e.g. OgHg.SH. 3. Compound ethers and acid derivatives of the alcohols. 4. Nitrogen bases of the alcohol radicles. 5. Other metalloid compounds of the alcohol radicles. 6. Metallic compounds of the alcohol radicles, or organo- metallic compounds. A. Ethers Proper, (Alcoholic Ethers). Under ethers of the monatomic alcohols are understood compounds of neutral character derived from the alcohols by elimination of the elements of water, (1 molecule water fi-om 2 molecules alcohol). They can frequently be prepared by treating the alcohols with sulphuric acid, and are distinguished 98 IV. DERIVATIVES OF MONATOMIC ALCOHOLS. from the latter by not combining with acids to form ethers, and by being substituted and not oxidized by the halogens, etc. Only the lowest member of the series is gaseous, most of them are liquid, and the highest are solid. The more volatile ethers are characterized by a peculiar odour which vanishes as the series ascends. Unlike the alcohols, no one hydrogen atom in the ethers plays a part different to that of the others ; consequently metallic sodium has no action upon them. (See p. 18.) Constitution. The ethers may be regarded as the anhy- drides of the monatomic alcohols, analogous to the anhydrides of the mono-acid bases : K.;OH C,H,iOH_C,H j.q:jj = KP + H,0, ^^^-^^P>0 + U^. For their re-transformation into alcohols, see below. They may also be considered as the oxides of the alcohol radicles, e.g. (02115)20, ethyl ether; or, lastly, as alcohols in which the typical hydrogen atom is replaced by an alcoholic radicle : C,H5.0H 02H5.0(02H5) Gfi,.0{CIl,) Alcohol. Ether. Ethyl-methyl ether. The alcoholic radicles contained in them may either be the same, as in ordinary ether and in methyl ether, (0113)20, in which case they are termed " simple ethers" ; or they may be different, as in methyl-ethyl ether, when they are known as "mixed" or "intermediate ethers." The compound ethers of the acids are also frequently termed "ethers," e.g. "acetic ether'' = ethyl acetate; also frequently "esters." Ethers of tertiary alcohols are not known. Modes of formation. 1. By heating the alcohols, CnHan+i.OH, with sulphuric acid. The reaction goes on in two phases, e.g, for ethyl ether thus : 0. C2HBOH-^SO^H.H = CJH5.(SO^H)-t-H20. b. OjH^SO^H + O2H5.OH = C2H5.O.C2H5 + H2SO4. In phase a an ether-sulphuric acid is formed, which, when further heated with alcohol, as in b, yields ether and regener- ates sulphuric acid. The latter is therefore free to work anew, PROPERTIES OF THE ETHERS. 99 and in this way to convert a very large quantity of alcohol into ether. Thia process is theoretically a continuous one, but practically it has its limits, through secondary reactions, such as the formation of SO^, etc. The method is only suitable for primary alcohols, secondary and tertiary going too easily into olefines. Hydrochloric, hydrobromic and hydriodic, among other acids, act similarly to sulphuric acid ; thus ether is obtained upon heating alcohol with dilute hydrochloric acid in a sealed tube to 180°, ethyl chloride, CjHjGl, being formed as intermediate product, and then reacting to yield alcohol in a way analogous to that given in the following mode of formation. Upon heating alcohol with hydrochloric acid there ensues, however, a state of equilibrium between the alcohol, ether, ethyl chloride, hydrochloric acid and water, after which the same quantity of each of these products is destroyed as is formed in unit of time. 2. By the action of halogen-alkyl upon sodium-alkylate, or also upon alcoholic potash : C2H5I + CjHj.ONa = O2H5.O.C2H5 + Nal. 3. From halogen-alkyl and dry silver oxide, AgjO, (also HgO and NajO): 2C2H5I + Ag^O = CjHb. 0. C2H5 + 2AgI. Modes of formation 1 and 2 yield mixed as well as simple ethersj e.g. : C2H5.SO4H + CH3.OH = C2H5.O.CH3 + H2SO4. C5H11I + CHg-ONa = CjHii.O.CHj + Nal. Properties. 1. The ethers are very stable. Ammonia, alkalies, dilute acids, and metallic sodium have no action upon them, nor has phosphorus pentachloride in the cold. 2. When superheated with water in presence of some acid, such as sulphuric, the ethers take up water and are re-trans- formed into alcohols, the secondary more readily than the primary. This change also goes on, but extremely slowly, simply upon standing. 3. Upon warming with concentrated sulphuric acid, alcohol and ethyl-sulphuric acid are formed : CjHsO. CaHj -1- HHSOi = CjHj. OH + C2H5. (SO4H). 4. Saturated with hydriodic acid gas at 0°, the ethers split up into alcohol and alkyl iodide : C A.0.C,H5 + HI = C2H5.OH -.- C2H5I. When the ethers are " mixed," the iodine attaches itself to the radicle poorer in carbon ; further interaction yields, of course, two molecules alkyl iodide. 100 IV. DERIVATIVES OF MON ATOMIC ALCOHOLS. 5. When heated with halogen-phosphorus, the oxygen atom is replaced by two of halogen, two molecules of halogen-alkyl resulting. 6. Like the alcohols, the ethers are oxidizable, e.g. by nitric and chromic acids, but halogens substitute in them and do not oxidize ; in this latter respect they resemble the hydrocarbons. Ethyl Bihex*'' Ether," {0^1^^)^). Discovered by VaUr'ms Oordua about 1544, and possibly before that time by Raymond Lully. It was also called " sulphuric ether," and " vitriol ether, " on account of its being supposed to contain sulphur. Its composition was established by Saussun in 1807, and Gay Lussac in 1815. Preparation. By the continuous process from ethyl alcohol and sulphuric acid at 140°, with gradual addition of the alcohol, according to Boullay. It is freed from alcohol by shaking with water, and dried by distillation over lime or calcium chloride, and finally over metallic sodium. Theories of the formation of Ether. At first the action of the sulphuric acid was considered to consist in an abstraction of water. Later on, it was thought that the acid gave rise to a contact action, (Mitscherlich, Berzelius), but Liebig showed that this view was incorrect, since ethyl- sulphuric acid is formed. Liebig assumed that ethyl-sulphuric acid broke up, upon heating, into ether and SOj, but Graham, on the other hand, proved that the acid gives no ether when heated alone to 140°, but only when heated along with more alcohol. After this, Williamson propounded the theory of etheri- fication at present held, a theory based on the opinion of Laurent and Gerhardt that ether contains two ethyl radicles. Its correctness was proved by mode of formation 2, and also by the preparation of mixed ethers. Properties. Mobile liquid with powerful ethereal odour, very volatile. M. Pt. - 129°; B. Pt. -t- 34''-9; Sp. Gr. at 17°4, 0-72. Vapour tension equal to 10 atmospheres at 120°. Produces great cold on evaporation. Is easily inflammable, and there- fore dangerous as a cause of fire, from the dissemination of its very heavy vapour; a mixture of it with oxygen or air is explo- sive. It is somewhat soluble in water (1 part in 10), and, con- versely, 3 volumes of water dissolve in 100 volumes of ether ; the * £thane-oxy-ethane, ISOMERIC ETHERS. 101 presence of water can be detected by the milkiness which ensues upon the addition of carbon bisulphide. Miscible with concen- trated hydrochloric acid. Ether is an excellent solvent or ex- tractive for many organic substances, and also for I, Br, CrOg, FejOlg, AuClg, PtCl^ and other chlorides. It forms crystalline compounds with various substances, e.g. the chlorides and bromides of Sn, Al, P, Sb, and Ti, being present in them as " ether of crystallization." When dropped upon platinum black it takes fire, and wlien poured into chlorine gas an explosion results, hydrochloric acid being set free. In the dark, however, and in the cold, sub- stitution by chlorine is possible ; the final product of the substitution, perchloro- ether, Gfi\fP, is soHd and smells strongly like camphor. Uses. Ether was first employed as an anaesthetic by Simpson in 1848, but this property had been previously observed by Faraday. It is further used as an extractive in the colour industry, as SoffmanrHs drops when mixed with 1 to 3 volumes of alcohol, for ice machines, and for the preparation of col- lodion, etc. Dichloro-ether, CiHsClaO. Two isomeric forms of this are known, of which the unsymmetrioal is prepared from ether and chlorine, and the symmetrical from aldehyde and hydrochloric acid. Both are liquids. Hethyl ether, (CHajaO (Dumas, Peligot), closely resembles common ether; gaseous at the ordinary temperature, but liquid under - 20°. It is pre- pared on the large scale for the production of artificial cold. Ethyl-cetyl- and Di-cetyl ethers are solid at the ordinary temperatures. Several ethers with unsaturated alcohol radicles are also known, e.g. Allyl ether, (C3H5)20, and Vinyl-ethyl ether, C2H3— 0— CaHg, B.Pt. 35° "5. These can combine directly with bromine. Isomers. The general formula of the saturated ethers is CnHsn-i-aO- To each ether there is therefore a corresponding saturated alcohol which is isomeric with it, thus C2HgO = methyl ether or ethyl alcohol, C4HJQO = diethyl ether or butyl alcohol, and so on. From O^Hj^O on, however, several different isomeric ethers are not only possible, but are also known, e.g. di-ethyl ether, (02115)20, is isomeric with methyl-propyl ether, CHj.O.CjHy; similarly methyl-amyl ether, CHg.O.CsHjy 102 IV. DERIVATIVES OF MONATOMIC ALCOHOLS. ethyl-butyl ether, CgHj.O.G^Hg, and di-propyl-ether, C3H7.O.O3H7 are all isomeric. Isomerism of this kind depends upon the fact that the alcoholic radicles — and hydro- gen — are homologous, so that for equal sums total of carbon atoms the sums of the hydrogen atoms must also be equal. Such isomerism, which depends upon the grouping together by a polyvalent element — ^in this case, oxygen — of alcohol radicles which are individually unequal, but the sums of whose elements taken together are equal, is called metamerism. One of the alcohol radicles may here be replaced by hydrogen. The establishing of the constitution of the ethers is based upon (a) their syntheses according to modes of formation 1 or 2, and (J) their decomposition by HI according to p. 99. Alcohols and ethers containing an eqnal number of .carbon atoms are therefore metamerio. Alcohols are accordingly compounds which con- tain hydrogen and one alcohol radicle joined together by means of oxygen. Ethers, on the other hand, are compounds containing two alcohol radicles similarly joined. It stands to reason, of course, that all those varieties of isomerism which are found in the alcohols, and therefore in the alcohol radicles, can also occur in the ethers which contain these radicles. Varieties of Isomerism. The cases of isomerism which have been mentioned up to now are of three kinds. The first was the isomerism of the higher paraffins, which, since it is based upon the dissimilarity of the carbon chains, is often termed chain-isomerism. The isomerism between ethylene and ethyl- idene chlorides or between primary and secondary propyl alcohols depends upon the differences in position of the substi- tuting halogen or hydroxyl in the same carbon chain, and is termed isomerism of place or position. In addition to these there is the third kind, metamerism. Further cases will be spoken of under the Benzene derivatives. B. Thio-alcoliols and -ethers. Methyl mercaptan, CH3.SH, (Dmnas and P&igot). B. Pt. 6'. Ethyl mercaptan, O2H5.SH, {Zeise, 1833). B. Pt. 36°. Methyl sulphide, (0113)28, {RegnauU). B. Pt. 37°. Ethyl sulphide, (02H5),S. B. Pt. 92°, etc. From the alcohols and ethers sulphur compounds are derived, THIO-ALCOHOLS AND -ETHERS. 103 by the replacement of one atom of oxygen by one of sulphur. These are liquids of a most unpleasant and piercing odour, something like that of leeks; they are nearly insoluble in water and the lower members are very volatile. The higher homologues are not so soluble in water, but continue soluble in alcohol and ether, and their smell is less strong on account of the rise in the boiling point. They are readily inflammable. The Thio-alcohols, also called mercaptans*or alkyl sulph- hydrates, e.g. mercaptan,t OgHg.SH, although of neutral reaction, possess the chemical characters of weak acids and are capable of forming salts, the "mercaptides," especially mercury compounds. The name " mercaptan" is derived from "corpus mercurio aptum." They are soluble in a strong solution of potash, and they boil at temperatures distinctly lower than the corresponding alcohols do. The Thio-ethers, also termed alkyl sulphides, e.g. ethyl sulphide, (C2H5)2S, are on the other hand neutral volatile liquids without acid character. Both classes of compounds are derived from hydrogen sulphide by the replacement of either one or both atoms of hydrogen by alcohol radicles, just as alcohol and ether are derived from water : If only one of the atoms in hydrogen sulphide is substituted by an alcohol radicle, the remaining atom preserves in the new compound its original character and is easily replaceable by metals. The mercaptans are therefore monatomic compounds of faintly acid character. The above thio-compounds are not termed ethers of hydrogen sulphide because they are not saponifiable. The emstitution of these compounds follows at once from their mode's of formation. Formation. The mercaptans result : 1. By warming halogen alkyl or alkyl sulphate with potassium sulph-hydrate in concentrated alcoholic or aqueous solution : OoHjBr + KSH = CgHj.SH + KBr. • " O.N " Thiuls t Ethane-thioL 104 rv. DERIVATIVES OF MONATOMIC ALCOHOLS. 2. By heating alcohol with phosphorus sulphide, the oxygen being thus replaced by sulphur, (KekuU). The thio-ethers are similarly obtained — 1. From halogen alkyl or alkyl sulphate and neutral potassium sulphide : 2C2H5.SO,K + K,S = {G,1I,),S + 2K,S0,. 2. By treating ether with phosphorus pentasulphide. 3. From halogen alkyl and sodium meroaptide. 4. By the distillation of mercury meroaptide, HgS being formed at the same time. 5. In the case of certain complex compounds, especially in the aromatic group, sulphur may be directly substituted for hydrogen on heating ; this cannot be done, however, with the paraffin hydrocarbons. "Mixed sulphides," comparable with the "mixed ethers," can also be prepared, e.g. methyl-ethyl sulphide, CjHj.S.CHg. Behaviour. A. The Mercaptans. Sodium and potassium act upon the mercaptans to form sodium and potassium salts, white crystalline compounds, which are decomposed by water. The mercury salts are got by warming an alcoholic solution of mercaptan with mercuric oxide, e.g. mercuric meroaptide, Hg(C2H5S)2, (white plates). With mercuric chloride difficultly soluble double compounds are formed, e.g. (C2H5.S)Hg.01, a white precipitate. The lead salts are mostly yellow- coloured, and are produced upon mixing alcoholic solutions of mercaptan and lead acetate. The copper salt of mercaptan is a bright yellow precipitate. 2. Upon oxidation with nitric acid the mercaptans are transformed into alkyl-sulphonic acids, thus : C2H5.SH + 30 = C2H5.SO3H, (ethyl-sulphonic acid). 3. The mercaptans in the form of sodium salts are oxidized by iodine or by sulphuryl chloride, SOgClg, (B. 18, 3178), and also frequently in ammoniacal solution in the air to di-sulphides, e.g. ethyl di-sulphide, (02115)282, thus : 202H5S.Na4-l2 = (C2H5)2S2-^2NaI. These are disagreeably smelling liquids, which have a much higher boiling point than the mercaptans, are again reduced by nascent hydrogen, and yield with nitric acid di-sulph-oxides, e.g. ethyl di-sulph- oxide, (02115)28202. THIO-ETHERS. 105 4. By the action of concentrated sulphuric acid disulphides result, and not compounds analogous to ethyl-sulphuric acid. B. The Thio-ethers. 1. They yield double compounds with metallic salts, e.g. {G^^)^, HgClg, which can be crystallized from ether. 2. They are capable of combining with halogen or oxygen. Thus ethyl sulphide forms with bromine a dibromide, crystal- lizing in yellow octohedra : ■(C2H5),S + Br, = (C,H,),SBr,; and with dilute nitric acid, di-ethyl sulph-oxide : (C,H,),S + = (CA)2S0 a thick liquid soluble in water, which combines further with nitric acid to the compound, (C2Hg)2SO, HNO3. Concentrated nitric acid or permanganate of potash oxidizes the sulphides or sulph-oxides to sulphones, e.g. ethyl sulphide to (di)-ethyl sul- phone, (02115)2802, and methyl-ethyl sulphide to methyl-ethyl sulphone, (OH3)(02H5)S02. The sulphones are solid well- characterized compounds which boil without decomposition. The sulph-oxides are reduced by nascent hydrogen to sulphides, but not the sulphones. 3. The behaviour of the sulphides towards the halogen alkyls is of especial interest. Thus the substances (OH3)2S and CH3I combine even in the cold to the white crystalline tri-methyl- sulphine iodide, (0Hg)3SI, which is soluble in water, and which goes back into its components upon heating, This compound behaves exactly like a salt of hydriodic acid, and yields with silver oxide — (but not with alkali) — an oily base, tri-methyl-sulphine hydroxide, (0113)38.01!, which cannot be volatilized without decomposition. This is as strong a base as caustic potash and resembles the latter so closely that it absorbs carbonic acid, cauterizes the skin, drives out ammonia, and gives salts with acids with the evolution of heat, etc., etc. ; it also yields salts with hydrogen sulphide which are extremely like the alkaline sulphides, e.g. they dissolve 8b2S3, {Oefele, 1833; Cahours). Methyl Snlph-hydrate (Methane-thiol), CHs.SH {Dumas and Piligot). This is found among the gaseous products of the fermentation of albumen, 106 IV. DERIVATIVES OF MON ATOMIC ALCOHOLS. etc., when air is excluded, and therefore (e.g.) in human intestinal gases; also in urine after the consumption of asparagus. It is a liquid of repulsive odour, lighter than water; B. Pt. 6°. Methyl Sulphide {Methane-thio-methane), (CHs)aS {SegnauU). A colour- less liquid of unpleasant odour; B. Pt. 37°. Ethyl Sulph-hydrate (" O.N." Ethane-thiol), Ethyl mercapian, "Mercapian," CgHySH, = CH3— OH2.SH {Zeise, 1833). A liquid of extremely repulsive odour; B. Pt. 36°. It yields with me- tallic sodium or with sodium ethylate in alcohol : — Sodium Mercaptide, CjHj.SNa, a white crystalline mass. Mercuric Mercaptide (C2H5.S)2 Hg (see above), crystallizes from alcohol in colourless plates. Mercaptan yields with mer- curic chloride the compound CjHj — S — HgCl, as a white pre- cipitate. Ethyl Sulphide, "Diethyl Sulphide," Thio-ethyl, (62115)28. A liquid insoluble in water; B. Pt. 92°. Its bromine compound, (62115)2 SBr (see above), forms yellow octahedra. Ethyl Bisulphide (Ethane-dithio-ethame), (02116)282, is prepared by act- ing on mercaptan with iodine. It is an unpleasant smelling liquid of relatively high boiling point (151°). Ethyl Snlph-oxide {EtJiane-sulpJioxy- ethane). Diethyl sulph-oxide, (C2H5)2SO. This is a thick liquid which is misoible with water. It can unite with 1 mol. nitric acid; is easily reducible to the sulphide. Ethyl Sulphoae (Ethane-mlphone-ethane), Diethyl sulphone, (C2H5)2SOj. Crystalline; boils without decomposition, and is not reducible. Trimethyl-sulphine iodide, (CHs)3SI (see above), is also obtained by warming methyl iodide and sulphur together. It forms colourless crystals which are soluble in water. Trimethyl-sulphine hydroxide, (CHsJaS.OH [Oefele,18ZS, Cahours). This is prepared by acting upon the iodide with moist oxide of silver. For its properties see preceding page. The compounds just described are of particular interest with regard to the question of the valency of sulphur. Since in ethyl sulphide both the alcohol radicles are bound to the sulphur, this wiU also be the case in ethyl sulphone, otherwise the sulphones would manifestly be easily saponifiable. (See Ethyl -sulphur- ous acid.) Probably the sulphur in them is hexavalent, corresponding ETHERS OF THE ALCOHOLS. 107 with the formula, o^H;fl>S:^. Isomers of the sulphones, which are readily saponiflable, have recently been prepared {Otto, B. 18, 2500). The sulphinio hydroxides also can only be explained very insufficiently as addition compounds, on the assumption of the divalenoe of sulphur. The formula (CH3)2S + CH3OH for tri-methyl-sulphine hydroxide does not indicate in the least the strongly basic character of this substance, since it is not explicable why the mere addition of the neutral methyl alcohol to the equally neutral methyl sulphide should produce such an effect. More probable is one of the two formulae — (CH5)3=S-(OH) ; or, (CH3)3=S'-(0H) ; II even if they do not overcome all the difficulties involved. With respect to isomers, the same general conditions prevail in the sulphur as in the corresponding oxygen compounds. Sulphides of Unsaturated Alcohol Radicles. Vinyl Sulphide,* (033:3)28. Present in Allium ursinum. B. Pt. 101°. AUyl sulphide,t (CgH5)2S {Wertheim, 1844), present in the oil of Allium sativum— oil of garlic, — in Thlapsi arvense, etc. Prepared from allyl iodide and KgS {Hofmann, Gahowrs). B. Pt. 140°. Analogous selenium and tellurium compounds of alcohol radicles are also known. They are in part distinguished by their excessively disagree- able, nauseous and persistent odour. 0. Ethers (Esters) of the Alcohols with Inorganic Acids and their Isomers. The compound ethers may be considered as derived from the acids, (see pp. 79 and 87), by the exchange of the replace- able hydrogen of the latter for alcoholic radicles, just as salts result by exchanging the hydrogen for a metal — HNO3. KNO3. (C2H5)N03. Or, they are derived from the alcohols by exchange of the alcoholic hydrogen atom for an acid radicle, i.e. for the acid residue which is combined with OH — C2H5.O.H. G^U,.0.{^0^). C2H5.0.(S03H). The different ways of writing the formulae of ethers, such as (C2H5)N03, C2H5.O.NO2, etc. are all equally justifiable. * Ethene-thio-ethene. t Propene-thio-propene. 108 IV. DERIVATIVES OF THE MON ATOMIC ALCOHOLS. Monobasic acids yield only one kind of ether, " neutral ethers," which are analogous to the neutral salts of those acids. Dibasic acids yield two series of ethers, (1) acid ethers and (2) neutral ethers, corresponding respectively with acid and neutral salts ; thus, CjHj.H.SO^ and (02115)2 . SO4 are the acid and neutral ethyl ethers of sulphuric acid. Tribasic acids yield three series of ethers, etc. The composition of the compound ethers is therefore exactly analog- ous to that of salts, so that in the definition of polybasio acids their behaviour in the formation of ethers may also be included. The neutral ethers are mostly liquids of neutral reaction, and often of very agreeable odour, with relatively low boiling points, and volatile, eventually in a vacuum, without decom- position. Most of them are either almost or quite insoluble in water. The acid ethers, also called ether-acids, on the other hand, are of acid reaction, without smell, usually very easily soluble in water, much less stable than the neutral ethers, and not volatile without decomposition. They act as acids, i.e. form salts and ethers. All compound ethers are characterized by the property of combining with water and going back again into their com- ponents, i.e. of undergoing " saponification,'' when boiled with alkalies or acids, or when heated with steam to over 100°, e.g. 150-180°. This sometimes takes place simply upon mixing with water at the ordinary temperature. General modes of formation. 1. The ethers frequently result directly from their components, with elimination of water. Such a reaction, however, is only possible when the water produced by it is rendered harmless, e.g. by being taken up by the acid employed, for instance, concentrated H2SO4, HCl, or HNOg ; otherwise the ether obtained would be retransformed into its alcohol. A direct formation of ether does not proceed quantitatively on account of the disturbing effect of the water produced in the reaction. When equivalent proportions of alcohol and acid are used, a definite point of equilibrium is arrived at which cannot be passed even upon prolonged heating ; an excess of acid or alcohol increases the yield. The acid is therefore frequently allowed to act in the nascent state, by distilling a mixture of one of its salts with concentrated H2SO4 and the NITRIC ETHERS, ETC. 109 alcohol in question ; or a mixture of the alcohol and acid is allowed to drop into concentrated sulphuric acid heated to 130°, when the ether distils over ; or the same mixture is saturated with gaseous hydrochloric acid. This last method is very often followed, the reaction going partly according to mode of formation 3. (Cf. also p. 99, 1.) 2. The alcohol is heated with the acid chloride, thus : SOgClj + 2C2H5.OH = SO(O02H5)2 + 2HC1. 3. The silver salt of the acid is heated with alkyl iodide, this being a method generally applicable, although it often leads to isomers of the expected ether : 2C2H,I + SO.Ag, = SO,(C,H,), + 2AgI. Besides the real acid ethers, there are also treated under this division several other classes of acid derivatives isomeric with them, but dis- tinguished from them by not being saponifiable, i.e. by being more stable, e.g. nitrocompounds, sulphonic and phosphinio acids, etc. The hydrocyanic derivatives of the alcohols will also be described here for the sake of convenience. These latter likewise do not show the normal ether-saponiflability into alcohol and acid, but are broken up by saponifying agents in another direction. 1. Ethers of Nitric Acid. Methyl Nitrate, CH3.(N03), = CH3.0.(N02); colourless liquid, B. Pt. 66°. Ethyl Nitrate, or Nitric Ether, CjHj.O.NOg, (Millon). B. Pt. 86°. Mobile liquid of agreeable odour and sweet taste, but with a bitter after-taste; burns with a white flame. Both these ethers are soluble in water. The latter is prepared directly from its components, with the addition of some urea. Like all nitric ethers, the above compounds contain a large proportion of oxygen in a form in which it is readily given up, and they therefore explode upon being suddenly heated strongly. They saponify easily upon boiling with alkalies. Tin and hydrochloric acid reduce them to hydroxylamine : OaHjCNOg) + 3Sn + 6HC1 = CgHjOH + NH3O + SSnCl^ + Ufi. Here also the nitrogen separates from the alcohol radicle, a reaction similar to saponification. 2. Derivatives of Nitrous Acid. These include Nitrites and Nitro-compounds, 110 IV. DERIVATIVES OF THE MONATOMIC ALCOHOLS. a. Ethers of Nitrous Acid, HNOj. These are obtained by tbe action of nitrogen trioxide or of potassium nitrite and sulphuric acid, or of copper and nitric acid upon the alcohols. They are liquids of aromatic odour, neutral reaction and very low boiling point, and are easily saponifiable. Nascent hydrogen also reconverts them into alcohol, ammonia being formed at the same time. For constitution, see nitro-compounds. Ethyl Nitrite, C2H5.0.(NO), {Kunkel, 1681). Formerly called "sweet spirits of wine" or "saltpetre ether." Mobile liquid of a piercing ethereal odour, somewhat resembling that of Borsdorf apples, and of a peculiar stinging taste. B. Pt. + 18°. Burns with a bright white flame. Its alcoholic solution is the officinal " Spiritus aetheris nitrosi," and is used as a taste corrective. Ethyl nitrite, as well as amyl nitrite, finds application, e.g. in the preparation of diazo-compounds and nitrosates (which see). 'Eov preparation, cf. Wallach, A. 253, 251. Methyl Nitrite, CHgO.NO. Gaseous. Amyl Nitrite, O5H11O.NO. B. Pt. 96°. Pale yellow liquid. Is used in medicine; it produces expansion of the blood vessels and relaxation of the contractile muscles. Isomeric with these ethers are ji. The Nitro-derivatives of the Hydrocarlons. These are colourless liquids of ethereal odour, almost or quite insoluble in water, and boiling at temperatures up to 100° higher than their isomers. Like the latter they distil with- out decomposition, and occasionally explode upon being quickly heated. They are fundamentally distinguished from the nitrous ethers by not being saponifiable, and by yielding amido-compounds (see these) on reduction, the nitrogen being thus not separated : CH3.NO2 + SHj = CH3.NH2 + 2H2O. Nitro-methane, CHyNO^, {Kolle, V. Meyer, 1873). B. Pt. 99°-101° ; Sp. Gr. > 1. Nitro-ethane, C2H5.NO2, {V. Meyer and Sliiber, 1872). B. Pt. 113°-114°; the vapour does not explode even at a much higher temperature. Bums with a bright flame. NITRO-COMPOUNDS. Ill General modes of fommtion. 1. By treating alkyl iodide with silver nitrite, {V. Meyer), nitro-methane alone results, nitro-ethane in about an equal proportion with its isomer, and the higher homologues in regularly decreasing amounts as compared with those of their isomers, from which however they are easily separated by distillation : CH3I + AgNOa = CH3.NO2 + Agl. 2. Nitro-methaaie is further formed from mono-chloraoetate and nitrite of potassium, by exchange of CI for NOj and separation of CO,, (Kolbe). Mtro-compounds do not, on the other hand, result from the action of nitric acid upon the fatty hydrocarbons, or at least extremely seldom. (B. 25, E. 108.) (Difference from the aromatic hydrocarbons.) The constitution of the nitro-compounds is arrived at from their not being saponifiable, and from the fact that the nitrogen is not split off on their reduction but remains directly bound to the carbon in the resulting amines, (see these). Conse- quently the nitrogen in them must be directly joined to the alcohol radicle, i.e. to the carbon, and so their constitutional formula is R.NOg ; for instance : K?„ " ---° CH3— N< 1 , or CH3— NC O according as N is taken as tri- or pentavalent. Nitrogen which is bound directly to an alcohol radicle is therefore not separated by saponifying agents. Since the nitrogen of the isomeric nitrous ethers, on the other hand, is easily split off from the alcohol radicle either by saponification or by redaction, it is manifestly not directly combined with the carbon but only through the oxygen. The nitrous ethers therefore receive the constitutional formula E.O.(NO), e.g. CH3— 0— ]sr=o, taking nitrogen as trivalent. From this follows for the hypothetical hydrated nitrous acid the formula H.O.N:0, and for anhydride the formula (N0)20. Simultane- ously we attain from this to the constitution of nitric acid. The aromatic hydrocarbons, e.g. benzene, CgHg, yield with the latter nitro- compounds, which will be treated of later on, thus : C8H5.H + HNO3 = CeH5.NO, -I- HjO. 112 rV. DERIVATIVES OF THE MONATOMIC ALCOHOLS. Nitric acid therefore contains a nitro-group bound to hydroxyl, cor- responding with the formula : H.O.NO2 = H— 0— N:^^, or H— 0— N<^>. Behaviour. 1. They yield amines with reducing agents, such as iron and acetic acid, tin and hydrochloric acid, etc., substi- tuted hydroxylamines being formed as intermediate products (difference from the nitro-compounds of the benzene series); B. 25, 1714. 2. When the alcohol which corresponds to the nitro-com- pound is a primary or secondary one, so that the carbon atom which is joined to the nitro-group is at the same time joined to hydrogen,, as in the groups — CHg.NOg and =CH.N02, this hydrogen is replaceable by metals, and consequently such nitro-compounds possess the characteristics of acids. For instance, by the action of alcoholic soda upon nitro-ethane and nitro-methane, the compounds CHg.CHNa.NOj and CHaNa.NOa are formed, both crystallizing in fine needles and being explosive. The nitro-compounds of tertiary alcohols behave otherwise. Since they contain no hydrogen joined to the carbon atom which is bound to the nitro-group, they have not an acid character ; the acidifying influence of the nitro-group does not therefore extend to those hydrogen atoms which are joined to other carbon atoms. The hydrogen in the primary and secondary mono-derivatives, which is attached to the same carbon atom as the NOj-group, can also be replaced by bromine. So long as hydrogen, as well as this bromine and the nitro-group, remains joined to the carbon atom in question, the compound is of a strongly acid character, but when it also is substituted by bromine, the compound becomes neutral ; e.g. dibromo-nitro-ethane, CH3.CBr2.NO2, is neutral. 3. The primary nitro-compounds yield with concentrated hydrochloric acid at 140°, acids of the acetic series containing an equal number of carbon atoms, and hydroxylamine. 4. The behaviour of the nitro-alkyls to nitrous acid is very varied. The primary yield nitrolic acids and the secondary pseudo-nitrols, while the tertiary do not react with it at all. Thus from nitro-ethane, CH3— C<^5 , "ethyl-nitrolic acid," CHj-C^^^^, an acid crystal- lizing in light yellow crystals and whose alkaline salts are intensely red, is formed. Normal nitro-propane acts similarly. Secondary nitro- ETHERS OF SULPHURIC ACID. 113 propane, (CH9)i$=CH(N0i!), gives on the contrary " propyl-pseudo-nitrol," {CHs)r=C(NO) (NOa) (?), a white crystalline, indifferent, non-acid substance, which is blue either when fused or when in solution. These reactions, which, moreoTer, only go on in the case of the lower molecular alcohols (in the primary up to Ce, and in the secondary up to C5), are specially applicable for distinguishing between the primary, secondary, or tertiary nature of an alcohol (see p. 87). The nitro-hydroearbons, which are easily prepared from the iodides, are dissolved in a solution of potash to which sodium nitrite is added, the solution acidified with sulphuric acid and again made alkaline, and then observed for the production of a red colouration (primary alcohol), a blue colouration (secondary alcohol), or no colouration at all (tertiary alcohol). Appendix. Chloropicrin, CCI3NO2, a heavy liquid of excessively suffo- cating smell, B. Pt. 112°, is formed from many hydrocarbon compounds by the simultaneous action of nitric acid and chlorine, chloride of lime, etc. It is best obtained from picric acid and bleaching powder. Di-nitro derivatives of the saturated hydrocarbons, e.g. Sl-nltro-ethane, CjH4(N02)2, whose potassium salt is an explosive yellow crystalline com- pound obtained from CHs.CHBr(N02)-fKN02, also exist; further, some tri-nitro-derivatives, e.g. Nitroform, CH(N03)a (yellow crystals), and even tetra-nitro-methane, C(N02)4 (white crystals), which last boils without decomposition. 3. Derivatives of Hypo-nitrous Acid. Hypo-nitrous acid, HNO or HaNjOj, can be transformed into an ether of the formula (CaHsJaNaOa Siazo-ethoxane (Zorn), an oil which explodes even at 40°. 4. Ethers of the Chlorine Acids are known, e.g. ethyl hypochlorite, C2H5.O.CI, and ethyl perchlorate, CjHs.O.ClOs, both violently explosive liquids. The first of these is prepared by leading chlorine into a mixture of alcohol and aqueous caustic soda ; it boils at 36°. 5. Ethers of Sulphuric Acid. The neutral ethers are formed — (a) From fuming sulphuric acid and alcohol ; (6) From silver sulphate and alkyl iodide ; (c) From sulphuryl chloride and alcohol : SO^Cl, -1- 2C2H5OH = S0,(002Hj), + 2HC1. (BOB) H 114 IV. DERIVATIVES OF THE MONATOMIC ALCOHOLS. The acid ethers or " ether sulphuric acids " of the primary alcohols result directly from their components. Secondary and tertiary alcohols do not yield them. (a) Ethyl sulphate, (022^5)280^, is a colourless oily liquid of an agreeable peppermint odour, insoluble in water, and solidi- fying on exposure to a strong cold ; B. Pt. 208°. It is quickly saponified (to ordinary ether) upon warming with alcohol, also upon boiling with water, but only slowly with cold water; in the latter cases alcohol and sulphuric acid are produced. (J) Ethyl-sulphuric acid, C2H5.SO4H, = CgHj.O.SOgH, (Dabit, 1802), is obtained from a mixture of alcohol and sulphuric acid, as given under Ethyl ether, method 1, but not quantitatively, on account of the state of equilibrium that ensues, (see p. 108). It is also formed from ethylene and sulphuric acid at a somewhat higher temperature. It difi'ers from sulphuric acid by its Ba-, Ca-, and Pb-salts being soluble, and it can therefore be easily separated from the former by means of BaCOg, etc. It yields salts which crystallize beauti- fully, but which slowly decompose into sulphate and alcohol on boiling their concentrated aqueous solution, especially in presence of excess of alkali. They are often used instead of ethyl iodide in the preparation of other ethyl compounds by double decomposition. The free acid is prepared by adding the exact quantity of sulphuric acid required to the barium salt. It is a colourless oily liquid which does not adhere to glass, and which slowly decomposes into alcohol and sulphuric acid, ie. is saponified, on evaporating or preserving its solution, and quickly upon boiling it. The methyl-, amyl-, etc. compounds are analogous; the former is also a syrup which does not adhere to glass. 6. Derivatives of Sulphurous Acid. ut. Ethers of Sulphurous A(M. (a) Ethyl sulphite, SOs(C2Hb)2, is an ethereal liquid of peppermint odour, which can be prepared from alcohol and SO Clj, and which is rapidly saponified by water. SULPHONIC ACIDS. 115 (5) Ethyl sulphurous aoid, SOs-HiCjIIs). The very unstable potassium salt of this acid is obtained by the partial saponiiication of ethyl sulphite by potash solution — S08(C2H6)j + KOH = SOsKiCjHj) + CsHjOH. The free acid is incapable of existence, decomposing immediately into its components. Analogous ethers of other alcohols are known. /3. Sulpho- or Sulphonic Adds and their Ethers. (a) Ethyl -Sulphonic Acid, CjH^.SOgH (Loivig, 1839; H. Kopp, 1840), is a strong monobasic acid, very easily soluble in water and hygroscopic, and sharply distinguished from ethyl- sulphurous acid by its stability, not being saponified upon boiling its aqueous solution either with alkalies or acids. Boil- ing concentrated nitric acid and free chlorine do not act upon it, and it requires fused potash to effect its decomposition. It has a strongly acid and disagreeable after-taste. It yields crystallizable salts, e.g. C2Hg . SO3K -h H2O (hygroscopic), CaHj.SOaNa-^HjO, {C^'R,.S0s)^B3. + 211^0, etc. Modes of formation. 1. From sodium or ammonium sulphite and alkyl iodide (or alkyl hydrogen sulphate; B. 23, 908; 24, Eef. 431): C2H5.I -f- NaaSOg = CjHs.SOgNa -1- NaT. 2. By the oxidation of mercaptans by KMnO^ or HNO3: C2H5.SH -H 30 = C2H5.SO3H. 3. Sulphonic ethers are formed by the action of alkyl iodide on silver sulphite : 2G,nji + AgaSOa = (CaHsjaSOs + 2AgI. The sulphonic acids yield chlorides with PCI5, e.g. ethyl- sulphonic acid gives ethyl- sulphonic chloride, C2H5SO2CI, a liquid which boils without decomposition at 177°, fumes in the air, and is reconverted by water into ethyl-sulphonic and hydrochloric acids. Nascent hydrogen reduces it to mercaptan. With zinc dust it yields the zinc salt of a peculiar, syrupy, easily soluble acid, viz.— Ethyl -sulphinic acid, CjHs.SOaH, which is likewise converted into mercaptan upon further reduction. Its sodium salt yields ethyl sulphone when treated with ethyl bromide, CjHsBr. It also forms an unstable ether, isomeric with this latter compound (see p. 106;B. 24, 2272). Methyl -sulphonic acid, CH3.SO3H, was prepared by Kolbe in 1845 from trichloro-methyl-sulphonic chloride, CClg.SOgCl (produced from CSj, CI, and HjO). It is a syrupy liquid. 116 IV. DERIVATIVES OF THE MON ATOMIC ALCOHOLS. Ethyl-sulphonic ethyl ether, C2H5.SO3.C2H5, is isomeric with ethyl sulphite, and, being an ether of the more stable ethyl-sulphonic acid, is only partially saponifiable. It is pre- pared from silver sulphite and ethyl iodide. B. Pt. 213°. The sulphonic ethers have considerably higher boiling points than the isomeric sulphurous ethers. , Constitution. From the formation of the sulphonic acids from mercaptans by oxidation, and the (indirect) reversibility of this reaction, it follows that the sulphur in them is directly bound to the alcohol radicle ; if, then, sulphur is regarded as hexavalent, ethyl-sulphonic acid has the constitution 0A.SO3H, = g^o'Xo- From this we arrive at the constitution of sodium sulphite as being Na — (SOsNa), of the hypothetical sulphurous acid as H — (SO3H), and of sulphuric acid as H — — (SO3H). The real easily saponifiable sulphurous ethers therefore manifestly contain the sulphur not bound directly to the carbon but through oxygen, so that for them the following formulae hold : ethyl-sulphurous acid, CgHj.O.SOjH, and ethyl- sulphurous acid ether, CgHgO.SO.O.CjHg, or SOCOC^H,),. Belated to methyl-sulphonic acid are : IQethane-dl-sulphonlc acid, CH2(S03H)2, a, crystalline body, Methane-tri-sulplionlc acid, CH(S03H)3, also crystalline. Ethylene- and Ethidene-di-sulphonlc acids, 02114(80311)2, Propane-trl-sulphonlc acid, C3H5(S03H)3, etc. ; these may also be regarded as sulphurous acid derivatives of polyatomic alcohols. 7. Ethers of Tri- and Polybasic Acids. Ethers of phosphoric acid: P0(0R)3, P0(0E)2(0H), and P0(0R)(0H)2, (R = alkyl), exist, as do also similar compounds of phosphorous and hypophosphorous acids. The phosphinic acids, etc., are related to the two last-mentioned classes. (See phosphines.) Ethers of boracic and silicic acids are also known. NITRILES AND ISO-NITRILES. 117 8. Alcoholic Derivatives of Hydrocyanic Acid. (Nitriles and Iso-nitriles.) Hydrocyanic acid, HON, yields two classes of derivatives by the exchange of its hydrogen atom for alcohol radicles, neither of which can be grouped among the ethers, since they do not go back into alcohol and hydrocyanic acid on saponification, but decompose in another direction. a. Cyanides of the Alcohol Radicles (Nitriles). These are either colourless liquids, volatile without decom- position, or solids, of a not unpleasant ethereal odour slightly resembling that of leeks, lighter than water, and relatively stable. The lower members are miscible with water, but the higher ones insoluble in it. They boil at about the same temperatures as the corresponding alcohols. Formation. 1. By heating alkyl iodide with potassium cyanide, or potassium ethyl-sulphate with potassium ferro- cyanide : CH3I + KCN = KI -^ CH3.CN Methyl cyanide. 2. By distillation of the ammonium salts of monobasic acids which contain one atom of carbon more than the alcohol which would be used in method 1, and treatment of the amides which are at first produced with separation of water, with a dehydrating agent such as P2O5, (Hofmann), PCI5 or PjSj, (see imide chlorides and thiamides) ; also by treating the ammonium salts of the acids directly with P20g : a. CH,.COOH + NH„ = H,0 + CH,.CO.NH, Aoetamide. 6. CH3.CO.NH2 - H^O = CH3.CN. As a consequence of this mode of formation these com- pounds are also termed nitriles of the monobasic acids, e.g. CH3.CN, methyl cyanide or Aceto-Nitrile ; CjHj.CN, propio- nitrUe, etc. 3. The higher nitriles, in which C>5, result from the amides of acids of the acetic series containing one atom of 118 IV. DERIVATIVES OF THE MON ATOMIC ALCOHOLS. carbon more in the molecule, and also from the primary amines with the same number of carbon atoms, upon treatment with bromine and caustic soda solution (Hofmcmn). See Amides. 4. From the oximes of the aldehydes, by warming with acetic anhydride. Behaviour. 1. These compounds are very active chemically. When heated with acids or alkalies or superheated with water, they break up into the acids from which they were originally prepared and ammonia; amides may be formed here as inter- mediate products : CH3.CN + 2H2O = CHg.OOOH + NHg. This is a reaction of great moment, because it leads from the alcohols GJl^^^j.OH to the acids of the acetic series, CnHjn^i.COOH, richer than those alcohols by one atom of carbon. (Dumas, Malaguti, Le Blanc, and also Frankland and Kolhe, 1847.) 2. Just as aoetamide is formed by the taking up of water, so is thio- aoetamide by the taking up of sulphuretted hydrogen. 3. By the addition of hydrochloric acid, amido-ohlorides or imido- chlorides result; by the addition of ammonia bases, amidines. Halogens also form easily decomposable addition-products (see acid derivatives). 4. Combination with hydrogen leads to amines (p. 123): CH3.CN + 2H2 = CH3.CH2.NH2. Ethylamine. 5. Metallic potassium or sodium frequently induces polymerization; thus methyl cyanide yields in this vpay cyanmethine, a mono-acid base crystal- lizing in prisms. The "official name " of the nitriles is formed by adding the word " -nitrile '' to the name of the hydrocarbon containing an equal number of carbon atoms in the molecule. For Constitution, see Iso-nitriles. Aceto-nitrile (Ethane-nitrile), CH3.CN, is present in the pro- ducts of distillation from the vinasse of sugar beet and in coa] tar. B. Pt. 82°; combustible, and miscible with water. Propio-nitrile {PropoMi-nitrile), C2H5.CN, Butyro-nitrile, CsHj.CN, and Valero-nltrile, O4H9.CN, are liquids of agreeable bitter almond oil odour; Palmito-nitrile, CisHa.CN, is like paraffin. Cyanogen compounds of unsaturated alcohol radicles also exist, e.g. Allyl Cyanide, CsHj.CN (see Crotonic Acid). Fulminic Acid. Fulminate of Mercury, C„HgN202, is prepared by warming alcohol with nitric acid and mercuric nitrate (direct heating of the containing vessel by a flame is of course inadmissible). It ISO-NITRILES. 119 forms silky lustrous prisma, which explode with the utmost violence upon being heated or struck; hence it is extensively used for percussion caps, dynamite cartridges, etc. Concentrated hydrochloric acid decomposes it into formic acid and hydroxylamine. The analogous Fulminate of Silver is stiU more explosive. Free rulminio Acid is unstable in the highest degree. The constitution of fulmiuic acid is still a matter of doubt. Against KekuWs formula of a nitro-aoetonitrile, CH2(N02).C]Sr, we have, above all other arguments, the fact of its decomposition by hydrochloric acid (see above). The compound may perhaps be regarded as a polymeric oxime of carbonic oxide (B. 24, 573); of. also, however. Divers, Oh. Soo. J., 45, 15. p. Iso-cyanides (Iso-nitriles or Carbamines). Colourless liquids easily soluble in alcohol and ether, but only slightly soluble or insoluble in water, of weak alkaline reaction, unbearable odour, and poisonous properties, and boiling somewhat lower than the nitriles. Formation. I. By heating the iodides of the alcohol radicles with silver cyanide instead of potassium cyanide, (Gauiier), a double compound with cyanide of silver being first formed : CNAg + C AI = Agl + C£^ Ethyl iso-cyanide. 2. In small quantity, along with the nitriles, when potassium alkyl- sulphate is distilled with potassium cyanide. 3. By the action of chloroform and alcoholic potash upon primary amines, (Eofmann, 1869) : CH3.NH2 + CHCI3 + 3K0H = CH3.NO + 3KC1 + 3H2O. Behaviour. 1. The iso-nitriles differ fundamentally from the nitriles by their behaviour with water or dilute acids. When strongly heated with water, or with acids in the cold, they split up into formic acid and amine bases containing one atom of carbon less than themselves, from which latter compounds they can be prepared : CH3.NC + 2H2O = CH3.NHJ, + HCOjH. Unlike the nitriles, they are very stable towards alkalies. 2. The iso-nitriles are also capable of forming addition products with the halogens, HCl, HjS, etc., compounds different from those given by the nitriles; thus, with HCl they yield crystalline salts which are violently de- composed by water into amine and formic acid. 3. Some of the iso-nitriles change into the isomeric nitriles on being heated. 120 IV. DERIVATIVES OF THE MONATOMIC ALCOHOLS. Methyl Iso-cyanlde, CH3.NC. B. Pt. 58°. Ethyl Iso-cyanide, C2H5.NC. B, Pt. 82°. Constitution of the Nitriles and Iso-nitriles. The constitu- tion of the nitriles follows from their close relation to the acids. The carbon atom of the cyanogen group — ON remains attached to the alcohol radicle after the action of saponifying agents, and is therefore directly bound to the carbon atom of the latter. The nitrogen on the other hand is split off, and is thus not directly bound to the alcohol radicle. Consequently aceto-nitrile has the constitution : CH3 — C^N, In the case of the iso-nitriles, however, it is the nitrogen which must be directly bound to the alcohol radicle, as their close connection with the amine bases shows, the amines being easily prepared from and reconverted into the iso-nitriles. The carbon atom of the cyanogen group, on the contrary, is split off on decomposition by acid, and is consequently not bound directly to the alcohol radicle but only through the, nitrogen. The constitutional formula of the iso-nitriles there- fore is E — NCj either R — N=C, e.g. methyl carbamine, CH3 — N=0, etc., or E — N^C^, with an unsaturated carbon atom (cf. Nef,A. 270, 267). The difference between nitriles and iso-nitriles is sufficiently emphasized as a rule by writing them CHs-CN and CHj-NO. D. Nitrogen Bases of the Alcohol Radicles. By the introduction of alcohol radicles in place of hydrogen into ammonia or its salts, the important class of ammonia bases or amines and ammonium bases of the alcohol radicles is produced. The amines containing the lower alcohol radicles bear the closest resemblance to ammonia, being even more strongly basic than the latter. They have an ammoniacal odour, give rise to white clouds with volatile acids, combine with hydro- chloric acid, etc. to salts with evolution of heat, and yield double salts with platinic and gold chlorides. They further precipitate many metallic salts, the precipitates being -fre- quently soluble in excess. The lowest members of this class are combustible gases NITROGEN BASKS. 121 readily soluble in water. The next are liquids of low boiling point, also at first easily soluble, but the solubility in water diminishes with increasing carbon (more quickly in the nitrile- than in the amido-bases), and also the volatility, until the highest members of the series, such as tricetylamine, (Ci5H33)3N, are at the ordinary temperature solid odourless substances of high boiling point, insoluble in water but soluble in alcohol and ether, readily combining however with acids to salts, like the others. All amine bases are considerably lighter than water. The ammonium bases are solid and very hygroscopic, and exceedingly like potash in properties. Olassification. The nitrogen bases of the alcohol radicles are divided into primary, secondary, tertiary, and quaternary bases, according as they contain one, two, three, or four alcohol radicles ;' the three first are derived from ammonia, and the last from the hypothetical ammonium hydroxide, NH,.OH. Amines or Ammonia Bases. Ammonium Bases. Primary or Amido-bases. Secondary or Imido-bases. Tertiary or Nitrile-bases. Quaternary Bases. NH^iCHa) Methylamine (B. Pt. -6°). NHj(C.H5) Ethylamine (B. Pt. 19°). etc. NH(CH3)2 Di-methylamine (B. Pt. 7°). NHICH,), Di-ethylamine (B. Pt. 56°). etc. N(CH3)a Tri-methylamine (B. Pt. 3°). N(C,H5)8 Tri -ethylamine (B. Pt. 89°). etc. N(CH3)4l Tetra-methyl- amraonium iodide. N(CsH5)40H Tetr-ethyl-am- monium-hydroxide. etc. The alcoholic radicles may be either saturated or unsaturated. Occurrence. Some individuals of this series occur in nature, e.g. methylamine and tri-methylamine. Modes of formation. 1. Methylamine, ethylamine, etc., are obtained by treating methyl or ethyl etc. iso-cyanate with potash solution {Wwrtz, 1848): CO.NlC^Hs) + 2K0H = CaH^.NH^ + K^COg. This method of formation yields only primary bases. 122 IV. DERIVATIVES OF THE MONATOMIC ALCOHOLS. 1*. The iso-thiocyanic ethers or mustard oils (see these) also yield those bases upon heating with concentrated acids. 2. By the direct introduction of the alcohol radicle into ammonia by heating a concentrated solution of the latter with methyl iodide, chloride, or also nitrate, ethyl iodide, etc. In . this reaction an atom of hydrogen is first exchanged for an alcoholic radicle, and then th') base produced combines with the halogen hydride, formed at the same time, to a salt, thus : (I.) NH^H + CH3I = NH2.CH3, HI. From the methylamine hydriodide thus produced, free methylamine can easily be got by distilling with potash : NH2(CH3), HI + KOH = NH2(CH3) + KI + H^O. The methylamine can now combine further with methyl iodide to hydriodide of di-methylamine : (11.) NH2(CH3) + CH3l = NH(CH3),HI, which, in its turn, yields the free base with potash. This latter can again combine with methyl iodide : (III.) NH(CH3)2 + CH3l = N(CH3)3HI, the salt so produced yielding tri -methylamine as before. Finally the tri-methylamine can once more take up methyl iodide : (IV.) N(CH3)3 + CH3l = N(CH3)J. The compound obtained, tetra-methyl-ammonium iodide, is however no longer a salt of an amine base but of an ammonium one, and is not decomposed on distillation with potash solution. Primary and secondary bases can also be transformed into secondary and tertiary by warming with alkyl-sulphates (e.g. B. 84, 1678). By using various dissimilar alkyl iodides instead of methyl iodide alone, bases are got containing different alcohol radicles together, i.e., "mixed" amines, etc., e.g., methyl-propylamine, NH(OH3)(C8H,) methyl-ethyl-propylamine, N(GH3)(02H5)(CsHi,). The reactions I. to IV. , given above, do not in reality follow each other in perfect order but go on simultaneously, the bases being partly liberated from the hydriodides by the ammonia, and so being free to react with new halogen alkyl. The product obtained by distillation with potash is therefore a mixture of all the three amine bases. These cannot be separated by fractional distillation, and so their different behaviour with oxalic ether, C20j(OC2H5)2, is made use of for the purpose. Methylamine reacts with this ether to form chiefly (1) NITROGEN BASES ; FORMATION OF. 123 di-methyl-oxamide, CA(NH.CH3)2, (soUd), and (2) some methyl- oxamio ether, C20j(OC2H6)(NH.CH3), (liquid) ; di-methylamine yields (3) the ethyl ether of di-methyl - oxamio aeid, CjOjCOCjHjjNlCHaJs, (liquid), while tri-methylamine does not react with oxalic ether. Upon warming the product of the reaction on the waterbath, the latter base distils over, and the remaining compounds can then be separated by special methods, (for which see B. 3, 776 ; 8, 760), and individually decomposed by potash, (1) and (2) yielding methylaraine, and (3) di- methylamine. 3. The nitro-compounds yield primary amido-compounds on reduction (see p. Ill), thus : CH3.NO2 -I- 3H2 = CH3.NH2 + 2H2O. 4. The nitriles, including hydrocyanic acid, are capable of taking up four atoms of hydrogen (seep. 118), and forming primary amines, (Mendius, 1862) : Ethylamine. CH3.CN + 2H2 = CH3.CH2.]SrH2 = c^H^lmi^. Methylamine. H.CN + 2H2 = CH^jra^ 4". The iso-nitriles are decomposed by hydrochloric acid, with formation of the primary amine ba^es from which they are also obtained (p. 119). 5. Primary amines, in which < 6, are prepared according to Eofmann's method, by the action of bromine and caustic soda solution upon the amides of acids containing one carbon atom more than themselves (see Amides). 6. Primary amines likewise result from the reduction of the oximes or hydrazones (see pp. 150, 146, and 155): CH3 — CH=N.OH + 2H2 = CH,— OHj.NHs -t- HjO. <■ , ^ Aldoxime. Isomers. Numerous isomers exist among the amine bases, as the following table shows : C^H^N. C3H5N. C^HuN. NH,(C,H,) NH(CH3)j NH.iCaH,) NH(CH3)(C3Hb) N(CH3), NH(CHg)(C3H.) and NH(CiiH6)s N(CH3)2(C2Hg) This kind of isomerism is the same as that of the ethers (p. 101), i.e., metamerism. From (O3H7) onwards, isomerism can also occur in the alcohol radicles. According to theory, as many amines Cn as alcohols Cn+i are capable of existence. 124 rV. DERIVATIVES OF THE MONATOMIC ALCOHOLS. Behaviour. 1. For general behaviour, see above. When combined with acids to salts, the amines behave exactly like ammonia, and the ammonium bases like potash : CH3.NH2 + HOI = CH3.NH2, HCl = (CH3)NH3C1. psr(CH3)J0H + HOI = [N(CH3)4]01 + HgO. The salts so obtained are white, crystalline, frequently hygroscopic compounds, easily soluble in water. The chlorides form, with platinic chloride, crystalline double compounds whose composition is analogous to that of ammonio-platioic chloride, 2NH4OI, Pt0l4 ; e.g., hydrochlorate of methylamine- platinic chloride, 2(NH2[0H3]HC1), PtOl^. The same applies to the gold double salts, e.g'., NH2(02H5)H01, AUOI3. 2. Saponifying agents such as alkalies and acids do not afiect the nitrogen bases of the alcohol radicles, and oxidizing agents only with difficulty. (See B. 8, 1237.) 3. The different classes of amine bases are distinguished from each other by the primary having two hydrogen atoms, the secondary one, but the tertiary none replaceable by alcohol radicles; the same applies to substitution by acid radicles. The products thus resulting from isomeric amines are dis- tinguished from one another by analysis. Thus propylamine gives with methyl iodide the base OgHyN(CH3)2, = CjHjjN • the isomeric methyl-ethylamine the base (0H3)(02H5)N(0Hg), = O4H9N; while tri-methylamine, (CH3)3N, = OgHgN, likewise isomeric, remains unaltered. The primary bases further differ from the others in their behaviour with chloroform, carbon bisulphide and nitrous acid. 4. Only the primary bases react with chloroform and alco- holic potash, with formation of iso-nitriles (p. 119). 5. "When warmed with carbon bisulphide in alcoholic solution, the primary and secondary, but not the tertiary bases, react to form derivatives of thio-earbamio acids. (See carbonic acid derivatives.) Should the amines be primary ones, the characteristically smelling iso- thio-cyanates are produced upon heating the thio-carbamio derivatives with a solution of HgClj, ("Senfdl" reaction). 6. Nitrous acid acts upon the primary bases to reproduce the alcohols, e.g.: NITROGEN BASES; BEHAVIOUR OF. 125 CH3.NH2 + H.O.NO = CH3.OH + N2 + H2O. A molecular transformation sometimes takes place here, e.g. the produc- tion of iso-propyl alcohol from N-propylamine. Secondary bases, on the other hand, yield with nitrous acid nitroso-compounds, 6:g. " dimethyl-nitrosamine " : (CH3)2NH + NO.OH = (CH3)2N.NO-i-H5,0. These nitroso-compounds are yellow-coloured liquids of aromatic odour, which boil without decomposition. (Geuther.) They regenerate the secondary bases upon treatment with strong reducing agents, and also upon warming with alcohol and hydrochloric acid. Weak reducing agents however convert them into hydrazines (p. 128). The nitrosamines are frequently of great service in the purification of the secondary bases. Nitrous acid has no action upon tertiary amines. 6a. By the indirect action of nitric acid (B. 22, Eef. 295), nitramines result, i.e. amines -in which an amido-hydrogen atom has been replaced by the nitro-group, e.g. CHg — NH — ^N02, methyl-nitramine. Similarly, by the indirect introduction of an amido-group, hydrazines (p. 128) are formed, e.g. CHj — NH — NHg, methyl-hydrazine. 7. While the amine bases are liberated from their tealts by alkalies, the free bases of the quaternary salts, e.g. tetra-methyl- ammonium iodide, cannot be prepared from these by treatment with potash, because they are as strongly basic as the latter, if not even more so. The salts however behave like hydriodates, for instance towards AgNOg, and their bases, e.g. N(CH3)40H, can be separated by acting upon them with moist silver oxide. They are extraordinarily like caustic potash. They cannot be distilled without decomposition, but break up on distillation with reproduction of the tertiary base, the tetra-methyl base yielding in addition methyl alcohol, and the homologous bases olefine and water, thus: N(CHg),.OH =N(CH3)3-|-CH3.0H. N(C2H5)^. OH = N(C2Hj)3 -f CgH, -i- Hp. They are of great interest for the question of the valency of nitrogen, since they are more difficult to explain on the assumption of its being trivalent than pentavalent. (Cf. trimethyl-sulphine hydroxide.) The fact 126 IV. DERIVATIVES OF THE MONATOMIC ALCOHOLS. that the salts N(0Ha)s(CjH5) + CjHsCl, and N{CHa)(C2H5)j + OH8Cl are identical, is in agreement with the latter assumption. {Meyer and Leceo.) Lastly, optically active isomers are met with among the quaternary am- monium salts (see p. 26), a point which receives its readiest explanation from the asymmetry of the pentavalent nitrogen. 8. The quaternary iodides go back into tertiary base and alkyl iodide upon heating. They combine with two or four atoms of bromine or iodine to tri- and penta-bromides or -iodides, e.g. N(CH3)4.I.l4 (dark needles), and 'N{C2B.^}J..l2 (azure-blue needles). These latter must be looked upon as addition-compounds, since they readily lose their additional halogen again. Hepta- and Ennea-iodides also exist. Methylamine, CHgNHj. Occurs in Mercurialis perennis and annua (" mercurialin "), in the distillate from bones and wood, and in herring brine. It is produced in many decom- positions of organic compounds, e.g. from alkaloids, as when caffeine is boiled with hydrate of baryta; also by heating hydrochlorate of tri-methylamine to 285°. It is most easily prepared from acetamide, caustic soda and bromine. (B. 18, 2737.) It is more strongly basic and even more soluble in water than ammonia, has a powerful ammon- iacal and at the same time fish-like odour, and burns with a yellowish flame. Its aqueous solution, like that of ammonia, precipitates many metallic salts, frequently redissolving the precipitated hydroxides; unlike ammonia, it does not dissolve Ni(0H)2 and Co(OH)2. Below - 6° it is liquid. The hydrochlorate, NH2(CH3), HCl, forms large glittering plates, and is very hygroscopic and easily soluble in alcohol, the platinum salt crystallizes in golden scales or hexagonal tables, the sulphate forms an alum with Al2(SOi)8-l-24H20, and a carbonate also exists. Methyl-nitramine, CH, — ^NH — NOj, has been prepared from methyl- urethane (B. 22, Eef. 295). M. Pt. 38°. It has an acid character, the imido- hydrogen atom being replaceable by potassium, etc. Di-methylamine, (CHg)2NH. Occurs in Peruvian guano and pyroligneous acid, and is formed e.g. by decomposing nitroso- dimethyl-aniline by caustic soda solutioa B. Pt. 7°. TRI-METHYIj AMINE, ETHYLAMINE, ETC. 127 Tri-methylamine, (CH3)3N. Is pretty widely distributed in nature, being found in considerable quantity in Chenopodium vulvaria, also in Arnica montana, in the blossom of Crataegus oxyacantha and of pear, and in herring brine. {Wertheim.) It is obtained as a decomposition product from complicated organic compounds containing nitrogen, e.g. from the betaine of beetroot, and therefore along with ammonia, di-methylamine, etc., methyl alcohol and aceto-nitrile by the distillation of vinasse. It possesses an ammoniacal and pungent fish-like odour; is liquid below 3°. For its preparation see A. 267, 254. Tetra-methyl-ammonium iodide, N(CH3)J, is obtained in large quantity directly from NH3 + CH3I. It crystallizes in white needles or large prisms, and has a bitter taste. Tetra-methyl-ammonium hydroxide, ]Sr(CH3)40H. Fine hygroscopic needles. It forms a number of salts, among others a platinum double salt, sulphide, polysulphide, cyanide, etc.; many of these are poisonous. Ethylamine, CjHjNHj. For its preparation by Hofmann's method, the crude ethyl chloride which is obtained as a bye- product in the manufacture of chloral may be used. It has a strongly ammoniacal smell and biting taste, mixes with water in every proportion with evolution of heat, and burns with a yellow flame. It dissolves Al2(0H)g but not FejCOH)^, also Cu(0H)2 with difiiculty, but not Cd(0H)2. B. Pt. 19°. Ethyl-nitrogen chloride, C2H5 .NCIj, is a yellow oil of a most unpleasant piercing odour, obtained from the above compound with chloride of lime, Di-ethylamine, (C2H5)2NH, does not dissolve Zn(0H)2. Tri-ethylamine, (C2H5)3N, is an oily strongly alkaline liquid, only slightly soluble in water. The precipitates which it gives with solutions of metallic salts are mostly insoluble in excess of the precipitant. Vinylamine, (CaHsjNHj. Easily decomposable, etc. etc. 128 IV. DERIVATIVES OE THE MONATOMIC ALCOHOLS. Appendix: Hydroxylamines; Hydrazines. The Alkyl-hydroxylamines, which are derived from hydrox- ylamine, NHj.OH, just as the amines are from ammonia, be- long to two different series, in accordance with the constitution of hydroxylamine, thus: NH2.OCH3 and NHCH3.OH a-Methyl-hydroxylamine. jS-Methyl-hydroxylamine. The compounds of the first series, which are obtained from the oxime-ethers (p. 150), are — as ethereal compounds — toler- ably stable, and do not reduce Fehling's solution. Those of the second series, which likewise result from certain oxime derivatives, but at the same time also from the reduction of the nitro-hydrocarbons (p. 112), very readily undergo change, reduce Fehling's solution even in the cold, and pass into primary amines upon further reduction (B. 33, 3597; 24, 3528; 25, 1714). E. Fischer (A. 190, 67; 199, 281, 294) has given the name of hydrazines to a series of peculiar bases, mostly liquid and closely resembling the amines, but containing two atoms of nitrogen in the molecule, and difiering from the latter especially by their capability of reducing Fehling's solution, for the most part even in the cold, and by the ease with which they are oxidized. They are derived from " Diamide " or " Hydrazine," NHj— NHj {Curtim and Jay, J. pr. Oh. (2) 39, 27). They result, e.g., from the action of nascent hydrogen on the nitros- amines (p. 125): (CH3)2KNO + 2H2 = (CH3)2N.NH2 + Bfi. We distinguish between primary hydrazines, E — NH — NHj, and secondary, E2=N — NHg, according as one or both of the hydrogen atoms which are attached to an atom of nitrogen are replaced by alcohol radicles (R). Methyl-hydrazine, OH3— NH— NH^ (Cf. A. 253, 5). An excessively hygroscopic liquid, which fumes in the air, and has an odour similar to that of methylamine. B. Pt. 87°. HYDRAZINES. 129 Ethyl-hydrazine, CjHg— NH— NHa. When di-ethyl urea is treated with nitrous acid, a nitroso-compound is formed, which is changed by reduction with zinc dust and acetic acid into the so-called "di-ethyl-semi-carbazide." This last decom- poses upon being heated with hydrochloric acid into carbonic acid, ethylamine, and ethyl-hydrazine : ^°3. B. Pt. of the ethyl compound 159°. They are permanent in the air butinflamraable, and both — especially the methyl compound— V. ALDEHYDES AND KETONEa 139 are very poisonous. HCl reacts to produce Mercury-methyl chloride, Hg(CH3)Cl, a colourless salt, thus : Hg(CH5)j-i-HCl = Hg(CH3)CI + CH4. To this there is a corresponding iodide and also a, hydroxide, HglCHjjOH, of strongly alkaline reaction. Mercury-ethyl hydroxide, Hg(C2Hj)0H, is an oily odourless liquid of extremely Caustic taste, slippery to the touch like potash, and gradually hlistering the skin. Alnminium methlde, Al(CHa)3, is spontaneously inflammable and decom- poses violently with water. B. Pt. 130°. For Vap. Dens, see B. 23, 551. Cadmium and Magnesium methldes are also known. Lead methlde, Pb(CH3)4, and ethide, Pb(C2H5)4 (Cahours). These are formed according to method 3, curiously with separation of lead : 2PbCl2 + 2Zn(CH3)i, = PMCHj)^ -t- Pb -I- 2ZnCl2. They are stable in the air, and are interesting from the lead in them being tetravalent. The Hydroxide, Pb(CH3)3.0H, forms pointed prisms, smells like mustard, and is a strong alkali ; thus. It saponifies fats, drives out anmionia from its salts, precipitates metallic salts, etc. The compound Pb2(C2H5)g is also known. The tin compounds are similar (Ladenhurg, Franldand). Tin tetra-methlde, Sn(CH3)4, Tin tetra-ethlde, Sn(C2HB)4, Tin trl- ethlde, Sn2(CjHj)5, Tin dl-methlde, Sn2(CH3)4, etc., are of interest as proving the tetravalence of tin. V. ALDEHYDES AND KETONES, G^B.Jd. The aldehydes and ketones are substances which result from the oxidation of the primary and secondary alcohols respec- tively, with separation of two atoms of hydrogen. The Aldehydes are formed from the primary alcohols, and are easily converted by further oxidation into the correspond- ing acids containing an equal number of carbon atoms, oxygen being taken up. They possess in consequence strongly re- ducing properties. The Ketones result from the oxidation of the secondary alcohols, and are more diflBcult to oxidize further; they do not possess reducing properties. Their oxidation does not lead to acids containing an equal number of carbon atoms in the molecule, but to others containing a smaller number, the carbon chain being broken. 140 V. ALDEHYDES AND KETONES. The lower members of both classes are neutral liquids of peculiar smell, easily soluble in water and readily volatile, only CHjO being gaseous. With increasing carbon they soon become insoluble in water, and their odour becomes less marked with rise of melting point until the highest members are solid, odourless, like paraffin, and only capable of being distilled without decomposition in a vacuum. The aldehydes are also perfectly analogous to the ketones as regards other modes of formation and in many of their pro- perties. A. Aldehydes. The homologous series of the aldehydes, C„H2„0, corre- sponds exactly with that of the acids, GJI^aO^. Their boiling points lie decidedly lower than those of the corresponding alcohols, and rise, in the normal aldehydes, at first by about 27° for each CHj, and later on by a less amount. Modes of formation. 1. By the regulated oxidation of the primary alcohols, C^Han+iOH, by potassium bichromate or manganese dioxide and dilute sulphuric acid ; often slowly by the oxygen of the air alone, especially in the presence of bone black or platinum : CH3.GHPH -^ = CH3.CHO + Rfi. Alcohol. Acetic aldehyde. Aldehydes are also produced by the oxidation of many complicated organic substances, such as albumen. 2. From the acids of the acetic series, by distilling a mixture of their calcium or barium salts with calcium or barium formate, (Limpricht). The formic acid acts in this instance as a reducing agent, producing calcium carbonate, thus : CH8.C00ca + HCOOca = CH3.CHO + CaCOg. (ca = ^Ca.) Other reducing agents have for the most part no action. 3. From the di-halogen substitution products of the hydro- carbons containing the atomic group CHXg, by superheating with water or by boiling with water and PbO : CH3— CHCI2 + H2O = CH3— CHO + 2HC1. Ethylidene chloride. ALDEHYDES; CONSTITUTION OF, ETC. 141 By the oxidation of the primary alcohols, R — CHg-OH, to their corresponding acids, whose constitution follows as R — CO. OH, the new oxygen atom affixes itself only to that carbon atom which is already combined with oxygen — ^in the form of hydroxyl — , the hydrocarbon radicle R remaining unaltered. It must consequently also remain unchanged in the intermediate products of the oxidation, the aldehydes, which therefore possess the constitution R — OHO : OH3— CH2,0H CH3— OHO OH3— CO.OH Alcohol. Aldehyde. Acetic acid. The aldehydes thus contain the atomic group — CHO or — O^TT, bound either to hydrogen as in formic aldehyde, H — CHO, or to an alcohol radicle as in all the other cases. Isom&rs. Isomerism in the aldehydes is caused solely by isomerism in the alcohol radicles R, which are combined in them with the group — CHO, and therefore contain an atom of carbon less. Otherwise the aldehydes^from CgHgO on — are isomeric with the ketones, with the oxides of the olefines {e.g. aldehyde with ethylene oxide, CgH^O), and with the alcohols of the allylic series. The "official names" (p. 28) of the Aldehydes end in "al." Behaviour. The aldehydes are distinguished by being exceptionally active chemically. 1. For oxidation, see above. The aldehydes are very readily oxidizable, slowly even by the air alone, and quickly by chromic acid, salts of the noble metals, etc. They conse- quently reduce an ammoniacal solution of silver and often one of copper; this reaction is characteristic and is especially delicate in the presence of caustic soda solution. 2. The aldehydes are easily reducible by nascent hydrogen, e.g. sodium amalgam and dilute acid or zinc dust and glacial acetic acid, to the primary alcohols from which they are derived by oxidation, e.g. : CH3— CHO + H2 = CH3.CH2OH. A glycol is formed as intermediate product, e.g. butylene glycol, C4H8(OH)2, from G^p. 142 V ALDEHYDES AND KETONES. 3. Phosphorus pentachloride and -trichloride convert the aldehydes into ethylidene chloride and analogous di-chloro- substitution products of the hydrocarbons. 4. Addition-reactions. One would expect that upon treat- ing ethylidene chloride or analogous chlorides with water and lead oxide, for instance, two hydroxyl groups would replace OH two chlorine atoms, and a compound, CHg — CH<^qtt, would be produced, which would be a diatomic alcohol, " ethylidene glycol." Such compounds are however not formed, being apparently broken up at once into aldehyde and water, thus : CH3— CH0 (KeMU and ZincJce). \0— CH/CHg (The connection of 3 molecules of aldehyde by C-bonds cannot be assumed, on account of the readiness with which para-aldehyde breaks up into the former.) With regard to these and other polymeric compounds, the general rule has been proved to hold, that in the case of bodies of similar constitution, the one of simpler composition is the more soluble, possesses the lower melting point, and is the more easily vaporized. Acetal, C2H^(OC2H5)2. B. Pt. 104°. This, as well as methylal, is frequently used instead of aldehyde for the carrying out of condensation reactions (see p. 144). Aldehyde-ammonia (l-Ethmol-amine), CHg — CH(0H)(NH2). Cf. pp. 143 and 147. This may be used for the preparation of hydrazine, H^N— NH^ (cf. Curtius and Jay, B. 23, 740). CHLORAU 149 Propylic aldehyde, CjH5.CH0, is present in wood tar. Normal Heptylio aldehyde (Omanthol), C,HuO, is obtained by the dry distillation of castor oil under diminished pressure, etc. The normal aldehydes, Cu, Cu, Ci8 and Cig are also known. Mono- and Di-chlor-aldehyde, CH2CICHO, and CHCI2CHO, are liquids boiling respectively at 85° and 89°. Chloral 'COlg. OHO, (lAeUg), is a liquid which boils at 98°, and which — when impure — easily changes intq a solid poly- meric modification, meta-chloral, but is regenerated from this upon heating. It combines readily with water to chloral hydrate CCl3.CH(OH)2, (see p. 143, b), and with alcohol to Chloral alcoholate, CCI3— CH(0H)(0C2Hs), and Tri-chloro- acetal, CCI3 — CH(O.C2Hg)2. The end product of the action of chlorine upon alcohol consists chiefly of the last three sub- stances, which are converted into chloral by distilling with sulphuric acid, and rectifying over lime. Chloral is an oily liquid of a sharp and characteristic odour. It combines with sodium bisulphite, ammonia, hydrocyanic acid and acetic anhydride, and reduces an ammoniacal solution of silver. It is easily oxidized to tri-chloracetic acid, and broken up by alkali into chloroform and alkaline formate : CClsCH.O-fHKO = CCI3H-I-HCO2K. Chloral Hydrate, CCl3.CH(OH)2, forms crystals readily soluble in water, melting at 57°, and boiling with dissociation at 97°. It acts as a soporific and antiseptic. Sulphuric acid converts it into chloral. Chloral alcoholate and Trichloro-acetal (see above) both form colourless crystals. Of the aldehydes poorer in hydrogen must be mentioned, in addition to Crotonic aldehyde (p. 145), Acrolein, t/^cryZic aldehyde, Allyl aldehyde, CHj^OH — CHO, which is produced by the oxidation of allyl alcohol, by the distillation of fats, and by heating glycerine with bisulphate of potash. It is a liquid boiling at 52°, of pungent odour (the smell of burning fat being due to it), and of violent action * "O.N." 2-Triohloro-ethanal. t "O.N." PropenaL 150 V. ALDEHYDES AND KETONES. upon the mucous membrane of the eyes. It unites in itself the properties of an aldehyde and of a compound poorer in hydro- gen, and therefore combines with ammonia and with bromine; it also unites with hydrobromic acid to Bromo-propionic aldehyde, CHjBr— CHs— CHO. Acrolein-ammonia yields piooline, C6H7N, upon distillation (see Pyridine bases), and crotonio aldehyde-ammonia, by an analogous reaction, coUidine, CsHnN. Acrolein is capable of combining with two atoms of bromine to Di-bromo- aorolein (di-bromo-propyl aldehyde), CHjBr — CHBr — CHO, a compound which is of importance in the synthesis of the sugars. (See p. 307.) Crotouic aldehyde, CjHs — CHO, is obtained by the action of zinc chloride or, better, sodium acetate (B. S5, B. 732) upon aldehyde (see p. 145), and also by the distillation of aldol. It is a colourless liquid of suffocating odour; B. Pt. 104°. Aldoximes. Aldoxime (Ethane-cmme), CH3 — CH=N — OH, is prepared from an aqueous solution of aldehyde and hydroxylamine hydrochloride, with the addition of sodaj it boils at 115° with- out decomposition. The Constitution of the Aldoximes is arrived at from the fol- lowing reactions (see also p. 145): — 1. They yield primary amines upon reduction (p. 123; B. 19, 3232; 20, 728). 2. By virtue of the " hydroxyl " hydrogen of the " oxime " group (=N — OH), they are capable of forming alkyl derivatives (ethers) and acid derivatives (esters). The alkyl compounds are broken up by hydrochloric acid into aldehyde and alkyl- hydroxylamine (see p. 128); the hydroxyl of the oximes is therefore linked to the nitrogen. 3. The aldoximes are split up by acetic anhydride (all of them, at least, upon being warmed) into nitrile and water : CH3— CH==NOH = CH3.CN + H2O. 4. The oximes of the fatty series readily take on HON to the group =C=N— , forming the group =C<^^-^ , just as in the case of the aldehydic group =0=0 (p. 144). The aldoximes are structural isomers of the amides, into KETONES; FORMATION OF. 151 which they can pass by an interesting molecular transformation {Bechnann). Many of the aldoximes exist in two isomeric modi- Jications, which can be readily converted, the one into the other, and which are structurally identical {H. Goldschmidt); this iso- merism rests upon stereo-chemical grounds. For further details see the Ketoximes (p. 158), which are in every respect analogous. B. Ketones. The lowest member of the series, Acetone, contains three atoms of carbon. The higher meinbers, from Cjj on, are solid. They are all lighter than water, e.g., the Sp. Gr. of acetone is 0-81 at 0°. Occurrence. Acetone is present in urine, methyl-nonyl ketone in on of rue, Euta graveolens. Modes of formation. 1. By the oxidation of secondary alcohols, which lose thereby two atoms of hydrogen : CH3.CH(OH).CH3 + = CH3.CO.CH3 + HjO. Iso-propyl alcohol. Acetone. Many other compounds also, which contain secondary hydro- carbon radicles, yield ketones upon oxidation, e.g. iso-butyric acid. 2. From acids by the dry distillation of their calcium or barium salts, carbon dioxide being formed: 2CH3— COOca = CH >C'0 + COjCa. In the case of the higher molecular fatty acids, this reaction can be brought about by heating with phosphoric anhydride (B. 23, Kef. 502). When two different acids are employed, mixed ketones, i.e. ketones containing different alcohol radicles, result, thus : CH3— COOca -f CH3.CH2.COOca = ^ >C0-i-C03Ca. Calcium acetate and propionate. Methyl-ethyl ketone. 152 V. ALDEHYDES AND KETONES. From an acid C^ there is thus formed a ketone C2u_i, from two acids C^ and C„ a ketone C„+„_i. When formate of calcium is used, formic aldehyde results. 3. From di-chlorides containing the atomic group =CCl2 : (CHglaCCla + HgO = (CH3)2CO + 2HC1. Acetone chloride. Acetone. One might expect here that two chlorine atoms would be exchanged for two hydroxyls, and a compound of alcoholic character, a diatomic alcohol, acetonyl-glycol, (CHg)2C^(OH)2, would be formed. But the law, already mentioned under aldehyde, that several hydroxyls cannot as a rule exist beside one another joined to the same carbon atom, is further exemplified in this instance also. Derivatives of such a glycol are, however, capable of existence. 4. By the action of zinc-alkyl upon an acid chloride, e.g. acetyl chloride, CH3.COCI: GH3.COOI + CHgZn = qh5>C0 + Clzn. (zn = iZn.) An addition compound is first formed, which must be quickly decomposed by water, otherwise tertiary alcohols are produced. This method of formation, which was devised by Freund in 1861, allows of the preparation of any possible ketone by using the corresponding zinc-alkyl and acid chloride, O3H7.CO.OI + CsHjZn = C3H7.CO.C2H5 + Clzn. Butyric chloride. Ethyl-propyl ketone. At the same time it elucidates, together with method 2, the constitution of the ketones, from the constitution of the corre- sponding acids. Theoretically, therefore, ketones are com- pounds which contain the carbonyl group, CO, linked on both sides with an alcohol radicle, E — CO — R. If the alcohol radicles are the same, "simple" ketones result, and if different, " mixed " ketones. The ketones may also be regarded as derived from monobasic acida by the exchange of their hydroxyl for alkyl, corresponding with modes of formation 2 and 4, and also from aldehydes by exchange of hydrogen for alkyl. KETONES; FORMATION OF. 153 The existence of ketones with less than 3 atoms of carbon is theoretically impossible. 5. From the ketonic acids or their ethers, e.g. aceto-acetic ether, CHg — CO — CHg — CO.OOgHg, by warming with moder- ately dilute sulphuric acid or with dilute alkalies. This im- portant reaction will be treated of at greater length under aceto-acetic ether. 6. From the hydrocarbons of the acetylene series (see p. 63), by the action of mercuric salts and also of dilate sulphuric acid. 7. Acetone and some of its homologues result from the dry distillation of wood, and are therefore present in crude wood naphtha. Isomers. The ketones show among themselves the same isomerism as the secondary alcohols. This isomerism depends on the one hand upon the isomerism of the alcohol radicles which are linked together by the CO-group, (different carbon atom chains), and on the other by the position of the oxygen atom on similar carbon chains, (isomerism of position) ; thus, C^Hg— CO— CHg is isomeric with C3H7— CO— CgHj. The aldehydes containing an equal number of carbon atoms in the molecule are always isomeric with the ketones, since both classes of compounds are formed from isomeric alcohols by the separation of Hj. This kind of isomerism may also be compared with metamerism, e.g. with that of methyl-butyl ether and ethyl-propyl ether. Further, acetone is isomeric with allyl alcohol. Such an isomerism of a saturated with an unsaturated compound is termed "saturation isomerism" (cf. p. 37). Nomenclature. After the name of the alcohol radicle the syllable "ketone" is appended, e.g. di-ethyl ketone, (C2H5)2CO, and methyl-ethyl ketone, CHg— CO— CgHg. Acetone is con- sequently di-methyl ketone. The names of the simple ketones are also derived from the acids which yield them, e.g. "Valerone," (C4Hg)2CO, from valeric acid. Baeyer (B. 19, 160) terms the ketones Keto-substitution products of the hydrocarbons, e.g. acetone is keto-propane, and ethyl-methyl ketone is o-keto- butane (the oxygen is attached to the a-carbon atom; see Substituted fatty acids). The "official name" (p. 28) of the ketones ends in " one," e.g. Propanone, etc. 154 V. ALDEHYDES AND KETONES. Behaviour. 1. The ketones are reducible to secondary alco- hols: (CHs)2CO + H2 = (CH3)2CH.OH. At the same time pinacones are formed in small quantity, (see p. 86), these going into the pinacolines (pp. 157 and 207) corresponding to the ketones, when warmed with acids. 2. Oxidizing agents, e.g. KjCrjOy and dilute HjSO^, slowly convert the ketones into acids containing a lesser number of carbon atoms in the molecule, (not — as in the case of the aldehydes — into acids containing an equal number), the carbon chain being broken : CH3— CO.CHg +04 = CHg-COOH + CO2 + H2O. Since carbon is tetravalent, the CO group in the ketone, being already linked to two alcohol radicles, can only pass into the group COOH, which characterizes the acids (p. 166), if one of the alcohol radicles be split off. For the laws which govern the course of these oxidations, see B. 25, K. 121, Since the acids formed by oxidation bear no reciprocal relation to the ketone, and the oxidation process is more complicated than in the case of the aldehydes, it is easy to understand why the ketones do not possess reducing properties. 3. Phosphorus pentachloride, POI5, converts the ketones into the corresponding dichlorides, acetone, for instance, into acetone chloride, (CH8)2CCl2. 4. Addition-reactions, {a) The ketones do not as a rule combine with water and alcohol, for the reasons given under the aldehydes and at p. 152. They form with mercaptan " mercaptols," analogous to aoetal, e.g. (CH3)2C(SCjH5)3. (B. 18, 883.) (6) With ammonia there result the (basic) acetone-amines, with separation of water, e.g. di-acetone-amine, CjHigNO, tri- acetone-amine, GgHjyNO, (Heintz); this reaction is more complicated than that with the aldehydes, two or three molecules of acetone combining with one molecule of ammonia, with elimination of water. (c) The ketones which contain the group CHg — 00 — , and also some others, combine with acid sodium sulphite to crystal- OH line compounds, e.g. acetone to (0x13)2 C^qq x^ + HjO, (glancing mother-of-pearl plates) ; these go back into ketones, KETONES; BEHAVIOUR OF. 155 for the most part, when treated with soda solution. This very important reaction is made use of in separating and purifying the ketones. (d) With hydrocyanic acid are formed the nitriles of higher acids, as in the case of the aldehydes; e.g. (GIi^).fi<^^. 5. The ketones, unlike the aldehydes, do not possess the property of polymerizing, but they form condensation products. Just as aldehyde is converted into crotonic aldehyde, so is acetone, by the action of many reagents — e.g. CaO, KOH, HCl, and HgSO^ — converted with elimination of water, into mesityl oxide, CgHjoO, phorone, CgHj^O, or mesitylene, CgHjj, accord- ing to the conditions, (see benzene derivatives) : 2C3H6O = OeHioO + H2O. SCgHgO = CgHj^O + 2H2O. SCfiP = OgHi2 + SH^O. Analogous condensations also ensue with other ketones or aldehydes under the influence of dilute caustic soda or of sodium ethylate, (B. 20, 655). In this way the more compli- cated ketones result, (A. 218, 121). 6. Sulphuretted hydrogen converts the ketones into thio-oompounds, e.g. acetone into thio-acetone, CHj — CS — CHj, (B. 16, 1368). 7. Halogens give rise to substitution products. 8. Like the aldehydes, the ketones — even C35 — combine with hydroxy lamine to oximes, which are termed Acetoximes or Ketoximes. {v. Meyer, B. 15, 1324, 2778; 16, 823, 1784, etc.) Thus: (CH3)2CO + NH2OH = H^O -f- (CH3)2C=N.OH. ^ , ' Acetoxime. These are for the most part solid, readily volatile compounds which react in a manner exactly analogous to the aldoximes (p. 150), and which therefore possess a similar constitution. For further particulars, see p. 158. 9. Analogous reactions follow with the hydrazines, e.g. 156 V. ALDEHYDES AND KETONES. phenyl-hydrazine, CgHs— NH— NH^ (E. Fischer, B. 17, 572). with the formation of "hydrazones" (p. 146). (CH3)2CO + HjN— NH— CgHs = (CH3)20=N— NH— CeHs + Hp. - ■* Aoetone-phenyl-hydrazone. Phenyl-hydrazine and hydroxylamine are therefore of great value for the recognition of the aldehydic or ketonic character of a substance. 10. Nitrous aoid (nitrous ether and sodium ethylate) gives rise to Iso- nitroso- ketones, e.g. iso-nitroso-acetone, CH3— CO — CH=N.OH, by the separation of HjO and the replacement of Ha by the group =N.OH (oxime). These are converted by reduction into Amido-ketones, e.g. amido-acetone, CHs — CO — CH2.NH2, unstable basic compounds which readily give up water and change into ketines (p. 530). The oxime group in the iso-nitroso- ketones can be replaced by an atom of oxygen, whereby ketoue-aldehydes or di-ketones (p. 238) are produced. Acetone {2-Propanme), CaHgO, = CHg— CO— CHj. Acetone has been known for a long time; its formula was established by lAebig and Dvmas in 1832. It is present in very small quantity in normal urine, in the blood, in serum, etc., but in much larger quantity in patho- logical cases such as acetonuria and diabetes mellitus. It is produced, among other ways, by the distillation of sugar, gum, cellulose, etc., and is therefore present in wood spirit; also by acting upon allylene, OgH^, with HgClj (p. 63). On the large scale it is prepared by the dry distillation of acetate of lime. Properties. (See under general behaviour of the ketones.) Liquid of peculiar ethereal and refreshing odour; B. Pt. 56°; Sp. Gr. 0-81 at 0°. Soluble in water, and separated from the aqueous solution on addition of salts. Miscible also with alcohol and ether. KMnO^ does not oxidize it in the cold, but CrOg does, with formation of acetic and carbonic acids. Shows the aldehydic reaction with fuchsine and sulphurous acid. Detection of acetone, e.g. by the formation of indigo when it acts upon 9-nitro-benz-aIdehyde in presence of a little caustic soda solution. VARIOUS KETONES. 157 Chloro-acetone, metacyl chZoride, CHs — CO — CH2CI, ia a liquid which produces a copious flow of tears. B. Pt. 119°. Fer-bromo-acetone, CBrj — CO — CBrs, is also known. (See p. 336.) Cyano-aoetone {2-Butanone-i-Nitrile), CH3— CO — CHa — CN, is a colour- less liquid which polymerizes very readily. It yields a sodium compound. Iso-nitroso-acetone, CHs— CO— CH=N.OH (B. 16, 3067), is formed by the action of nitrous acid upon acetone or aceto-acetic ether; M. Pt. 65°. Amido-acetone, CHs — CO — CH2.NH2. A basic compound, which readily loses water and passes into dimethyl-pyrazine. Snlphonal, (CHs)2 — C(S02.C2Hs)2, is formed when a mixture of acetone and mercaptan ia treated with hydrochloric acid, and the Uercaptol, (CH8)2C(SC2H5)2 [a derivative of the hypothetical acetone - glycol, (CH3)2C(OH)2], which is thus formed, ia oxidized by potassium perman- ganate to the corresponding sulphone. Prisma, M. Pt. 125°; acta as a soporific. Mesityl oxide, CeHmO, = CHs— CO— CH=C(CH3)2 {S'ane, 1888; Baeyer), ia a liquid of aromatic odour, boiling at 132°. Phorone, CsHuO, = CHj— CO— 0H=C(CHa)[CH=C(CHs)2], forms yellow crystala which melt easily. Both of these compounds are obtained by saturating acetone with hydrochloric acid gas (A. 180, 1). Methyl-ethyl ketone {2-Butanone), CHs — CO — O2H6, is present in crude wood spirit, and also reaulta from the oxidation of secondary butyl alcohol. B. Pt. 81°. Isonitroso-metliyl-acetone{2-5Mj£TOonc-3-oa»me),CH3-CO-C(N.OH)-CHs. From methyl - aoeto - acetic ether and nitrous acid (B. 20, 531). Tor its conversion into di-acetyl, see p. 238. Di-ethyl ketone {S-Pentanone), propione, (CjH5)2CO. M. Pt. 104°. Di-propyl ketone [i-ffeptanone), butyrone, (CsH;)2C0. M. Pt. 144°. Finacoline {2-Dimethyl-3-£utanone), methyl-tertiary -iutyl Jcetone, CH3 — 00 — C=(CH3)3, results by a peculiar molecular transformation, the "pinaooline reaction," from the action of dilute sulphuric acid upon pina- oone. (See p. 207.) B. Pt. 106°. Methyl -N.-nonyl ketone, CH3 — CO — C9H19, is the chief constituent of oil of rue (from Buta graveolena). B. Pt. 225°. ketones with 11, 12, 13, 14, 15, 16, 17, 18 and 19 carbon atoms are alao known; further, Laurone, O2SH45O, from calcium laurate. Myristone, Gk^hO, from calcium myriatate. Falmitone, CgiSsfl, from calcium palmitate. Stearone, C85H70O, from calcium stearate; and, finally, the ketones, Cjo, 158 V. ALDEHYDES AND KETONES. C22 and C34, which are obtained by distilling the normal heptylate with myristate, palmitate, or stearate of lime. All these ketones have been converted by Kraft into the corresponding paraffins, by first transforming them into the chlorides, CuH^nClj, by means of FCI5, and then heating the latter with hydriodic acid and phosphorus. Ketoximes. Acetoxime {^Propane-oxiTne), (CH3)2C = N.OH, forms crystals which are readily soluble in water, alcohol and ether; these melt at 65°, and volatilize without decomposition at 135°. Stereo -isomeric oximes. Like the aldoximes (p. 150), many of the ketoximes show cases of structural isomerism, this depending upon the configuration of the molecule, i.e. upon the position of the hydroxy] which is linked to the nitrogen (see Nitrogen-isomerism, p. 25). These isomers, which can be transformed one into the other, show certain chemical differ- ences, the latter being manifestly conditioned by the spacial proximity of the reacting groups. The one variety of aldoximes — as opposed to the other — gives up water even in the cold, when acted upon by acetic anhydride, and passes into a nitrile, from which the conclusion is drawn that the hydroxyl and aldehydic hydrogen are spacially near to one another (the "syn" position, i.e. syn-aldoximes, in contradistinction to the "anti" position, i.e. anti-aldoximes). (See figs. I. and II.): — (I.) R_C— H (II.) E— C— H (III.) E— C— E' II II II N— OH HO— N N— OH " Syn "-Aldoximes. "Anti "-Aldoximes. Ketoximes. In the case of the Ketoximes an analogous difference exists when they are asymmetric (i.e. E different from E'), since they show a different behaviour in the " Beckmann molecular trans- formation" (see Tolyl-phenyl-ketoxime), according as they belong to the "syn" or to the "anti" series (see B. 24, 23; Beckmann, B. 22, 431; Hantzsch and Werner, B. 23, 1; B. 24, 13, 3479, 4018; 25, 1908, 2164). ALDEHYDES AND KETONES. 1B9 COMPARISON OP THE ALDEHYDES AND KETONES. Aldehydes, X.CHO. Ketones, ^/>C0. Modes of formation. Modes of formation. 1. By the oxidation of primary 1. By the oxidation of secondary alcohols, On* (and other sub- alcohols, Cn (and other com- stances). pounds). 2. By the reduction of acids. On. 2. From acids by distillation of (Distillation of the Ca salts their mixed calcium salts. with calcium formate). From dl-chlorides, ^^CCls. 3. Fromthedi-chlorides.X. CHCla. 3. A From acid chlorides and zinc alkyl. '±, K TTtt^tvi Ir airmi /. a/iina ixritli aanay. 0. ation of CO2. Properties. Properties. 1. Reducible to primary alcohols. 1. Reducible to secondary alcohols. 2. Oxidizable to acids, Cnj strongly 2. Oxidizable to acids, Cn-x; not reducing. reducing. 3. Yield with PClj di-chlorides. 3. Yield with PClj diohlorides. — CHOlj. >CCLj. 4. Capable of combining with [(a) 4. Capable of combining with [(a) water ; (6) alcohol, acetic acid water; (J) alcohol, both sel- (seldom)]; (c) ammonia; (d) dom], (c) ammonia, to acetone- sodium bisulphite, to crystal- amines with separation of line compounds ; (e) hydro- water; (d) sodium bisulphite, cyanic acid, to nitriles of to crystalline compounds ; (e) higher acids. hydrocyanic acid, to nitriles of higher acids. 5. Capable of polymerization, often with production of resin when KOH is used. 5. 6. Condensible, e.g. to aldol, 6. Condensible, e.g. to CjHioO, C4H8O2, and to crotonic alde- C9H14O, C9H12. hyde. 7. Capable of substitution, e.g. to 7. Capable of substitution, e.g. to chloral, CCls.CHO. chloro-acetone, CH3— CO-CH2CI. 8. Yield with HjS, thio-aldehydea. 8. Yield with H^S, thio-acetones. 9. Yield with hydroxylamine, ox- 9. Yield with hydroxylamine, ket- imes,— CH = N.OH. oximes, >0 = N,OH. 10 Yield with hydrazines, hydra- 10 Yield with hydrazines, hydra- zones. zones. n means an equal number of carbon atoms. 160 VI. MONOBASIC FATTY ACIDS. The proof, furnished by Krafft, that (what are termed) the "normal" paraffins, etc., contain a straight carbon-atom chain, rests upon the possi- bility of preparing the ketones On+i from the acids Cn, by distilling their barium salts with barium acetate, without any branching of the carbon chain (since the carboxyl of the acid occupies an end-position, and conse- quently also the methyl group which replaces the hydroxyl) ; the oxidation of those ketones into the acids Cq— i; and, lastly, the conversion of these jhree compounds into the corresponding paraffins On, Cn+i and On_i. Paraffins which contain the same number of carbon atoms in the molecule are proved to be identical, even though they may be derived from different sources. The paraffin Cn— i results from the acid Cn— 2,. according to the above reaction. If, therefore, the acid Cn— 2 is normal, so are also the paraffin Cn_i, the acid Cn, and so on. The question of the constitution of any paraffin is thus referable to that of one which contains two atoms of carbon less in the molecule (or its corresponding acid). If we follow those relations downwards, beginning with the acids Cu, Cm, Gu and C12 which occur in nature (see these), we arrive finally at nonylic acid, which is undoubtedly normal from its synthesis; consequently those acids and their derived paraffins, ketones, etc., are also normal. We have, for instance, the following relations ; Paraffins. Ketones. Acids. CiiHjjO 1 CiiHji^ ..^^^-—^-^^^^C^S^O^ S CljHjB ^ ... --;.^s^r^^---;— a_C]2H24G2 J 12**26 ■<•— • , _ _, _ _ 13H28 ^ CijHjjOa 5 Cf. the Aldehydes and Ketones on p. 159. VI. MONOBASIC PATTY ACIDS. A. Saturated Acids, CnH^nO,. (See Table, p. 161.) By the oxidation of tlie primary alcohols or of their corre- sponding aldehydes the monobasic fatty acids are formed, the saturated alcohols yielding the saturated monobasic fatty acids, or " acids of the aliphatic series " as they are termed, corresponding to which, as to the alcohols, there are unsaturated compounds. These acids are monobasic, i.e. contain in the molecule only one replaceable atom of hydrogen, because they give rise to only one series of salts or of ethers. They are known as the fatty acids, on account of many of them being either contained in fats or resulting from these by oxidation. The lower members of the series are liquids of pungent odour and corrosive action which boil without decomposition. MONOBASIC FATTY ACIDS. 161 O d M a o 02 Q M o . t^ CO t^ 03 OOOOOOOOOOOOOO |i3li1|ijjiJ!i]|i]|T{pdpqM!i3n|ij|ij OOOOOOOOOOOOOO n a EH S Ph ra fc_i 43 i^ <« »u .pH- m PhSmIZhOJMiJO iC lO -^^ CO -* OS (N t- O CM CO O CO O 1-1 IN IM IN cq S llN 3 iJ Hi kI rH M CO r? O O O tfl W W H o d" o" o o O o o o '-i M ^ to « S to t~ at oi iH o o o o o o o PM • .3 i- "p. n-1 ■J- Hf- +- * •a i ■s ">» ;: " :: fl ja' rt i •i 1 o g 1 'a 'o •PH -i? '§ Pi h!" ^ > ^ IN CO ri: is o M O 12; a, a O m' pi3 -« (IJ 1 1 E3 fj » fl Ph-^ bjD ■s ^ m X % 1 ^ r4 !=! t:) D a 4S fH ^ S J3 (506) 162 VI. MONOBASIC FATTY ACIDS. dissolve readily in water, and show a strongly acid reaction. The middle members have an unpleasant smell like that of rancid butter or perspiration, and are oily and but slightly soluble in water. Mobility, odour and solubility diminish with increasing carbon. The higher members, from Cjq on, are solid, like paraffin, and insoluble in water, and can only be distilled without decomposition in a vacuum. Their acid character no longer finds expression in their reaction, but in their capability of forming salts with bases. They remain easily soluble in alcohol and especially in ether. For the laws governing the melting and boiling points, see pp. 35 and 33. The Sp. Gr. of the liquid acids is at first > 1, and from Cj onwards < 1, and it decreases continuously down to about 0'8, the paraflSn character of the hydrocarbon radicle becoming preponderant. Occurrence. Many of the acids of this series are found in nature in the free state, but more frequently as ethers, viz. : — (a) ethers of monatomic alcohols (see wax varieties), (b) ethers of glycerine or glycerides, in most of the vegetable and animal fats and oils. For further particulars see p. 176. Formation. 1. By the oxidation of the primary alcohols, CnHa^+iOH, or their aldehydes, GJLjiJ}, by means of KaCraO, or MnOg and dilute H2SO4, or by the oxygen of the air in presence of platinum or of nitrogenous substances, e.g. acetic acid from alcohol. 1». Acids containing less carbon are formed by the oxidation of many other compounds, such as ketones, secondary and tertiary alcohols, etc. , with separation of carbon. The higher molecular acids of this series are likewise converted into their lower homologues upon oxidation. 2. Several acids have been prepared from the halogen com- pounds C„Ha,_iX3, which contain the group — CX3, e.g. : HCCI3 + 4K0H = H.CO2K + 3KC1 + 2H2O. From this mode of preparation one might expect an exchange of the three chlorine atoms for thiree hydroxyls, with formation of the intermediate compounds H . C^(0H)3 or E — C(0H)3. Such compounds are however incapable of existence for the reasons stated under the aldehydes and ketones, going over into acids with elimination of water, thus : E— C(0H)3 = E— CO.OH + H„0. MODES OF FORMATION. 163 But derivatives of these (which may be regarded as triatomie alcohols and termed "ortho-acids,") are known, e.g. ortho-fonnio ethyl ether, HC(OC2H5)3, a neutral liquid of aromatic odour, insoluble in water, and boiling at 146°. 3. From the cyanogen compounds of the alcohol radicles, C^Hju+iCN. The cyanides, i.e. nitriles, which are prepared by warming the iodides of the alcohol radicles with cyanide of potassium, are converted into the fatty acids and ammonia by saponification, e.g. by heating with potash, with dilute or concentrated hydrochloric acid, or with sulphuric acid diluted with its own volume of water, thus : CHg.CN + 2H2O = CH3.CO2H + NH3. In this way hydrocyanic acid yields formic acid and ammonia, and it may therefore be regarded as the nitrile of the former. Amides are formed as intermediate products. (See pp. 118 and 194.) The great importance of this reaction, by means of which we can obtain an acid O^+i from an alcohol C^, has been already indicated, (p. 118). And since the acids, albeit with some difiiculty, can be converted by reduction into the corre- sponding alcohols, it is thus possible to build up synthetically, step by step, the alcohols richer in carbon from those poorer in carbon, a circumstance which is of especial importance in the case of the normal alcohols. {Lieben and Rossi, see p. 86.) 4. The acids may be regarded as resulting from the paraffins Cn-iHain—D^-j and CO2, e.g. acetic acid from CHj and COj, and formic acid from H2 and CO2. These two components can in fact be mad§ to combine indirectly, thus carbonic acid unites with potassium or sodium allCH— COOH can be prepared from acetic acid by first converting the latter into aceto-acetic ether, CH3 — CO — CHj — COO.CjHj, intro- ducing the alcohol radicle into this, and then breaking up backwards the compound so obtained by concentrated alcoholic potash. This reaction will be gone into more fully under aceto-acetic ether (p. 243). lOa. An analogous reaction follows on the use of malonic ether (see p. 252). BEHAVIOUR. 165 Separation. Natural fats are nearly all glyoerides of several acids, so that a mixture of acids results on their saponification. This mixture may be separated into its components as follows : (o) By fractional distillation in a good vacuum ; (6) by fractional pre- cipitation of an alcoholic solution of the acids by means of magnesium acetate, calcium chloride, etc., the acids richer in carbon being pre- cipitated first; (c) by fractional solution : the dry barium salts of formic, acetic, propionic and butyric acids are very differently soluble in alcohol, the solubility increasing rapidly with increasing carbon ; (d) by frac- tional saturation, and distillation of the non-combined acid. Behaviour. 1. Salts. The foregoing acids being monobasic, they form neutral salts, e.g. (C2H302)Na. But they also yield acid salts — the so-called per-acid salts — from the existence of which one might feel inclined to doubt their monobasic nature. These salts are, however, only crystallizable from a strongly acid solution, break up on addition of water, and also lose their excess of acid upon heating. It is therefore permissible to regard them as molecular compounds of the neutral salts with the acids, in which the latter play the part of water of crystalli- zation. All the other chemical characteristics of the acids go to prove their monobasicitj. 2. Besides salts, the monobasic acids, simple or substituted, yield other derivatives in a manner exactly analogous to that of the monatomic alcohols. The typical hydrogen atom is replaceable by an alcohol radicle with formation of a compound ether, or by a second acid radicle with formation of an an- hydride; the hydroxy 1 may further be replaced by halogen, especially chlorine, to an acid chloride or chloro-anhydride, by SH to a thio-acid, by NHg to an amide, etc. (See Acid derivatives, p. 187.) 3. Halogens act upon the acids as substituents (see p. 182.) 4. Upon heating the alkali salts with soda-lime, or in many cases by heating the silver salt alone, carbonic acid is separated and a paraflBn formed, see e.^.TVlethane. Paraffins also result from the electrolysis of the alkaline salts of the acids (see Ethane). 5. Most of the acids are relatively stable towards oxidizing agents, formic acid alone being readily oxidized to carbonic acid, and being therefore a reducing agent. 6. When the lime salts of the acids are heated with calcium formate they are reduced to aldehydes, and when heated for 166 VI. MONOBASIC FATTY ACIDS. a lengthened period with hydriodic acid and phosphorus, to paraffins. 6a. When the lime salts are distilled alone, or are heated with phosphorus pentoxide, they are transformed into the ketones, 7. For their transformation into the amine bases,Cn_i,seep.l96. 8. For the "degradation" of thehigheracids,seepp. 154 and 196. Constitution. It follows from their modes of formation, especially 3, 4, and 6, and also from their behaviour (see 3 above), that acetic acid and its higher homologues contain alcohol radicles. The conversion of the alcohols into acids containing one atom of carbon more, by means of the cyanides, is especially strong proof of this. The latter contain the alcoholic radicle bound to the cyanogen group — C=N, and when they are saponified the alcohol radicle remains un- changed, and the trivalent nitrogen is replaced by 0" and (OH)', both of these attaching themselves to the carbon atom of the original cyanogen, and so forming the group -CO,H = -C 211 isomeric forms are possible. Among all such isomers there is always only one normal acid. On the other hand, the number of iaomerio acids with n carbon atoms is always equal to that of the isomeric primary alcohols contain- ing the same number of atoms of carbon. Formic Acid {Methanoic acid), acidum formicicum, CHjOg (Samuel Fisher a,ni John Wray, 1670; Marggraf), occurs free in ants, especially Formica rufa, in the processionary caterpillar (Bombyx processionea), in the bristles of the stinging nettle, the fruit of the soap tree (Sapindus saponaria), and in tamarinds and fir cones; also in small quantity in various organic liquids, in perspiration, urine and the juice of flesh. Fffrmatim. From HCN, CHCI3, CH3OH, COj, etc., (see general methods of formation). It also results from the action of sodium amalgam upon ammonium carbonate or alkaline hydrocarbonates, etc. ; by the dry distillation or oxidation of many organic substances, e.g. starch, (Schede) ; also by decom- posing them — e.g. sugar — by concentrated sulphuric acid. Preparation. 1. Carbonic oxide is readily absorbed by soda- lime at 210°, with formation of sodium formate {Merz). 2. When oxalic acid is heated, formic acid is obtained in small quantity together with carbonic oxide, carbonic acid and water, and the same effect is produced by the direct action of sunlight upon its aqueous solution containing uranic oxide : C,H,0, = CO2 + CH^O,. This decomposition is best effected by heating oxalic acid with glycerine to 100°-110°, {Berthelot, Lorin), the formic acid produced combining with the glycerine to an ether, Monofor- min, (see p. 217): .(OH), ■-(O.HCO) Glycerine. C3H,(OH)3 + H.CO.OH = C3H,< '!, -hH,0. Monoformin. rORMIC ACID. 169 The monoformin is then saponified either by boiling it with excess of water or by the addition of more oxalic acid, through the water of crystallization of the latter. In this case mono- formin and carbon dioxide are again produced, the process repeating itself time after time, a very small amount of glycerine being thus sufficient to convert considerable quantities of oxalic into formic acid. (B. 15, 928.) The anhydrous acid is got by decomposing its lead or copper salt with sulphuretted hydrogen. Properties. Colourless liquid which solidifies in the cold and fumes slightly in the air. M. Pt. + 9°; B. Pt. 99°; Sp. Gr. 1 "22. Has a pungent acid and ant-like odour, acts as a power- ful corrosive, and produces sores on the soft parts of the skin. Is stronger than acetic acid and a powerful antiseptic. De- composes completely into carbonic oxide and water when heated with concentrated sulphuric acid : CHjOg = CO + HgO. Saits. Potassium-, HCOjK, Sodium-, HCOjNa, and Am- monium formate, HCOjNH^, form deliquescent crystals. The first two go into oxalates when strongly heated, with evolution of hydrogen (see p. 241) ; the ammonium salt into formamide and water at 180° : HCO2.NH4 = H.CO.NH2 + HjO. The lead salt, Pb(HC02)2, forms glancing, difficultly soluble needles, the copper salt, Cu(HC02)2 + 4H2O, large blue mono- clinic crystals, and the silver salt colourless crystals. The last-mentioned separates silver upon warming, consequently a solution of nitrate of silver is reduced' when heated with formic acid. The easily soluble mercuric salt, Hg(HC02)2, gives up carbonic acid upon being gently warmed, and goes into the sparingly soluble mer- curous salt, Hg2(HC02)2, which separates in white plates; on increasing the temperature further, this decomposes in its turn into carbon dioxide and metallic mercury. Similarly an aqueous solution of mercuric chlor- ide is reduced by formic acid to the merourous salt, HgjClj. Formic acid is thus a strong reducing agent : HCO.OH = CO2 + Hj. It decomposes into carbonic acid and hydrogen when heated alone to 160°, or when brought into contact with finely divided rhodium. 170 VI. MONOBASIC FATTY ACIDS. This power of reduction, which distinguishes formic acid from all its higher homologues, may be explained by its close relationship to carbonic acid, and also by the aldehydio character which one can read in its constitutional formula, H— — CHO. Acetic Acid,* acidum aceticum, CjH^Oj, was known in the dilute form, as crude wine vinegar, to the ancients. Sfahl prepared the concentrated acid about 1700. Glauber mentions wood vinegar, (1648). Its constitution was established by Berzelius in 1814. Occurrence. Salts of acetic acid are found in various plant juices, especially those of trees, and in the perspiration, milk, muscles and excrementa of animals. Ethers of acetic acid also occur, e.g. triacetin in croton oil, (see p. 176, and also under glycerine). Formation. (See p. 162 et seq.) Is the final product of the oxidation of a great many compounds, and also of their treat- ment with alkalies. The following synthesis is of historical interest. Perchloro-ethylene, C2CI4, which is prepared from CCI4, i.e. from CI and CS^, yields with chlorine in presence of water in direct sunlight tri-chloracetic acid, carbon trichloride, OjClj, being obviously formed as intermediate product, {Kolbe, 1843) : CCI3— CCI3 + 2H80 = CCI3— CO2H +3HC1. The latter acid is reduced to acetic by nascent hydrogen, (Mdsens). Preparation. 1. From Alcohol. A dilute aqueous solution of alcohol, containing up to 15 p.c, is slowly converted into acetic acid on exposure to the air and in presence of nitrogen- ous substances, by the agency of the " mother of vinegar," a film composed of micro-organisms (mainly the Bacterium aceti). The acetic fermentation is manifested in the souring of beer or wine, with the production of beer or wine vinegar. Vinegar is an aqueous solution of acetic acid, usually containing only 3 to 5 p.c, but containing also small quantities of alcohol, of the higher acids, e.g. tartaric and succinic, the ethyl ethers of the acids, albumin- ous matters, etc. It is manufactured on the large scale either, as in France, by the older method in a series of half-full oaken casks, or by the newer quick vinegar process, [Schiitzenbach). 2. From Wood. The dry distillation of wood, which is con- * Ethanoic acid. ACETIC ACID. 171 ducted in cast-iron retorts, yields (1) gases, e.g. hydrogen 15 p.c, methane 11 p.c, carbon dioxide 26 p.c, carbonic oxide 41 p.c, and higher hydrocarbons 7 p.c. ; (2) an aqueous solution known as pyroligneous acid which, in addition to acetic acid, contains methyl alcohol, acetone, homologues of acetic acid, and strongly smelling combustible products, (em- pyreuma) ; and (3) wood tar, which contains compounds of the nature of carbolic acid. The pyroligneous acid is worked up for acetic acid by converting it into the sodium or calcium salt, heating these — the former up to its melting point and the latter to 200° — to get rid of empyreumatic substances, and then distilling with sulphuric acid. Properties. Acetic acid is a strongly acid liquid of pungent odour, which feels slippery to the touch and burns the skin, and which solidifies in the cold to large crystalline plates melting at 17°; (Glacial acetic acid). B. Pt. 118°, Sp. Gr. at 15°, 1'055. Its vapour bums with a blue flame. When mixed with water, contraction and consequent increase in density ensue, the maximum point corresponding with the hydrate CHgCOgH + HjO, = GH3C(OH)3, (ortho-acetic acid), which contains 77 p.c. acid and has a Sp.Gr. of 1'075 at 15-5°; after this the specific gravity decreases with further addition of water, so that a 50 p.c. acid has almost the same density as one of 100 p.c. The amount of acid present in a solution is determined either by its Sp. Gr., this contraction being borne in mind, or by titration. The vapour density near the boiling point is much higher than that required by theory, but is normal above 250°. The acid is hygroscopic, and stable towards chromic acid and cold permanganate of potash. It dissolves phosphorus, sulphur and many organic compounds, is corrosive, and gives rise to painful wounds on tender parts of the skin. Salts. All the neutral salts of acetic acid are soluble in water. Potassium acetate, KC2H3O2 ; hygroscopic colourless plates. Acid potassium acetate, CjHgOjK + CjH^Og, crystallizes from the concentrated acid in glancing mother-of-pearl plates. A salt of the composition C^fi^ + 2C2H^02 is also known. 172 VI. MONOBASIC FATTY ACIDS. Sodium acetate, NaC^HgOg, forms transparent easily soluble rhombic prisms, (terra foliata tartari crystallisabilis). Ammonium acetate, NH^CgHgOj, resembles the potassium salt. It is used in medicine as a sudorific, (Liquor ammonii acetici). Its solution loses ammonia on evaporation, and it yields acetamide when distilled. Ferrous acetate, Fe (0311302)2, is largely used in the form of " iron liquor " as a mordant in dyeing. The normal ferric salt, Fe2(02H3O2)6, which is employed for the same purpose, is obtained when a soluble ferric salt is mixed with sodium acetate. Its solution is deep brown-red in colour, and deposits the iron as basic salt when heated with excess of water : Fe2(C2H30)e + 4H2O = FeJ(^^*Q . + iG,Bfi,. It is used in medicine as " liquor ferri acetici." The analogous aluminium acetate is only known in solution, and finds a wide application as " red liquor " mordant in calico printing and dyeing. Its use depends upon its easy decom- posability by water, e.g. when exposed to the action of steam, and on the affinity of the residual alumina compound for the colouring matter. It is employed in small doses as an astringent in cases of diarrhoea, etc. Lead salts. (1) Neutral lead acetate or sugar of lead, Pb(02H3O2)2 + 3H2O, is manufactured from sheet lead and acetic acid. It forms colourless lustrous four-sided prisms, which are poisonous and of a nauseous sweet taste. It com- bines with lead oxide to (2) Basic salts of alkaline reaction, termed sub-acetates. The simplest basic salt has the composition Pbxne-l-acid). (For similar cases see the higher homdogues ef acetylene, p. 65, and the hydro-phthalio acids.) Such changes, which are termed "molecular transformations," are explained by the assumption that atoms or atomic groups (in this case the elements of water) are taken on by the original compound, and given up again in a different manner. Acrylic acid (Propenic acid), ethylene-carboxylic acid, CgH^Og, = CH2=CH^— COgH (Bedtenbacher). Is prepared by the oxida- tion of acrolein by oxide of silver, or by the distillation of /3-iodo- propionic acid with oxide of lead. (Cf. mode of formation 3.) It is very similar to propionic acid. M. Pt. + 7°, B.' Pt. 180 VI. MONOBASIC FATTY ACIDS. 139°-140°. Miscible with water and capable of polymerization. It is reduced to propionic acid when warmed with zinc and sulphuric acid, and is broken up, on fusion with alkali, into acetic and formic acids. Crotonic acids, CiHeOj. (la) Ordinary or solid crotonic acid {Butenic add), CHs — OH=CH — COjH, occurs along with iso-crotonic acid in crude pyroligneous acid, and is prepared from allyl iodide by means of the cyanide, which, instead of having the anticipated formula, CH2=CH — CHa — ON, has the isomeric one, CHj — CH=CH — ON; this is another case of mole- cular transformation. It is also easily prepared by heating malonio acid with para-aldehyde and glacial acetic acid. It crystallizes in woolly needles or large prisms, M. Pt. 72°, B. Pt. 189°, has an odour like that of butyric acid, and is fairly soluble in water. (16) Isocrotonlc acid, CHa — CH=CH — COaH, whiih results from the action of sodium amalgam upon chloro-isocrotonic acid, is liquid, and changes into ordinary crotonic acid at 180°. It is present in croton oil. B. Pt. 172°. Isoorotonic acid was formerly held to have the composition CHa =CH — CHa — COjH. But it shows almost the same chemical behaviour as crotonic acid, e.g. on fusion with potash, and is stereo-chemioally isomeric with the latter jfcf. p. 24). The constitution of both, according to Widi- cenus (A. 248, 281), is:— H — G — CH3 CH3 — C — H II and II H— 0— COjH H— C— CO2H Crotonic acid. Isocrotonic acid. 0 + NaCL 1'. By the direct action of phosphorus oxychloride upon the alkaline salts of the acids, acid chlorides being formed in the first instance, (see p. 190). 2. By the action of phosgene on the acids, (B. 17, 1286) : 2CHs.C0.0H + COCI2 = (CH3— COJaO + 00^ + 2HC1. 2*. The anhydrides of the higher acids are conveniently prepared by treating these with acetyl chloride, (B. 10, 1881): 2R.C0.0H + CHg-COCl = (R.CO)ijO + CH8.C00H + HCl. Properties. The majority of the acid anhydrides are liquids, but those of higher molecular weight solids, of neutral reaction and soluble in alcohol and ether. They are insoluble in water, but are gradually decomposed by it into acid hydrates. On warming with alcohol, compound ethers are formed, and by ACID ANHYDRIDES; THIO-ACIDS. 193 the action of ammonia, amides. They yield with HCl gas, acid chloride and free acid : (C2H30)20 + HC1 = C2H3O.CI+C2H3O.OH. Acetic anhydride,* (C2H30)20, is a mobile liquid of suffocat- ing odour, boiling at 137°, and having a Sp. Gr. at 20° of 1-073. Like acetyl chloride it is a reagent of great importance, since it converts primary and secondary ammonia derivatives into acetyl compounds. Intermediate or Mixed anhydrides containing two different acid P TT O ^ radicles are also known, (Oerhardt, Williamson), e.g. p tt' fj J-O. They break up into two simple anhydrides upon distillation. We are likewise acquainted with peroxides of the acid radicles, e.g. Acetyl peroxide, (OjHjOjgOj, a thick liquid insoluble in water, whi-ib acts as a strong oxidizing agent and explodes upon warming ; it is pre- pared by the action of barium peroxide, BaO^, upon acetic anhydride. D, Thio-acids and Thio-anhydriaes. Just as in the alcohols and ethers, so in the acids and their anhydrides is oxygen replaceable by sulphur. There are thus theoretically possible: (1) Thio-acids ("O.N." Thiolic acids), e.g. thiacetic acid, CH3.CO.SH, and their isomers (" O.N." Thionic acids), e.g. CHj.CS.OH (as yet unknown); (2) Thio- anhydrides, e.g. acetyl sulphide (€21130)28; (3) Di-thio-acids, e.g. CH3CS.SH {Ethane-thionic-thiolic acid), (as yet only known in the aromatic series). Thiacetic acid (Ethane-ihiolic acid), CgHjO.SH, is a colourless liquid boiling below 100°, which smells of acetic acid and sulphuretted hydrogen, and readily decomposes with water into those two components. It is prepared from acetic acid and phosphorus pentasulphide, P2S5. The other thio-compounds are likewise easily saponifiable, with formation of acetic and hydrosulphuric acids. • ;^thanoic anhydride. (606) jr 194 VII. ACID DERIVATIVES. Ethers of thiacetic acid are also known, 6.17. ethyl thiacetate, CH3CO. S. CjHj, which is obtained from acetyl chloride and sodium meroaptide ; they are liquids which distil without decomposition, and are easily saponified back to acid and meroaptan. E. Amides. By the replacement of the hydrogen in ammonia by acid radicles or, in other words, by the replacement of the acid hydroxy! by amidogen, etc., amides result, these being primary, secondary, or tertiary, according to the number of hydrogen-atoms substituted : NH,.C,H30 NH(0,H30), NCC^s- Acetamide. Di-acetamide. Tri-acetamide. Of these the primary amides are the most important. They are solid crystalline compounds, at first soluble in water but becoming insoluble with increasing carbon, and soluble in alcohol and ether. They distil without decomposition {in vacuo, if necessary). They differ characteristically from the amines in being easily saponifiable, breaking up into their components, acid and ammonia, when superheated with water or when boiled with alkalies or acids. Alkylated amides are compounds derived from ammonia by the replacement of its hydrogen by alcoholic and acid radicles at the same time, e.g. ethyl acetamide, C2H30.NH.(C2H5) and di-methyl aceta- mide, (CH3)3N.C2H30. They are to be regarded as acid, e.g., aoetyl- derivatives of the nitrogen bases of alcohol radicles ; thus, ethyl aceta- mide is the same as acetyl ethylamine, C2H5.NH(C2H30). Modes of formation. 1. By the dry distillation of the ammonium salts of the fatty acids or, better, by heating them in a closed vessel to 230° (Hofmann, B. 15, 977), thus : CH3CO.ONH4 = CH3CO.NH2 + B.p. 2. By addition of water to the cyanides of the alcohol radicles containing one atom of carbon less than them- selves : OHj— ON + up = CH,— CO.NHy AMIDES. 295 This assimilation of water is frequently effected by dissolv- ing the nitrile in concentrated sulphuric acid, or in acetic and concentrated sulphuric acids, or by shaking with concentrated hydrochloric acid in the cold; also, and often quantitatively, by hydrogen peroxide, HgOj. 3. By the action of acid chlorides upon aqueous ammonia or solid ammonium carbonate; if amines are employed here, in place of ammonia, alkylated amides result: CH3.COCI + 2NH3 = CHg-CONHj + NH^CL 3*. In an analogous manner from acid anhydrides : (C2H80)20 + 2NH8 = OjHsO.NH. + CjHsO.ONHi. 4. By heating compound ethers with ammonia, sometimes even on shaking in the cold : CH3.CO.OC2H5 + NH3 = CH3.CONH2 + C2H5OH. 5. The secondary and tertiary amines result upon heating the acids or anhydrides with their nitriles : CH3.CN + CH3.COOH = (CH3.00)2NH; CH3.CN-l-(CH3.CO)20 = (CH3.CO)3N. Behaviour. 1. The amides, although derivatives of ammonia, are hardly basic, the strongly positive character of the hydrogen atoms of the ammonia being cancelled by the entrance of the negative acid radicle. Still the primary amides are capable of forming addition-compounds with some acids, e.g. acetamide yields the compound (C2H30.NH2)2HC1, " acetamide hydrochloride " ; these are however unstable, and are decomposed for the most part by water alone. On the other hand the hydrogen of the amido-group can be replaced by par- ticular metals, especially mercury (also sodium; cf. B. 23, 3037), the amides therefore playing the part of weak acids in the com- pounds so obtained, e.g. mercury acetamide (CH3.CONH)2Hg. 2. The amides are readily saponifiable. When they also contain alcoholic radicles, only the acid and not the alcohol radicle is separated on saponification, in accordance \nth the fact that the amine bases are not saponifiable, thus : CjHjO.NHCaHj + NaOH = CgHgO.ONa + C^H^NHj. 196 VII. ACID DERIVATIVES. 3. Nitrous acid converts the primary amides into the corre- sponding acids, with liberation of nitrogen : C2H3O.NH2 + NOgH = CaHsO.OH + N^ + H^O. This reaction is a general one, and corresponds exactly with the action of nitrous acid upon the primary amines. 4. Upon heating the primary amides with phosphorus pentoxide, P2O5, nitriles are produced (seep. 117). These, are also obtained upon heating with PgSg, and PCI5, amido- chlorides or thiamides being in this case formed as inter- mediate products, (see pp. 198 and 199). 5. If bromine in the presence of alkali is allowed to act upon primary amides, there ensue in the first instance amides whose NHg-hydrogen is replaced by halogen, e.g. CH3.CO.NHBr, aceto-bromamide, (colourless rectangular plates), and CHg.CO.NBrg : CH3— CO.NH2 + Bra = CH3— CO.NHBr + HBr, etc. These yield peculiar urea derivatives with more amide and alkali, e.g. methyl-acetyl-urea, CO ■! tsttt'ptt \ which are split up by further addition of alkali in the normal manner, with formation of amines — in this case CHg.NHg— containing one atom of carbon less than the original product. (See urea.) This is an excellent method for preparing the amines from Cj to Cg, but less desirable for those from Cg onwards, as in the case of the higher molecular compounds the production of amine diminishes, a nitrile being formed instead by the further action of the bromine, (see below). Such nitriles C«, in which m > 5, can therefore be obtained directly from the amine by the action of bromine and alkali upon it, thus : C»Hi5— CH„.NH, + 2Br2 = C-H„-CH„.NBr„ + 2HBr ' '' = cMs-CN + 4HB'r. (Eeversal of the Mendius reaction, p. 123 ; cf. Eofmann, B. 15, 407, 752; 17, 1407, 1920; 18, 2737). Since these nitriles go on saponification into acids containing one atom of carbon less than the amide originally taken, this reaction renders it possible to descend in the series successively AMIDO- AND IMIDO-CHLOKIDES. 197 from one acid to another (pp. 166 and 160). This has been done in the case of the normal acids from G^^ to Cj, and it furnishes a further proof of their normal constitution. Constitution. The properties and modes of formation of the amides agree with the constitutional formula: But, besides this, the following one is conceivable, in favour of which certain arguments have recently been adduced (B. 22, 3273; 23, 103; 25, 1435): This last formula easily passes into the first by the migration of one hydrogen atom, and most of the reactions of the simple amides are explicable almost equally well by either formula. The case of the alkylated amides is, however, different. The formulae : (I.) E— C<§g' and (II.) E— CO.NHE' represent chemical isomers. A transformation of one of these into the other could only take place by the detachment of the alkyl E' from the oxygen or the nitrogen, an event which experience has shown does not occur. The compounds of the type I. are therefore essentially distinct from those of the type II. They will be treated of as " imido-ethers " on p. 200. The " official name " of the amides is formed by adding the word " amide " to the name of the hydrocarbon. Formamide (Methane-amide), HCO.NHg, is a liquid readily soluble in water and alcohol, which boils with partial decom- position at about 200°, and breaks up into CO and NHg when quickly heated. It yields hydrocyanic acid when heated with P2OS. 198 VII. ACID DERIVATIVES. It unites in molecular proportions with chloral to form the so-called " chloral-amide," which is used as a disinfectant, preservative, and hypnotic. Aoetamide {Ethane-amide), CjHgO.NHg. Long needles, readily soluble in water and alcolioL M. Pt. 82°, B. Pt. 222°. Aceto-brom-amide, CaHaO.NHBr. Colourless rectangular plates. Di-acetamide, (CsHaOJjNH. M. Pt. 78°, B. Pt. 223°. Tri-acetamide, (OjHaO)aN. See B. 23, 2394. The high boiling points of the amides are worthy of notice; they stand in striking contrast to the low boiling points of the amines containing the same number of carbon atoms. Among the amides of haloid-substitution acids may be mentioned : Mono-chlor-acetamide, CHjCl— CO.NH2, M. Pt. 116°, B. Pt. 225°. Tri-chlor-acetamide, CCla— CO.NH2, M. Pt. 136°, B. Pt. 239°. For Isomers of the Amides, see p. 200. P. Amido-chlorides and Imido-chlorides. By the action of PCI5 upon the primary amides, an exchange of OI2 for takes place, giving rise in the first instance to the so-called amido-chlorides, e.g. acet-amido chloride, CH3 — CClj-NHg; these are extremely easily decomposable compounds, being reconverted by water into amide and hydro- chloric acid, and readily giving up HCl, with formation of imido-chlorides, e.g. CHg — CCl=NH,acet-imido chloride. The imido-chlorides also decompose easily as a rule, likewise yielding with water the amide and hydrochloric acid. When heated, they break up into nitrile and hydrochloric acid. The alkylated amides (p. 194) also yield amido-chlorides, e.g. CH3.CO.NH.C2Hs gives CH8.CCl2.NH.CjHs, ethyl acet-amido chloride, and GHs— CO.NE2 gives OHs — CCI2.NR2; if these still contain amido- hydrogen, they likewise pass readily into imido-chlorides, e.g. CHj.CCl=N.C2H5, ethyl acet-imido chloride. The chlorine in these compounds is very active, chemically; it can be exchanged for sulphur or for an ammonia (amine-) residue by the action of sulphuretted hydrogen, ammonia, or amine, with the formation of thiamides and amidines, thus- THIAMIDES, ETC. 199 CH3.CCI2.NHR + HjS = CH3.CS.NHR + 2HC1. CH3.CCI : NR + NH3 = CH3.0(NH2) : NR, etc. Most of the amido- and imido-chlorides known, (0. Wallacli, 1875), contain aromatic radicles, e.g, C5H5, phenyl, and the same remark also applies to the following classes of compounds. G. Thiamid.es and Imido-tMo-ethers. Thiamides are compounds derived from the amides by the exchange of oxygen for sulphur, e.g. CHg.CS.NHj, aceto- thiamide or thiacetamide,* CHg.CS.NHCgHj, thiacetanilide. They are mostly crystalline compounds, and result from the addition of HgS to the nitriles, (Cahours), e.g. : CH3.CN + HjS = CH3.CS.NH2; by treating acid amides with P2S5J from the amido- etc. chlorides, as given above ; and by the action of HgS or CSj upon the amidines. Both simple and alkylated thiamides are known. The thiamides, R — CS.NHj, break up upon heating into nitrile and sulphuretted hydrogen,'(see p. 117). They are all easily saponified by alkalies, etc., with formation of the corre- sponding acid, ammonia (amine) and HgS, thus : R— CS.NHR + 2H2O = R— CO.OH + H^S + NHj-R. They are rather more acid in character than the amides, and thus many of them are soluble in alkali and yield metallic derivatives. Consequently for them, as well as for the amides, the formula R — Ca^-h^tt is taken into consideration (see below; also under the cyanogen compounds, Section F). The alkylated thiamides of formic acid also result from the addition of hydrogen sulphide to the iso-nitriles : CN.R + HjS = H— CS.NHR. From such a hypothetical " pseudo-form " of thiacetamide, viz. : CH3— C<^jjg.^ which one may term acetimido-thio-hydrate, or iso-thiacetamide, there are de- rived a number of compounds, the Imido-thio-ethers, by the replacement of the * Ethane-tblon-amide. 200 VII. ACID DERIVATIVES. sulphydril, and also of the imido-, hydrogen by an alcohol radicle, e.g. acetimido-thio-ethyl, CHj — C^S;^ '; methyl iso-thio-acetanilide, CH3 — O^Sf p -A . They are decomposed by hydrochloric acid into ethers of thiaoetic acid, thus : CH3— C(NH).S.0H3 + H2O = CHj— CO.SCH3 + NH3. These imido-thio-ethers are prepared by the action of mercaptans upon nitriles in presence of hydrochloric acid gas (Pinner), and by the action of alkyl iodides upon thiamides ( WcUlach, Bemthaen) : ^•^lo'-'';-Jrm, C2H4CI2, etc. The ether-alcohols which result from the action of halogen hydride may also be regarded as mono-substitution products of the monatomic alcohols, which cannot be prepared directly, e.g. CaH^CllOH), monochlor-ethyl alcohol. Similarly the neutral halogen hydride ethers, C2H4CI2, CaH^Brj, etc., are nothing else than the di-substitution products of the paraffins. 4. The chlor-, brom-, and iodhydrins, as the chlorides, etc. of the monatomic alcohols, constitute the bridge for the preparation of most of the other glycol derivatives ; thus they yield thio-glycols with potassium hydrosulphide, glycollic amines with ammonia, glycollic sulphonic acids with bisulphite of soda, etc. 206 VIII. POLYATOMIC ALCOHOLS. 5. By the splitting off of HCl from ethylene chloihydrin by means of alkali, there is formed an anhydride of glycol, OH,, ethylene oxide, | '^O, (see p. 208), homologues of which CH/ have also been prepared. 6. The glycols frequently yield aldehydes or ketones by giving up water, for instance, ethylene glycol is converted into aldehyde by warming with chloride of zinc, or with water to 230°. This reaction is explained by assuming the intermediate formation of unsaturated alcohols which are not in themselves capable of existence, e.g. CH2=CH(0H), but which immediately undergo transformation into the isomeric aldehydes or ketones. 7. i* or the oxidation products of glycol, see above, also p. 219. Methylene- and Ethylidene glycols. See Aldehydes. Ethylene s^y col* glycol, C2H^(OH)2, (Wurtz, A. 100, 110). Is prepared from ethylene bromide by means of potassium acetate in alcoholic solution (Demote), or of potassium carbonate in aqueous solution, as given above, (A. 192, 250). For pro- perties, see above. Its formula has been corroborated by the determination of its vapour density. Oxidizing agents tranp form it into glycoUic and oxalic acids. Propylene glycol is known in two isomeric forms, viz. : (a) Tri-methylene glycolt or /3-Propylene glycol, CH2(0H) — CHj — CHjOH, which is prepared from tri-methylene bromide, and is a di-primary glycol; B. Pt. 216°. It is also produced by tlie .''chizomycetes fermentation of glycerine, (B. 14, 2270). (6) a-lTopylene glycol,! CH3— CH(OH)— CH2(0H), can be prepared from propylene bromide in an analogous manner, but is most easily got by distilling glycerine with caustic soda. B. Pt. 188°. Becomes optically ( — ) active on fermentation, i.e. fission fungi convert it into two active modifications ( -1- and — ), the former of which is more readily attacked by fermentation than the latter. Four Butylene glycols, and various Amylene- and Hexylene- glycola, etc., are also known. Among them, the 7-glycol9 (in which both the hydroxyls are in the 7-position, and which therefore contain the group — C(OH) — C — C — C(OH) — ), yield compounds of the furfurane series by the • 1-2-Ethane-diol. 1 1-3-Propane-diol. J l-2-Propane-(Jiol. DERIVATIVES OP THE GLYCOLS. 207 formation of anhydride (B. 22, 2567), and therefore stand in close relation to thiophene and pyrrol. Knacone or Tetramethyl-ethylene glycol {2-S-Dimethyl-2-Z-Butam,e-diol), (CH8)j=C(0H)— C(OH)=(CHs)j. For formation see p. 205. Its hydrate, ( + 6H2O), forms large quadratic tables; in the anyhydroua state it is a crystalline mass melting at 38° and boiling at 172°. When warmed with dilute sulphuric acid it yields plnacoline, CHa — CO — C=(CH8)i (see p. 157). Derivatives of the Glycols. oil Ethyl ethers. Glycol ethyl ether, C2H4<^q q „ and Glycol di-ethyl ether, C2H4(O.C2H5)5, are liquids of pleasant ethereal odour, boiling at about 70° lower than glycol. OH Acid derivatives. GlycoUic acetate, CJii<^Q c H ^'^^ Glycollic dl-acetate, C2H4(O.C2H30)2, are liquids easily soluble in water, which boil at a slightly lower temperature than' glycol. The former is converted by gaseous hydrochloric acid into glycol chlor-acetin, PI C3H4<^^ r H O ^^^''^ ™^y *^° ^® regarded as chlorinated ethyl acetate. Glycol chlorhydrin, C2H4.CI.OH, is obtained by passing hydrochloric acid gas into warm glycol, (B. 16, 1407), or by the direct combination of ethylene and hypochlorous acid. It is a liquid miscible with water, and boiling at 130°, differing in this point from its corresponding alcohol to almost the same extent as ethyl chloride does from alcohol. Glycol hromhydrln, C2H4.Br.OH, and Glycol iodhydrln, C2H4.I.OH, are analogous compounds ; the last named decomposes upon distillation. Sulphuric ethers of glycol, e.g. Glycol-suphuric acid, C2H4<^ gQ -g also exist. The latter is similar to ethyl-sulphuric acid in its behaviour. Grlycollic di-nitrate, C2H4(N03)2, is prepared by acting on glycol with sulphuric and nitric acids : G,li,{OB.), + 2NO2OH = C2H,(O.N02)2 + mfi. It is a yellowish liquid, insoluble in water, which is saponified by alkalies and explodes on being heated. The formation of such nitric ethers is characteristic of the poly- atomic alcohols, (see glycerine, p. 216). By treating ethylene bromide with potassium cyanide, ethylene cyanide, G^SiiGN)^, is obtained. It is crystalline, and goes into succinic acid, 0211^(00211)2, on saponification. 208 VIII. POLYATOMIC ALCOHOLS. whence it may be termed the nitrile of this acid. Nascent hydrogen transforms it into butylene diamine, C4Hg(NHj)2, (see p. 210). Similarly ethylene chlorhydrin is converted by potassium cyanide into the HCN-derivative of glycol, Ethylene cyanhydrin,* CH2(0H)— GHj-CN, which also possesses the properties of an acid nitrile, (see lactic acid). Isomeric with it is ethylidene cyanhydrin, 0H3.CH(0H) — CN, the addition product of hydrocyanic acid with aldehyde, (p. 144). Acetone cyanhydrin, (CH3)2=C(OH) — CN, see p. 155. The anhydride, Ethylene oxide, CjH^O, (Wurtg), is obtained by distilling glycol chlorhydrin with caustic potash solution. It is a mobile liquid of ethereal odour, mixing and gradually combining with water to ethylene glycol. B. Pt. 13-5° ; Sp. Gr. < 1. It also combines with acids to chlorhydrins or mono-ethers of the glycols, this affinity for acids being so strong as to give it a well marked basic character, which is further shown by its precipitating the hydrates of the heavy metals from solutions of their salts. It is isomeric with aldehyde. Ethylene oxide oombmes with glycol to form the Bo-called Poly- glycols, e.g. Dl-ethylene glycol, CaHilOH)— 0-C2H4(0H). Mercaptans and sulphides of the glycol series also exist, e.g. Glycol mercaptan,t 02H4(SH)2, Ethylene mono-thlo-hydrate, CaHi(OH)(SH:), and Di-ethylene di-sulphlde, (02114)282, the last of which forms a sulph-oxide and a sulphone. TMo-dl-glycolUc chloride, S(C2H4C1)2, is an extremely poisonous liquid. Amines of the Diatomic Alcohols. These are derived from glycol by the replacement of one or two hydroxyl groups by amidogen : ^A{nH2 ^2H4{Ni^ Oxy-ethylamine. Ethylene diamine. In the former case monatomic (primary) amines containing oxygen result, compounds which retain at the same time their • 3-FTopanol-iiitrile. i 1-2-Ethane-dithiol. AMINES OF THE GLYCOLS. 209 alcoholic character j in the latter, diatomic (primary) bases free from oxygen, the diamines, which are in every respect analogous to ethylamine. These compounds may also of course be held as being derived from one or two molecules of ammonia by the exchange of H for (CjH^.OH), "oxy-ethyl," or of Hg for {G^B.^), thus : (CA-OH ((C,H,)" Tl^is latter view permits of the prediction of secondary and tertiary bases, e.g. ■ MZ ^"^^^y^ and N,(0,H,)"3 ; and also of quartern ary ammonium bases, of such, among others, as still contain monatomic alcohol radicles, e.g. : ((CH3)3 N<^(C„H^.OH), Choline. Such bases actually exist, and show, according to their con- stitution, the behaviour of primary, secondary, etc., amines or ammonium bases. Ethylene diamine, for instance, can react not only with ethylene bromide, but also with the halogen compounds of the monatomic alcohol radicles. The bases containing oxygen, such as oxy-ethylamine, etc., are termed Ozy-alkyl-bases or Hydramines, and, by Ladetibv/rg, Alkines (B. 22, 2583); the carbinol-group, ^C(OH), he designates here "Alkine," and (e.g.) the compound NtCHs)^— CHj— CH2(0H), « trimethyline-alkyl." If two hydrogen atoms in a molecule of ammonia are replaced by a divalent alcohol radicle, "Imines" result, e.g. pentamethylene-imine, (CsHio)"NH (see Piperidine). Their Modes of formation are likewise for the most part analogous to those of the monatomic alcohol bases, viz.: (1) By heating ethylene bromide, etc., with alcoholic ammonia to 100° (Hofmwnn). ' C2HiBr2 + 2NH, = CjH4(NHs)j + 2 HBr; CjH4{NH2)2 + CsHiBrj = (C2H4)sNsHj+2HBr, (606) 210 VIIL POLYATOMIC ALCOHOLS. The primary, secondary and tertiary bases, which are formed simultaneously, can be separated by fractional dis- tillation. The oxy-alkyl bases are obtained in an analogous manner by using ethylene chlorhydrin, thus : C2H,(0H)C1 + NHg = C2H^(OH)(NH2) + HCl. In this case also primary, secondary and tertiary bases are produced at the same time, and are separated by the fractional crystallization either of their HCI salts or of their double platinum chlorides. Ethylene chlorhydrin yields choline hydrochlorate with tri- methylamine. (2) Primary diamines result from the reduction of the nitriles, OnH2i,(ON)2, which is best effected by metallic sodium in the hot alcoholic solution : C2H4(CN)2+4H2 = C2Hi(CHj.NHj)j, = C4H8(NHj), Ethylene cyanide. Butylene diamine. (3) Hydramines ensue by the direct combination of ammonia with 1, 2, or 3 molecules of ethylene oxide ( Wurtz), thus: CzH^O + NHs = C2H4(OH)(NHs). Ethylene oxide, tri-methylamine and water combine to choline: CjH40 + H20 + N(CH8)3 = C2H4(OH)[N(CH3)3.0H]. Ethylene diamine, CaHifNHaji, Di-ethylene diamine, (CjHijjNsHs, etc., are colourless liquids distilling without decomposition. The former boils at 123°, and has an ammoniacal odour; the latter melts at 104° and boUs at 146°, and is identical with piperazine, i.e. hexahydro-pyrazine. Hence it possesses the constitutional formula OsHi^^'-j^-rrJ^CaHi, and has a ring- shaped atomic linking (Hofrrmrm, B. 23, 3297). Tri-methylene diamine, C3H6(]SrH2)2 (see B. 17, 1789). By the loss of NHs, it yields Trimethylene-imine (Propane-imine), CsH8=NH, a liquid resembling piperidine (B. 23, 2727). Tetramethylene-diamine (X-^^Sutame-dicMnine), putrescine, hutylene- diamine, CH2(NH2) — CH2 — CHj — CH2(NH2), is prepared according to method 2, and also results {e.g.) from the putrefaction of flesh. As a "7-diamine," i.e. the diamine of a 7-glycol (p. 208), it is nearly related to pyrrol, from which it is formed by the action of hydroxylamine (whereby a dioxime is first produced), and subsequent reduction (B. 22, 1968). Penta-methylene diamine, eadaverine, C6Hio(NH2)2, = GH2(NH2)— (0H2)a— CH2(NH2), is formed by the reduction of tri-methyl- ene cyanide, ON — (CH2)s — ON, which on its part is prepa)red from tri- methylene bromide, CH2Br — CH2 — CH2Br, and KCN (Ladenhurg). It is a colourless syrupy liquid of very pronounced spermaceti and piperidine odour, which solidifies in the cold, and boils at 178°-179°. It possesses CHOLINE; NEURINK 211 especial interest, because, being a S-diamine, it gives up ammonia and yields piperidine, C5H11N, synthetically. Oxy - ethylamiue (1-2-Ethanol- amine) and the other hydramines are colourless bases which decompose on distillation (c£. Knorr, B. 22, 2081). Bromo-ethylamine, CHjBr — CHj.NHj, is the brorahydrin corresponding to the "alcohol" oxy-ethylamine. It is of use for synthetic reactions (B. 21, 566; 22, 1139). For S-ohloro butylamine and e-chloro-amylamine, see B. 24, 3231; 25, 415. Choline, bilineurine, ethylol-trimethyl- ammonium hydroxide, N(CH3)3.(0,H,.OH)(OH) or C,H,.CO.OH CH2.OH CO. OH Glycol. \ Oxalic acid \ CH2.OH CHj.OH CHO y^ ^CHO > CO. OH > CO. OH Glycollio aldehyde. GlycoUio acid. Glyoxalic acid. Possible products : diatomic aldehydes, dibasic acids, alcohol- aldehydes, alcohol-acids, aldehyde-acids. (i) Of the diatomic primary -secondary alcohols. CH3 CH.OH CHj,.OH- CH3 rCO CHj.OH Acetone-alcohol. CH. ^00 CHO Methyl-glyoxal. CHs -> CH.OH CO. OH Lactic acid. in o Pyro-racemie acid. -°.2 a-Propylene ^^CH.OH — glyooL CHO (Lactic aldehyde, unknown). Possible products : aldehyde-alcohols, aldehydes, alcohol-acids, ketone-acids. (c) Of the diatomic dl-seoondary alcohols: ketone-alcohols, di-ketones, (No dibasic acids or alcohol-acids, Cn.) e.g. : — ketone-alcohols, ketone- IX. POLYATOMIC MONOBASIC ACIDS. 221 CH:i— CH.OH I CHa— CH.OH CHs— CO CH,— CH.OH CHs— CO CHj— CO Di-secondary butylene glycol. Dimethyl-ketoL Di-acetyL {d) Of the other diatomic alcohols : easy to tabulate. (e) The tri- and polybasic alcohols are capable of yielding the most various products upon oxidation, especially polyatomic ketone - alcohols, alcohol-acids, ketone-aoids, and polybasic acids. We have now, therefore, to consider the aldehyde-alcohols, ketone- alcohols, polyatomic aldehydes and ketones, monobasic alcohol-acids, alde- hyde-acids and ketonic acids, and polybasic acids. The most important among these compounds are the alcohol-acids, the polybasic acids, and the ketonic acids. Tor the sake of convenience the polyatomic monobasic acids wiU be treated of first. IX. POLYATOMIC MONOBASIC ACIDS AND COMPOUNDS RELATED TO THEM. A. Diatomic Monobasic Acids. Summary. GlycoUic acid, Oxy-propionio acids, CaHiCOHXCOaH) Oxy-butyrio acids, C3He(0H) (CO^H) Oxy -valeric acids, C,H8(0H)(C0sH) Oxy-caproic acids, CjHi„(0H)(C0jH) etc. The diatomic alcohol-acids or diatomic monobasic acids are compounds which unite in themselves the characteristics of an alcohol and of an acid, and are consequently capable of forming derivatives as alcohols, as acids, and as both together. These derivatives are in part easily saponifiable, and corre- spond therefore with the acid derivatives, i.e. the compound ethers, chlorides and amides ; in part they are relatively stable as regards saponifying agents, and therefore correspond with the alcoholic derivatives, i.e. the ethers, amine bases, etc., (see table, p. 226). 222 IX- POLYATOMIC MONOBASIC ACIDS. The lowest members of the series of diatomic monobasic acids, which are at the same time the most important, are glycoUic acid and lactic acid, both syrupy liquids which solidify to crystalline masses in the exsiccator, and easily give up water to form anhydride. They cannot be volatilized without decomposition. They are readily soluble in water, and for the most part also in alcohol and ether. They are termed diatomic, because they may result from the oxidation of the diatomic alcohols, and contain in accord- ance with theory two hydroxyls. As acids they are mono- basic. They are also frequently called oxy-fatty acids, on account of their being derived from the fatty acids by the exchange of one hydrogen atom for hydroxyl, in the same way as the alcohols are derived from the hydrocarbons : CH3 — COjH, acetic acid ; CH2(0H) — COjH, oxy-acetic acid. We may also regard them as carboxylic acids of the mona- tomic alcohols, e.g. lactic acid, C2H^(OH).C02H, is ethyl alcohol-carboxylic acid. Formation. 1. By the regulated oxidation of the glycols, (see Summary, p. 220). 2. From the fatty acids, through their mono-haloid substitu- tion products, the halogen of these being easily replaced by hydroxyl, either by means of moist oxide of silver or often by prolonged boiling with water alone : CHjCI.COsH-hH^O = CH2(OH).C02H-i-HCl. This reaction is conditioned by the halogen having the a-position with respect to the hydroxyl (of. p. 184). i'or a reaction of these haloid-substitution products in a different direction, see /3- and y-oxyacids. 3. From the aldehydes and ketones containing one atom of carbon less, by the preparation of their hydrocyanic acid com- pounds, (see pp. 144 and 155), and saponification of the latter. Thus, from aldehyde is produced ethylidene cyanhydrin, and from this lactic acid : CH3.0H(OH)(CN)-i-2H20 = CH3.CH(OH).C02H + NH3. DIATOMIC MONOBASIC ACIDS. 223 Since the aldehydes and ketones are easily got from the correspond- ing alcohols, this reaction furnishes a means of preparing the acids, CnH2n(0H) (OOjH), from the alcohols, OnHan+iCOH), i.e., of introducing carboxyl into the latter in place of hydrogen; this is a very important synthesis. 4. From the glycoUic cyanhydrins by saponification, e.g. ethylene lactic acid from ethylene cyanhydrin : CH5(0H)— CH2.CN + 2H2O - CH2(0H)— CH2— CO2H + NH3. The cyanhydrins being easily obtained from the glycols, this formation of oxy-acids represents an exchange of a hydroxyl of the glycol for carboxyl, and is analogous to the formation of acetic acid from methyl alcohol. 5. By the reduction of aldehyde-acids or ketonic acids, e.g. lactic from pyroracemic acid (p. 229). This reaction corresponds with the formation of the alcohols from the aldehydes or ketones by reduction. 6. By the action of nitrous acid (NaOj) upon amido-acids (see Glycocoll); a reaction analogous to the formation of alcohols from amines, 7. Oxy-acids of the fatty series containing an equal number of carbon atoms result by direct oxidation, if a CH-group, i.e. a " tertiary " hydrogen atom, is present in the original acid : ■ (CHs)2=CH-C02H-fO = (CH8)a=C(0H)-C0jH Isobutyric acid. a-Oxy-isobutyric acid. Constitution and Isomers. As oxy-compounds of the fatty acids, the acids of the foregoing series can exist in as many modifications as there are possible mono-haloid substitution products of the fatty acids. Thus there is only one glycoUic acid, corresponding to mono-chloracetic acid, but two lactic acids — corresponding to a- and yS-chloro-propionic acids — are possible, and both actually exist ; they are designated as a- and ^-oxy-propionic acids : CH3— CHOI— COjH CH3— CH(OH)— CO2H a-Chloro-propionic acid. a-Oxy-propionic acid or common lactic acid. CH2I— CHg— COjH CH2(0H)— CH2-C0.,H yS-Iodo-propionic acid. ;8-Oxy-propionic acid or ethylene lactic acid. From the two butyric acids can be theoretically derived : (a) From the norma} acid : CHs— CHj— CHj— CO3H, 7 P an 0-, P; and -y-oxy-butyrio acid ; 224 IX. POLYATOMIC MONOBASIC ACIDS. (6) From iso-butyric acid : an a- and ;8-oxy-isobutyric acid. The constitution of these oxy-acids is often apparent from their formation alone. Thus the preparation of common lactic acid from aldehyde, CHg — CHO, according to method 3, shows that it contains the group CHg — CH=:, "ethylidene" j it is therefore termed " ethylidene lactic acid." On the other hand the formation of ^-oxy-propionic acid from glycol, i.e. glycol cyanhydrin, according to 4, is a proof of its containing the group — CHg — CHg — , "ethylene"; hence the name "ethylene lactic acid." The behaviour of the oxy-aoids usually explains their constitution also ; if they can be oxidized, for instance, to dibasic acids (which con- tain two carboxyls), then they must contain a primary alcohol group, — CH2.OH, since only such a group yields a new carboxyl on oxidation. Ethylene lactic acid is therefore a "primary" alcohol-acid. Its isomer, ethylidene lactic acid, is similarly a "secondary" alcohol-acid, while o-oxy-isobutyrio acid is a "tertiary" alcohol-acid, i.e. acid and tertiary alcohol at the same time. Behaviour. 1. The double chemical character of the oxy- acids will be gone into more particularly under glycoUic acid. As acids they form salts, compound ethers and amides; as alcohols they yield ethers, amines, etc. Among those deriva- tives the alcoholic amines of the acids, the so-called amido- acids, are of especial interest. (See GlycocoU, p. 227). 2. The oxy-acids form different kinds of anhydrides, viz.: — (a) as alcohols, (see di-glycoUic acid); (6) one molecule as alcohol forms with a second molecule as acid, a compound ether, with separation of HgO, (see glycoUic anhydride) ; (c) such a formation of ether as this proceeds a second time, (see glycolide) ; (d) one molecule loses HjO, with formation of an " intra-molecular " anhydride, a so-called lactone, (see p. 233). 3. For behaviour upon oxidation, see p. 220, and also the individual compounds. 4. Just as the alcohols go into defines with separation of water, so GLYCOLLIC ACID. 225 can many of the oxy-acids, especially the ;8-, be transformed into unsaturated monobasic acids. (See hydraorylic acid, p. 232). 5. Halogens oxidize and do not substitute. 6. Warming with HI gives rise to the corresponding fatty acids, just as the alcohols are converted by this reagent into hydrocarbons. 7. When the o-oxy-acids are warmed with dilute sulphuric acid, formic acid is separated and the aldehyde or ketone which would give rise to the acid, according to method 3, is reproduced. The /S-oxy-aoids on the other hand break up in this way, and also when heated alone, into water and acids of the acrylic series. The a-, ;8-, 7-, etc. oxy-acids also differ from each other in the facility with which they form anhydrides. (See Lactones. ) GlycoUic acid {EthanoUc acid), CH2(0H)— CO.OH {Streaker, 1848). Occurrence. In unripe grapes, in leaves of the wild vine, etc. Formation. (See also p. 222.) 1. By the oxidation of glycol with dilute HNO3 {Wurtz). 2. Together with glyoxal and glyoxalic acid, by the oxida- tion of alcohol with dilute HNO3. Further, by the oxidation of glucoses by AggO (A. 205, 193). 3. By the reduction of oxalic acid with Zn H- HgSO^. 4. From formic aldehyde synthetically, according to method 3, p. 222. 5. Preparation from mono-chloracetic acid, according to p. 222; best when boiled with marble (A. 200, 76). Properties. Colourless needles or plates, stable in the air, and easily soluble in water, alcohol, and ether. M. Pt., 80°. Nitric acid oxidizes it to oxalic acid. The alkaline salts are hygroscopic, the calcium salt and the magnificent blue copper salt sparingly soluble in water. Derivatives. (See table, p. 226.) As an acid, glycoUic acid forms salts, compound ethers, — e.g. glycoUic ethyl ether, — a chloride, glycoUyl chloride, and glycoUamide, all of which are readily saponified, some of them even on warming with water. All those derivatives still retain their alcoholic character. If, on the other hand, glycoUic acid forms derivatives as an alcohol, the properties of the alcoholic derivatives in question are combined with those of an acid, since the hydroxyl of the ^606} ? 226 IX. POLYATOMIC MONOBASIC ACIDS. alcoholic group, — CHg-OH, enters into reaction, while the car- boxyl group remains unchanged. These derivatives are either ethers, such as ethyl-glycoUic acid (see table), or e.g. amines, such as glycocoU, and, as alcoholic derivatives, they are not saponifiable ; or they are compound ethers of glycoUic acid as alcohol, e.g. acetyl-glycoUic acid, CH2(O.C2H30) — COjH, or mono-chloracetic acid, CHj.Cl — COjH (the hydro- chloric ether of glycoUic acid), and then they are of course saponifiable. These latter compounds still retain their acid character and therefore form, on their part, compound ethers, chlorides and amides, which are readily broken up backwards ^ by saponification. The following table gives a summary of the more important derivatives of glycoUic acid. Acid Derivatives. Alcoholic Derivatives. Mixed Derivatives. CHalOH)— CO.ONa Sodium glycoUate. CHj(ONa)— CO.ONa Di-sodium glycollate. Hygroscopic ; decomp. by HoO into Na salt and NiOH. CHjIOHl-CO.OCaHj Ethyl glycollate. Liquid, B. Pt. 160°. CH2(OC5H5)-CO.OH Ethyl-glycoUic acid. Liquid, B. Pt. 206°. CHj(0CjH;)-C0(0C2Hb) Ethylic ethyl-glycoUate. Liquid, B. Pt. 152°. CHjlOH)— CO.Cl GlycoUyl chloride. Oil ; deeomposes on volatilizing. CHjCl— CO.OH Mono-chloracetic acid. CHjCl-COCl Mono-chlor-acetyl chloride. Liquid, B. Pt. 120°, of suffocating odour. CHalOH)— CO.NHj Glycol] amide. Crys. M.Pt. 120°; does not form salts with bases. CH2(NH2)-CO.OH GlycocoU. Crys. M. Pt. 236°. Forms salts with acids and bases. CH2(NH2)--CO(NH3) Glycocollamide. Ciys. To the compounds of the second vertical row belong also, among others,Thio-glycollic acid {l-Ethane-thiol-2-Acid), CHjISH) — CO.OH, which ia at the same time an acid and a mercaptan; to those of the third row belong mixed compounds such as CHjINHj) — CO(OC2H6) (see Glyoocoll). It is easy to see that the corresponding derivatives of the first and second vertical rows are always isomeric. GLYCOCOLL. 227 Anhydrides of GlycoUic acid. 1. Di-glycoUic acid, CiHjOj, — 0(CH2 — CO.OH)^, is an alooholio anhydride and a dibasic acid. It is obtained e.g. by boiling mono-chloraoetic acid with lime. Large rhombic prisms. Being an alcoholic ether, it is not saponified on boiling with alkalies, but on heating with concentrated hydrochloric acid to 120°. As a dibasic acid it yields : 2. Di-glycoUic anhydride, CiHiOi, - 0(CHi— 00)20. 3. GlycoUic anhydride, CiHeOs, = CHjiOH)— CO.OtCHj— OO.OH), is a compound ether- anhydride, which is formed upon heating gly collie acid to 100°. It becomes hydrated again when boiled with water. CHj— 0-CO 4. Glycolide, C4H40i,= | | is an ether-acid anhydride iso- 00 0— CH2, meric with 2 (and with fumaric acid), which results upon distilling bromo- aoetate of sodium in a vacuum. Lustrous plates; M. Pt. 87°. It becomes hydrated again upon boiling with water, Glycocoll (Amino-ethanoic acid), glycodne, amido- acetic acid, CH2(NH2)— CO.OH {Braconnot, 1820). This is the simplest representative of the important class of "amino- (or amido-) acids,'' so called because they are derived from the fatty acids by the exchange of a hydrogen atom of the hydrocarbon radicle for amidogen, e.g. CHg.COgH, acetic acid; CH2(NH2).C02H, amido- acetic acid. Its methods of formation include those of the other amido-acids. Formation. 1. By the action of concentrated ammonia upon monochlor-acetic acid {Heintz, A. 122, 261; Kraut, A. 266, 292): CH2CI— C02H-)-2NH3 = CH2(NH2)— COaH + NH^Cl (cf. also B. 23, Ref. 654). Di- and Tri-glycollamic acids, NH(CH2— C02H)2 and N(0H2— C02H)3, are produced at the same time. a-Chloropropionic acid in like manner yields alanine with ammonia (see Lactic acid), and so on. 2. By boiling glue with alkalies or acids. 3. Together with benzoic acid by decomposing hippurio acid, i.e. benzoyl-glycocoll, by HCl: CH2[NH(CO O(iH5)]-C02H + H^O = CHslNHjjCOjH-HCeHjOO.OH. Hippurio acid. Benzoic acid. 4. Together with cholio acid, by the analogous decomposition of glyco- cholio acid, 026H4sNOe. 5. From cyano-carbonic ether, ON — CO.OC2H5, and nascent hydrogen, or from cyanogen and hydriodic acid : ON— CN-t-2F2-f2H20 = CH2(NH2)— CO.OH -f NHj. 6. By the reduction of isonitroso-fatty acids (p. 185). 228 IX. POLYATOMIC MONOBASIC ACIDS. 7. (Of the homologues of glycocoU): By treating ethylidene-cyanhydrin (p. 144), etc. with alcoholic ammonia, or aldehyde-ammonias with hydro- cyanic acid, amido-oyanides are formed, e.g. CHs — CH(NH2)(CN), which are saponified to amido-acids upon boiling with HCL Properties. GlycocoU forms large colourless rhombic prisms, easily soluble in water, but insoluble in absolute alcohol and ether. It has a sweet taste, hence the name "gelatine sugar" or glycocoU {yXvKis, sweet, niWa, glue). It melts at 236°, with much decomposition. Behaviour. GlycocoU, like all the amido-acids, unites in itself the properties of a base (being, as an alcoholic amine, non-saponifiable) and those of an acid. It therefore forms salts with acids as well as with bases, e.g. glycocoU hydrochlorate, CjHjNOj.HCl, which crystallizes in prisms, and the character- istic copper salt, glycocoU copper, (G2H^N02)2Cu + HjO, which crystallizes in blue needles, the latter being obtained by dissolving copper oxide in a solution of glycocoU. Most of the other amido-acids also form characteristic copper salts of this nature, which serve for their separation. GlycocoU also yields compounds with salts, and, as an acid, forms an ethyl ether, an amide, etc. (see table, p. 226). Heated with BaO, it is decomposed into methylamine and COg, while NjOg converts it into glycoUic acid (the normal reaction of the primary amines). Ferric chloride produces with it an intense red, and copper salts a deep blue colouration. Glyoocol ethyl ether yields with NjOs the interesting Diazo-acetic ether, CNaH — CO.OC2H5, from which, by a complicated reaction, hydrazine, NH2 — NHj, and its hydrate were first prepared; and, from the latter, the remarkable compound, Hydrazoio acid, NsH (Curtius J. pr. Ch. (2) 88, 396, 472; 43, 207; B. 24, 3341). See also under Amido-guanidine. Constitution (see B. 16, 2650). Free glycocoU may be regarded as an intramolecular salt, corresponding to the formula CHj's^pQ ?-v^ (see Betaine). Alkyl derivatives of GlycocoU: Methyl-glyooooll Tri-methyl-glycocoll Aoetyl-glycoeoU or Sarcosine, or Betaine, or Aceturic acid, CH2-NH(CHa) CHj-NlCHs),^ CH^— NH(CaHaO) CO.OH CO.O y" CO.OH. (a decomposition (contained in beetroot etc. product of creatine and related to and caffeine). choline). The above have all been prepared synthetically. LACTIC ACIDS. 229 Lactic acids, OgHsOg, = C2H4(OH)(C02H). {Wislkenus, A, 128, 1; 166, 3; 167, 302, 346.) As has been already men- tioned at p. 223, two isomeric lactic acids are theoretically possible, viz., a- and |S-oxy-propionic acids, or ethylidene- and ethylene-lactic acids, and both of these are known. The minute investigation of the different lactic acids has been of very great importance for the development of chemical theory ; they were formerly held to be dibasic, and the recognition of their diatomic monobasic nature has materially contributed to the acceptation of the theory of the linking of atoms. According to the theory of Le Bel and van 't Hoff (p. 40), two stereo- isomeric modifications of ethylidene-lactic acid are possible, seeing that it contains an asymmetric carbon atom, viz. a laevo- (1-) and a dextro- (d-) rotatory form; and, by mixing these together, a third optically inactive (i-) acid is produced. The two last have long been known, but the laevo- acid has only been discovered recently, the theory thereby receiving further confirmation. Modes of Formation. Fermentation lactic acid 1. By the regulated "» oxidation of J 2. By the exchange"! of halogen for >- hydroxyl from J 3. By saponification"! of • / 4. By action of NjOa^ upon / 5. By. the reduction "\ of / d-Propylene glycol, CH3-CH(0H)-CH2(0H a-Chloro-propionio acid, CHs— CHCl— CO.OH. Aldehyde-cyanhydrin, CHj— CH(OH)^CN. Alanine, CH3-CH(NH2)-CO.OH. Pyro-racemic acid, CH,— CO— CO. OH. 6. By the lactic fermentation of sugar, etc. Ethylene-lactic acid. ^-Propylene glycol, 0H2(OH)-CH2-CH2(OH) S-Iodo-propionic acid, — CO.OH. Ethylene-cyanhydrin, CHjCOH)— CHj— CN. 1. i-Ethylidene-lactic acid (2-Propanolic acid), ordinary fer- mentaiim lactic acid, CHg— CH.(OH)— CO2H. Discovered by Scheele, and recognized as oxy-propionic acid by Kolbe. Occurs in opium, sauerkraut, and in the gastric juice. 230 IX. POLYATOMIC MONOBASIC ACIDS. Preparation. This depends upon the so-called lactic fermen- tation of sugars, e.g. milk, cane and grape sugars, and of substances related to them, such as gum and starch; it is in- duced by the lactic bacillus [which forms small rods (£ujppe)]. The fermentation proceeds best at a temperature of 34°-35°, in a nearly neutral solution, this last condition being attained by the. addition of chalk or zinc white to the fermenting mixture. The free acid can then be liberated from the lactate of zinc by sulphuretted hydrogen. When a non-homogeneous ferment (e.g. cheese) is used, the lactic acid at first produced is trans- formed by other organisms into butyric acid (p. 174). Lactic acid is also produced in large quantity by heating grape or cane sugar with caustic potash solution of a certain degree of concentration (B. 15, 136). The relations of lactic acid to the sugar varieties appear at a superficial glance to be very simple; thus grape sugar, CgHijOj, and lactic acid, CgHgOj, are polymers. Lastly, the inactive aoid ia produced by mixing equal quantities of the two active modifications. In syntheses the latter are formed in equal amounts, and hence the inactive acid is obtained. Properties. The acid has not been obtained free from water. When its solution is evaporated in an exsiccator, a thick, non- crystallizing and hygroscopic syrup is got, which is miscible with water, alcohol and ether, and which gradually gives up water, with the formation of (solid) lactic anhydride, CgHijOj, before all the water of solution has been got rid of. When heated, it partly goes into the anhydride, lactide, CgHgO^, and partly breaks up into aldehyde, CO, and HjO. Similarly it decomposes into aldehyde and formic acid upon heating with dilute sulphuric acid to 130°, concentrated sulphuric giving rise to carbon monoxide instead of formic acid : CH3— CH(0H)-C02H = CH3-CHO + HCO2H. Upon oxidation it yields acetic and carbonic acids; hydro- bromic acid converts it into a-bromo-propionic acid, and boiling with hydriodic acid into propionic acid itself. The inactive aoid is split up into the two active modifications by the crystallization of the strychnine salts; further, when the fungus penicillium DERIVATIVES OF LACTIC ACID. 231 glaucum is sown in a solution of the inactive acid, the laevo- acid is assimi- lated more rapidly than the dextro-, and the solution thus becomes dextro- rotatory (of. p. 39). Calcinm lactate, (OaHsOsjaCa + SHjO : warty masses of microscopic rhombic needles. Zinc lactate, (CaHjOsjaZn + 3HjO : glancing needles. Ferrous lactate, (CsHsOaJz+SHjO: bright yellow needles; both the ferrous and zinc salts are used in medicine. When sodium lactate is heated with sodium, Si-sodium lactate, CH3 — CH(ONa) — COjNa, which is at the same time a salt and an alcoholate, is formed. The Derivatives of lactic acid are derivatives of it either as acid or as alcohol, and are perfectly analogous to those of glycollic acid (see table, p. 226). Thus Ethyl-lactic acid, CH3— OH(OC2H5)— CO2H, a thick acid liquid which boils almost without decomposition,* corresponds to ethyl-glycollic acid; Ethyl lactate, which can be distilled without decomposi- tion, to ethyl glycoUate; Lactamide, CHg— CH(OH)— CO.NHg to glycollamide, and Alanine, CHj— CH(NH2)— CO.OH, to glycocoll. Alanine results from the action of hydrocyanic acid upon aldehyde-ammonia (see p. 228), and forms hard needles of a sweetish taste. By the action of PClj, lactyl chloride, CH3— CHCl— CO.Cl (p. 192) is formed; as the chloride of a-chloro-propionic acid it yields the latter acid and HCl with water. The acid just named is therefore to be regarded as the hydrochloric ether of lactic acid. The following anhydrides of lactic acid are known : 1. Lactylic acid or Lactic anhydride, CuHmOs, which is analogous to glycoUio anhydride, and forms a yellow amorphous mass; 2. Laetide, C6H8O4, analogous to glycolide (tables, M. Pt.-125°); 3. Di-laetic acid, CsHioOs, the alcoholic anhydride, analogous to di-glycollic acid. 2. d-Ethylidene-lactic-acid, Sarco-lactic acid, para-ladic acid, CH3— CH(OH)— CO2H {LieUg). This occurs in the juice of flesh, and is therefore to be found in Liebig's extract of meat. It results from certain fermentations. In its chemical pro- perties it is almost identical with ordinary lactic acid; for in- stance, it possesses an equal facility in forming laetide or * By the entrance of the ethylio group, the hydroxyl is in a certain degree paralysed as regards its action, in consequence of which ethyl-lactic acid resembles propionic acid much more nearly than lactic acid itself does. 232 IX. POLYATOMIC MONOBASIC ACIDS. aldehyde. Its salts differ to some extent, however, from those of the latter; thus, the zinc salt: + 2H2O, is much more easily soluble, and the calcium salt: +4H2O, much more difficultly soluble than the corresponding common lactates. 3. 1-Ethylidene-lactic acid is obtained from the fermenta- tion of cane sugar by means of the l-ladic bacillus (Monatsh. f. Chem. 11, 551). 4. Ethylene-lactic acid {Z-Propanolic acid), hydracrylic acid, 0H2(0H)— CH2— CO.OH {Wislicenus, A. 128, 1), forms a syrupy mass. It differs from lactic acid : (a) By its behaviour upon oxidation, yielding carbonic and oxalic acids, and not acetic; (6) By not yielding an anhydride when heated, but by breaking up into water and acrylic acid, hence the name hydracrylic acid : CH2(0H)— CH2— COOH = CH2=CH— COOH + H2O; (c) In solubility, and in the amount of water of crystallization of its salts (e.g. zinc salt: -l-iHaO, very easily soluble in water; calcium salt : + 2H2O). Oxy-ftutyrlo acids, (see p. 223). ^-Oxy-Dutyrlo acid, CH3— CH(OH)— CHj— CO2H, a syrup, is related to aldol and aceto-acetic acid. An optically active ( — ) modification is contained in diabetic urine and blood. 7-Oxy-Dutyric acid, CH2(0H)— CHj— CHj— CO2H, is only capable of existence in its salts and not in the free state, as it bi-eaks up into water and its lactone, butyro-lactone. o-Oxy-isobutyric acid, (CH3)2=C(OH)— COjH, ( WuHz), results from acetone cyanhydrin (p. 155), and is therefore also called aoetonic acid. Amido-butyrlc acids are known, e.g. Piperic acid, C5H5(NH2)(C02H). Oxy-valeric acids. Several amldo-valerlc acids have been prepared synthetically, while others have been obtained by the decomposition of albumen and of conine and piperidine derivatives, and have also been found in the pancreas of the ox. Oxy-caproio acids. Leucine or o-Amido-caproic acid, CH3— CH2— CH2— CH2— 0H(NH2)— COgH, is a derivative of a-oxy-caproic or leucic acid (Strecker) ; it forms fatty glancing plates and, like other amido-acids, is nearly related to albumen. It is found in old cheese, also abundantly in the animal organ- ism in the gastric salivary gland, and in the shoots of the vetch and gourd, etc. It forms, along with tyrosine, a con- HIGHER OXY-ACIDS; LACTONES. 233 stant product of the digestion of albumen in the small intestine and of the decay of albuminous substances, and results from the latter by boiling them with alkalies or acids. It also appears to have been prepared synthetically. It closely re- sembles glycocoll, and forms a characteristic sparingly soluble blue copper salt. Leucine is dextro-rotatory. A laevo- and an inactive modification are also known (B. 24, 669). Conic acid, CjHisNOa, and Homo-conic acid, CaHuNOj, are higher homologuea of leucine which have been prepared from conine. Ozy-stearic acid, OisHasOa, is obtained by the action of cold concentrated HjSOj on oleic acid — (addition of H2O) — and forms , ' Aoeto-aoetone. When ethyl formate is employed, ketonio aldehydes do not result, but their structural isomers oxy-methylene compounds (p. 239); with acetone, for example, oxy-methylene-acetone, thus : — (606) Q 242 IX. POLYATOMIC MONOBASIC ACIDS. H— CO.OOjHj + CHs— 00— 0H8=CH(0H)=CH— CO— CH, + OaHj.OH. ^ . ' • , ' Ethyl formate. Oxy-methylene-aoetone. 3. Higher homologues of aceto-aoetic ether (/S-ketonio acids) are easily obtained from it by the action of sodium ethylate and halogen-alkylene (p. 245). i. Ketonic acids are produced by the cautious oxidation of secondary alcohol-acids : — OH,— CH(OH)— CO.OH + = CHs— 00— CO.OH + HsO. > . ' * « ' Lactic acid. Pyroraoemio acid. 5. Special modes of formation are given below. Behaviour. (See also above.) 1. While the a- and 7-ketonic acids are stable liquids, some of them even withstanding distillation, the j3-ketonio aoids are exceedingly unstable in the free state, breaking up very readily into the corresponding ketone and carbon dioxide. 2. Bednction converts the ketonic acids into secondary alcohol-acids ; in the case, however, of the 7-ketonic acids, 7-lactoneB are produced instead of alcohol-acids, water being separated. . 3. In the ethers of the ;8-ketonic acids, one hydrogen atom is readily replaceable by a metal; thus, aceto-acetic ether and sodium ethylate yield sodio-aceto-acetic ether, C4H4Na03(C2H5). Its behaviour with halogen-alkyl (see p. 245) shows- that the replaceable hydrogen atom comes from the methylene group, as shown by the formula: CH3— CO— CHNa— CO.OC2H5. This capability of replacement is explained by the acidifying influence exerted by the two oarbonyl groups which are linked directly to the methyl- ene, i.e. the carbonyl of the group CH3 — CO — , and that of the group — CO. OH. [Of. the relation of hydrated carbonic acid, CO(OH)a to (two molecules of) water, 2H(0H).] 4. For the synthesis of the higher ;8-ketonic acids; and 5. For the decomposition of the ;S-ketonic acids, with pro- duction of ketones or of acids, see Aceto-acetic ether. 6. The ketonic aoids show the most varied condensation reactions ; with aniline the ;3-ketonio acids yield quinoline derivatives, and with phenyl hydrazine, derivatives of pyrazole. Pyroraoemic acid, C3H4O3, = CH3 — CO — COjH, is a liquid which is readily soluble in water, alcohol and ether, boils with slight decomposition at 165°-170°, and smells of acetic acid and extract of beef. Formation. 1. By the dry distillation either of tartaric or of racemic acid, hence its name. ACETO-ACETIC ETHER. 243 2. By the oxidation of lactio aoid by means of KMUO4. 3. By saponifying acetyl cyanide with HOI, {Claisen, Shxdwell) ; CH3-CO— CN + 2H2O = OHs-CO-COjH + NH3. Pyroracemic acid has a tendency to polymerize. Its salts crj'stallize only with difficulty. Nascent hydrogen reduces it to ethylidene-lactic acid : OHg— CO— CO2H + H^, = CH3 — CH(OH) — COgH, from which reaction and from mode of formation 3, its constitution follows. It possesses in a marked degree the ketonic property of forming condensation products, going either into derivatives of benzene, (B. 5, 956), or — in presence of ammonia — into those of pyridine. Sulphuric acid causes it to condense with the aromatic hydrocarbons, just as in the case of the ketones, (B. 14, 1595). Cystine, 051112^28204, the disulphide of amido-thio-lactic acid or cysteine, C2H3(NH2)(SH)C02H, is to be regarded as a derivative of pyroracemic acid, (see ethyl di-sulphide). It is found in urinary sediments and gravel, (B. 18, 258). o-Keto-lJUtyrlc sicUL,propionyl-carboxyUc acid, CHj — CHj — CO — CO^H, resembles pyroracemic aoid. Aoeto-acetle slcH, p-keto-butyricacid, CHj — CO — CHg — COgH. A strongly acid liquid, miscible with water, and breaking up into acetone and carbonic acid upon warming. It is prepared by the cautious saponification of its ethyl ether, (B. 15, 1376 ; 1871). Its aqueous solution is coloured violet-red by ferric chloride. The Nar or Ca-salt is sometimes contained in urine, (B. 16, 2314). Aceto-acetic acid may also be looked upon as acetone-carboxylic acid, C3H50(C02H). Aceto-acetic ether, CHg — CO — CH2— CO2C2H5, is obtained in the form of its sodium compound, sodio-aceto-acetic ether, by the action of sodium or sodium ethylate upon ethyl acetate (see above; Geuther, 1863; Frankland and Duppa); 2CH3— CO.OO2H5 -I- NaO.C2H5 = CH3— CO— CHNa— CO.OC2H5-I-2C2H5OH. The ether is obtained from the sodium compound upon the addition of acid. It is a liquid of neutral reaction, boiling at 244 IX. POLYATOMIC MONOBASIC ACIDS. 181°, only slightly soluble in water but easily in alcohol and ether, and of a pleasant fruity odour. Ferric chloride colours its aqueous solution violet-red. It is split up upon being boiled with alkali, dilute aqueous alkali or baryta water (or also dilute sulphuric acid) producing mainly carbon dioxide, acetone and alcohol (" ketonic decomposition ") : CHg— CO— CH2— C02(C2H5) + H2O = CH3— CO— CH3 + CO2 + HO.C2H5; very concentrated alcoholic potash, however, produces chiefly (2 mols.) acetic acid; ("acid decomposition,'' Wislicenus): OH3— CO— CH2 -C02(C2H5) + 2H2O = 2CH3— CO.OH + HO.C2H5. The constitution of aceto-acetic ether follows from its forma- tion and behaviour. Besides the formula: — (I.) CH3— CO— CH2— CO.OC2H5, we have also to take into consideration that of /3-oxy-isocrotonic ether : — \ (II.) CH3— C(OH)=CH— CO.OC2H5. A comparison with ;8-oxy-acrylie ether (p. 240), in which the presence of the oxy-methylene group, — C(OH), has been proved, is a decisive argument in favour of formula I. (see B. 25, 1041, 1176). On the other hand, the sodium compound of aceto- acetic ether comports itself with several reagents as if it were derived from formula II., the "pseudo-form" of the ester, and as if it possessed the constitution CH3 — C(ONa)^ CH — COjOjHj. Unless, therefore, those reactions are to be regarded as abnormal, sodio-aceto-acetic ether must be held to possess both formulae, i.e. to be tautomeric; see Cyanogen com- pounds, section F. One atom of hydrogen in aceto-acetic ether is easily replace- able by metals (Geuther; Conrad, A. 188, 269). The sodium salt results with evolution of hydrogen upon the addition of sodium, and also upon mixing the alcoholic solution of the METHYL-ACETO-ACETIO ETHER. 245 ether with the calculated amount of sodium dissolved in absolute alcohol: C,H,03(02H5) + C2H,.0Na = CANaOgCCA) + G,U,.OTL In agreement with this the ether dissolves in dilute alkali, being again separated from the solution by the addition of acid. Sodio-aceto-acetio ether, CHg— CO— CHNa— CO2C2H5; long needles or a faintly lustrous loose white mass. Copper salt: bright green needles. The metal in sodio-aceto-acetic ether is readily replaced by an alcohol radicle by the action of iodo- or bromo-alkyl, sodium iodide or bromide being formed at the same time. We thus obtain alkylated aceto-acetic ethers, e.g. : Methyl-aceto-acetic ether or Ethylic methyl-aceto-acetate, CHg— CO— CH(CH3)— C02(C2H5), and the corresponding Ethyl- and Propyl-aceto-acetic ethers, etc. In these com- pounds the H may be again replaced by Na, and this again substituted by alkyl, with the production of di-alkylated aceto- acetic ethers, e.g. : Dimethyl-aceto-acetic ether or Ethylic di- methyl-aceto-acetate, CH3-CO-C(CH3)2-C02(C2H5) ; Methyl- ethyl-aceto-acetic ether, CH3-C0-C(0H3)(02H6)-C02(C2H5), and so on. These alkylated aceto-acetic ethers exactly resemble their mother substance, especially in that they undergo either the " ketonic decomposition " or the " acid decomposition," accord- ing to their degree of concentration, upon treatment with alkalies; the latter decomposition also upon treatment with dilute acids, (see above, also A. 190, 275). The first-named decomposition leaves the substituting alcohol radicles in the acetone residue of the molecule, and the last-named in one of the two resulting acid molecules, i.e., there are formed either alkyl-acetones (homologues of acetone), or alkyl-acetic acids (homologues of acetic acid). We have thus at command here a most excellent method for the synthesis of any simple or double alkyl ketone or acid : 246 X. DIBASIC ACIDS. 1. CHg— CO— OER'— CO2C2H5 + H2O = CH3— CO— CHER' + HO.C2H5 + COgj 2. CH3— CO— CRR'— CO2C2H5 + 2H2O = CHg— CO.OH + CHRR'— COjH + HO.C2H5. (RE' = alcohol radicles. Cf. Wislkenus and his pupils, A. 186, 161.) In a perfectly analogous manner we can introduce acid instead of alkyl radicles into aoeto-acetio ether, and thereby give rise . to the most various compounds, eg., from acetyl chloride, di - aceto - acetic ether, (CHs— C0)2CH— OOaiCjHs) ; from chloro-carbonio ether, CI— CO2C2H5 (p. 290), chiefly a mixed carbonic ether, CH3— C(O.C02CzH5)=CH.C02C2H5, derived from the pseudo-form of sodio-aceto-acetic ether (p. 244), but also aceto-malonic ether, (CHa — CO) — CH(C02C2H5)2; from monochlor-acetio ether, CHjCl— C02(CaHj), aeeto-succinio ether, CHs— CO— CH(CH2— C02C2H5)(C02C2H5) (see Malonic and Succinic acids, and also the Synthesis of dibasic acids), etc. Iodine acts upon sodio-aceto-acetic ether to produce di-aceto-Bnccinic ether, which is interesting from its transformations, thus : CHrCO-CHNa^COjCjHs CHs-CO-CH-COjCjHj + Ij= I +2NaI. CHj-OO-CHNa-COjCjH, CHs-CO-CH-C02CaH5 Chlor- and Bichlor-aceto-acetic ethers, which are very active chemi- cally, are produced by the replacement of the H of the methylene group by CI. The two methylene hydrogen atoms are also replaceable by the iso- nitroso group, =N — OH (by the action of NaOj), and by the imido group, =NH (cf. A. 226, 294). Levulinic acid, CjHeOs, = CH,— CO— CHj— CHj— CO2H. Plate crys- tals, M. Pt. 33°, B. Pt. 239°. Eesults from the action of acids upon cane sugar, leevulose, cellulose, gum, starch and other carbo-hydrates (A. 176, 181; 206, 207), and has also been prepared synthetically. For its constitu- tion, cf. A. 256, 314. It is employed in cotton printing, and for the pre- paration of anti-thermine (which see), etc. X. DIBASIC AOIDS. Dibasic acids are those which are capable of forming two series of salts, acid and neutral, with monatomic bases, and likewise two series of ethers, chlorides, amides, etc. The dibasic acids proper are characterized theoretically by the presence of two carboxyls in the molecule. OXALIC ACID SERIES. 247 These acids may either possess the acid character pure and simple, or also at the same time the character of an alcohol, e.g. lactic acid ; in the latter case they still contain alcoholic hydroxyl. A distinction is drawn between diatomic dibasic and tri-, tetra-, etc. atomic dibasic acids. They may be either saturated or unsaturated compounds. Lastly, they may also be at the same time acid and aldehyde, or ketone, etc. The dibasic carbonic acid will be treated of later on (p. 287 et seq.). A. Saturated diatomic dibasic Acids, GJLia-A. Oxalic acid, CgHg 0^ Suberic acid, Cg Hj^O^ Malonic „ CgH^ 0^ Lepargylic, „ Cg HigO^ Succinic „ C4Hg O^ Sebacic „ CioH^gO^ Pyrotartaric „ Gfi^ O4 Brassylic „ C^HaoO^ Adipic „ CfiHioO^ Eocellic „ Oi^H3204 Pimelic „ CJHJ2O4 Dicetyl-malonic „ CgjHggO^ Oxalic acid is to be considered as the isolated group oarboxyl, (CO.OHjj. Its homologues are di-oarboxylic acids of the paraflSns; thus, malonic is methane-di-carboxylic acid, CHjICOaH);,, etc. The above are solid crystalline compounds of strongly acid character, and most of them are readily soluble in water. Upon heating, they either yield an anhydride or carbon di- oxide is given off; but most of them can be volatilized in vacuo. Formation. — 1. By the oxidation of the di-primary glycols. (See table, p. 220.) la. By the oxidation of primary oxy-acids and, generally, of many complex compounds, such as fats, fatty acids and carbo- hydrates. 2. By the saponification of the corresponding nitriles; thus, oxalic acid is formed from cyanogen, and succinic acid from ethylene cyanide : O2N2 + 4H2O = ■ C2O4H2 + 2NH8. CaH^CCN)^ + 4H2O = G^R^iCO^R)^ + 2NH3. Since ethylene cyanide is a glycol derivative, its conversion into succinic acid represents the synthesis from a glycol of an acid contain- ing two atoms of carbon more than itself, i.e. the exchange of 2(0H) for 2(C0jH), or the indirect combination of ethylene with 2C0jH. 248 X. DIBASIC ACIDS. 2% By the saponification of the cyano-fatty acids (p. 185), and consequently of the haloid fatty acids also. Thus chlor- or cyan-acetic yields malonic acid, ;S-iodo- (or cyano-) propionic, common succinic acid, and a-iodo- (or cyano-) propionic, ethy- lidene-succinic acid. A dibasic acid can therefore be formed from each oxy-acid by the exchange of OH for CO2H, or indirectly from a fatty acid by the replacement of H by COjH. 3. The homologues of malonic acid can be prepared from malonic acid itself by a, reaction exactly analogous to the aceto- acetic ether synthesis (the " malonic ether synthesis," p. 253). 3'. The dibasic acids are also obtained by means of the aceto-acetic ether synthesis. Aceto -malonic and aceto - succinic acids, which have already been mentioned at p. 246, yield respectively malonic and succinic acids by the separation of acetyl ("acid decomposition"). 4. Higher homologues are obtainable by the electrolysis of the ester potassium salts (p. 251) of the simpler acids, e.g. adipic acid from the ester potassium salt of succinic : — 2COjCsH5— CHj— CHj— COjK + 2H2O - COaCaHs— (OHj),— CO2C2H5 + 2KHCO3 + Hj. 5. !For further modes of preparation, see under Succinic acid. The Constitution of the acids CnH2u_204 is as a rule very easy to determine from the above-mentioned modes of formation, especially 2 and 3. According to these, one has to decide between the malonic acids proper, i.e. malonic acid and its alkylated derivatives (p. 252), whose two carboxyl groups are both linked to one carbon atom : CH2(C02H)2, E— CH(C02H)2, ER'C(C02H)2, and ordinary succinic acid and its homologues, which contain the carboxyls bound to two different carbon atoms. The divalent acid residues, CjOj = " bxalyl," CjHjOj = " malonyl," and O4H4O2 = " succinyl," which are combined with the two hydroxyls, are termed the radicles of the dibasic acids. Isomers. — Isomers of oxalic and malonic acids are neither theo- retically possible nor actually known. We know, however, two succinic acids, viz., /,tt''~/-i/-» Vvtt ^^^ CHg— OH(CO„H)„. OHj — OU.Uxl The former corresponds to ethylene chloride and the latter to ethylidene chloride, from which they are respectively DIBASIC ACIDS; BEHAVIOUR OF. 249 derived by the exchange of two chlorine atoms for two car- boxyls. Hence the names, ethylene- and ethylidene-succinic acids. Since ethylene cyanide can be prepared from the chloride, the above derivation of ethylene-succinic acid is also an experimental one ; this ia not the case however with the isomeric acid, since, speaking generally, when several chlorine atoms are bound to the same carbon atom, as in ethylidene chloride, they cannot be exchanged for cyanogen. -Those of the dibasic acids whose carboxyls are attached to different carbon atoms yield intra^molecular anhydrides by the separation of a molecule of water. These anhydrides result in part by direct heating, in part by the action of phosphorus pentachloride, acetyl chloride or carbon oxy-chloride upon the acids, (B. 10, 1881 ; 17, 1285). They recombine slowly with water to the hydrates. This formation of anhydride is favoured by the presence of methyl groups in the molecule (B. 23, 101, 620). The " malonic acids," on the other hand, lose COj on being heated, and yield monobasic fatty acids, malonic acid itself giving acetic acid. Similarly oxalic acid breaks up into COj and formic acid. (Compare the analogous formation of CH^ from CHg — COjH.) The derivatives of the dibasic acids, i.e. their ethers, amides, etc., show precisely the same character- istics as the analogous derivatives of the monobasic acids, especially in the readiness with which they are saponified. Summary. Derivatives. Salts. Ethers. Chlorides. Amides. Acid. Acid sodium oxalate. Ethyl-oxalic acid. ^M|o(H) (only known in derivatives). Oxamio acid. Neutral. ^2"40Na Neutral sodium oxalate. p f. / OC2H5 Oxalic ester. CA|g} Oxalyl chloride. Oxamide. 250 X. DIBASIC ACIDa As in the case of the glycols, complications only ensue here either where mixed derivatives exist, such e.g. as are partly ether and partly amide (as in the case of ethyl oxamate, p. 252), or on account of many of the acids being capable of forming imides. Such imides are derived from the hydrogen-ammonium salts of the acids by the elimination of two molecules of water, thus : ^2H*NH. Succinic acid. Succinimide. Like the amides they are easily saponifiable, (cf. succini- mide). Oxalic acid ("O.N." Ethane di-acid), acidvm oxalkum, C2H2O4 + 2H2O. This acid has been known for a very long time; it was investigated by Scheele. Occurrence. In many plants, especially in Oxalis acetosella (wood sorrel), and in varieties of Eumex, as KHO2O4, free in varieties of Boletus, as Na2C204 in varieties of Salicomia, and as calcium salt in rhubarb root, etc. Formation. (See also p. 247) : 1. By the direct combination of carbon dioxide with sodium at 360° : 2CO2 + Naj = G^0^1NH, is got by the action of PCI5 upon oxamic acid, and forms colourless prisms easily soluble in water and of neutral reaction. It is quickly saponified by hot water, and transformed into oxamide by ammonia, (6. 19, 3228). Malonic acid {Propane di-acid), CgH^O^, = CH2(CP2H)2. Occurrence. In beetroot. Formation. (1) By the oxidation of malic acid by means of chromic acid, hence its name; (2) by the saponification of malonyl-urea (303. p), {Baeyer); (3) by the saponification of cyan-acetic acid, {Kolbe, MuUer; A. 131, 348; 204, 121) : CH2(CN)— CO2H + 2H2O = CHaCCOaH)^ + NH3. Large plates or tables, readily soluble in water, alcohol and ether. M. Pt. 132°. Decomposes upon heating, as given at p. 249. Ethyl malonate, malonic ether, CH2(CO.O02H5)2. This ether, which is directly obtainable from cyan-acetic acid by leading HCl gas into its solution in absolute alcohol, is a liquid of faint aromatic odour boiling at 195°, and having a remark- able similarity to aceto-acetic ether. Thus the hydrogen of the methylene group is here, as in the case of the latter, replaceable by sodium, through the influence of the carbonyl groups, CO, which are also bOund to the methylene ; and the resulting sodio-malonic ether readily exchanges the metal for SUCCINIC ACIDS. 253 alkyl upon treatment with alkyl iodide. By this means the higher homologues of malonic ether, e.g. methyl-, ethyl-, propyl- etc., malonic. ethers, are obtained. Further, the second hydrogen atom in these can be exchanged in exactly the same manner for sodium and then for alkyl, whereby di-alkyl malonic acids result. This is an important method for the preparation of the higher dibasic acids, being applicable even in complicated cases ; it is termed the " malonic-ether synthesis." (Of Cmrad and Bischoff, A. 204, 121.) By the splitting off of COj from these, the higher monobasic acids are obtained, (indirect synthesis, see p. 164, 10"). Upon heating malonic ether with its sodium compound, a derivative of phloroglucin results. (See this, also B. 18, 3454.) Cliloro-malonlc ether, CHCI(C02C2H5)2, a liquid boiling at 222°, is employed in analogous syntheses, and otherwise reacts in a similar way to ohloracetic ether. Succinic acids. (1) Common Succinic acid,* ethylene-succinic acid, symmetrical ethane-dicarhoxylic acid, acidum succinicum (from succinum, amber), COgH — CH^ — CHg — COgH. This acid has been known for a long time j its composition was determined by Berzelius. Occurrence. In amber, in various resins and lignites, in many compositse, in Papaveracese, in unripe wine grapes, urine, blood, etc. Formation, (a) From ethylene cyanide, according to 2, p. 247 ; (b) From yS-iodo- (and cyano-) propionic acid, according to 2' ; (c) By the reduction of fumaric and maleic acids, C^H^O^ ; (d) By heating its oxy-acids, malic or tartaric, with hydriodic acid, and also by certain fermentations of these, e.g. from the former according to the equation : C4H5(0H)0, -f- 2HI = C,He04 + 1^; («) As a bye-product in the alcoholic fermentation of sugar ; (/) By the oxidation of fats, fatty acids and parafSns by means of nitric acid. Preparation. From calcium malate according to d, by fer- mentation, or by the distillation of amber. « Butane di-acid. 254 X. DIBASIC ACIDS. Properties. Monoclinic prisms or tables of an unpleasant faintly acid taste. Eather easily soluble in water. M. Pt. 185°, B. Pt. 235°. Yields succinic anhydride — (long needles) —upon distillation.. For its electrolysis, see pp. 58 and 248. Is very stable towards oxidizing agents. Of the Salts of suooinio acid, the basic ferric salt, obtained by the addition of a ferric salt to ammonium succinate, is used in analysis for the separation of iron from alumina. The calcium salt is soluble in water. The Derivatives of succinic acid correspond exactly with those of oxalic, e.g. Succinamic acid, C2H4(C02H)(CO.NH2), is analogous to oxamic acid ; in this case, however, the normal chloride, Sucelnyl chloride, 05,114(0001)2, the analogue of acetyl chloride in all its important properties, is known (of. B. 24, Kef. 319). There also exists — as in the case of other dibasic acids — an imide, Succlnlmide, 00 C2H4<^PQ^NH. The latter crystallizes in rhombic plates, and is formed by heating acid succinate of ammonium. The basic properties of the NH3 are so modified by the two carbonyl groups of the acid radicle that the imido-hydrogen is replaceable by metals, such as K, Ag, etc. (Of. B. 25, Eef. 283.) Mono- and Di-bromo-succlnlc acids, 02H3Br(C02H)2 and 02HjBr2(C02H)2, are easily prepared and are valuable for the syntheses of the oxy-suc- cinic acids. By the action of sodium upon succinic ethyl ether there is formed succino-succinlo ether, C8H5Oa(0O2C2H5)2, a derivative of benzene. For Aceto- and Di-aceto-succinic ethers, see p. 246. (2) Iso-succinic acid {Methyl-propane di-add), eihylidene-succinic acid, CH3 — CH(C02H)2, is formed, e.g. by the malonic ether synthesis, or from a-chloro- (or iodo-) propionic acid (pp. 253 and 248). Needles or prisms. Decomposes upon heating into CO2 and propionic acid, and yields no anhydride (p. 249). Pyrotartaric acids, C3H5(C02H)2. Of these four are known, this being the number theoretically possible. The two follow- ing may be mentioned here: 1. Glutaric acid (Penfane di-acid), normal pyrotartaric acid, COjH — CHj — CHg — CHg — COjH, is of interest on account of its relation to piperidine; can be prepared (e.g.) from glutamic acid indirectly. 2. Pyrotartaric acid (Methyl-hitam di-add), methyl-succinie acid, COjH — CHg — CH(CH3) — COjH, results, among other UNSATURATED DIBASIC ACIDS. 255 methods, along with pyroracemic acid by the dry distillation of tartaric acid, by the aceto-acetic ether synthesis, etc. Small triclinic prisms. M. Pt. 112°. Forms an anhydride. The higher homologues (see Summary, p. 247) are formed along with succinic and oxalic acids by the oxidation of fats, oils, cork, etc., by means of nitric acid; adipic acid also by the oxidation of tetrahydro-a-naphthyl- amine. The symmetrical dialkyl-sucoinic acids show interesting cases of stereo-isomerism. B. Unsaturated dibasic Acids, C„H2„_i04. Fumaric acid,'l p tt ,prs tt-, Itaconic acid,l Maleic „ |^2^2^^^2^;2- Citraconic „ C3H,(C02H)2. Mesaconic „ J Hydro-muconic acid)Q TT Q Teraconic „ G^R-^^O^. Pyro-cinchonic „ ) 8 8 4- gtc. The unsaturated acids stand in the same relation to the saturated dibasic acids as acrylic acid does to propionic. As acids they yield derivatives analogous to those of the acids CnH2,,_204, while as unsaturated compounds "they possess, in addition, the faculty of combining with two atoms of hydrogen or halogen, or with one molecule halogen hydride. Formation. 1. By the elimination of water from the dibasic oxy-acids. Thus malic acid yields upon distillation water and maleic anhydride, which volatilizes, and also fumaric acid, which remains behind : C,HA = C.HA + H^O. Citric acid yields in a similar way COj, HjO, itaconic acid and citraconic anhydride. 2. By the separation of halogen hydride from the mono-haluiu substitu- tion products of succinic acid and its homologues, monobromo-succinic acid yielding fumaric, thus : CiHsBrOi - HBr = CiHjOi. 2*. !From the analogous di-substitutiou products by the separation of the halogen. 3. rumario acid has been prepared synthetically from acetylene iodide, just as succinic acid has been from ethylene bromide. The cases of isomerism among the acids C„H2„_iOi are of great interest 256 X. DIBASIC ACIDS. Constitution. The acids of this series may be regarded as di-carboxylic acids of the defines, e.g. fumaric and maleic acids, C2H2(C02H)2, as those of ethylene. Their mode of formation 1. corresponds exactly with the production of ethylene from alcohol, or with that of acrylic from ethylene-lactic acid, while 2. agrees with that of ethylene from ethyl iodide. Maleie acid (cis-Butene di-aoid), C2H2(002H)2. Large prisms of a grating nauseous acid taste, very readily soluble in cold water. Distils unchanged, excepting for partial transformation into maleic anhydride, C2H2(C02)20. Is conveniently prepared by heating the acetyl derivative of malic acid (see p. 258), or from fumaric acid and POClj (A. 267, 255). Fumaric acid (trani-Butene di-acid), C2H2(C02H)2. Small prisms of a, strong, purely acid taste, almost insoluble in cold water. Sublimes at about 200° with formation of maleic anhydride. Occurs in Fumaria officinalis, various fungi, truffles, Iceland moss, etc., and is obtained from maleic acid either by prolonged heating of the latter at 130°, or by the action upon it of hydrobromio or other acids. (For its preparation, see A. S67, 255. ) Both acids are converted into their ethers on treating their silver salts with alkyl iodide, these ethers also standing in very close relation to one another; thus ethylic maleate is changed into ethylic fumarate when warmed with iodine, and the latter results directly from the etherification of maleic acid in alcoholic solution by means of HOI. Both acids yield common succinic acid with nascent hydrogen, and contain in consequence the same carbon chain, which leads to the same constitutional formula for both, viz., OO2H — CH=OH — COjH. The two acids are therefore stereo-isomeric, and according to van 't Eoff they thus receive the following formulae, which allow of an explanation of the tendency shown by maleic acid to form an anhydride, from the " corresponding " position of the carbonyl groups (cf. p. 25) : H— C— OO.OH HO.OC-C— H II II H—C— OO.OH H— 0— CO.OH Maleic acid. Fumaric acid. This view renders intelligible most of the transformations of maleic acid into fumaric, and vice versa (see the memoir on the subject by /. Wis- licenus, already referred to on p. 22). Compare, on the other hand, Fittig, A. 195, 56; 269, 30; AnscMts, A. 254, 168; see also KehuU, A. Suppl. I., 129 ; II., Ill ; Skraup, B. 24, E. 822 ; Wislicenus, A. 272, 97. For higher hoinologues, see Fittig, B. 26, 40. Appendix. Acetylene -dicarboxylic acid (Butine di-acid), OO2H — CfeC — CO2H, results from dibromo-succinio acid by the separation of HBr (Baudx'owski, B. IS, 2694). It gives up carbon dioxide readily. TARTRONIO AND MALIC ACIDS. 257 thus passing into propargylio acid. Di- acetylene -dicarboxylic acid, CO2H — C^O — C^O — CO2H, and Tetracetylene-dicarboxylio acid (Deca- teirine di-aoid), CO2H— 0=0— 0=0— 0=0— 0=0— COaH, have been prepared by Baeyer (B. 18, 678 and 2269). With increasing length of chain they show an increasing tendency to explode (cf. copper-acetylene). For Baeyer's theory of explosions see B. 18, 2277. O. Triatomic dibasic Acids, OJl^^O^. 1. Tartronic acid {Propanol dv-add), oxy-malonie acid, O3H4O5, = CH(OH)(C02H)2. This acid forms large prisms { + l'H.^O), easily soluble in water, alcohol, and ether. It cannot be dis- tilled unchanged, since it breaks up on heating into carbon dioxide and glycolide. Formation. 1. As oxy-malonic acid, from chloro-malonio acid by the exchange of 01 for OH. 2. As a derivative of the triatomic glycerine, by oxidizing the latter with permanganate of potash. 3. By reduction of the corresponding ketonic acid, mesoxalic acid, 00(002H)2, just as lactic acid is obtained from pyroracemic acid. Preparation. By the spontaneous decomposition of the so-called nitro- tartaric acid (p. 263, Dessaignes), dioxy-tartaric acid being formed as inter- mediate product (KelcuU) ; also from chloral hydrocyanate (B. 18, 2852). 2. Malic acid (Buianol di-acid), oxy-succinic add, addummalicum, C.HaOy = C,Il,{OB.){GO,R)„ = C0,H-CH2-CH(0H)- CO2H {Scheele, 1785). Occurrence. Is very widely distributed in the vegetable kingdom, being found in unripe apples, sorb -apples, grapes, barberries, quinces, Crassulacese, etc. Formation. 1. As oxy-succinic acid, by treating bromo- succinic acid with moist oxide of silver: C,-a,-BT{GO,B), + H^O = C2H3(OH)(C02H)2 + HBr. 2. By the reduction of tartaric or racemic acid with HI, and of oxalo-acetic acid (p. 265) with Na-amalgam. 3. From aspartic acid or asparagine by means of NjOg. 4. By heating fumaric or maleic acid with water (A. 192, 80). Properties. Hygroscopic glancing needles, usually in round (606) " « 258 X. DIBASIC ACIDS. groups, readily soluble in water and alcohol, but only slightly in ether. M. Pt. 100°. When it is distilled, maleic anhydride passes over and fumaric acid remains in the retort (p. 256). Yields, when heated with concentrated H2SO4, Cumalio acid, CsHsOjICOjH). {v. Pechmarm, A. 264, 261 ; 273, 164.) Malic acid exists in several optically different modifications which corre- spond exactly with those of tartaric acid. The dilute solution of the natural acid is leevo-rotatory; the acid obtained from dextro-tartaric acid is dextro- rotatory; while the acid prepared from racemic, succinic, or fumaric acid is inactive, and can be separated into the active modifications. The alkaline salts and the acid calcium salt of malic acid are readily soluble in water, while the neutral calcium salt is only sparingly soluble. As an alcohol, the acid yields ethers, e,g. an Aceto-malic acid, C2H.(O.CjH80)(C02H)j. Amides and Amines of malic acid. Like glycoUic acid, malic acid forms — as an acid — amides (saponifiable), and — as an alcohol — an amine (not saponifiable). The amides are: Malamide, C2H3(OH)(CO.NH2)2, crystallizing in prisms, and Malamio acid, C2H3(OH)(CO.]SrH2)(C02H), the latter being known as ethyl ether. The alcoholic amine, aspartic acid, C2H3(NH2)(C02H)2, unites in itself like glycocoll the properties of a base and of an acid, but the acid character predominates. Its acid amide is asparagine. Asparagine, C2H3(NH2)(CO.NH2)(C02H), which is isomeric with malamide, is very widely distributed in the vegetable kingdom, being present in the young leaves of trees, in beet- root, potatoes, the shoots of peas, beans and vetches, and in asparagus; it was first found in the last-named vegetable in the year 1805. It forms glancing rhombic prisms (-(-HjO), easily soluble in hot water, but insoluble in alcohol and ether. Goes into aspartic acid on saponification. Is optically active. A dextro-rotatory asparagine has likewise been obtained from the shoots of vetches (B. 20, Kef. 510) ; it possesses a sweet taste, and unites with the lEBvo-rotatory compound to an inactive modification. For the synthesis of the asparagines and their constitution, see Piutti, B. 22, Eef. 241 and 243. Aspartic acid, C2H3(NH2)(C02H)2, is present in beet molasses, and forms an important product of the decomposition of ASPAKTIC ACID; TARTARIC ACID. 259 albuminoid substances by means of acids or alkalies; it has been synthetized (e.g.) from bromo-succinic acid and ammonia. Small rhombic tables, rather easily soluble in hot water. It exists in several optically different modiiications, which differ in taste and are convertible, the one into the other (B. 20, R. 510). Nitrous acid transforms it, as well as asparagine, into malic acid (normal amine and amide reaction). Just as glycocoU is to be regarded as amido-acetic acid, so is aspartic acid to be looked upon as amido-succinic. Isomers and homologues of malic acid aie both possible and known. Higher Homologues. a-andj3-0xy-glu-1 Diaterebio acid, C5H9(OH)(C02H)3. Itamalio acid, j ^'^''^-^'^^^^-^'^'Diaterpenylic „ C6H„(OH)(C02H)j. Citramalio acid, J etc. Glutamine, C3H5(NH2)(CO.NH2)(C02H), and Glutamic acid, C3H5(NHj)(C02H)2, are the ammonia derivatives of o-oxy-glutario acid, being homologous with asparagine and aspartic acid. The former is like- wise found in beetroot and in the shoots of the vetch and gourd, while the latter is produced, together with aspartic acid and leucine, by boiling albuminous compounds with dilute sulphuric acid. Terebio acid, CyHioOj, a lactone of diaterebic acid, results from the oxidation of terpenes. D. Tetratomic dibasic Acids. Tetratomic dibasic acids are such as unite in themselves the properties of a diatomic alcohol with those of a dibasic acid. Theoretically they are characterized by the presence of two alcoholic hydroxyls and two carboxyls in the molecule. The simplest possible member of the series, the compound C(OH)2(002H)2, is unstable and has not the characters of an alcoholic acid, but those of the hydrate of a ketonic acid, since it contains two hydroxyls bound to the same carbon atom. (See Mesoxalic acid, p. 265.) Tartaric acid {Butane-diol dirocid), dioxy-succinic acid, oxy-malic add, C^HeOg, = G^R^{OB)^{GO^B.\, = CO,H— CH(OH)— CH(OH)— (COjH). This acid exists in four "physically isomeric " modifications (p. 39). 1. d- or Dextro-tartaric acid, M. Pt 170°j 260 X. DIBASIC ACIDS. 2. ^ or Lasvo-tartaric acid, anti-tartaric acid, M. Pt. 170°j 3. Sacemic acid, para-tartaric acid, M. Pt. 206°; 4. i- or Inactive tartaric acid, meso-tartaric acid, M. Pt. 143°. The two first of these acids turn the plane of polarization of light in an equal degree, but in opposite directions. By their union the inactive racemic acid is formed, and this can, conversely, be separated into its components. The fourth tartaric acid, likewise inactive, cannot be broken up in this way, but it is convertible into the other modifications. Formation. 1. The oxidation of mannite by means of HNOa yields racemic acid, and that of sorbin, meso-tartaric acid. 2. The treatment of dibromo-succinic acid, C2H2Br2(C02H)2, with moist oxide of silver yields racemic and meso-tartaric acids {KehvM). 3. Bacemic acid results from the saponification of the cyanbydrin of glyoxal (cf. p. 238); and also upon the reduction of glyozalic acid, two molecules of this " condensing " together. 4. The oxidation of fumaric acid by means of KMnOj yields racemic acid, and that of maleic, meso-tartaric acid (KekuU). 5. When dextro- or laevo-tartaric acid is heated with some water to 170°, racemic and meso-tartaric acids are formed; meso-tartaric acid changes partially into racemic acid under analogous conditions, a state of equili- brium being reached here. For the splitting up of racemic acid, see above. The Constitution of tartaric acid follows both from its relations to succinic acid (see mode of formation 2), and to glyoxal (mode of formation 3). Isomerism of the Tartaric Acids. Tartaric acid, CO.OH— CH(OH)— CH(OH)— CO.OH, contains according to Le Bel and van 't Soff's theory (p. 22), two asymmetric carbon atoms, which determine the optical activity of the molecule ; and this activity is connected with the spacial arrangement of the atoms or groups, H, OH and COOH, round those atoms (p. 40). This arrangement may be the same with respect to both carbon atoms, or it may be different. If it is the same, the optical action is intensified ; if different, it ceases. In the former case the molecules may be either dextro-rotatory or laevo-rotatoiy in an equal degree (dextro- and Isevo-tartaric acids) ; in the latter they are optic- ally inactive (meso-tartaric acid). An inactive compound also results from ISOMERISM OP THE TAETARIC ACIDS. 261 the presence (or the combination) of equal numbers of dextro- and Isevo- rotatory molecules (racemic acid). These relations may be depicted by the following figures: — ^^ /-N H H ^OHHO CO,H LsBTO-tartaric acid. Dextro-tartarie acid. Kacemic acid. MeBO-tartaric acid. If, in Fig, II,, we divide the combination of the two tetrahedra at the point which is common to both, and place the tetrahedron which was uppermost alongside of the other, the point just referred to being directed upwards, we can easily turn the latter so as to bring it into a position which shows clearly that the direction of motion of the group (OH) towards (H) and (CO2H) is the same for both tetrahedra, viz,, in the direction of motion of the hands of a watch. The same holds good for Fig, I,, only in this case the analogous direction of motion for both tetrahedra is the opposite one. In Fig, III., on the other hand, the order of this succession in the upper tetrahedron, which has been lowered, is the opposite to that of the under one. If, therefore, the optical activity of the tetrahedra be dependent upon the order of succession of the substituting groups, the corresponding forces will be intensified in I. and II., but will neutralize each other in III.; the molecule III. is inactive, while I. and II. are active, although in opposite directions. By projecting the figures on the surface of this paper we obtain the following projection-formulae (E. Fischer, B. 34, 2684) : — CO2H I HO— 0— H I H— 0— OH I COjH Iisevo-tartaric acid. CO2H I H— C— OH I HO— 0— H CO2H Dextro-tartarie acid. CO2H I HO— C— H I HO— 0— H I CO2H Meso-tartaric acid. (M) 262 X. DIBASIC ACIDS. The relations between the above may be exemplified more concisely in the following manner : — I d I /I I I I I d d IiCBvo-tartaric acid. Deztro-tartaric acid. Meso-tartaric acid. Bacemic acid. 1. Dextro-tartaric acid, acidum tartaricvm, is the tartaric acid found in nature. It was discovered by Scheele in 1769. It occurs in the free state or as salt, chiefly acid potassium salt, in various fruits, especially in the juice of grapes, from which bitartrate of potash or tartar — (tartarus) — separates in crystals during fermentation. When this is boiled with chalk and chloride of calcium it is transformed into the neutral lime salt, from which the acid is liberated on addition of HgSO^. Large transparent monoclinic prisms, of a strong and purely acid taste, very easily soluble in water, readily also in alcohol, but almost insoluble in ether. M. Pt. 170°. Eeduces an am- moniacal silver solution upon warming. When melted, it is changed into an amorphous modification, and then into an an- hydride, and when heated more strongly it carbonizes with the dissemination of a characteristic odour and formation of pyro- racemic and pyrotartaric acids. Oxidation converts it either into dioxy-tartaric or tartronic acid, and then into formic and carbonic acids, etc. It is employed in medicine, dyeing, etc. Neutral potassium tartrate, CiHiOsKz + JHaO, forms monoclinic prisms easily soluble in water. Acid potassium tartrate, Tartar, or Cremor tartari, C^HsOsK. Small rhombic crystals of acid taste, sparingly soluble in water; is much used in dyeing, medicine, etc. Potassium-sodium tartrate, Boehelle or Seignette salt, C4H406ElN'a + 4H2O (1672), forms magnificent rhombic prisms. Calcium tartrate, C4H408Ca + 4H2O, is a powder insoluble in water but soluble in cold caustic soda solution; on warming the solution it separates as a jelly, which redissolves upon cooling. Potassio-antimouious tartrate, Tartar emetic, CiHilSbOyKOj-f- JH2O (see B. 15, 1540), is obtained by heating cream of tartar with antimony oxide and water. Ehombio efiloresoent ootahedra, easily soluble in water. It is poisonous and acts as an emetic, and is used as a mordant in dyeing. Fehling'i solution is a solution of cupric sulphate mixed with alkali and seignette salt. The Dl-ethyl ether is a thick oil, while the Uono-ethyl ether crystallizes LiEVO-TARTARIC AND KACEMIO ACIDS, 263 in prisms. Aceto-tartaric acid and Amides of tartaric acid are known, and also various anhydrides. As an alcohol, it forms with nitric acid a di- nitric ether, the so-called Nitro-tartaric acid, C2Hj(O.NOs)a(C02H)2, which as an ether is readily saponifiable and, generally speaking, easily decompos- able with formation of Dioxy-tartaric or of tartronio acid. 2. LsBVO-tartaric acid is identical in its chemical and also in almost all its physical properties with ordinary tartaric acid, but differs from it in that it turns the plane of polarization of light to the left, in a degree equal to that in which the other turns it to the right. The crystallized salts show hemihedral faces like the salts of dextro-tartaric acid, but oppositely situated (see below). When equal quantities of both acids are mixed together in aqueous solution, the solution becomes warm, and we obtain: — 3. Eacemic acid, C4HgOg + HjO, the composition of which was first established by Berzelius, who recognized it as being different from tartaric acid, and who developed the idea of isomerism from this first example in 1829. Eacemic acid is obtained from tartar mother liquor. It differs from dextro- tartaric acid in that its crystals are rhombic and efilorescent and also less soluble in water than the former; further, the free acid is capable of precipitating a solution of calcium chloride and is optically inactive (see below). The salts, which are termed racemates, and also the ethers (B. 21, 518), show small differences from the tartrates in the proportions of their water of crystallization and in solubility. In dilute aqueous solution racemic acid is completely split up into d- and Z-tartaric acids. When a solution of sodium-ammonium racemate, 04HiNa(NH4)06 -^ 4H2O, is evaporated, beautiful rhombic crystals which show hemihedral faces are obtained. Pasteur observed that these faces were not always similarly situated, but that certain crystals were dextro-hemihedral while others were Isevo-hemihedral, so that one crystal formed the reflected image of the other. The laevo-hemihedral crystals are optically dextro-rotatory and vice verm. If now the two kinds of crystals be separated from one another mechanic- ally and the free acid liberated from each, this will be found to consist, not of racemic acid, but in the one case of dextro- and in the other of laevo- tartaric.acid. An analogous decomposition of racemic acid is also possible by means of the cinchonine salts or by the addition of certain ferments (cf. p. 39). 264 X. DIBASIC ACIDS. 4. Meso-tartaric acid, a fourth tartaric acid, is inactive like the foregoing, but not decomposable into the active acids, although it can be transformed into the latter (see p. 260). It crystallizes in efflorescent rectangular plates. The acid potas- sium salt is easily soluble in water. E. Penta- and Hexatomic dibasic Acids. Pentatomic: Trioxy-glutaric acid, C3H3(OH)3(C02H)2. Hexatomic: Dioxy- tartaric acid, C2(OH)4(0O2H)2 (see Ketonic acids). Saccharic acid,i Mucic „ lc,H4(OH),(C02H)2. Iso-saccharic „ J Many of these acids form lactones (p. 233), the so-called lactonic acids, and some of them also double lactones (cf. FitHg, A. 255, 1, et seq.). Trioxy-glutaric acid, COjH — (CH.OH)s — COaH, is a frequent oxidation- product of sugar- varieties, e.g. of xylose and arabinose. According to theory, four stereo-isomers may exist. Saccharic acid, Ci'B.i{OS.)i{G02'H)2, is produced by the oxidation of cane sugar, glucose, gulose, gulonio acid, mannite, or starch by nitric acid, and exists in the dextro-, Isevo-, and inactive-forms (see Glucoses) ; (i-saccharic acid passes into glycuronic acid upon reduction (see p. 240). All the three varieties are deliquescent. Mucic acid, OiH4(OH)4(OP2H)2, is formed by oxidizing duloite, the gums, mucilages, and mUk sugar. It is a sparingly soluble, colourless, crystalline powder. . The molecule being symmetrical in structure, it is optically in- active. It is easily converted into derivatives of furfurane (p. 326). Iso-saccharic acid, CBHi(OH)i(COi!H)j, is obtained by the oxidation of glucosamine, C6Hn05(NH2). Theoretically ten stereo-isomeric acids of the formula, C6H4(OH)4(COjH)a are possible, most of which (e.g. d- and i-Uauno-saccharic acids, Talo- mucic acid, etc.) have been prepared by E. Fischer (B. 24, S39, 2137, 3622). For their relations to the hexoses, see the table appended to these (p. 311). P. Dibasic Ketonic Acids. Dibasic ketonic acids unite in themselves the properties of a ketone and of a dibasic acid. The following are known: MESOXALIC ACID, BTC. 265 1. Mesoxalic acid, CO(C02H)2 or C(OH)2(C02H)2 (see p. 259), is prepared from dibromo-malonic acid, CBr2(C02H)2, and baryta water or oxide of silver, thus: CBrsjCCOsH)^ + H^O = CO(C02H)2 + 2HBr; also by boiling alloxan (p. 303) with baryta water. It crys- tallizes in deliquescent prisms ( + HjO). As a ketone it combines with NaHSOj, reacts with hydroxyl- amine (p. 155), and is reduced by nascent hydrogen to the corresponding secondary alcohol-acid, tartronic acid: CO(C02H)2 -)- Ha = CH(OH)(C02H)2. Since the acid and its salts still retain a molecule of water at tempera- tures above 100°, this may be chemically bound as in chloral hydrate, cor- responding to the formula, C(OH)2(C02H)2, " di-oxy-malonic acid." In fact, two modifications of the ethyl ester are known, viz., 0(OH)2(COsC2H5)2 and CO(C0202H5)2. 2. Oxalo-acetic acid {Butanone di-acid), OO2H— CH2 — CO— CO2H, is formed as ethyl ether by the action of sodium ethylate upon a mixture of oxalic and acetic ethers, and also by the action of concentrated sulphuric acid upon acetylene-dioarboxylio ether. It is a colourless oil, but the alcoholic solution gives an intense dark red with ferric chloride. Like aceto-acetio ether, it is of service for many syntheses ( W. WisUcenus). 3. Acetone - dicarboxylic acid { Pentanone di-acid), CsHjOs, = C0=(0H2 — COzHjj, results upon treating citric acid with concentrated H2S04. It breaks up readUy into acetone and 2OO2 (see A. 261, 151). 4. Dioxy-tartaric acid, CO2H — CO — CO — CO2H, or probably COjH— C(0H)2— C(0H)2— CO2H, is formed from pyro-catechin and nitrous acid, and by the gradual decomposition of nitro-tartario acid. It is crystal- line. M. Pt. 98°. The characteristic difficultly soluble sodium salt decom- poses easily into CO2 and tartronate of sodium. It reacts with two mols. hydroxylamine. With phenyl- hydrazine -sulphonio acid, a yellow dye "tartrazine" is produced (cf. KehuU, A. 281, 230). Sodium bisulphite converts it into glyoxal. 5. Acetone-diacetic acid, hydrochelidonio acid, CO(CHa — CH2 — C02H)2. Cf. A. 263, 206. OHs— CO.CH.CO2H 6. Diaceto-succinic acid, | (see p. 246). The ester CHa— CO.CH.COjH 266 XI. TRI- TO HEXABASIO ACIDS. of this is closely related to acetonyl-acetone, the latter being readily obtain- able from the former by the action of caustic soda solution ("Ketonic decomposition;" cf. B. 22, 2100). XI. TRI- TO HEXABASIO AOIDS. The tribasic organic acids are those which, like phosphoric acid, are capable of forming three series of salts, viz., neutral, mono-acid, and di-acid salts. They contain according to theory three carboxyl groups. There are not only triatomic tribasic acids, such as methane- and propane-tri-carboxylic acids, etc., which are of purely acid character, but also tetratomic, penta- tomic and hexatomic tribasic acids, alcoholic acids which possess at the same time the characters of alcohols. Further, these may be derived either from saturated or from unsaturated hydrocarbons. A. Triatomic tribasic Acids. 1. Ethane-tricarboxylic acid, C2H3(C02H)3, 2. Propane-tricarboxylic „ OgH5(C02H)3, 3. Tricarballylic „ C3H5(C02H)3. The above acids 1 and 2 have been prepared by the malonic ether syn- thesis ; they are best known as ethers, since, in the free state, they readily break up upon heating into CO2 and dibasic acids. Propane-tricarboxylic acid is unsymmetrically constituted. Tricarballylic acid (Pentane di-acid-3-ca/rboxylic acid), synir metrical prc^ane-tricarboxylic acid, 03115(00211)3. Occurs in un- ripe beet, and is prepared (a) by the addition of hydrogen to aconitic acid; (b) by heating citric acid with hydriodic; and (c) synthetically from glycerine by transforming it into tri- bromhydrin, OgH^Brg, treating this with KON, and saponifying the cyanide formed, 03H5(ON)3. Since the three hydroxy Is in glycerine are distributed among three carbon atoms, the same holds good for the carboxyls in the acid, which has therefore the symmetrical constitution: ACONITIC AND CITRIC ACID& 267 CH^— CO2H CH— CO2H CHj— COjH. This acid is of importance in determining the constitution of citric acid, from which, as already seen, it can be obtained by heating with HI. It crystallizes in rhombic prisms, easily soluble in water, etc. M. Pt. 166°. For a synthesis of aconitio acid from acetic and oxalic acids (which per- haps approximates to the method of its formation in plants), see B. 24, 120. B. An Unsaturated tribasic Acid is Aoonitic acid, CgHgOg, = C3Hg(C02H)3, which contains two atoms of hydrogen less than tricarbaJIylic acid. It is found in nature, in Aconitum Napellus, shavegrass, sugar cane, beetroot, etc., etc., and is prepared by heating citric acid, CgHgOy, water separating. It is a strong acid, crystallizable, and easily soluble in water. M. Pt. 191°. Nascent hydrogen transforms it into tricarballylic acid, hence it is an unsaturated acid and its constitution is : CH— CO2H C— COjH CHg— COjH. O. Tetratomic tribasic Acids. Citric acid, addwm citricum, CgHgO^, = C3H^(OH)(C02H)3. (Scheele, 1784; recognized as tribasic by Liebigm 1838.) Occurs in the free state in lemons, oranges and red bilberries, and mixed with malic acid in gooseberries, etc., also as calcium salt in woad, potatoes, beetroot, etc. Preparation. From the juice of lemons by means of the lime salt. Properties. Large rhombic prisms (+ HjO), very easily soluble in water and rather easily in alcohol, but only slightly in ether. It loses its water of crystallization at 130°, melts 268 XL TBI- TO HEXABASIC ACIDS. at 153°, and breaks up at a higher temperature first into aconitic acid and water, and then into carbon dioxide, itaconic acid, citraconic anhydride, and acetone. Oxidizing agents eifect a very thorough decomposition. Citrate of calcium is precipitated as a white sandy powder upon boiling a mixture of calcium chloride and alkaline citrate. The three series of salts are well characterized ; the alkaline salts are soluble in water, the others mostly insoluble. Among the derivatives may be mentioned mono-, dl-, and trl-etbyl citrates and trl-ethyl aceto-citrate, C3H4(O.C2H30)(C02C2Hb)3, wMch last forms a proof of the alcoholic character of citric acid ; it boils without decomposition. The Amides of citric acid are converted by concentrated HjSO^ into Citrazinic acid, CJH5NO4, a pyridine derivative, (B. 17, 2681.) The constitution of citric acid is arrived at both from its relation to aconitic acid, which results from it as ethylene does from alcohol, and from various syntheses j it is : CH„— CO„H C(OH) CO2H CH2— COjjH. Thus it is obtained from ^-dichloro-acetone as follows : CH,C1 CHgCl CH2CI CHj.GN CH2.CO2H CO C(OH)-CN C(OH)-COsjH C(0H)-C02H C(0H).C02B CH2CI CH2CI CH2CI CH2.CN CH2.CO2H. An Iso-citric acid, isomeric with citric, has also been pre- pared synthetically, (Fittig, B. 20, 3179). Appendix. D. Pentatomiotribasic acids. DesoxaUc acid, CbHjOs, = C2H(OH)j(C02H)5, and Oxy-cltrlc acid, CeHjOa, the latter of which is present in the juice of turnips. E. Tetra-, penta-, and hexabasic acids do not occur in nature but have been prepared in considerable numbers by means of the aceto-aoetio or malonic ether synthesis, e.g., ethane-tetra-carboxylio acid, propane-penta-oarboxylio acid and butane-hexa-carboxylio acid. They are obtained in the form of ethers, most of them being either very unstable or incapable of existence in the free state. For their preparation, see B. IS, 1109; 17, 2781; A. 214, 31. Acids up to a basicity of fourteen have now been synthetized (B. 21, 2111), CYANOGEN COMPOUNDS; FORMATION OF. 269 XII. CYANOGEN COMPOUNDS. Under the name of the cyanogen compounds is included a group of bodies which are derivable from cyanogen, OgNj. Cyanogen itself is a gas of excessively poisonous properties which behaves in many respects like a halogen, and its hydrogen compound, hydrocyanic acid, HON, is an acid which is very similar in many ways to hydrochloric. In many cyanogen compounds the monovalent group (ON) plays the part of an element ; cyanogen is to be regarded as the isolated radicle (ON), often written Cy, which however possesses the double formula CjNj, just as a molecule of chlorine (Clg) is made up of two atoms. The cyanogen group is further capable of combining with the halogens, hydroxyl, sulphydril (SH), amidogen, etc., etc. From the compounds so obtained numerous others are derived by the entrance of alcohol radicles in place of hydrogen. Such derivatives invariably exist in two isomeric forms, sharply distinguished from one another by their properties, and whose isomerism is of very great interest. (See table, pp. 270 and 271.) There exist further polymeric modifications of most of those compounds (see table). The number of cyanogen compounds known is thus a very large one. Formation. 1. Carbon and nitrogen cannot combine directly with one another but only when they are heated in presence of an alkali ; thus, when nitrogen is led over a red-hot mixture of coal and carbonate of potash, potassium cyanide, KCN, is formed (this especially under a high pressure). 2. By passing ammonia over red-hot coal, ammonium cyanide, NH4CN, is produced. 3. Carbon and nitrogen combine most readily with metals when in the nascent state, e.g., when nitrogenous organic compounds such as leather, horn, claws, wool, blood, etc., are heated with potashes. 4. Hydrocyanic acid is formed when electric sparks are passed through a mixture of acetylene and nitrogen, and also by. the action [Continued on p, 272. 270 XII. CYANOGEN COMPOUNDS. STTMMAEY OF THE CYANOGEN COMPOUNDS AND OE Belation to carbonic Original Compounds. acid, etc. (See p. 290.) Normal Isomeric Form. Nitrile of oxalic acid, Gyanogm, C3N3 Nitrile of formic acid, Hydrocyanic acid, Alcoholic derivatives : (a) Nitriles, (6) Iso-nitrilea, N=C.H CH3— C=N CHj— NC Cyanogen chloride, bro- mide, iodide. N=C.C1 003113 + NH3-2H2O, (Partial Nitrile, event- ually Carbimide, see p. 290), Cyanic acid. Alcoholic derivatives ; (a) Methyl cyanate, (6) ,, iso-cyanate, NsC-OH N=C-0.CH3 0=C=N.CH, Thiocycmic acid. Alcoholic derivatives : (a) Ethyl thiocyanate, (6) AUyl Iso-thio- cyanate. NsC-SH N=C— S.CaHj S=C=NCsH„ CO3HJ+2NH3-3H2O, (Nitrile and amide, eventually Carbo-di- imide, see p. 290), Cyanamide, Alkylated : (0) Alkyl cyanamide, (6) Carbo-di-imide, N=C— NH3 N=C-NH.CH3 RN=C=NR* CO3H3+NH3-HSO, (Aminic acid). Carbamic acid, C0(NHi,)OH — CO3H2+2NH3-2H3O, (Carbamide), Urea, CO(NH3)3 — . Tkio-urea, Alkylated : (a) Alkyl-thio-ureas, (6) Imido-thio-oarba- mine compounds, CS(NH3)3 CSNjHsR C(NH)fH, COjHs + SNHj-SHjO, (Amidines), Guanidine, C(NH)(NH3)3 ~~ R Alcohol radicle. SUMMARY. SEVERAL RELATED CARBONIC ACID DERIVATIVES. 271 Polymeric CoMPonNDS. Normal Isomeric Form. Paraq/anogen, (CN)„ perhaps (CsNs), — " Tri-hydrocycmic acid," Alcoholic derivatives : Tri-ethyl tri-oyanide, (CNH)x (CN)3(CaH.)3 — Cyajmric chloride, etc.. {CN),Cl3 — Cya/nwric add. Alcoholic derivatives ; (a) Cyanurates, (6) lao-cyanurates, (CN),.(0H)3 (CN)3.(OCA)3 (CO\J^O^YL,\ Thio-cyanurie acid. Alcoholic derivatives ; (a) Thio-cyanurates, (CN)3.(SH)3 (CN)3.(SC2H,)3 — Uicyan-diamide, Mdamine, Alkylated : (a) Alkyl-melamine, (6) Alkyl-iao-melamine, CaN4H4 (CN)3.(NH,)3 (CN)3.(NHC,H„)3 (0:NH)7NCaHB)3 No Polymers. 272 XII. CYANOGEN COMPOUNDS. of the silent electric discharge on a mixture of cyanogen and hydrogen. For further modes of formation, see below. The original material for the preparation of most of the cyanogen compounds is potassic ferrocyanide, which is manu- factured on the large scale and possesses the great advantages over potassium cyanide of being stable in the air and non- poisonous. A. Cyanogen and Hydrocyanic Acid. Cyanogen, 02^5. Discovered by Gay-Lussac in 1815. Occv/rs in the gases of blast-furnaces. Formation. 1. As the nitrile of oxalic acid, by the abstraction of the elements of water from oxalate of ammonia by means of PgOg ; also in the same way from the intermediate product of this reaction, oxamide : C20,(NH,)2 - 4H2O = C2N2; C202(NH2)2 - 2H2O = C^N^. 2. By heating silver cyanide, AgCN, or mercuric cyanide, Hg(CN)2, strongly ; this is the method followed for its pre- paration : Hg(CN)2 = Hg + C^N,. Further, in the wet way, by heating a solution of cupric sulphate with potassium cyanide, (B. 18, Eef. 321). Cyanogen is a colourless gas of a peculiar unpleasant odour resembling that of bitter almonds, and is terribly poisonous. Sp. Gr. 1-8. Easily condensible. M. Pt. -34°. B. Pt. of liquid cyanogen - 21°. Soluble in \ vol. of water and in even less alcohol. The solutions become dark upon standing, with separation of a brown powder (" Azulmijs acid "), while oxalic acid, ammonia, formic acid, hydrocyanic acid and urea are to be found in the liquid. The formation of the oxalic acid and ammonia depends upon normal saponification, and that of formic acid upon the saponification of the HYDEOCYANIC ACID. 273 hydrocyanic acid formed as an intermediate product. In presence of a minute quantity of aldehyde, oxamide results from the taking up of water. Cyanogen combines with heated potassium to KCN, and dis- solves in aqueous potash to form KCN and KCNO. It yields with HjS the thiamides Flavean hydride, NC — CS.NHj, and Rubean hydride, CS(NHa)— CS(NHj). Faracyanogen (CN)i is a polymer of cyanogen. It is an amorphous brown powder which results as a bye-product when mercuric cyanide is heated ; upon further heating, it is transformed into cyanogen. Hydrocyanic acid, prussic acid, CNH. Discovered about the year 1782 by Scheele, and investigated closely by Gay- Lussac. Formation. 1. By decomposing metallic cyanides by means of stronger acids ; also by the distillation of potassic ferro- cyanide with dilute sulphuric acid : KiFe(CN)g -I- SHaSO^ = 6HCN -l- FeSO^ -^ 4KHS0^. The ferrous sulphate produced reacts with more ferrocyanide to form ferro-potassio ferrocyanide, FeKjIFeCys) (see p. 277), which is not affected by dilute acids ; consequently only half of the cyanogen present is converted into hydrocyanic acid. When concentrated instead of dilute sulphuric acid is employed, carbonic oxide and not hydrocyanic acid is obtained. 2. From ammonium formate or formamide by the separation of water : H.OO.O(NH^) = H.CO.NH2 -t- HjO = HON + mp. Hydrocyanic is therefore the nitrile of formic acid. 3. Together with oil of bitter almonds, C^HgO, and grape sugar, CjHijOg, through the decomposition of amygdalin under' the influence of " emulsin," (see p. 322) : C20H27NO11 -1- 2H2O = CNH + G^np + 2C6H12O6. The oil of bitter almonds and its aqueous solution — (aqua amarum amygdal- arum) — prepared from the almonds themselves, consequently contain HON. 4. By the action of ammonia upon chloroform under pressure : CHCI3 + NHs = HON -1- 3HC1. 5. Through the oxidation of many organic substances by means of nitric acid. For other syntheses, see p. 269. (606) 3 274 XII. CYANOGEN COMPOUNDS. Preparation. From yellow prussiate of potash. In order to obtain the anhydrous acid, the vapours are dried over calcium chloride. Properties. Colourless liquid, solidifying at - 15°. Sp. Gr. 0"70. B. Pt. 26-5°. It has a peculiar odour and produces an unpleasant irritation in the throat, is miscible with water, etc., and burns with a violet flame. Like potassium cyanide, it is one of the most terrible of poisons. When absolutely pure it can be preserved unchanged, but it decomposes in presence of traces of water or ammonia-, with separation of a brown mass and formation of amm'onia, formic acid, oxalic acid, etc. The addition o.f minute quantities of mineral acids renders the aqueous solution more stable. Hydrocyanic acid combines with nascent hydrogen to methylamine : HON + 2H2 = HCH2.NHJ. With hydrochloric acid it forms a white crystalline product (HON + HCl), which appears to be the imido-chloride of formic acid, H — CC1=NH. It also combines with many metallic chlorides to crystalline compounds which are easily decomposable. Hydrocyanic acid is a weak monobasic acid, in accordance with the mildly acidifying nature of the cyanogen radicle ; its salts are decomposed even by carbonic acid. Its constitutional formula, H — C=N, follows from its relations to formic acid and chloroform. In some reactions, however, it yields com- pounds which are derived from its hypothetical isomer =0^N — H or C=N — H. Its alcoholic derivatives each exist in two isomeric modifications, nitriles and iso-nitriles, which are derived from the two atomic groups H — CN and ON — H. (See table, p. 270, and the appendix to the cyanogen group, p. 286.) Hydrocyanic acid can be detected by converting it either into Prussian blue or into ferric sulphocyanide. In the former case the solution to be tested is treated with excess of caustic soda and some ferrous and ferric salt, boiled, and acidified, when Prussian blue results ; in the latter the solution is evaporated to dryness along with a, little yellow sulphide of ammonium, the residue taken up with water and ferric chloride added, when the blood-red colour of ferric sulpho- cyanide is obtained. POTASSIUM CYANIDE, ETC. 275 Trl-hydrocyanio acid, (CNH)i, results from the polymerization of hydrocyanic acid under certain specified conditions. It forms white acute-angled crystals which go back into hydrocyanic acid with violence when heated above 180°. Its molecular weight is still unknown. Potassium cyanide, KCN. Yot formation, see p. 269. Preparation. 1. Anhydrous ferrocyanide of potassium is heated to fusion : K^Fe(CN)a = 4KCN + Fe + 20 + N,. In order to prevent the decomposition of a portion of the cyanide, potash may be added to the melted mass, but the product will in this case contain potassic cyanate, (Liebig's cyanide of potash.) 2. By heating potassium in cyanogen gas. 3. By the combination of HON with KOH, and precipita- tion from the aqueous solution by means of alcohol. Properties. Colourless deliquescent cubes, readily soluble in water but only slightly in alcohol. It is sold in sticks. It ibsorbs water from the air and is decomposed by the carbonic j,cid of the latter. The aqueous solution precipitates nearly all the metallic salts, the precipitates redissolving in excess, with formation of double cyanides. Simple Cyanides. Ammonium cyanide, NH4.CN. White deliquescent mass. It is also produced by the passage of the silent electric discharge through a N mixture of marsh gas and nitrogen. Mercuric cyanide, Hg(CN)2. Colourless prisms, stable in the air and readily soluble in water. Excessively poisonous. Silver cyanide, AgCN. White flocculent precipitate, closely resembling chloride of silver both in appearance and solubility. Double Cyanides. The double cyanides, which are produced by dissolving the insoluble metallic cyanides in a solution of cyanide of potas- sium, are divided into two classes. The members of the one class are broken up again on the addition of dilute mineral 276 XII. CYANOGEN COMPOUNDS. acids, with separation of the insoluble cyanide and formation of hydrocyanic acid, e.g. KON + AgCN ; 2KCN + Ni(CN)sj. The members of the other class do not separate hydrocyanic acid, but comport themselves as salts of particular acids; to the latter belong, in especial, potassic ferrocyanide, K^FeCyg, (= 4K0y + FeCyj), and potassic ferricyanide, K^FeCy^, ( = 3KCy + FeCyj),* which yield with acids hydro-ferro- and hydro- ferricyanic acids. Many salts of the latter acid are not decomposed at all by dilute acids, for instance Prussian blue, but they are by caustic potash (which converts Prussian blue into Fe(0H)3 and K^FeCyg). Potassium ferrocyanide, yellow prussiate of potash, K^FeCyg + SHjO. Formation. 1. By adding excess of potassium cyanide to a solution of ferrous sulphate. 2. By dissolving iron in a solution of cyanide of potassium, when hydrogen is evolved, thus : 2KCN + Fe + 2H2O = Fe(C^)^ + 2K0H + Hj ; Fe(CN)2 + 4K0N = K^Fe(CN)g. Iron is therefore previously added to the "melt" in practical working (see p. 269, 3). It forms large lemon -coloured tetragonal plates, which are stable in the air and easily soluble in water, but insoluble in alcohol. Concentrated HCl separates Hydro-ferrocyanic acid, H^FeCyg, in white decomposable needles. With a solution of CuSO^, a red-brown precipitate of Cupric ferrocyanide, or Hatchett's brown, CujFeCyg, is thrown down, and with solutions of ferrous and ferric salts the well known characteristic precipi- tates. Chlorine oxidizes it to Potassium ferricyanide, red prussiate of potash, KgFeCyg, thus: SK^FeCyg + G\ = 2K3FeCy6 + 2KC1. This crystallizes in long dark-red monoclinic prisms which are readily soluble in water. The solution decomposes upon standing, and acts as a strong oxidizing agent in the presence of alkali, K^FeCyg being reproduced. * For the sake of brevity, irou is here and in the following pages regarded as di- and trivalent. FEREO- AND FERRI-CYANIDES OF IRON. 277 Hydro-ferricyanic acid, HgFeOyg, forms brown needles, and is easily decomposed. FERRO- AND FERRI-OYANIDES OF IRON. Ferroeyanides. Ferricyanides. Ferrous salts, Ferric salts. Potassium-ferro-ferrooyanide, K2Fe''(Feay6)", fromFeS04 + K4FeCy5 ; white, becom- ing rapidly blue in the air from conversion into Potassium-ferri-ferrocyanide, KFe"'(PeCy8). Insoluble Prussian blue or Williamson's blue, Fe4«'(FeCy8)3, from FeClj + K4FeCye ; blue powder with a copper glance. TumhvXVs blue, Fee''(FeCye)2'", from FeS04 + KaFeCy,. (FeCla + KgFeCye give no precipitate, but only a brown colouration. ) KFe'"(reCye)" = KFe"(PeCy8)'" = Soluble Prussian blue, from ferric or ferrous salts and excess of ferro- or ferri-cyanide of potassium. The formation of Prussian blue was first observed by Diesbach soon after the year 1700. As regards the constitution of hydro-ferro- and hydro-ferricyanic acids, one may make the assumption that they contain the trivalent radicle (CsNs)"", " tricyanogen," of cyanuric acid (see p. 280): K,={C,-N,)>^^ K,=(CiN3r*^ Potassium ferrocyanide. Potassium ferricyanide. p.ui<^(C3N3) Fe" (C3N3)=^j, u, , *® <(C3N3)=Fe'' Fe"=(C3N3)<^^® ' ^^'^ ^° °°- TumbuU's blue. When ferrocyanide of potassium is oxidized by nitric acid, there is formed Nitro-prussic acid, whose sodium salt, FeOy5(NO)Na2 + 2H2O, crystallizes in red prisms soluble in water and forms a valuable reagent for the detection of sulphuretted hydrogen, an alkaline solution yielding with the latter a splendid but transient purple-blue colouration. 278 XII. CYANOGEN COMPOUNDS. B. Halogen Compounds of Cyanogen. Cyanogen chloride, CN.Cl, (Berthollet). Colourless con- densible gas of a most obnoxious pungent odour, somewhat soluble in water. B. Pt. of its liquid 15-5°. It is prepared by the action of chlorine upon mercuric cyanide or upon dilute aqueous hydrocyanic acid, thus : CNH + Clj = CNCl + HCl. It polymerizes readily to cyanuric chloride, and yields potassic chloride and cyanate with aqueous potash, appearing thus as the chloride of cyanic acid : CKCl + 2K0H = CN.OK + CIK + R^O. Cyanogen bromide, CNBr. Analogous to the chloride. Transparent prisms. Cyanogen Iodide, CNI. Beautiful white prisms, smelling intensely both of cyanogen and iodine, and subliming with the utmost ease. Very poisonous. Prepared from mercuric cyanide and iodine. Cyanuric chloride, tri-chloro-cyanogen, (CN)3Cl3. This polymer is obtained from cyanogen chloride, or from hydro- cyanic acid and chlorine in ethereal solution. It forms beauti- ful white crystals, of an unpleasant pungent odour. M. Pt. 145°, B. Pt. 190°. Boiling water decomposes it with formation of hydrochloric acid and cyanuric acid, (CN)3.(OH)3, of which latter it appears as the chloride. It contains the trivalent radicle (CN)3'" = tri-cyanogen, (see Cyanuric acid). C Cyanic and Cyanuric acids. Cyanuric acid is formed when urea is heated, either alone or in a stream of chlorine gas ; by subjecting it to dry distillation and condensing the vapours evolved in a freezing mixture, one obtains Cyanic acid, CNOH, as a mobile liquid of a pungent odour : C3N3O3H3 = 3CN0H. It is exceedingly unstable ; when taken out of the freezing mixture it changes, with explosive ebullition, into the poly- CYANIC ACID AND CYANATES. 279 meric Cyamelide, (CONH)„ a white porcelain-like mass which goes into cyanic acid again upon heating. Cyanic acid com- bines with ammonia to cyanate of ammonium. Potassium cyanate, CNOK, frequently also termed potassium isocyanate, is prepared by the oxidation of an aqueous solution of potassic cyanide by means of permanganate (A. 259, 377) ; or by fusing potassic cyanide or yellow prussiate of potash with PbOa or MnOj: (CNK + = CNOK). White plates, readily soluble in water and alcohol. It yields hydrazo-dicarboxylic amide (p. 299) with hydrazine sulphate (A. 271, 127). Ammonium cyanate, CN0(NH4), forms a white crystalline mass, and is of especial interest on account of the readiness with which it changes into the isomeric urea, CONjH^. When hydrochloric acid is added to these salts, there result — instead of free cyanic acid — its products of saponification, CO2 and NH3 :— CONH + H^O = CO^ + NH3. This decomposition is avoided by the addition of dilute acetic acid (instead of hydrochloric), but in the latter case the cyanic acid changes into its polymer cyanuric acid, the hydrogen- potassium salt of the latter slowly crystallizing out From cyanic acid are derived two isomeric classes of alco- holic derivatives, by the replacement of the hydrogen by alcohol radicles. The derivatives which are constituted on the type N^C.OR are termed the normal, and those on the type 0=C^NE the iso-compounds. I. When potassium cyanate is distilled with ethyl iodide or, better, with potassium ethyl-sulphate, there is obtained Ethyl iso-cyanate or cyanic ether, CO.NCjHj, a colourless liquid of suffocating odour, which boils unchanged at 60° and is decomposed by water. It does not possess the properties of a compound ether, but is broken up by alkalies or acids into ethylamine and carbon dioxide, thus : CONCA -1- H^O = CO2 + NH^-CgHs. Water, which acts in a similar manner, gives rise to the more complicated urea derivatives ; ammonia and amine bases 280 xn. CYANOGEN COMPOUNDS. also produce derivatives of urea (p. 292), and alcohol yields derivatives of carbamic acid (p. 291). Constitution. — The formation of ethylamine proves that the N of the cyanic ether ia linked directly to the alcohol radicle, so that the consti- tution is : 0=C=N.C2Hb. It is questionable, however, whether free cyanic acid and cyanate of potassium possess analogous constitutions, since frequent observations have shown that the normal cyanic com- pounds readily change into the iso-(see below); theoretical considerations indeed make it more probable that cyanic acid has the constitution N=C — OH, according to which it appears as the normal acid, with cyanogen chloride as its chloride. Potassium cyanate would then be N=C— 0— K. Normal cyanic ethers are not known with certainty: cyan- etholine, CN.OCjHj, obtained by the action of cyanogen chloride upon sodium alcoholate, is looked upon as one of them. Cyanuric acid, CgNgOgHg, = (C]Sr)3(OH)3 {Seheele). The formation of cyanuric acid by heating urea, already mentioned on p. 278, is easily understood when one remembers that it is made up of the constituents of cyanic acid and ammonia, so that, when the latter is split off, the former becomes free and then polymerizes. Cyanuric acid forms transparent prisms which contain 2 mols. HgO of crystallization and weather in the air, and which are readily soluble in hot water. It is a tribasic acid. The sodium salt is sparingly soluble in cone. NaOH; the (Cu-NH^) salt possesses a characteristic beautiful violet colour. Upon prolonged boiling with hydrochloric acid it is saponiiied to COj and NHg, while phosphorus penta- chloride converts it into cyanuric chloride, the acid being regenerated from this by water. Cyanuric acid also gives rise to two isomeric classes of alcoholic derivatives, viz. : 1. The Normal cyanuric ethers, e.g. C8N3(00jHb)3 (a colourless liquid), which result from the polymerization of the cyan-etholinea and also by the action of methyl iodide etc. upon cyanurate of silver at the ordinary temperature. They easily change into the isomeric 2. Iso-oyanuric ethers or tri-cwrhimido ethers, e.g. C30j(NC2H5)3, colourless liquids which frequently result instead of the cyanic ethers, OYANURIO ACID. 281 for example, on the distillation of oyanurate with ethyl-sulphate of potassium. They are further formed by the polymerization of the iso- oyanic ethers, being thus obtained as bye-produots in the preparation of the latter. The normal compounds are broken up by saponification with the formation of alcohol, and the isomers with formation of ethylamine. The constitution of oyanurio acid follows from its relation to cyanuric chloride as (CN)3(0H)3, and that of the alkyl derivatives from their behaviour upon saponification. The normal compounds therefore contain, like cyanuric chloride, the trivalent radicle tri-cyanogen, (CN)3, whose N- and C-atoms one assumes to be linked to each other alternately by single and double bonds in a "closed ring," while the iso-oyanic ethers are to be regarded as derived from a hypothetical original substance consisting of three CO- and NH-groups joined together in the form of a ring (cf. A. W. Bofmann, H, 18, 2755; Ponomarew, B. 18, 3261 ; also Benzene derivatives) : CI OH (OCjHs) I I I N N K ^N K N II I II I II I 01— C C— CI HO— C C-OH (CjHjO-C C-(OC2H5) Cyanuric chloride. Cyanuric acid. Cyanuric ether. (CA)N/ ^N(CA) I I 00 ,C0 (C2H5) Isocyanuric ether. In addition to cyanuric acid and oyamelide, various other polymers of cyanic acid have been described, but only some of them have been closely studied. (Cf. among others, J. pr. Ch. 32, 461.) Further, in the aromatic series, derivatives of a Di-lsocyanio acid, (CO)2.(NH)2, are known, (B. 18, 764). 282 XII. CYANOGEN COMPOUNDS. D. Thiocyanic Acid and its Derivatives. Potassium thiocyanate, -sulphocyanate, -mlphocyanide, -rhodanide, CNSK. Potassium cyanide not only combines readily with oxygen to cyanate but also with sulphur to thio- cyanate, either when fused with sulphur or when its solution is evaporated with yellow sulphide of ammonium ; KCN + S = CNSK. It is prepared by fusing yellow prussiate of potash with sulphur and potashes. It forms long colourless deliquescent prisms, extremely soluble in water with absorption of much heat, and also easily soluble in hot alcohol. Ammonium thiocyanate, ammonium rhodanide, CNS(NH4), results upon warming a mixture of carbon bisulphide, concen- trated ammonia and alcohol {Millon), di-thiocarbamate and tri-thiocarbonate of ammonia being formed as intermediate products (see p. 296): CS2 + NH3 = CNSH + HgS. Colourless deliquescent plates, readily soluble in alcohoL Upon being heated to 130°-140°, it is partially transformed into the isomeric thio-urea, just as ammonium cyanate is into ordinary urea. It precipitates silver thiocyanate, CNSAg, (white) from solutions of silver salts, and is therefore employed in the titration of silver, with ferric sulphate as indicator ; and it gives with ferric salts a dark blood-red colour- ation of Potassium-ferri-thiocyanate, 2 Fe(CNS)3 + 9KCNS -H 4 HjO. This last reaction is exceedingly delicate. MercurouB thiocyanate, Hg2(CNS)2, is a white powder insoluble in water, which increases enormously in volume upon being burnt, (Pharaoh's serpents). The Aluminium salt is used in printing with alizarin red. The free Thiocyanic acid, CNSH, is obtained by decomposing its mercury salt with hydrochloric acid. It is a pale yellow liquid of pungent odour, and is only stable in a freezing mixture, or when in dilute aqueous solution. At the ordinary temperature it polymerizes to a yellow amorphous substance, and decomposes in concentrated aqueous solution, with formation of Fersnlphocyanic acid, CjNaSsHj (yellow crystals). TIIIOCYANATES. 283 Concentrated sulphuric acid decomposes the thiocyanates with formation of carbon oxy-sulphide : CNSH + HgO = COS + NHg J sulphuretted hydrogen decomposes them into carbon bisulphide and ammonia : CNSH + HjS = CSg + NHg. Cyanogen sulpMde, (CNJaS, ia to be regarded aa the thio-anhydride of thiocyanio acid ; it is prepared from cyanogen iodide and silver thio- cyauate, and forms readily soluble plates of sharp odour. Just as in the case of cyanic acid, so are there derived from thiocyanic acid two isomeric classes of alcoholic derivatives, by the replacement of hydrogen by alcohol radicles. I. Compound ethers of thiocyanic acid result from the entrance of alcoholic radicles in the place of the hydrogen of the acid. Ethyl thiocyanate, CN.SC2H5, is obtained either (1) by the distillation of potassium ethyl-sulphate with potassium thio- cyanate, or (2) by the action of cyanogen chloride upon a mercaptide. It is a colourless liquid with a peculiar pungent odour of leeks, and almost insoluble in water. B. Pt. 142°. Alcoholic potash saponifies it in the normal manner with reproduction of potassium thiocyanate ; in other reactions, however, the alcoholic radicle remains united to the sulphur. Thus nascent hydrogen reduces it to meroaptan, and fuming nitric acid oxidizes it to ethyl-sulphonic acid. It follows from mode of formation (2) and also from the reactions of the thiocyanic ethers that the sulphur in them is linked to the alcohol radicle. Consequently in the salts it is linked to the metal in question, and in the free acid to hydrogen. We have therefore the following constitutional fonriulae : N=C— SH N=C— SK N=C— SCjHj Thiocyanic acid. Potassium thiocyanate. Ethyl thiocyanate. Allyl thiocyanate, CN.SC3H5. Colourless liquid smelling of leeks. B. Pt. 161°. Changes upon distillation into the isomeric mustard oil. II. Isomeric with the thiocyanic ethers are the mustayd oils (" Senfole.") Allyl iso-thiocyanate, common mustard oil, CS : N.CgHj, is 284 XIL CYANOGEN COMPOUNDS. prepared by distilling the seeds of black mustard (Sinapis niger) with water. It is a liquid sparingly soluble in water and of exceedingly pungent odour, which produces blisters on the skin. B. Pt. 151°. It results on distilling allyl thiocyanate, by a molecular rearrangement, and it is also obtained by the action of carbon bisulphide upon the corresponding primary amine, allylamine, thus : CSa + NH2.G3H5 = OS : N.C3H5 + H^S. This reaction does not, however, proceed exactly as indicated in the above equation, there being first formed the allylamine salt of allyl- di-thiocarbamie acid, which is changed into allyl iso-thiocyanate upon distillation with mercuric chloride. (See di-thiocarbamic acid, p. 297.) Ethyl Iso-tMocyanate, C2H5N.CS, (B. Pt. 134°), and Methyl iso-thlo- cyanate, CH3N.CS, (solid, M. Pt. 34°, B. Pt. 119°), etc., closely resemble the allyl compound, and are obtained in an analogous manner by the action of carbon bisulphide upon ethylamine, methylamine, etc. The mustard oils also result from the distillation of alkylated thio- ureas (p. 298) with syrupy phosphoric acid {Hofmann, B. 16, 985), or with concentrated hydrochloric acid. They break up on being saponi- fied, with reproduction of the primary amines from which they can be prepared : CS.NC3H5 + 2H2O = NH2.C3HB -t- HjS + COj. They are connected with the thio-ureas by various reactions, and also with the cyanic ethers, since in the latter can be replaced by S, but in the mustard oils, on the contrary, S by 0. The coTistitution of the mustard oils follows from their relation to the primary amines, the alkyl being linked to nitrogen in both classes of compounds ; the constitutional formula of methyl iso-thiocyanate is therefore S=C=N — CHj. Iso-thiocyanic acid, SC=NH, is itself unknown. Polymers. Dithlo-dicyanic acid, OjNjSaHj. The potassium salt of this polymer has been described, but little is known about it. Thlo-cyanuric acid, (C8N3)(SH)3, is a tribasic acid. Yellow powder. The primary sodium salt, C3Ns(SH)2SNa, crystallizes well. It is formed e.g. Jby the action of oyanuric chloride upon sodium sulphide, whence its constitution follows. Its Trl-methyl ether results along with methyl iso-thiocyanate upon heating methyl thiocyanate to 180°, by the polymerization and subsequent molecular transformation of the latter (A. W. Eofmwrm, B. 18, 2196; Klason, B. 19, Bef. 136). Polymeric mustard oils are also known (Hofmann, B. 2S, 876). CYANAMIDE. 285 E. Cyanamide and its Derivatives. Cyanamide, CN.NHg, (Bineau), is formed : 1. By leading cyanogen chloride into an ethereal solution of ammonia : CNCl + 2NH3 = CN.NH2 + NH.Cl. 2. By the action of HgO upon thio-urea in aqueous solution, (" desulphurization ") : NHj— CS— NH2 = NC.NH2 + H^S. Colourless crystalline hygroscopic mass, readily soluble in water, alcohol and ether. M. Pt. 40°. When heated to 150°, it changes into the polymeric dicyan-diamide with explosive ebullition; also on evaporating its solution or allowing it to stand. Dilute acids cause it to take up the elements of water, with formation of urea: CN-NHg + HgO = CONgH^; and it combines in an analogous manner with sulphuretted hydrogen to thio-urea. When heated with ammonia salts it yields salts of guanidine. Cyanamide behaves as a weak base, forming crystalline easily decomposable salts with acids and, at the same time, as a weak acid, yielding a sodium salt, CN.NHNa, a lead and a silver salt, etc. The last is a yellow powder and has the composition CNjAgg. Cyanamide also gives rise to two isomeric series of alcoholic deriva- tives, by the replacement of the hydrogen by alkyl. I. Methyl- and Ethyl-cyanamides are prepared e.g. from methyl- and ethyl-thio-urea. Dl-ethyl-cyanamide, CN2(C2H5)2, is obtained by treat- ing sUver-oyanamide with ethyl iodide. Acids saponify it to COj, NHj and NH(C2H5)2, hence it possesses the constitution N=C — N(C2H5)2 : N=C— N(C2Hb)2 + 2H2O = NH3 -I- CO2 + NHICaHjjj. From this it follows that cyanamide has most probably the constitu- tion which corresponds with its name, viz., N=C — NHj. II. Other cyanamide derivatives, which are chiefly known in the aromatic series, spring from a hypothetical isomer of cyanamide, viz., Carbo-di-imide, NH=C=NH ; for instance, Dlphenyl-carbo-di-lmide, CN2(C8H5)2. Boiling with acids likewise decomposes them into COj and an amine, but the latter can only be a primary one. 286 XII. CYANOGEN COMPOUNDS. Polymers. Dicyan - diamide, parame, CjNjH, (p. 285). Crystallizes in beautiful broad needles or prisms, and has probably the constitution N=C— NH— C^^ (B. 24, 899). Like cyanamide, it yields melam when strongly heated. Melamiue, cyanuramide, CaNeHe (Liebig, 1838), forms glancing rhombic octahedra, insoluble in alcohol and ether, and possesses basic properties. When it is boiled with acids, the NHj- groups are successively replaced by OH with the formation of Ammeline, (CN)8(NH2)20H, Ammelide, (CN)8NH2(OH)2, and finally cyanurio acid, (CN)3(OH)3. Melamine has therefore the constitution (CN)s(NH2)8, = trioyan-triamide. Further, alkylated melamines are derived from melamine by the replacement of hydrogen by alkyl, and in addition to these there exists an isomeric class of compounds of which the hypothetical " Iso-melamine," [C(NH)]3(NH)s, is the basis. To this class belong the polymerization pro- ducts of the alkyl cyanamides. The following constitutional formulae are ascribed to these two series (E=Alcohol radicle) : NRj II '/^\ /^ \ N^ ^N and RN'^ UN I II II NE^-C^ ,C.NRa NE=C >C=NE, Melamines. Iso-melamines. For particulars see >1. W. Eofmarm,'R. 18,2755,3217; iJatMe, B. 20, 1056. Melam, [{CN)3(NH2)2]2NH, is an imide of melamine, into which it is con- verted by ammonia (Rathke, SmolJca), and by sulphuric acid. It forms a white powder, insoluble in water. It is prepared by heating cyanamide, dicyan-diamide, or ammonium thiocyanate strongly. F. Appendix. Theoretical Considerations as to isomerism in the Cyanogen Group. As has already been explained, there are derived from hydrocyanic acid, cyanic acid, thiocyanic acid and cyanamide, and also from their polymers, two classes of isomeric alcoholic derivatives which differ sharply from one another in their products of decomposition. They correspond, properly speaking, to two isomeric mother substances — the " normal " and " pseudo " forms {Ad. Baeyer) — only one of which, however, is known in the free state, viz., the normal compound (of. Hofmamn, loc. oit. ; Klason, B. 20, Ref. 317). The fact that the isomeric form has never been obtained may be explained by assuming that it represents an unstable state of equilibrium of the atoms and that when attempts are made to ISOMERISM IN THE CYANOGEN GROUP. 287 prepare it, it immediately undergoes molecular tranaformation into the other, stable, form. When the hydrogen is replaced by alkyl, both varieties of atomic groups are in most cases capable of existence, although even here also a difference in stability is observed, the normal compounds changing very readily into the iso- (or pseudo-) com- pounds. In consequence of this one obtains the iso-cyanie ether directly from potassium oyanate instead of . the normal one, allyl thiocyanate readily changes into the iso-thiocyanate, and iso-cyanurio ether is usually got instead of oyanurio, etc., etc. It is also conceivable that the mother substances may possess both the above constitutional formulae, i.e. that, by the wandering of an atom of hydrogen, their atoms may sometimes arrange themselves in the one and sometimes in the other form, and that they may accordingly show the reactions of either ("Tautomerism ;" see.p. 26; Butlerow, A. 189, 76; of. Laar, B. 18, 648; 19, 730; Bamberger, B. 23, 1856). Among other compounds, regarding which considerations of this nature have been advanced, may be specially mentioned thio-urea, CS(NH2)ii or C(NH)-{ oji'' (p. 297), amides of mono- basic acids (see p. 197) and their thiamides, K — CS.NHj or R — C!<^gg- (p. 199), sodio-aoeto-acetic ether (p. 245), diazo-benzene, phloroglucin, isatin, carbostyril, etc. One of the formulae in question of these substances is convertible into the other simply by the wandering of a hydrogen atom : — " hydrogen-isomerism," It has been proved that many of these compounds react in a manner which corresponds as well with the one formula as with the other. When a "change in the bonds" of such "tautomeric" sub- stances occurs, it is termed " desmotropism " {Hantzseh and Herrmann, B. 20, 2081; 21, 1754; Baeyer, A, 245, 189; Forster, B. 21, 1857), or " iso-dynamic molecular transformation " (A rmstrong). There can be no desmotropism when there is no longer present in the molecule a hydrogen atom capable of " wandering " (cf. B. 23, 1856). XIII. CARBONIC ACID DERIVATIVES. Carbonic acid is a dibasic acid, forming two series of salts, e.g. NagCOg and NaHCOg. The hydrated acid itself, OH COgHj, = 0=0<^QTT, is unknown, but may be supposed to exist in the aqueous solution. Its empirical formula shows carbonic to be the lowest oxy-aoid CaHanOj, i.e. it is homologous with glycoUio acid and may be looked upon 288 XIII. CARBONIC ACID DERIVATIVES. as oxy-formio acid. Its dibasic nature is explained by the carbonyl group apparently extending its acidifying character over both hydroxyls equally. Since the latter are both linked to one carbon atom, the non- existence of the free hydrate is readily understood (see p. 142, etc.). The salts of carbonic acid and those of several of its deriva- tives, such as carbon bisulphide, CSg, and carbon oxy-sulphide, COS, have been already treated of under inorganic chemistry. But there still remain for description the compound ethers, chlorides and amides of carbonic acid, two series of which exist, acid and neutral, as in the case of all the dibasic acids, 0„H2„_204. The neutral compounds are well characterized and are very similar to those of oxalic or succinic acid ; the acid compounds on the other hand are unstable in the highest degree when in the free state, and are known almost only as salts. Many mixed derivatives have also been prepared, e.g. carbamic ether, CO(NH2)(OC2H5), analogous to oxamethane (p. 252). Swnmary. Neutral derivatives. COCOCjH,)^ Ethyl carbonate. COClj Carbonyl chloride. C0(NH2)j Urea. Acid derivatives. CO(OC2H5).OH Ethyl carbonic acid. C0(C1)(0H) Chloro-carbonic acid. CO(NHj)(OH) Carbamic acid. Mixed derivatives. CO(Cl)(OCsH„) Chloro-carbonic ether. CO(NHs)(OCA) Urethane. The modes of formation of these compounds are for the most part exactly analogous to those of the corresponding derivatives of the monobasic acids and of oxalic acid. A. Ethers of Carbonic Acid. Ethyl carbonate, CO(O02H5)2, is formed : 1. By the action of ethyl iodide upon silver carbonate : CHLORIDES OF CARBONIC ACID. 289 2. By the action of alcohol upon chloro-carbonic ether, and therefore indirectly from carbon oxychloride and alcohol : CO(OC2H5)Cl + C2H5OH = CO(O02H5)2 + HOI. It is a neutral liquid of agreeable odour, lighter than water and insoluble in the latter. B. Pt. 126°. Analogous Methyl-, Propyl-, etc. cartonatea are known, and also ethers containing two different alcohol radicles. It is a matter of no consequence which of these radicles is introduced first into the molecule, a proof of the equal valency of the two hydroxyls. Ethyl-carbonic acid, CO(OC2H5)(OH), corresponds exactly with ethyl-sulphuric, but is much less stable and only known in its salts. Potassium ethyl-oarUonate, C0(0C2Hb)(0K), results upon passing CO2 into an alcoholic solution of potassium ethylate : CO3 + KOCgHj = COsCCjHjjK. It crystallizes in glancing mother-of-pearl plates, but is decomposed by water into potassium carbonate and alcohol. B. Chlorides of Carbonic Acid. Carbon oxy-chloride, carhonyl chloride, phosgene, COCl^, (/. Davy). This compound is analogous to succinyl chloride, C2H^(C0C1)2, and to sulphuryl chloride, SOgClg. It is ob- tained by the direct combination of carbonic oxide and chlorine in sunlight, etc., and also by the oxidation of chloro- form by means of chromic acid. Colourless gas, condensing to a liquid below -f8°, of exceptionally suffocating odour. Soluble in benzene. As an acid chloride it decomposes violently with water into COg and HCl. It therefore trans- forms hydrated acids into their anhydrides, with separation of water, and converts aldehyde into ethylidene chloride. It yields urea with secondary amines of the fatty series, and carbamic chlorides with secondary amines of the aromatic (B. 30, 783). Is employed in the preparation of dyes. Chloro-carbonic acid, COCl(OH), the acid chloride of car- bonic acid analogous to chlor-oxalic acid (p. 249), has too great a tendency to break up into COj and HCl to allow of its (606) T 290 XIII. CARBONIC ACID DERIVATIVES. existence either in the free state or in that of salts. As a monobasic acid, however, it forms ethers, e.g. Chloro-carbonic ether, CO(Cl)(OC2H5) ( = chloro-formic ether, CI— CO.OOaHg), which results from the action of carbon oxy-chloride upon alcohol, (Dumas, 1833) : COCI2 + C2H5OH = COOKOC^Hs) + HCl. This is a volatile liquid of very pungent odour, which boils at 93°. It reacts as an acid chloride, being decomposed by water, and is therefore specially fitted to effect the synthetical entrance of the carboxyl group into many compounds. The corresponding Methyl- etc. ethers are very similar. O. Amides of Carbonic Acid. The neutral amide of carbonic acid is urea or carbamide, the acid amide or aminic acid is carbamic acid. Imido-carbonic OTT acid, C(NH)qtt, would be an imide of carbonic acid, but it is only known in its derivatives, (Sandmeyer, B. 19, 862^). The hypothetical form of cyanic acid, CO=NH (see table, p. 270), would also be an imide of carbonic acid, and that of cyanamide, C(NH)2, a di-imide, while cyanic acid itself is to be regarded as a half nitrile, with cyanamide as its amide. The amidine of carbonic acid is guanidine. The " ortho-amide " of carbonic acid, which woiild. possess the formula C(NIl2)4, is unknown ; when it might be expected to be formed, guanidine and ammonia result instead. The modes of formation of urea and of carbamic acid are exactly analogous to those of the amides in general ; 1. By the action of ammonia upon ethyl carbonate : GOiOG^'R,)^ + 2NH3 = C0(NH5)j + 2GjjHs.0H. CO(OC2H5)i, + NH3 = CO(OC2H5)NHi, + C^HgOa 2. By the abstraction of the elements of water from car- bonate or carbamate of ammonia. Dry carbon dioxide and ammonia combine together directly to ammonium carbsimate, the CARBAMIO ACID; URETHANE. 291 so-called anhydrous carbonate of ammonia, C0(NH2).0H, NH3, which goes into urea when heated to 135°, or when exposed to the action of an alternating current of electricity, thus : CO(NH2).OH,NH3 = COCNHj)^ + Rfi. 3. By the action of ammonia upon carbon oxy-chloride : COCI2 + 4NH3 = CO(NH2)2 + 2NH,C1. CO(OC2H5)Cl + 2NH3 = CO(OC2H5)NH2 + NH.Cl. Carbamic acid, C0(]SrH2)0H. Carbamate of ammonia, which forms a white mass, dissociates at 60° into 2NH3 + COj. Its aqueous solution does not precipitate a solution of chloride pf calcium at the ordinary temperature, since calcium carbam- ate is soluble in water, but, if it is heated, saponification into CO2 and NH3 ensues and calcium carbonate is thrown down. Urethane, CO(NH2)(OC2H5), is the ethyl ether of carbamic acid. It is formed according to method 3, and by the direct union of cyanic acid with alcohol; also from urea nitrate and sodium nitrite in presence of alcohol. Large plates, easily soluble in water, etc. M. Pt. 47°-50°. Boils unchanged and acts as a soporific. One of its hydrogen atoms is replaceable by sodium. Urethane may be employed instead of cyanic acid for certain synthetic reactions (B. 23, 1856). Analogous Methyl- etc. ethers of carbamic acid are also known. They are all readily saponified by alkalies into the alcohol, CO2 and NHs, and pass into urea when heated with ammonia. Carbamic chloride, COp, ^ is obtained by the action of hydrochloric acid upon cyanic ( WShZer, A. 45, 357), and of COClj upon NHjCl at 400°. 'It forms long, compact, colourless needles of pungent odour. M. Pt. 50°, B. Pt. 61°-62°. It reacts violently with water, amines, etc., and serves tor the synthesis of organic acids (see these). Among its derivatives is e.g. Di- methyl-carbamic chloride, C0[N(GH3)2]C1. In the same way alkylated carbamic acids, CO(NHE)OH, which are only stable as ethers, have been prepared, e.g. Ethyl-carbamic ether, ethyl- urethane, CO(NH.C3Hs)(OC2Hs), a liquid, B. Pt. 175°, which is formed e.g. by the direct combination of cyanic ether with alcohol at 100°. Imido-dicarboxylio-diethyl ether, NH(C0202Hs)2, is the imide corre- sponding to the amide urethane (cf. diacetamide). It results from the sodium compound of urethane and chloro-carbonic ether. Colourless crys- tals; M. Pt. 50°. By the exchange of one (OC2H5) group for NH2, it gives rise to allophanio ether, and by the exchange of two, to biuret. 292 XIIL CARBONIC ACID DERIVATIVES. Urea, carbamide, CO(NH2)2. Was first found in urine in 1773. Is contained in the urine of mammals, birds and some reptiles, and also in other animal fluids. An adult man pro- duces about 30 grm. daily. Urea is the final decomposition product from the oxidation of the nitrogenous compounds in the organism. Formation. From ethyl carbonate, carbamic acid and phos- gene, as given above, and synthetically by the molecular trans- formation of ammonium cyanate, bywarming its aqueous solution or allowing it to stand {JVohler, 1828; see pp. 1 and 279): OK OH, NHj = CO(NH2)2. It 13 further formed from cyanamide and water : CN-— NHa + HjO = OOlNHjjj ; from thio-urea and potassium permanganate (p. 298) ; by the partial saponification of guanidine (p. 299): C(NH) (NHajj -f HjO = CO(NH3)2 + NHs ; by heating oxamide with mercuric oxide, by the breaking up of creatine, by means of alkali, and by the oxidation of uric acid, etc. etc. Preparation. 1. By evaporating urine, adding nitric acid, and decomposing the separated and purified nitrate of urea by barium carbonate. 2. By mixing a solution of potassium cyanate (from the ferrocyanide), with ammonium sulphate and evaporating : 2CN0K + (NH,)2S04 = CO(NH2)2 + K^SO^. It crystallizes in long rhombic prisms or needles of a cooling taste, which are very readily soluble in water, readily also in alcohol, but not in ether. M. Pt. 132°. Sublimes in vacuo without decomposition. When strongly heated it yields am- monia;, cyanuric acid, biuret and ammelide. As an amide it is readily saponified by boiling with alkalies or acids, or by super- heating with water: CO(NH2)2 + HjO = CO2 -^ 2NH3. Nitrous acid reacts with it to produce carbon dioxide, nitrogen and water: CO(NH2)2 -t- 2NO2H = CO2 -I- 2N2 + 3H2O. Sodium hypochlorite and hypobromite act in a similar manner {Davy, Knop). Hufner's method of estimating urea quantitatively depends upon the measurement of the nitrogen thus obtained (J. pr. Ch. [2] 3, 1 ; cf. also B. 24, Kef. 330). When warmed with UKEA; ALKYLATED UKEAS. 293 aleo&olic potash to 100°, urea is converted into cyanate of potassium and ammonia. The basic character of ammonia is greatly weakened in urea by the influence of the negative carbonyl. Among the salts of urea with acids may be mentioned Vrea nitrate, CON2H4, HNOg, which crystallizes in glancing white plates, easily soluble in water but only slightly in nitric acid ; also the chloride, oxalate and phosphate. But like acetamide urea also forms salts with bases, especially with mercuric oxide, c. g. CON2H4 + 2HgO ; finally it yields crystalline compounds with salts, e.g. Urea sodium chloride, CON2H4 + NaCl + H2O (glancing prisms), and Urea sUver nitrate, CON2H4 + AgNOs (rhombic prisms). The precipitate which is ob- tained on adding mercuric nitrate to a neutral aqueous solution of urea has the formula 2CON2H4 + Hg(N03)2 + 3HgO ; upon its formation depends Liehig's method for titrating urea. (See the memoirs of Pfliiger and Bohland on the subject, e.g. Pfluger, Arch. f. Phys. 38, 575). Isomeric with urea is the amid-oxime Isuret, CH(NH)(NH. OH), which results from HON and NHjOH ; it crystallizes in prisms. Alkylated ureas are obtained by the exchange of the amido-hydrogen atoms for 1, 2, 3, or 4 alcohol radicles. They are produced by Wohler's method of synthetizing urea, viz. by the combination of cyanic acid with amines, or of cyanic ethers with ammonia or amines, thus : CO.NC2H5 + NH2.C2H5 = CO(NH.C2H5)2. Also from amines and carbon oxy-chloride. As examples may be men- tioned : Methyl urea, CO<^^Qg- ; a-Di-ethyl urea, CO<^g;^2^6. Ethyl urea, CO<^f f p^H, ' ^"Di-ethyl urea. C0<^g2^^^^. They are in part very similar to urea, in part however liquid and volatile without decomposition. Their constitution follows very simply from the nature of the products which result on their saponification ; thus, o-di-ethyl urea breaks up into COj and 2 mols. NHj.CaHg, and the /3-compound into CO2, NH3 and NH(C2H5)2, in accordance with the law enunciated on p. Ill, that alcoholic radicles which are directly bound to nitrogen are not separated from it by saponifying agents. For Hydrazine derivatives of urea, see p. 129. Acid derivatives. By the entrance of acid radicles into ■urea, its acid derivatives or "Ureides" result. These are 294 XIII. CARBONIC ACID DERIVATIVES. formed by the action of acid chlorides or anhydrides upon urea, or by the action of phosphorus oxy-chloride, POClg, upon a mixture of the latter with the acid. They correspond in their properties to di-acetamide (p. 198). To this class belong Acetyl urea, CON2H3(C2H30), and Allophanio acid, CO(NH2)(NH.C02H). Divalent monobasic acids also form ureides, not only in virtue of their alcoholic nature, but as alcohol and acid at the same time, thus : Hydantoio acid. CO<^|^cH,-CO,H, /NH.CH-CH^ Hydantom, CO caffeine, C5H(CH3)3N402, hypoxanthine, CgH^N^O, and guanine, C5H5N5O; further, purpuric acid, OgHjNjOg, alloxantin, CgH^N^Oi^, allantoin, C^HgN^Og, and other compounds. Many of these di-ureides occur in nature. Uric acid is contained in the urine, blood and muscle juice of the carnivora, in gravel and chalk stones, in guano, and in the excrementa of serpents ; xanthine in small quantity in the urine, hlood and liver, and sometimes in gravel, almost always together with hypoxanthine ; guanine in guano ; and carnine in extract of meat. Theobromine is present in the cocoa bean (Theobroma Cacao), and caffeine in the coffee bean, in tea, in Paraguay tea (Ilex paraguayensis), and in the guarana (the fruit of PauUinia sorbilis), etc. Many of these compounds are nearly related to one another; thus we have hypoxanthine formed by the action of sodium amalgam upon uric acid, (taking away of 0), xanthine by the action of nitrous acid upon guanine, (exchange of N and H for 0), theobromine and oafifeine by the methylation of xanthine, and hypoxanthine by the action of nitric acid upon carnine. Formation. The ureides mentioned above or other diureides result, frequently together with urea, by the oxidizing de- composition (or oxidation) of the diureides which have been enumerated. Thus uric acid yields allantoin with water and PbOj and either purpuric acid, alloxan, alloxantin or parabanic acid with nitric acid, according to the conditions, while caffeine yields dimethyl-alloxan and methyl-urea with chlorine. These decomposition products also stand in an intimate relation to one another, e.g., alloxan gives alloxan- tin, dialurlc acid and barbituric acid on reduction ; hydantoin results e.g. from the oxidation of alloxanic acid and is itself oxidized to allanturic acid ; while dialurio acid and alloxan combine to alloxantin with elimination of water, etc., etc. Some of these ureides have also been prepared synthetically from urea and the requisite acid, phosphorus oxy-chlorid,e having proved itself to be particularly useful as a dehydrating agent in such cases ; in this way parabanic acid has been obtained from oxalic, and barbituric 302 XIII. CARBONIC ACID DERIVATIVES. acid from malonic. Uric acid may be synthetized by heating glyoocoU with urea, and also indirectly from aceto-acetio ether and urea, methyl- uracyl being formed as intermediate product; therefore also xanthine, theo- bromine and caffeine indirectly. The constitution of tlie simpler ureides and ureide-acids follows directly from their decomposition products, syntheses and relations to one another, while considerations of a more com- plex nature have led to the constitution of uric acid, (Medicus), and of xanthine and its more nearly allied compounds, (E. Fischer, A. 215, 253) : NH— C— NH^ NH-C=N Co/ 0-HB>™' CO^"' C-NH>™ \ ■ \ .. (3) KH— CO NH— OH (2) Uric acid. Xanthine. Guanine is imido-xanthine (O being replaced by NH) ; theobromine and caffeine are di- and trimethyl-xanthines (the H atoms 1 and 3, or 1, 2 and 3 being replaced by CHj). From this it follows that uric acid is the di-ureide of the unknown compound, C(0H)2=C(0H) — CO2H, or of the hydrate of tartronio acid, C(OH)s— CH(OH)— COOH. Most of the ureides and di-ureides have the character of more or less strong acids. Since this acid character is not to be explained, as in the case of the ureide-acids, by the presence of carboxyl, one must assume that it depends upon reasons similar to those which apply in the case of cyanic acid and of succinimide, viz., that the replaceable hydrogen atoms are imido- hydrogen atoms whose chemical nature is determined by the surround- ing carbonyl groups. This explains, for instance, why parabanic acid is a strong dibasic acid. Only a few of the more important among these compounds can be discussed here. (Cf. LieUg and Wohler, A. 26, 241 ; Baeyer,.A. 127, 1, 199; 130, 129, etc.) /NH.CO Parabanic acid,*CO<(^ 1 , is prepared by the action of nitric upon uric acid, and crystallizes in needles or prisms soluble in water and alcohol. The salts, e.g., CgHKN^Og, CjAg^NjOg, are unstable, being converted by water into salts of the mono- basic Oxaluric acid, C0<^jttt2qq qq tt, which crystallize well. * Qxalyl-urea. BARBITURIC ACID. 303 JSr(CHa)— CO A Methyl-paxabanlc acid, C0<~. < , and a Dl-methyl-para- N(CH,)— CO banic acid, the so-oalled " Cnolestrophane," COC(0H)-0-CHC0. When heated with ammonia it is converted into Murexide, the acid ammonium salt of Purpuric acid, C8H5N50g( + HgO), perhaps CO^(OH)-NH-CHCO, which is formed when uric acid is evaporated with dilute nitric acid, and ammonia added to the residue ; this is the " murexide test " for uric acid. Murexide crystallizes in four-sided tables or prisms (-t-HjO) of a golden-green colour, which dissolve to a purple-red solution in water and to a blue one in potash. The free acid is incapable of existence. Allantoin is a di-ureide of glyoxalic acid, of the constitution NH— CH— NH C0<^ 1 "^CO, which is found in the allantoic ^NH— CO NHj^ ' liquid of the cow, the urine of sucking calves, etc. It forms URIO ACID, 305 glancing prisms of neutral reaction, yields salts with alkalies, and can be prepared synthetically from its components. Uric acid, CgH^N^Oj, {Scheele, 1776). For occurrence and synthesis, see pp. 301 and 303. Synthesis. 1. By heatmg glycocoU with urea (HorlaczewsU, B. 15, 2678). 2. By heating iso-dialuric acid with urea and concentrated sulphuric acid {R. Behrend and 0. Roosen, A. 251, 235) : NH-C(OH) CO:r C(OH) + g^g>co = Iso-dialurio acid. NH-C-NH. \rH— do TJrio acid. 3. By heating cyan-acetic acid with urea (B. 24, 3419). Preparation. It is prepared from guano and the excrement of serpents, and crystallizes in small tables. Almost insoluble in water and insoluble in alcohol and ether, but concentrated sulphuric acid dissolves it without decomposition, and from this solution it is thrown down unchanged by water. For the murexide reaction, see above. Uric acid is a weak dibasic acid; its common salts are the primary (ie., hydrogen) ones, e.g. C5H3KN4O3, a powder sparingly soluble in water. When the two lead salta are treated with methyl iodide, Methyl- and Dimethyl-uric acid are obtained, both of which also are weak dibasic acids, since they still contain replaceable imido-hydrogen atoms. Constitution. The constitutional formula, given above, was first proposed by Medicos, and afterwards proved to be correct by E. Fischer (A. 215, 253). His researches on the subject were of a difficult nature, but the following is a summary of their most important results: — (1) Uric acid yields alloxan and urea when cautiously oxidized, this proving that we have to deal here with a carbonic acid derivative and a carbon chain, C — — 0; (2) Uric acid contains four imido-groups (see Di- methyl-uric acid), since, by the introduction of four methyl groups, one after the other, all the four nitrogen atoms are (606) u 306 XIII. CARBONIC ACID DERIVATIVES. separated as methylamine; (3) Dimethyl- uric acid yield* methyl-alloxan and methyl-urea on oxidation, thus : CO^ C-NH"^ -t-0 + H20 = C0:^ CO NHa' ^NH-CO ^NH-CO Xanthine, C5H4N4O2, is produced from guanine and nitrous acid, and from uric acid and sodium amalgam. It is a white amorplious mass, and is at the same time base and acid ; thus it yields e.g, the lead compound C5H2PbN402, which is converted into theobromine by methyl iodide. Hypoxanthine, sarcine, C5H4N4O. Sparingly soluble in water and very like xanthine. Theobromine, CyHgN^Og. Crystalline powder of bitter taste, sparingly soluble in water and alcohol. Forms salts both as base and as acid. The silver salt, CjH^AgN^02, yields caffeine when treated with CH3I, {Streeker, Fischer). Caffeine or Thelne, CgHjoN^Oj. Crystallizes (-i-HgO) in beautiful long glancing silky needles of faintly bitter taste, which are sparingly soluble in cold water and alcohol, and can be sublimed. The salts are readily decomposed by water. Chlorine breaks it up into dimethyl-alloxan and mono- methyl-urea. Guanine, CbHbNjO. White amorphous powder insoluble in water but soluble in ammonia. It is a divalent base, but also forms salts with bases. Yields guanidine, parabanic acid and carbon dioxide with KCIO3 + HCl. Is an imide of xanthine, containing NH instead of 0, and hence nitrous acid converts it into the latter compound. Adenine, CgHoNg, which is a polymer of hydrocyanic acid, is a base which results from the decomposition of nuclein (see this) ; it has been obtained from the pancreatic glands of oxen and from tea leaves. It crystallizes in long needles and is converted by nitrous acid into hypoxanthine, whose imide it therefore is. Camlne. A powder rather easily soluble in hot water. THE CARBOHYDRATES. 307 XIV. CARBOHYDRATES. Most of the carbohydrates which occur in nature have been known for a long time. Cane sugar was found in the sugar beet by Marggraf in 1747, and dextrose in honey by Glauber. The transformation of starch into sugar (p. 320) was first observed by Kirchoff'm 1811. The name " carbohydrate " was formerly applied in particular to three groups of compounds nearly allied to one another and which are very widely distributed in nature, viz., those of grape sugar, CgHjjOj, of cane sugar, CijH^^Oji, and of cellulose, (C|;HjQ05)n. All of them contain 6 atoms of carbon or some multiple of 6, and hydrogen and oxygen in the same proportion in which these elements are present in water. They are nearly related to the hexatomic alcohols, CgHj^Og, from which they are respectively derived by the abstraction of Hj or of Hj + HjO. The carbohydrates of the grape sugar group, the hexoses, are distinguished from the hexatomic alcohols, 0511^405, by containing two atoms of hydrogen less in the molecule; chemi- cally they are aldehyde-alcohols or ketone-alcohols (see p. 309); The compounds of the cane sugar and cellulose groups are derived from those of the grape sugar group by the elimination of the elements of water from the latter, and they are anhy- drides or ethereal derivatives of these. The name carbohydrate has, however, acquired a much wider significance during the last few years, because on the one hand numerous isomers of grape sugar — hexoses — have been dis- covered and, in part, prepared synthetically; while on the other hand we have also become acquainted with aldehyde-alcohols, i.e., sugar varieties poorer in carbon (especially the pentoses, C5H10O51 which are widely distributed in nature, tetrose, C^HgO^ [B. 25, 2549], and glycerose, CgHgOg), and with others richer in carbon, which have been synthetized, — hep- toses, octoses, and nonoses. All of these contain two atoms of hydrogen less in the molecule than the corresponding poly- atomic alcohols. Tliese compounds might therefore be described in connection with the aldehyde- and ketone-alcohols (p. 237), of which glycolUo aldehyde is the 308 XIV. CARBOHYDRATES. first member. On account, however, of the many peculiarities which they possess, it has been preferred to treat them separately. The carbohydrates show many characteristic reactions, which will be referred to under the individual groups. They give, for example, a beauti- ful deep violet colouration with a-naphthol and csncentrated sulphuric acid (Moliseh, B. 19, Eef. 746). A. Pentoses. The pentoses are characterized, among other things, by the fact that they yield furfurol or methyl-furfurol upon prolonged boiling with hydrochloric acid, water being eliminated; this reaction allows of their quantitative estimation (B. 24, 3577). Arabinose gives furfurol itself, while its homologue rhamnose gives methyl-furfurol. Upon warming with hydrochloric acid and phloroglucin, cherry-red colourations are produced. The pentoses are not fermentable, and they yield characteristic compounds with phenyl-hydrazine (see Hexoses); unlike the hexoses they have not as yet been synthetized. 1. Arabinose, CgHioOj, = CH20H—CH(OH)3—CHO, is pro- duced by boiling gum-arabic, cherry gum, or beetroot chips with dilute sulphuric acid, and forms dextro-rotatory prisms. It takes on hydrocyanic acid, and thus yields the cyanides of two stereo-isomeric oxy-acids, which are derived from normal caproic acid, viz., Z-mannonic acid (Kiliani, B. 20, 339, 1233) and Z-gluconic acid (E. Fischer). The corresponding alcohol is arabite. 2. Xylose, wood sugar, OsHioOs, is prepared by boiling wood-gum (which see), straw and jute with dilute sulphuric acid, and is very similar to arabinose. For its constitution, see B. 24, 537. The corresponding alcohol is xylite. 3. Bibose, CjHioOs, is stereo-isomeric with arabinose (B. 24, 4214). Somologues. 4. Khamnose, iso-duloite, CeHijOs = CsHgOslCHa), is obtained from several gluoosides, e.g. quercitrin (which see), or xantho- rhamnin (yellow needles, present in French berries, Ehamnus tinotoria, etc.), by the action of dilute sulphuric acid. Colourless crystals (+ HjO); M. Pt. 93°. For constitution, see Fischer and Tafel, B. 20, 1091 ; 21, 1657, 2173). 5. Fucose, isomeric with rhamnose. Obtained from sea-weed. (Cf. A. 271, 86.) THE GRAPE SUGAR GROUP. 309 B. The Grape Sugar Group, CeHijOg. {Sexoses or Olncoses.) The glucoses are sweet and for the most part crystalline compounds easily soluble in water, sparingly soluble in absolute alcohol and insoluble in ether. They possess the character of pentavalent aldehyde- or ketone-alcohols and closely resemble mannite, etc., but differ from it in having strongly reducing properties, in their behaviour towards phenyl-hydrazine, and in certain cases also by being fermentable by germinating yeast. Like tartaric acid they exist in optically active isomeric modifications, one of which turns the plane of polarization of light to the right and another to the left, while the third is inactive, being produced by the union of the two active modi- fications. We thus distinguish between dextro-, Isevo-, and inactive-mannose, and designate the glucoses, fructoses, etc., which are genetically related to them, as belonging to dr, 1-, or i- series (without reference to their actual rotation). Formation. 1. The hexoses are produced, both in plants and artificially, from the carbohydrates of the cane sugar and starch groups by the taking up of water, this being brought about either by the action of enzymes or by boiling with very dilute acids, especially hydrochloric (see pp. 317 and 320). 2. Synthesis of hexoses. By the action of lime-water upon trioxy- methylene(p. 1.i7), BuUerow obtained the so-called "methylenitan," a mix- ture of several substances, one of which is acrose (see below). 0. Loew obtained formose in a similar manner from formic aldehyde and milk of lime, this being likewise a mixture containing a true glucose (acrose}. E. Fischer and Tafel then succeeded in synthetizing two sugar varieties, a- and ^-acrose, the first of which is identical with i-fructose, by the action of baryta water upon acrolein bromide or crude glycerine aldehyde (" glycerose," obtained by oxidizing glycerine with bromine and soda). Cf. E. Fischer, B. 23, 2114, etseq. From o-acrose, as the starting point, a number of other glucoses have been prepared. By fermenting it with yeast, i-fruotoae is isolated, the d-fructose (Isevulose) alone undergoing decomposition. Sodium amalgam, 310 XIV. CARBOHYDRATES. on the other hand, converts it into i-mannite, which in its turn yields I'-mannoae upon oxidation with nitric acid. From this latter the {-modifica- tion is obtainable by fermentation. The further oxidation of i-mannose produces t-mannonic acid. This last can then be split up into the d- and {-modifications by means of the strychnine or brucine salts ; the first of these, d-mannonio acid, is also got by the oxidation of the natural d-man- nite; while the second, {-mannonio acid, can be prepared (together with i-gluoonic acid, which see) by the taking up of hydrocyanic acid by arabinose, etc. All three mannonic acids have been reduced by sodium amalgam to the corresponding d-, I- and i-mannoses (E. Fisoher, B. 22, 2204). Now the three manuonio acids can be converted into d-, I- and i-gluconio acids (p. 236) ; and, upon reduction with sodium amalgam, d- and {-gluconic acids give d- and {-glucoses, of which the first is identical with natural grape sugar. By the union of d- with {-glucose, i-glucose is obtained, and by the reduction of cJ-glucose, the sorbite found in nature, d-fructose yields a mixture of d-mannite and sorbite when reduced. Further, the reduction of mucic acid yields i-galactonio acid, and the re- duction of the latter t-galactose, which gives {-galactose upon fermentation. Gulose (whose name is intended to express the relationship with glucose) can be prepared synthetically from gulonic acid. Hydrocyanic acid adds itself on to xylose with the (ultimate) formation of {-gulonic acid, which yields {-gulose on reduction. By the reduction of ordinary saccharic acid, d-gulonic acid is obtained, and this leads to d-gulose A mixture of these two hexoses then gives i-gulose. Lastly, the reduction of talose yields talonic acid, which is also obtainable (p. 236) by the molecular transformation of galac tonic acid (E. Fischer and his pupils, B. 24, 526, 3625 ; 25, 1031, 1247). For the genetic relations of these compounds, see table, p. 311. The synthesis of heptoses, octoses, etc., depends upon the property of the hexoses to unite — like aldehyde — with hydrocyanic acid to nitriles, which yield hexatomic-monobasic acids upon saponification, the latter being then reducible to the corresponding aldehydes (heptoses). These can in their turn be transformed in the same manner (see also p. 313), Thus, from mannose, CsHuOs, there is obtained mannose-carboxylio acid, C6H,(0H)s(C0aH), and, from the latter, Manno-heptose, C6H,(OH)6(CHO); from this we proceed to Manno-octose and Manno - nonose. Similarly glucose leads to Gluco-heptose, galactose to Gala-heptose, etc. Bhamnose (Methyl - pentose) yields Ehamno - hexose, C6Hii{CH3)Oii, Bhamno-heptose, and Ehamno-octose in an analogous manner. See table on following page. Behaviour. 1. Fermentation. Most of the hexoses are fer- mentable. They ferment with yeast, undergo the lactic or butyric fermentation with the respective bacteria, and are transformed under certain conditions into mucous dextrine- like substances by the " mucous " fermentation. HEXOSES. SUMMARY OP GENETIC RELATIONS. 311 Alcohols. Aldoses. Hexonic acids. Dibasic acids. Ketoses. C3 Arabinose- - Xylose Mannite 1 «- Slannoses Slannonio acidsj Nld Sorbite Maiino- saccharic acids -* 1 Fructoses 1 ,^ Gluconic acids Sulcite Galactoses Talose *r~ Gulonic acids .... .^ Galactonic acids Xalonic < acid Saccharic acids < Uucic acid ■ (i) Talo-mucio acid AUo-mucio acid Among others, d-mannose, d-gluoose, c?-fruotose and d-manno-nonose are fermentable, but not cj-manno-heptose or -ootose, or the pentoses; i-glucose, Z-mannose and i-fructose do not ferment with yeast, perhaps because the cells of the fungus have become accustomed to the d-compounds occurring in nature. 2. The hexoses are readily oxidizable, and they therefore reduce an ammoniacal silver solution, and also Fehling's solution if warmed with it. By careful oxidation the mannoses, glucoses, and galactose yield the hexonic acids mentioned in the above table. When the oxidation proceeds further, glucose gives saccharic, tartaric and oxalic acids, and galactose gives mucic 312 XIV. CARBOHYDRATES. acid, while from fructose glycollic acid and other decomposition products are obtained. 3. The hexoses form alcoholates (saccharates) with bases, especially with lime, compounds which are decomposed by COg, and which become brown in the air from oxidation. Alkalies decompose glucoses with production of a brown colour and for- mation, e.g. of lactic acid. By the further action of lime upon glucose and fruit sugar, saccharine (p. 235) is produced. 4. Fruit sugar is converted into a mixture of c^mannite and sorbite by sodium amalgam : ^56^120^ + Hg = CgHj^Ogj grape sugar is similarly transformed into sorbite, and galactose into dulcite. 5. When they are boiled with acetic anhydride and a little zinc chloride or sodium acetate, the hexoses are changed into pent-acetyl esters; they are therefore pentatomic alcohols. 6. With phenyl-hydrazine, O^Hj — NH — NHj, there are first produced, with elimination of water, compounds of the formula C5Hj205(N2HCuH5), compounds which are"hydrazones" (p.HG), and the formation of which demonstrates the aldehydic or ketonic character of the hexoses. When the action is allowed to go further, a second molecule of phenyl-hydrazine enters the compound, or rather ^tt > is replaced by ^N2HCgH5, and "osazones," Gg'H.■^fi^(N^'H.GgB.^)^ (p. 239), result, e.g. phenyl- dextrosazone, phenyl-acrosazone, and phenyl-lactosazone. These are yellow crystalline compounds which are of great value for the recognition of the carbohydrates. The hydrazones from diphenyl-hydrazine and from y-bromo-phenyl- hydrazine are also frequently characteristic for the sugar varieties, and serve for their recognition, like the above compounds. By the action of nascent hydrogen upon them, the phenyl-hydrazine radicles are eliminated down to one amido-group, and glucosamines result, e.g. iso-glucosamine, CsHnOsNHj, from phenyl-gluoosazone ; the latter may then in their turn be converted into glucoses by nitrous acid {Fischer and Tafel, B. 20, 2566). Concentrated hydrochloric acid acts upon the osazones to produce osones, e.g. Qhieosone, G^lltO^(0)^, = OoHioOe (B. 22, 87), from which the glucoses are again regenerated by means of zinc and acetic acid. HEXOSESj CONSTITUTION OF. 313 7. With hydroxylamine there result oximes, which are for the most part extremely soluble (B. 24, 993), and which render a breaking down {Abbau) of the hexose molecule possible. Thus, the oxime of grape sugar can be converted by acetic anhydride into the nitrile (cf. the aldoximes, p. 150), which readily separates hydrocyanic acid. An aldehyde-alcohol containing five carbon atoms is thus obtained, a pentose, whose optical action is the reverse of that of arabinose ( Wohl, B. 26, 730). 8. When boiled with dilute sulphuric acid, the hexoses — especially Isevulose — are, like other carbohydrates, converted into tevulinic acid (cf. A. 843), humio substances being formed at the same time. The influ- ence of dilute acids, however, may also lead to the production of substances of the nature of anhydrides like dextrine (B. 83, 2084). 9. When heated, the hexoses at first change into compounds of the nature of anhydrides and then into others of the nature of caramel (p. 319), and finally they become charred. 10. They do not show the aldehydic reaction with fuchsine and sulphur dioxide. 11. As already mentioned, the hexoses unite with hydrocyanic acid to NH, CH2.CO CH2.CO CH2 — CI12 — OH2 in 7- butyro- lactone, I I , in parabanic acid, CO alloxan, etc., and also in pyridine, quinoline, etc. At this point must be described three compounds in which closed atomic rings are likewise to be assumed, \ii.: 326 XV. TRANSITION TO THE AROMATIC COMPOUNDS. B. Purfurane, C^H^O, Thiophene, C4H4S, and Pyrrol, C,H,(NH). From these compounds a whole series of derivatives are ob- tained by the substitution of hydrogen by halogen, and also by the entrance of the groups — CH3, — CH2OH, — CHO, — COgH, etc. In their properties furfurane, thiophene and pyrrol remind one of benzene. Thiophene in particular is delusively like the latter, e.g. in odour and boiling point; and its various derivatives often show a marvellous similarity in their chemical and physical relations to the corresponding derivatives of benzene. (See table, below.) Summary. Fiirfwrane, O4H4O. Pyrrol, C4H,(NH). Thiophene, C4H4S. Benzene, Dibromo- furfurane C^HijBrjO. Tetra-iodo-pyrrol CAINH). Dibromo- thiophene CiHjBrjS. Diohloro-benzene CeH4Cl,. Methyl-furfurane C4H50(CH,). a-, j8-Methyl- pyrrol C^HaNHCCHa). a-, ^-Methyl- thiophene C4H3S(CH3). Toluene CeH^iCHs). Furfurane alcohol C4H30(CH2.0H). Thiophene alcohol C4H3S(CHj.OH). Benzyl alcohol CeHsCCHa-GH). Furfurol CiHaOlCHO). Thiophene aldehyde CiHsSCCHO). Benzoic aldehyde CeH6(CH0). Pyromucio acid C4H30(COjH). 0- , /S-Pyrrol- carboxylio acid CiHsNHCCOjH). a-, j3-Thiophene- carboxylic acid C4H3S(C02H). Benzoic acid CbH^ICOjH). Dimethyl- furfurane 0,H,0(CH,),. 0-, ;8-Dimethyl- pyrrol C4HjNH(CH,)j. Dimethyl- thiopheiie C4H,S(CH8)j. Xylenes CeH4(CH,)2. Etc. n-Methyl-pyrrol 0,H4(N.CHs). Amido-thiophene C4H3S(NH2). Thiophene- sulphonic acid C4H8S(S08H). Aniline CbHbINH,). Benzene- sulphonic acid CeH^CSOsH). FURFURANE, PYRROL, AND THIOPHENE. 327 Furfurane, pyrrol and thiophene also resemble one another in many respects. All three boil at relatively low temperatures, ( + 32°, 131°, 84°), are either insoluble or only slightly soluble in water, but easily in alcohol and ether, and show many analogous colour reactions. Thus pyrrol and thiophene and their derivatives give, for the most part, an intense violet to blue colouration when mixed with isatin and concentrated sulphuric acid, and a cherry-red or violet colouration with phenanthrene-quinone and glacial acetic or sulphuric acid. The vapour of pyrrol colours a pine shaving which has been moistened with hydrochloric acid carmine red {wyppos, fiery- red), while furfurol vapour colours it an emerald green j the latter likewise colours a piece of paper moistened with xylidine- or aniline acetate red. Furfurane is converted by hydrochloric acid, i.e. by mineral acids, into an insoluble amorphous powder, and pyrrol into an insoluble amorphous brown-red powder "pyrrol-red" (with evolution of ammonia), while thiophene remains unaltered ; the derivatives show a similar behaviour. Pyrrol is distinguished from the two other compounds by having weakly basic properties. Fm-mation. 1. From mucic acid, C4H4(OH)4(C02H)2. This is converted into pyromucic acid ( = furfurane-carboxylic acid), 0^1130(00211), upon dry distillation, the latter in its turn yielding furfurane when heated with caustic soda. By the action of ammonia, i.e. by the dry distillation of the ammonium salt, mucic and pyromucic acids are transformed into pyrrol. Lastly, thiophene -carboxylic acid, and from it thiophene, result upon heating mucic acid with barium sulphide : (a) 0,H,(OH),(002H)2 = 0,H,0 -f- 200^ -f 3H2O ; (6)O,H,(OH),(0O2H)2 + NH3 = 0,H,(NH) -n 2CO2 + iEjO ; (c)0,H,(OH),(0O2H)2-hH2S = 0,H,S +2C0, + m,0. 2. From succinic acid, 02H^(002H)2. Succinimide, CJlfi^i^^), yields pyrrol when strongly heated with zinc dust, and sodium succinate yields thiophene when heated with P2S3, {Volhard-Erdmann, B. 18, 454.) 3. Pyrrol also results from acetylene and ammonia at a red heat, and thiophene when ethylene is led over glowing pyrites. 328 XV. TRANSITION TO THE AROMATIC COMPOUNDS. 4. Pyrrol is produced from furfurane when the latter is heated with chloride of zinc and ammonia (B. 20, Bef. 221). 5. From acetonyl-acetone, CHg— CO— CHj— CHs— CO— CHg, dimethyl-furfurane results with separation of water, dimethyl- pyrrol by heating it with alcoholic ammonia, and finally dimethyl-thiophene with pentasulphide of phosphorus, (^Paal, B. 18, 58, 367 ; 20, 1074.) This behaviour would indicate that the acetonyl-acetone changes first into the isomeric compound, CHj— C(0H)=CH:— CH=C(OH)— CHj, or CH=C(CH,)(OH) ,^. ,. ,^ , ^. ^ ,. ^^ , fiTT <-(//~iTT \//-vrr» » upon this assumption the formation of dimethyl- Cii=C(OIi3)(OH) furfurane appears simply as that of an anhydride, that of dimethyl- pyrrol as an exchange of 2(0H) for NH (imide formation), and that of dimethyl-thiophene as the formation of a sulphide, i.e. exchange of 2(0H) for S, according to the following equations : CH=C(CHs).OH _ CH=C(CH3). CH=C(CH3).0H ~ CH=0(CH3)-^ ^ ^ NH + 9H=C(CH3).OH _ CH=C(CH3). ^^s + CH=C(CH3).0H - CH=C(CH3)^^" + ^"='"- CH=C(CH3).0H _ CH=C(CH3). ^^^ + CH=C(CH3).0H - CH=C(CH3)^^ + ^^^^- From the above we have the constitutional formulce: Furfurane. Pyrrol. Thiophene. CH=CH.Q CH=CH. 9H=CH^g OH=CH'^ CH=CH-^ ,„. CH=OH^ (;8) (a) iP) (a) (;8) (a) These formulEe receive corroboration from the frequently observed fact that those substances are capable of yielding addition compounds with bromine or hydrogen (see Pyrroline). For the constitution of these sub- stances, cf. also p. 384. According to the above formulee, two isomeric mono-derivatives of furfurane and thiophene are possible: (1) one in which the hydrogen atom (a) which stands nearest to the S, etc., and (2) one in which a quasi-middle hydrogen atom (/3) is substituted. As a matter of fact two such isomers have been observed in many cases, e.g. two thiophenic acids (see table). These crystallize mixed together, the crystals having a homogeneous appearance although they contain both acids {V. Meyer, A. S36, 200). In the case of pyrrol, on the other hand, three kinds of derivatives (a-, /3-, and n-) are both possible and known. FURFURANE, FURFUROL. 329 Furfurane, 04X1^0, is a colourless mobile liquid of chloro- form odour which boils at 32°. It is present in pine-wood tar, in the first runnings from ordinary wood tar, etc., and results from the distillation of sugar with lime. Methyl-furfurane or sylvane, C4HgO(CH3), is likewise present in pine-wood tar, and in the products of distillation of sugar with lime. B. Pt. 63°. Dimethyl-furfurane, C^H20(CH8)2, results (together with trimethyl-furfurane apparently) like the foregoing compounds from sugar and lime. For its formation from acetonyl-acetone, etc., see p. 328. It is a colourless mobile liquid of a character- istic odour, B. Pt. 94°. Concentrated acids convert it into a resin J it can be re transformed into acetonyl-acetone. Furfurol, furfurane aldehyde, CgH^Oj (Bobereiner), results from the action of moderately concentrated sulphuric acid upon carbohydrates, particularly arabinose and xylose, from which it is derived by a simple separation of the elements of water: CisHioOs - 3H2O = C5H4O2; and is dso found e.g. in fusel oil. It is a colourless oil of agreeable odour which is turned brown by the air; B. Pt. 162°. It has the nature of an aldehyde and shows characteristic reactions (B. 20, 540). Methyl-furfurol, C5H3(CH8)02, is obtained in an analogous manner from the homologue of arabinose, rhamnose, and closely resembles furfurol. It gives a green colouration with alcohol and sulphuric acid. B. Pt. 183°. Pyromucic acid, C5H4O3, = C4H30(C02H). Needles or plates of a character similar to that of the crystals of benzoic acid, subliming easily and being readily soluble in hot water and alcohol. M. Pt. 132°. Decolourizes alkaline permanganate almost instantaneously. For its preparation, see A. 261, 379. The furfurane derivatives are frequently termed "furane" derivatives for shortness' sake. See "Das Furfuran, etc.," by A. Bender (Oaertner, Berlin, 1889). 330 XV. TRANSITION TO THE AROMATIC COMPOUNDS. Pyrrol, C^H^NH, is a constituent of coal tar {Runge) and of bone oil {Anderson), and possesses, like many of its homologues, a chloroform odour. It is a secondary base. Its imido-bydrogen is replaceable by alkyl, acetyl or metals. B. Pt 131°. For formation, see p. 32ti, and B. 19, 3027. When pyrrol is acted upon by hydroxylamine the ring is broken, hydrogen being taken up and ammonia eliminated, and there is formed the dioxime pTT pTT__"M" QTT of succinic aldehyde, - ' ' ; this latter then yields tetra- CH2— CH=N.OH methylene-diamine upon reduction (B. 22, 1968). Dimethyl-pyrrol passes in a similar manner into acetonyl-acetone dioxime. Fotassium-pyrrol, C1H4NK, which is obtained from pyrrol and potassium or potash, is » colourless compound which is decomposed backwards by water, and which is converted into pyridine by CHjIj and NaO(CHa). By the action of iodine and alkali, substitution takes place with the formation of Tetra-iodo-pyrrol or lodol, OiIilNH), which crystallizes in yellow plates, and is an antiseptic of milder action than iodoform. Zinc and glacial acetic acid convert pyrrol into Pyrroline, CiHslNH), a colourless liquid and strong secondary base, B. Pt. 91°; and when this latter is heated with hydriodic acid, it is further reduced to Pyrrolidine, CiH8(NH), a colourless, strongly alkaline base resembling piperidine, and boiling at 85°-88°. This compound is also formed from sodium and succin- imide in alcohol. Pyrrolidine yields pyrrolylene, CiHe, with methyl iodide and caustic alkali (see Conine ; also p. 66). Pyrrolidine is formed synthet- ically by heating 8-chloro-butylamine (p. 211) with alkali, and by treating ethylene cyanide with sodium and alcohol, thus : CH^CN ^ ^ CH.-OH.NH, ^ C^^CW,^^^ ^ it is consequently designated Tetra-methyleue-imine {Ladenburg, B. 19, 782; 80, 442). Methyl-pyrrol, CtHs(CH3)NH, is found in bone oil in two modifications (a and p), and so is Dimethyl-pyrrol, CiH2(CIH8)2NH. PyroooU, C5H3NO, (yellow plates), the anhydride of a-Pyrrol- carboxyllc acid, C4H3NH(C02H), results from the distillation of gelatine. The acid itself crystallizes in metallic green prisms, M. Pt. 191°. (Cf. table of pyrrol derivatives, also B. 20, 2594.) Thiophene, C^H^S, {F. Meyer, B. 16, 1465 etc.), is likewise present in coal tar, being invariably found in benzene (up to THIOPHENK 331 0-5 p.c.) ; the same applies to its homologues thiotolene (methyl-thiophene), and thioxene (diinethyl-thiophene), which accompany toluene and xylene, etc. Its boiling point (84°) is almost the same as that of benzene (80 '4°), from which it is extracted by repeated shaking up with small quantities of concentrated sulphuric acid, which chiefly dissolves the thio- phene (to sulphonic acid). (Of. B. 17, 2641, 2852.) It is also attacked more readily than benzene by other reagents such as iodine and bromine. Thiophene is also obtained synthetically by leading the vapour of ethyl sulphide through a red-hot tube {Kehtli), and in small quantity by heating crotonic acid, normal butyric acid, para-aldehyde, erythrite, ether etc. with PjSj. The preparation and properties of the thiophene derivatives are in part almost literally the same as those of benzene. Thus nitric acid acts on thiophene to produce a Nitro- thiophene, analogous to nitro-benzene, which can in its turn be reduced to amido-thiophene ; the latter is, however, much less stable than the corresponding amido-benzene (aniline). Thiophene-sulphonio acid, 041138(80311), decomposes into thiophene and sulphuric acid when superheated with water. Thiotenol, C4H2S(CH3)(OH), the phenol of thiotolene, is formed by heating levulinic acid with P2S5, (B. 19, 553). The blue colouration which results upon shaking up benzene contain- ing thiophene with isatin and concentrated HjSO^, depends on the for- mation of the blue colouring matter "Indophenin," CijH^NOS. /ITT PfT Penthiophene, CH2<^pTT_riTj^S, would be an analogue of thio- phene containing five atoms of carbon. A methyl derivative of it has recently been prepared, which shows exactly the same character and colour reactions as thiophene, but is completely decomposed by KMn04. (Cf. V. Meyer's " Die Thiophengruppe," Braunschweig, 18S8.) 332 XV. TRANSITION TO THE AROMATIC COMPOUNDS. O. Azoles, Pyrazoles, Thiazoles, and related compounds. ' 1. Pyrazoles. By the action of phenyl-hydrazine upon aceto-acetic ether, water and alcohol are eliminated, and Phenyl-methyl-pyrazolone, OiQHijNgO, is formed, — very probably according to the equation : CH3— CO HjN I + I HjC— CO.OO2H5 NH— CeHj Aceto- acetic ether. Phenyl-hydrazine. = ^^':^6lco>^~^«^^ "^ ^'^ ^ c,H,.0H. Phenyl-methyl-pyrazolone. According to this view it appears as a derivative of: Pyrazole, jj^^^^H^^^' = ^'^'^^ Pyrazole is theoretically derivable from pyrrol in the same way as pyridine is from benzene, i.e. by the exchange of CH for N. It can be prepared by the action of hydrazine upon epichlorhydrin (B. 23, 1103), and also from acetylene-dioarboxylic ether and diazo-acetic ether by a complicated reaction {E. Buchner, A. 273, 214). It is a weak base of great stability, crystallizing in colourless needles; M. Pt. 70°, B. Pt. 185°. Fyrazoline, C3H0N2, and Fyrazolidine, CsHsNj, are derived theoretically from pyrazole by the addition of hydrogen, but only the first of these is as yet known (B. 26, 408). By the exchange of two atoms of hydrogen for one of oxygen, the formula of pyrazoline changes into that of: HO=N ^ Pyrazolone, • „_J>NH (an oil, B. Pt. 77°; see B. 25, 3441), SoU — CO and by the entrance of phenyl and methyl into this latter we get : Phenyl-methyl-pyrazolone (see above). This crystallizes in compact prisms,. melts at 127°, and boils without decomposition. As a weak base it dissolves in acids, and as an aceto-acetio ether derivative in alkalies ; further, as the latter, it still contains the chemically-active methylene group of this ester. When it is heated with methyl iodide and methyl alcohol it yields : Phenyl -dimethyl -pyrazolone or Antipyrine, CnHigNjO, which is also produced by the action of aceto-acetic ether upon methyl-phenyl-hydrazine, and which therefore possesses the THIAZOLES. 333 constitutional formula, " •• \ ^^">N— CeHj. It crys- tallizes in white tables or small plates; M. Pt. 113°. The aqueous solution is coloured red by feme chloride and blue- green by nitrous acid. Antipyrine is an excellent febrifuge. (L. Knorr, A. 238, 137.) If a solution of antipyrine in toluene is boiled with sodium, and if at the same time a current of carbon dioxide is led through it, hydrogen is taken up and /S-Kethyl-amido-oroton-anilide results (B. 25, 1870). All the compounds which are constituted similarly to aceto-aoetie ether (^-ketonio acids, /3-ketonic aldehydes, ^-diketones), likewise yield derivatives of pyrazole with phenyl-hydrazine. 2. Thiazoles. Thiazole, CaHsNS, = •• ^CH, is derived from thiophene in the HC— S'^ '^ same way as pyridine is from benzene, by the exchange of CH for N, and closely resembles — along with its derivatives — the bases of the pyridine series in properties. It is obtained from amido-thiazole (see below) by exchange of the amidogen group for hydrogen, in a similar manner to the conversion of aniline into benzene. It is a colourless liquid of 117° B. Pt., hardly distinguishable from pyridine; as a base it forms salts, but it is hardly affected by concentrated sulphuric acid, etc. (Santzsch, Popp, A. 250, 273). Dimethyl-thlazole, CsH(CH8)2NS, is produced from monochloro-acetone and aoeto-thiamide (p. 199), with elimination of H^O and HCl, arid is exceedingly like a-lutidine (dimethyl-pyridine) in character. Amido-thiazole, ■• ^0 — NHj, is formed by the action of mono- chloraldehyde (p. 149) upon thio-urea, thus: CHjCl HN.^ CH— N^ I + >C— NH, = >C— NHj -I- HCl -1- HA OHO HS / CH— S / Thio-urea (pseudo-form). The constitution of the thiazoles follows from this and similar modes of formation. Amido-thiazole is a base of perfect " aromatic " character, like that of aniline. (Cf. Hantzsch and his pupils, A. 249, 1, 7, 31; 280, 257; 266, 108.) 3. Imido-azoles; Oxy-azoles. Compounds analogous to the foregoing are derivable from , ., , HC— N ^^„ , „ , HO— ]sr^„„ Imido-azole, ■• >CH and Ozv-azole, •■ "5CH, HC— NH'^ HC— O^ which are related to thiazole as pyrrol and furfnrane are to thiophene. 334 XV. TRANSITION TO THE AROMATIC COMPOUNDS. Imido-azole, glyoxaline, C3H1N2, results from the action of concentrated ammonia upon glyoxal, and is a powerful base of weak fieh-like odour. It ia iBomeric with pyrazole. Permanganate of potash oxidizes it, and benzoyl chloride splits it up very readily, i,e. "the ring is broken " (B. 25, 281). For derivatives, see Wallach, A. 184, I (" Oxalo-ethylme" etc.); B. 13, 511; 22, 568 and 1353. Alloxan may likewise be regarded as an imido-aaole derivative. For isomers, the Isoxy-azoles, cf. {e.g.) B. 24, 130, 857, 3900. 4. Azoles richer in Nitrogen. Oso-triazole. Pyrro-diazole. Furfurazane. Tetrazole. CHsN, C,HaNs CjHaNjO CHaN^ 1 >NH ho=n/ N=CH\ 1 >NH HC=N / HC=N. 1 > hc=n/ 1 >NH N=N / (A. 262, 314). (B. 26, 225). (B. Si, 1165). (B. 25, 1411). M. Pt. 22°; Needles ; (Known as car- M. Pt. 155°. B. Pt. 204°. M. Pt. 121°. boxy lie acid.) Eeadily soluble Eeadily soluble Readily soluble in water. Is a in water. in water. weak acid; the Weakly basic salts detonate. and acid. The foregoing constitutional formulas (given in this Glass XV.) correspond with their double linkings to EekuU'i benzene formula. But formulse with diagonal (central) linkings have recently been recommended instead of them, these being analogous to the central benzene formula (p. 348). Cf. Bamberger, B. 24, 1758; A. 273, 373; also A. 249, 1 ; 262, 265; B. 21, Bef . 888 ; 24, 3485, etc. THE BENZENE DERIVATIVES. 335 Class II.— CHEMISTRY OF THE BENZENE DERIVATIVES. XVI. SUMMARY. The compounds which have been treated of in Sections I. to XIV. are derivable from the homologous hydrocarbons 0^115^4.2, CnHj„ CnH2i,_2, etc. by the exchange of hydrogen for halogen, hydroxyl or oxygen, amidogen, carboxyl, etc.; and since all the hydrocarbons already mentioned may also be regarded as deri- vatives of methane {e.g. CjHg = CH3(CH3) = methyl-methane, CgHg = CH2(CH3)2 = dimethyl-methane, G^B.^ = CH2=CH„ = methylene-methane, CjHj = CH=CH = methine-methane, etc.), we may term the compounds which have been described in the foregoing portion of this book Methane derivatives. But in addition to this first class of organic compounds there is a second great class, viz. that of the Aromatic corrir potmds or Benzene derivatives. The first of these two names is historical but no longer justified by facts, since compounds of agreeable as well as unpleasant odour are to be found in both classes. As benzene derivatives are designated the members of this class which are derivable from the hydrocarbon benzene, CgHg (and also from more complicated hydrocarbons such as anthracene, naphthalene, etc., which are themselves derivatives of benzene), just as the methane derivatives are from methane. Benzene is, as its formula CgHg shows, a compound much poorer in hydrogen than the parafBns, containing eight H-atoms less than Jiexane, CgHj^ ; in the same way all benzene deriva- 336 BENZENE DERIVATIVES. XVI. SUMMARY. tives are much poorer in hydrogen, i.e. richer in carbon than the analogous methane derivatives, as is seen by comparing e.g. benzoic acid, CjHgOj, with heptoic acid, C^Hj^^Oj, or aniline, CgH^N, with ethylamine CgHjN, etc. etc. The hydrogen atoms of benzene are, like those of methane, replaceable by the most various elements and atomic groups. By the entrance of halogens, substitution products result, by the entrance of NHj, aromatic bases, of OH, phenols, of NOg, nitro-compounds, and of CHg etc., the homologues of benzene ; there are, in addition to these, aromatic alcohols, aldehydes, acids, etc Those substituting groups are termed side chains. These benzene derivatives are partly analogous in their properties to the methane derivatives of corresponding com- position ; in part, however, they show new and peculiar properties of their own, (see pp. 338, 353 et seq.). One dis- tinguishes between mono-, di-, tri-, etc. benzene derivatives according as one or two or more hydrogen atoms are replaced by the elements or groups in question ; thus, for instance, toluene and chloro-benzene are mono-derivatives, dimethyl- benzene and dichloro-benzene di-derivatives, and so on. Further, just as it was found when speaking of the polyatomic alcohols and acids, that the replacing groups need not be identical, so in this class also innumerable compounds are known containing various substituents. Such compounds have usually some of the characteristics of all those mono- derivatives which result from benzene by the exchange of one H-atom for one of these substituents. All the derivatives of benzene can be converted either into benzene itself or into very nearly allied compounds by rela- tively simple reactions. Thus all the carboxylic acids of benzene (benzoic, phthalic, mellitic, etc.), yield benzene on distillation with lime, while other acids, such as salicylic, give up COg and yield phenol, and so on ; the last-named com- pound goes into benzene when distilled with zinc dust. The homologues of benzene are converted by oxidation into benzene-carboxylic acids, which give benzene when heated with lime. BENZENE DERIVATIVES; SUMMARY. 337 The relation of a benzene derivative to its mother substance is therefore a very simple one. This circumstance is one particularly worthy of note, since the atomic group CeHj is already a tolerably complicated molecule in itself, and also because benzene cannot by any means be transformed into a simpler hydrocarbon containing 5, 4, or 3 C-atoms ; when oxidized, which is a matter of difficulty, it goes into carbon dioxide or similar simple organic acids. Summary of a few Benzene derivatives. CsHj.CHs Methyl-benzene or toluene. OeH4{CH3)i, Dimethyl-benzenes or xylenes. C'6H3(CHg)3 Trimethyl-benzenes. CeH6.Cl Chlorobenzene. CeH^Cl^ Dichloro-benzenes. CeHsGls Trichloro-benzenea. Phenol. CeH4(0H)j Kesorcin, etc. C6H3(OH)3 Pyrogallol, etc. CjH5.CH2.OH Benzyl alcohol. C«H,.N02 Nitrobenzene. C,H4(N02)3 Dinitro-benzenes. C„H3(N02)20H Dinitro-phenols. CsHs-NHj AnUine. C„H,(NH2)2 Phenylene diamines. CeH3(NH2)3 Tri-amido-benzenes. CgHpSOaH Benzene-sulphonic acid. C6H,(NH2)(S03H) Sulphanilic acid, etc. CeH3(S03H)3 Benzene-tri-sulphonic acid. CsHj-CHO Benzaldehyde. CoHpCOaH Benzoic acid. CjH^CCOaH), Phthalic acids. CeH3(C02H)3 Hemi-mellitic acid, etc. CeH5.CN Benzo-nitrile. CeH4(0H)(C0,H) Salicylic acid, etc. The benzene derivatives are connected with one another by the most various reactions. The NOg-group is readily con- vertible into NHg, and the latter is replaceable by halogen, hydrogen and hydroxyl; the halogen is also replaceable by methyl, carboxyl, etc. (606) ^ 338 BENZENE DERIVATIVES. XVI. SUMMARY. Differences between the aromatic and fatty hydrocarbons. Benzene differs from the fatty hydrocarbons by the follow- ing reactions in particular : 1. It forms nitro-benzene with nitric acid : OgHe + HO.NOa = CgHg.NOa + H^O. 2. It yields benzene-sulphonic acid with sulphuric acid : CgHj + HO.SO3H = 06H5(SO3H) + HjO. Similarly, almost all the benzene derivatives are capable of forming nitro-compounds and sulphonic acids in nearly theor- etical quantity. As has been already seen, the paraflSns are either unaffected by con- centrated HNO3 or H2SO4, or only attacked with difficulty, while the defines form addition products with the latter acid, without separation of water. 3. The homologues of benzene differ from the parafSiis especially in their capability of oxidation ; while the latter are only attacked with difficulty by oxidizing agents, the former are readily converted into benzene-carboxylic acids. 4. There are not wanting other distinguishing characteristics between the aromatic hydrocarbons and the paraffins. Thus the halogen compounds CgH^X are less active chemically, and the hydroxyl compounds, e.g. CgH,(OH), are of a more acid nature than the corresponding fatty bodies. The phenyl radicle, CgHj, is therefore more acid or "negative" in character than the ethyl, CgHj (cf. V. Meyer, B. 20, 634, 2944; A. 250, 118). 5. Diazo-compounds are known almost only in the aromatic series, and so on. Characteristic of the benzene derivatives are their: — ISOMERISM IN THE BENZENE SERIES. 339 Isomeric relations. 1. While several isomeric mono-derivatives are both theor- etically possible and have been practically obtained from each hexane, CgHj^^, benzene is only capable of forming a single mono-derivative in each case ; isomeric mono-derivatives of benzene are unknown. The six hydrogen atoms of benzene thus possess an equal valvs. This is not merely an empirical law, but one which has been proved experimentally. Proof of the equal value of the bIx hydrogen atoms. Let the six H-atoms be designated as a, b, c, d, e and/ respectively. 1. Phenol, C8H5(0H), whose hydroxyl may have replaced the H-atom a, may be converted into bromo-benzene, CjHjBr, and this latter into benzoic acid, C8H5(C02H). The carboxyl in the latter has therefore also the position a, i.e. it has replaced the H-atom a. 2. The three existing oxy-benzoic acids, C8H4(OH)(COaH), can either be prepared from benzoic acid or converted into it ; their carboxyl therefore has the position a, and consequently their hydroxyl must replace some one of the other H-atoms, be it b, c, or d. 3. The oxy-benzoic acids can all give up carbon dioxide, yielding thereby the same phenol, CjHjOH, in every one of the three oases : CsH4(OH)(C02H) = CeHjCOH) + COj. And since the latter compound contains the hydroxyl in position a, according to 1, while the hydroxyl in the oxy-benzoic acids replaces the H-atoms b, c and d, it follows that the hydrogen atoms a, b, c and d are of equal value. 4. Now, as will be explained on p. 340, there are present for each H-atom two other pairs of similarly-linked or symmetrical hydrogen atoms, i. e. pairs of which either the one or the other may be replaced by any given atomic group, without different substances resulting. But the atoms of such a pair cannot be present in the positions a, b, c and d, as in this case three oxy-benzoic acids could not exist. It must therefore be the remaining H-atoms e and / which are respectively united symmetrically to one of the former, and which are therefore of equal value with them, i.e, e = e, f = b. Since, however, a = b = c = d, it follows that all the six hydrogen atoms are of equal value, {Laden- bwrg, B. 7, 1684.) 2. If two hydrogen atoms in benzene are replaced by other elements or groups, so that di-derivatives result, these latter 340 BENZENE DERIVATIVES. XVI. SUMMARY. must exist in three different isomeric forms. We have thus three di-chloro-benzenes, CgH^Clj, three di-amido-benzenes, CgH4(NH2)2, three di-methyl-benzenes, GJiJGll^)2, three oxy- benzoic acids, CgH4(OH)(C02H), and so on. And this is no mere empirical law, for it has been proved that only three isomeric di-derivatives of benzene are capable of existence. It can be shown that for each H-atom of benzene, e.g. for a, two pairs of other H-atoms, e.g. h and /, c and e, are symmetri- cally linked, so that it makes no difference whether, after a is replaced, the second substituent replaces the one or the other of the symmetrically linked hydrogen atoms. According to the above notation, therefore, ab = af, and ac — ae. On the other hand the combinations db and ac are not equivalent but represent isomers ; the combination ad, the only remaining case, represents the third isomer. Proofs, that for every H-atom (a) two other pairs of symmetrically linked H-atoms exist, have been advanced by various scientists, especially by Ladenburg, One of these may be shortly sketched here. 1. According to Hvhner and Petermann (A. 149, 129 ; of. also Hiibner, A. 222, 67, 166), the (so-called meta-) bromo-benzoic acid, which is obtained by brominating benzoic acid, and whose Br-atom may be in position c and COjH in position a, yields with nitric acid two nitro-bromo-benzoic acids, C8H3Br(N02)(C02H), the NOj being (say) in positions 6 and f. These are both reduced by nascent hydrogen to the same (so-called ortho-) amido-benzoio acid, C8H4(NH2)(C02H), the NO2 being here changed to NH2 and the Br replaced by H. Since the same amido-benzoic acid results in both cases, notwithstanding that the nitro groups must be in the place of different H-atoms (say 6 and /) from the fact of the two nitro -acids being dissimilar, it follows that 6 and /must be linked symmetrically to the H-atom a, i.e. db=af. 2. In an analogous manner the oxy-benzoic acid (salicylic acid), which can be prepared from the above-mentioned amido-benzoio acid, yields two nitro-derivatives C6H3(OH)(N02)(C02H). If, however, the hydroxyl in these is replaced by hydrogen (a reaction which can be effected by indirect methods), the resulting nitro-benzoic acids, CeH4(N02)(C02H), are identical, and therefore the H-atoms which have been replaced by NOj are in a position symmetrical to a. When this nitro-benzoic acid is in its turn reduced to amido-benzoic acid. ISOMERISM OF THE BENZENE DI-DERIVATIVES. 341 C6H4(NH2)(COaH), it is not the above (ortlio-) amido-acid (where ab = a/) which la obtained, but an isomer. The NOg-groups cannot therefore here be in the position 6=/, but must replace two other H-atoms which are likewise symmetric towards a, say c and e, i.e. ac=ae. {Hiibner, A. 195, 4.) Thus two pairs of H-atoms are symmetrically linked as regards the H-atom a : ah=af; ac = ae. There only now remains the third possible combination ad ; the sixth H-atom d is situated towards the first a in a position of its own, i.e. in one to which there is no corresponding position. For further particulars cf. Ladenhurg, " Theorie der aromat. Verbindungen," Braunschweig, 1876 ; Wroblewsky, A. 168, 153 ; 182, 196 ; B. 8, 573 ; 9, 1055 ; 18, Ref. 148. It has been assumed in the considerations just detailed that when one compound is converted into another by the exchange of atoms or atomic groups (NHg for NOg, H for OH), this exchange is effected without a so-called " molecular rearrange- ment" taking place at the same time (see p. 179). Experience has proved that this may be taken for granted in a large number of reactions which proceed with relative smoothness and at comparatively low temperatures. Those instances in which a molecular rearrangement ensues are now well known; especially is this the case in the fusion of sulphonic acids with potash (exchange of SO3H for OH), a reaction which only takes place at relatively high temperatures, and which frequently leads to isomers of the compounds expected.* Ortho-, Meta- and Para- Di-derivatives. Just as the mono-derivatives of benzene can be transformed * Such a rearrangement of the atoms in the molecule takes place especially at rather high temperatures. Thus, when potassium ortho- oxybenzoate is heated to 220°, the potassium salt of the para-acid results ; the three isomeric bromo-benzene-sulphonic acids, CsHiBrlSOjH), and the three bromo-phenols, CgHiBrCOH), yield only meta-dioxy-benzene (resoroin) C8H4(OH)2, when fused with potash, and not all the three dioxy-benzenes ; and ortho-phenol-sulphonio acid, C6H4(OH)S03H, goes into the para-acid when heated, and so on. Reactions of this nature probably arise from the successive taking up and splitting o£F of atoms or atomic groups, (see orotonio acid, p. 180). 342 BENZENE DERIVATIVES. XVI. SUMMARY. into one another, so from one di-derivative, e.g. G^J^O^^ can others, e.g. G^J^H^^, be prepared. And since all the di-derivatives of benzene exist in three modifications, they arrange themselves into three great classes, according to their connection with and convertibility into one another. Within each of those three classes the individual members are related by the most various reactions. In accordance with a proposal made by Korner (though upon grounds which are no longer tenable), the above three classes of di-derivatives are termed Ortho-, Meta- and Para- compounds, being written for the sake of shortness with the letters o-, m-, and p-. Thus, o-diamido-benzene is that one which results from the reduction of o-dinitro-benzene. It can be proved experimentally (p. 345). that the ortho- and meta- positions of the H-atoms are those which occur in the molecule in pairs, while there is no position symmetrical to the para- position. There are likewise experimental data for distin- guishing the ortho- and meta-compounds from one another, (see p. 346). Isomeric Tri- etc. derivatives. With regard to the tri-derivatives of benzene, CgHgXg, there are likewise always three isomers when the three hydrogen atoms are replaced by the same substituent, these being distinguished on theoretical grounds as v-, s-, and a-compounds (p, 345) When, however, only two of the substituents are the same, there are six isomers, and when all three are different, ten. Of tetra-derivatives, CgHjX^, with the same substituent, there are likewise three, and of penta- and hexa-derivatives only one ; these last three classes may of course be looked upon as di- or mono-derivatives of a completely substituted benzene, or as the latter itself. When the substituents are not the same, many cases of isomerism are known. CONSTITUTION OF BENZENE. 343 Constitution of Benzene ; the Benzene Theory. The views which are at present held as to the constitution of benzene and its derivatives rest principally upon KekiM's benzene theory (1865), which has found almost universal acceptance on account of the elegance with which it explains known facts, (see KehiU, "Lehrbuch der organischen Chemie,'' II., 493 ; A. 137, 129). Since its first proposal by him, it has found further support and confirmation from numberless researches. Its chief points are the following : 1. The equal value of the six hydrogen atoms of benzene and the existence of three isomeric di-derivatives would be incomprehensible if an open C-atom chain were ascribed to it, as in the case of the fatty compounds. The requirement that all the H-atoms of benzene shall be linked in a precisely similar manner can, however, be immediately fulfilled if one assumes that the first and last atoms of the six-atom carbon chain are bound together exactly as the remaining atoms are among each other, i.e. that the atoms form a "closed chain" or a "ring" (pp. 21 and 55), thus: C— C— C— C-C— C, = I I "Benzene ring." ! ! d. /A cr Since, according to this mode of combination, all the C-atoms are similarly grouped, the six H-atoms can also 1)6 linked to them symmetrically. 2. The further condition, that the benzene formula which is put forward shall render explicable the existence of three isomeric di-derivatives, is only fulfilled if one 0-atom binds one H-atom, i.e. if six CH-groups are joined together in ring form. Leaving aside in the meantime the question as to how the C-atoms are connected by their fourth affinities, we obtain the following graphical formula for benzene : 344 BENZENE DERIVATIVES. XVI. SUMMARY. H /\ HC'^ CH I I HC. .OH H /^\ or, more shortly. H H This "hexagon formula" is frequently made use of, on account of the perfect symmetry to which it gives expression. 3. We also arrive in the following manner at the conclusion that the carbon atoms of benzene form a closed chain. Benzene and its derivatives are capable of forming addition compounds, although with far more difficulty for the most part than ethylene, for instance; they can take up two, four or six atoms of hydrogen, chlorine or bromine, according to the conditions of the experiment. Thus benzene, for example, yields hexa-hydro-benzene, CgHu, upon prolonged treatment with hydriodic acid, and the phthalic acids, CgH^(C02H)2, yield di-, tetra-, and hexa-hydro-phthalic acids, etc. The resulting hexa-hydro-compounds can not only not combine with any more hydrogen or halogen, etc., but they readily give up the added atoms upon oxidation. Again, benzene hexa-chloride, O^HgClg, cannot be made to take up more hydrogen or chlorine by any means, but on the contrary it readily yields up 3H and 3C1. These compounds therefore differ materially from the defines or their derivatives with which they are isomeric. The incapacity of hexa-hydro-benzene to combine with more hydrogen leads unconstrainedly to the following constitu- tional formula, according to which it appears as hexa- methylene, (CHg)^, or "K-Hexylene" (cyclo-hexane): H.C CH, HjO v CH, KEKULES BENZENE THEORY. 345 4. The above graphical formula for benzene allows of a very simple explanation of the fact that two pairs of symmetrically linked C-atoms (2 and 6, 3 and 5)" exist for each C-atom (1), and that one of the modes of combination of two C-atoms (1 and 4) can occur only once in the molecule. The existence of three di-derivatives is also explained very easily thereby, for, according to this formula, only three classes of di-deriva- tives are possible, viz. : 1. those whose substituents (E) are linked to "neighbouring" C-atoms (1, 2=1, 6); 2. those whose substituents are linked to two C-atoms which are "separated" by a third one (1, 3 = 1, 5); and 3. those whose substituents replace "opposite" C-atoms (1, 4). These three varieties of isomers are designated shortly as follows : E \/ R R \/ R R R The existence of isomeric tri- etc. derivatives of benzene is likewise readUy explained by the above formula ; when the substituents, R, are the same, the following cases are possible for tri-derivatives : R \/ R R R R R R R^^R In tri-derivatives of the first kind the three substituents are linked to neighbouring or " vicinal" {v) carbon atoms, in those of the second to asymmetrically separated {a), and in those of the third to symmet- rically linked (s) C-atoms, and so on. Characterization of the Ortho-, Meta-, and Para-di- derivatives. Determination of Position. 1. The 0-, rrir, and ^-compounds are characterized by their genetic connection within each particular class. 346 BENZENE DERIVATIVES. XVI. SUMMARY. 2. The amido-benzoic acid (M. Pt. 145°), which has already been mentioned on p. 340 as resulting from the two nitro- (meta-) bromobenzoic acids, belongs to the class of ortho- compounds, and the amido-benzoic acid (M. Pt. 174°), also mentioned there as prepared from the two nitro- (ortho-) oxy- benzoic acids, to the class of meta-compounds. Consequently the ortho- and the meta-positions are those which are found twice in the molecule, corresponding to the notation used on p. 340: ab = af, ac = ae. Therefore the third amido-benzoic acid (M. Pt. 187°), which is isomeric with the above two others, is a para-compound, as are likewise all the bi-deriva- tives which can be prepared from or converted into it by reactions which proceed more or less quantitatively, ("glatt"). The para-di-derivatives are thus characterized as those, the position of whose substituents (ad) occurs only once in the benzene molecule. 3. The 0-, m-, and j^-compounds allow of further character- ization experimentally, apart altogether from theoretical con- siderations. The para-bi-derivatives yield always only one tri-derivative when a third H-atom is replaced by a substituent, the ortho- yield two, while the meta- yield three (CgHgRg or CgHgRjR')- It is assumed here that the bi-derivatives contain one and the same substituent. Thus, corresponding to one of the di-bromo-benzenes, C5H4Br2, (which is solid, M. Pt. 89°), there is only one tri-bromo-benzene, CeHjBrj ; corresponding to another (M. Pt. - 1°, B. Pt. 224°), there are two ; and corresponding to the third (liquid, B. Pt. 219°), three different tri-bromo-benzenea {Kilmer). The same holcls for the six nitro-dibromo-benzenes, CgHjBrjINOj). The first of the above di- bromo-benzenes is a para-, the second an ortho-, and the third a meta- oompound. Precisely analogous relations exist between the three isomeric di-amido-benzenes, 05H4(NH2)2, and the six di-amido-benzoic acids, CjH3(NH2)5(C02H), derivable from them, {Oriess, B. 7, 1223) ; between the three xylenes, C6H4(CH3)2, and the six nitro-xylenes, (Nolting, B. 18, 2687); and between the three phthalic acids, C8H4(C02H)2, and the six oxy-phthalio acids, C6H3(OH)(C02H)2. If the bi-derivatives which yield a given equal number of tri-derivatives be tabulated together, it will be found that they belong in every case to one and the same (o-, m-, p-) class, and are therefore convertible into one another. 4. ^The close agreement between the facts and the theory KEKULfi'S BENZENE THEORY. 347 with regard to the existence of isomeric di- etc. derivatives has lent a wonderful charm to the endeavour to determine which of the three modes of linking, 1.2 (=1.6), 1.3 ( = 1.5) and 1.4, indicates the ortho-, which the meta-, and which the para-di- derivatives, (" determination of position "). This point is, in the first instance, easy to solve in the case of the para-compounds. The C-atom 4 holds a position of its own with regard to C-atom 1, i.e. there does not exist a C-atom which is linked symmetrically to the position 4, 1 ; consequently the para-compounds are 1, 4 compounds. 5. Further, it is seen at once from the graphical formula of benzene and from the instances just to be given, that from a 1:4 di-derivative only one, from a 1:2 derivative two, and from a 1 : 3 derivative three different tri-derivatives are theoretically possible; should the third substituent be difierent from the two first, these compounds will be all dissimilar, but should it not, then they will be in part identical : R R R R' V R R \/« B /\r' /N v R R y/R R' R' '\y^ R /\ \/ R R /\r ^R R' The para- derivatives are therefore to be designated as 1 : 4, the meta- as 1 : 3, and the ortho- as 1 : 2 compounds, {Korner; see Ladenhurg's memoir, already cited). 6. Other arguments, which partly forestalled KOmer's proofs in point of date, have led to the same result. [Cf. Ladenhurg's proof of the equal value of the three hydrogen atoms of mesitylene, already conjectured by Baeyer, i.e. of the symmetrical nature of the latter ( = 1:3:5), from which the position 1 : 3 follows for meta-xylene, which can be prepared from it (A. 179, 163) ; Oraebe's arguments with 348 BENZENE DEEIVATIVES. XVI. SUMMARY. regard to the constitution 1 : 2 of ordinary phthalic acid, on account of its formation by the oxidation of naphthalene (A, 149, 22), etc.. etc.]. 7. The determination of position of the tri-derivatives depends upon that of the di-derivatives which can be transformed into the former or vice versa. If, for instance, both the 1:2 and 1:4 nitro-toluenes, CgH4(CH3)(N02), yield one and the same di-nitro-toluene, C6H3(OH8)(N02)2, on the introduction of a second nitro-group, the methyl in the latter will be in the ortho-position to one of the nitro-groups and in the para-position to the other, and the compound will therefore be a 1 : 2 : 4 or (a) compound. Special Benzene formulae. The graphical benzene formula which has been employed up to now only disposes, however, of three of the affinities of each carbon atom, and leaves undetermined how the fourth affinity is satisfied. The six carbon atoms having all an equal value, this saturation must be symmetrical. The following concep- tions are those mainly to be taken into account with regard to the point: H H C (I.) II I and (II.) I >/ I Hc. .CH Hc/ yen H H KekuMs Benzene formula. Claus and Koftier's Central or Diagonal formula. Other Benzene formulae : — According to Dewar, the carbon atoms 1 and 4 are linked by a single bond, 2 and 3, and 5 and 6 by double ones. According to Ladenlurg, there are only single bonds between 1 and 4, 2 and 6, and 3 and 5 (prism formula, Ladenburg, loc. cit. ; A. 172, 331 ; B. 23, 1007. Of. Baeyer, B. 19, 1797). Formula (I.) agrees excellently with the modes of formation of benzene and trimethyl-benzene from acetylene and acetone (see below), with its relations to naphthalene (p. 499), and especially with the capability — shown both by benzene and by its derivatives — of forming addition compounds. Combination with H, 01, etc. thus proceeds here exactly as in the case of ethylene, and a total of six monovalent atoms can be taken up. It is true that, according to formula (I.), two ortho-biderivatives appear possible, viz. 1, 2 and 1, 6, the two neighbouring carbon atoms being joined together in the first case by a single bond, and in the second by a double SPECIAL BENZENE FORMTJLiE. 349 one. As a matter of fact, however, only one ortho-biderivative is known in each case (cf. KehuU, A. 162, 86). Recent researches upon the constitution of benzene and its derivatives by Baeyer (A. 245, 251, 256, 268, 269, 176), and upon similar (and also nitro- gen) ring-systems by Bamberger (A. 257, 1), have shown that the nature of the groups entering the benzene molecule is of influence upon the special (fourth) linking of the atoms ; bo that the constitution of the ring in all benzene derivatives is not to be taken as established without further investi- gation because a particular formula applicable to benzene itself has been arrived at. On the contrary, KehuU's formula (I.) might suit for certain compounds (as has been proved by Baeyer for phloroglucin [B. 24, 2687]), and formula (II.) for others. The benzene ring " appears to be capable of existence in two farms, "which are tautomeric, in the sense that each particular deriva- " live possesses a definite constitution." Cf. further, BrUM, J. pr. Ch. [2] 49, 201. In this paper he brings forward arguments in favour cf KekuU's formula. In benzene and its oarboxylio acids, "para-" or " central-linkings " are probably present, in accordance with formula (II.). The peculiar character of these aromatic compounds, especially their great stability (they are unattacked by a solution of permanganate in soda) may possibly arise from these central bonds, and not from the ring-shape or from the number or nature of the constituents of the ring. And this also applies perhaps to pyridine, thiophene, pyrazole, etc. In partially reduced benzene and the carboxylio acids from it, e.g. in dihydro- and tetrahydro-terephthalic acids, no para-bonds but only double bonds are present, for these substances possess the same properties as unsaturated compounds with an open chain, being (for example) at once oxidized by alkaline permanganate; and bromine never adds itself on in the para- but always in the ortho - position. In completely reduced benzene and its carboxylio acids, e.g. in hexahydro- terephtbalic acid, there are only single carbon bonds, those bodies showing exactly the characters of saturated compounds of the fatty series, and their solutions in soda being unaflfeoted by permanganate. The benzene ring in G^,^ is designated by Baeyer as a "tertiary," and that in CjHjj, hexamethylene, as a "secondary" or " reduced " benzene ring. In a partially reduced benzene ring there are therefore, according to the above, still one or two double linkings, e.g. : COaH H,COjH (T.) (IL) I HaL ^H \ / -^ COjH H,COaH iiihf dro-terephtballc acid. Tetrahydro-terephthalic add. 350 BENZENE DERIVATIATES. XVL SUMMARY. In order to indicate the position of those double bonds quickly, the plan propoaed by Baeyer (A. 245, 111) is followed, viz.: — The carbon atoms being numbered 1-6, as given on p. 344, the sign A is prefixed to the number of that carbon atom which is linked to the succeeding one by a double bond. The two extended formulae, given above, wotdd thus be (I.) = A '''-Dihydro-terephthalio acid. (II.) = A '-Tetrahydro-terephthalic acid. Laws governing substitution, and influence of the substituents upon one another. 1. A polyvalent element never replaces several hydrogen atoms together in a single henzene nucleus; compounds such as OgH^=0 and OgHg^N are unknown. 2. In the formation of di-derivatives, etc. , several isomers usually result simultaneously, one of them generally in preponderating amount. The position of the new suhstituents depends upon that of those already present; thus nitrobenzene yields chiefly ?)vnitro-chloro-benzene when chlorinated, and chloro-benzene chiefly ^-nitro- chloro-benzene when nitrated. As a general rule, when 01, Br, I, NOj and SO3H enter chloro-, bromo- or iodo-benzene, phenol, CgHj. OH, .aniline, OjHj.NHg, or toluene, CgHj.OHg, it is always the para-compound which is produced in largest quantity, often together with the ortho-, but only in rare cases with the meta-compound. On the other hand when 01, Br, I, NOj and SO3H enter into a compound which already contains NO^-, SOgH-, or OOjH-, they almost always take up the meta-position to these latter groups. For a rule to determine whether a given benzene mono-derivative shall give a meta-di-derivativ6, or a mixture of ortho- and para-di-deriva- tives, see Grum Brown and Gibson, Oh. Soc. J., 61, 367. 3. Through the entrance of (negative) nitro-groups or of halogen atoms, the acid character of phenol, i.e. the negative nature of phenyl (p. 338), is heightened, while the basic character of amido-compounds is either dimin- ished or entirely done away with. The firm linking of halogen or amidogen ISOMERS OF THE BENZENE DERIVATIVES. 351 in the benzene nuoleits is thereby loosened, so that these substituents become more easily exchangeable, e.g. for hydroxyl. (Of. trinitro-chloro- benzene, trinitro-phenol and tri-nitraniline.) The intensity of the influence in question is dependent upon the position of the newly-entering substituent ; thus ortho- and para-chloro- (or bromo-) nitro-benzenes, C8H4C1(N02), are transformed into the corresponding nitro-pheuola, C6H4(OH)(N02), when heated with a solution of potash to 120°, and into the corresponding nitranilines, CgH4(NH2)(N02), with ammonia at 100°, while meta-chloro- (or bromo-) nitro-benzene does not react at all. In an analogous manner, o-dinitro- benzene exchanges a nitro-group for hydroxyl when boiled with caustic soda solution, while the p- and m-oompounds do not. Further Isomers of the Benzene derivatives. 1. The isomerism of the di-, tri-, etc. derivatives, " isomerism of position " or " nucleus isomerism," has already been treated of on pp. 341 et seq. 2. When a substituent enters the benzene nucleus in the first instance and a side chain (p. 336) in the second, the so-called " mixed isomerism " is the result, e.g. : CsH^Cl— CHg and CsH^— CH2CI ; CeH4(CH3)2 and C8H5(CH2.CH3). Mono-ohloro- Benzyl chloride. Xylene. Ethyl-benzene, toluene. 3. When the side chains are isomeric, one speaks of ' ' side chain Isomerism," e.g. ; CeHj— CH2-CH2-CH3 and CeH5-CH(CHs)2. Normal- and Iso-propyl-benzene. 4. Should the atoms in the side chains (including those chains which are built up from 0, S, or N) be unequally divided, " metamerism " in the narrower sense of the word results, e.g. : C8H4> HjC CH- (COjl \oloR ^Cq/ 2 mols. Succino-di-ethyl ether. Succino-suocinic ether. »R = CjHs. 6. When sodio malonio ether, CHNa(C02E)2, is heated, there is formed Phloroglucin-tricarboxylic ether, which passes into phloroglucin on saponi- iication, the carboxyl groups being broken up. 7. Hexyl iodide, CsHisI, is converted into hexa-chloro-benzene, CjCls, by heating it with IClj, and into hexa-bromo-benzene, CeBrc, by bromine at 260° ; the latter compound can also be obtained by. heating CBr4 to 300°. 8. Mellitic acid, C6(C0aH)s, is produced by the oxidation of graphite or lignite by means of KMnO,. 9. Potassium carboxide, which is formed by the action of carbonic oxide upon potassium, is the potassium compound of hex-oxy-benzene, C,{OH), (see p. 427). TRANSFORMATION OF BENZENE DERIVATIVES. 355 The converse transformation of Benzene derivatives into Fatty compounds. 1. When the vapour of benzene is passed through a red-hot tube, it is partially decomposed into acetylene. 2. Benzene is oxidized by chloric acid to " Trichloro-pheno- malic acid," i.e. yS-trichlor-aceto-acrylic acid, CCI3 — CO — CH= CH— CO2H {KekuU and Strecker, A. 223, 170). When chlorine is allowed to act upon phenol in alkaline solution, the benzene ring is broken, and the acids, O8H5CI3O4, C6H5CIO4, etc., are pro- duced {Hantzsch, B. SO, 2780). Pyrocatechin, resoroin, and phloroglucin are also ultimately converted into fatty compounds by treatment with chlorine (B. 25, 2219). Bromine, acting upon bromanilic acid, yields perbromo-acetone, CBra — 00 — CBrj. 3. Nitrous acid (NjOg) converts pyrocatechin into dioxy- tartaric acid (see p. 265), while permanganate of potash, acting upon phenol, gives rise to inactive tartaric acid and oxalic acid {Dobner, B. 24, 1753). 4. Oxidizing agents which are capable of destroying the benzene ring yield carbonic, formic and acetic acids. 5. The hexa-hydro-benzenes are transformed into hydro- carbons of the methane series when treated with hydriodic acid at 280° (Berthelot). This decomposition appears, however, to be very diflScult of accomplishment. 356 XVII. BENZENE HYDROCAKEONS. XVII. BENZENE HYDROCARBONS. A. Saturated Hydrocarbons. Summa/ry: [• ] = M. Pt. ; ( ) = B. Pt. CsHj CjEs, Benzene (79°). C7H8 CeHslCHj), Toluene (110°). CsHio C8H4(CH3)2, Xylenes (3) C8H6(CH2.CH3), Ethyl-benzene o- = (142°); m-=(137°);p-=(137°) (134°). C9H12 C6H8(CH3)3 0,H4(CH,)(C2H5) CeH5(C3H,) Trimethyl-benzenes (3). Methyl-ethyl- Propyl-benzenes s = Mesitylene (163°). benzenes (3) 1. Normal-propyl- a = Pseudo-cumene (169°) Ethyl-toluenes (157°) »=Hemellithene (175°). [e.g. 162°). 2. Iso-propyl- ( = Cumene)(153°). C,„H„ C8H,(CH:3)4 G,-H,{GIIMGA) CeH4(C2H5)2 C6H5(C,H,) Tetra-methyl- Dimethyl-ethyl- Diethyl-benzenes Butyl- benzenes (3): benzenes (3) benzenes s=Durene (6 isomers (181° -184°). (4 possible) [79°] (190°). possible). CoH,(CH3)(C3H,) (167° -180°). o=Iso-durene Cymene (195°). (176°) (6 isomers ■w=Prehnitene possible). [-4°] (204°). C11H16 C6H(CH3)5, Penta-methyl-benzene, [51°] (231°) ; CeH5(C5Hn), Amyl-benzene, etc. C„H„ C6(CHa)o, Hexa-methyl-benzene, [164°] (264°); CsHs{C2H5)8, Tri-ethyl-benzene, etc. C11H22 CoH5(C8H„), Ootyl-benzene; C6H:2(02Hs)4, Tetr-ethyl-benzene. CieHao c. CjHsJs, Hex- Bthyl-1 jenzene [126' ](305 °). MODES OF FORMATION. 357 The benzene hydrocarbons are for the most part colourless liquids insoluble in water but readily soluble in alcohol and ether, which distil without decomposition; (durene and penta- and hexa-methyl-benzenes are crystalline). They possess a peculiar and sometimes pleasant ethereal odour, and burn with a very smoky flame. In addition to benzene itself, the presence has been proved in petroleum of its methyl derivative toluene, the three xylenes, the three tri-methyl- benzenes and two tetra-methyl-benzenes. Modes of formation. 1. By treating a mixture of brominated hydrocarbon and iodo- (or bromo-) alkyl with sodium in ethereal solution, (the Fittig reaction, A. 131, 303, analogous to the Wurtz reaction, p. 46) : CgHsBr + CH3I + 2Na = CgHs-CHg + Nal + JSTaBr ; C6H,Br(C2H5) + C2H6l + 2Na = C(iH,(C2H5)2 + Nal + NaBr. 2. By the action of methyl chloride upon benzene or its homologues in presence of .aluminium chloride {Gustavson, the so-caUed " Friedel and Crafts" reaction), intermediate com- pounds, such as Al2Cl5(C3H5), being first formed : CgHg + CH3CI = C6H5CH3 + HCl CgHe + 2CH3CI = CgH^(CH3)2 + 2HC1, etc. This reaction is, like the preceding one, capable of very wide application ; by means of it all the hydrogen atoms in benzene can be gradually replaced by methyl. Zinc and ferric chlorides act in the same way as chloride of alum- inium, while ethyl chloride and other haloid compounds, such as chloroform and acid chlorides, may replace methyl chloride. (See respectively triphenyl-methane and the ketones ; cf also B. 14, 2624 ; B. 16, 1744; Ann. de chim. et phys. [6] 1, 419.) In addition to this synthetical action, aluminium chloride also exerts a "breaking up" or differentiating action on the homologues of benzene, e.g. it partly transforms toluene into benzene and xylene, and so on, (B. 17, 2816 ; 18, 338 and 657). Related to the Friedel-Crafts reaction is the Zincke reaction with zinc dust, (see diphenyl-methane). Alcohols also, like their haloid ethers, are capable of reacting in an analogous manner in presence of ZnCla : CeHe + OiHjOH = CjHj.CiHs + HjO. 358 XVII. BENZENE HYDROCARBONS. 3. The benzene hydrocarbons result from their respective carboxylic acids by the splitting off of the carboxyl, e.g., by distillation with soda-lime : CgHsCOgH = CgHe + COj; CaH,(CH3)C0,H = O.H^.CHa + CO^. 4. From sulphonic acids (p. 338) by the separation of the SOgH-group: C,H3(CH3)2S03H + H^O = G,B,{GH,), + H^SO,. This reaction can be effected by dry distillation, by heating with con- centrated hydrochloric acid to 180°, by distillation of the ammonium salt ((7aro), or by treatment with superheated steam, eg., in presence of some concentrated sulphuric acid {Armstrong, W. Kdhe); also by heating with concentrated phosphoric acid (B. 22, Kef. 577). 5. From the amido-compounds by transforming these into diazo-compounds (p. 394), and boiling the latter with absolute alcohol or with an alkaline stannous solution (B. 22, 587) 6. By distillation of the phenols (or ketones) with zinc dust. 7. For synthesis, see above. The method of synthesis for paraffins, which was mentioned on p. 47, ia also oooasionally applicable (see Propyl-benzene). Isomers and Constitution. The table given on p. 356 shows that the benzene hydrocarbons, from CgHjg on, exist in many isomeric modifications ; thus, isomeric with the three xylenes we have ethyl-benzene, with the three tri-methyl-benzenes the three methyl-ethyl-benzenes and the two propyl-benzenes, with durene, cymene, and so on. The constitution of these hydrocarbons follows very simply from their modes of formation. A hydrocarbon CjqHj^ for instance, which is obtained by means of CH3CI by the Friedel- Crafts reaction, can only be a tetra-methyl-benzene j another of the same empirical formula CjqHi^, which has been prepared from bromo-benzene, butyl bromide and sodium, must be a butyl-benzene ; while a third, from jp-bromo-toluene, normal propyl iodide and sodium, must be a ^-propyl-toluene (p-methyl-N-propyl-benzene), etc. The synthesis therefore determines the constitution. The (carbon containing) groups CH3, CjHj, etc., which replace hydrogen in benzene, are termed " side chains." BEHAVIOUR. 359 According to the number of side chains it contains, a benzene hydrocarbon is converted by oxidation into a benzene- mono-, di- or tri-, etc., carboxylic acid, e.g. benzoic acid, CgHg.COjH, 0-, TO-, ^-phthalic acid, C8H^(C02H)2, etc. In this way a further means is afforded of determining the constitu- tion of the compounds in question. If, for example, a hydrocarbon CgHjj yields a benzene-tri-carboxylic acid, CjH3(C02H)3, upon oxidation, it must contain three side chains, 8. e. , must be a tri-methyl-benzene ; should a phthalio acid on the other hand result, then it can only be an ethyl-toluene. Since cymene yields p- (or tere-) phthalic acid, CgH4(C02H)2, on oxidation, its two side ohaina must be in the ^-position towards one another. The respective isomers resemble each other closely in physical properties, their boiling points — for example — lying very near together. The ortho-derivatives often boil at about 5° and the meta- at about 1° higher than the para-compounds ; the boiling point rises with an increasing number of methyl groups. (Of. p. 33; also B. 19, 2513.) Behaviour. 1. The benzene hydrocarbons are as a rule easily nitrated and sulphurated, mono-, di- and even tri-derivatives being all usually capable of preparation, according to the conditions. It is only the H-atoms of the benzene nucleus which enter into reaction here, in accordance with the theory which regards the side chains as paraffinic residues, as which they behave. Hexa-methyl-benzene can thus neither be nitrated nor sulphurated. 2. Oxidation. Benzene can only be oxidized with diflSculty ; permanganate of potash converts it slowly into formic and oxalic acids, some benzoic acid and phthalic acid being produced .at the same time. These doubtless result from some previously formed diphenyl. The homologues of benzene, on the other hand, are readily oxidized to carboxylic acids, the benzene nucleus remaining unaltered, and each side chain — no matter how many carbon atoms it may contain — being converted as a rule into carboxyl. Nitric acid allows of a successive and often a partial oxidation of individual side chains ; chromic acid mixture (KjCrjO, + HjSO^) acts more energetically, converting all the side chains in the p- and m- 360 XVII. BENZENE HYDROCARBONS. compounds Into carboxyl, and completely destroying the o-compounds. The latter may be oxidized to the corresponding oarboxylic acids by KMnOi. As is manifest from these two points, the homologues of benzene differ somewhat materially from benzene itself ; the H-atoms of the side chains show a different function to those of the benzene nucleus, the former behaving like the hydrogen atoms in a paraifin. It thus follows that toluene and the higher homologues may be derived from methane, etc., by replacement of H by CeHs, " phenyl," etc. CHsCCeHs) C8H,(CsH5) Toluene or phenyl-metbane. Cumene or phenyl-propane. 3. Eeduction. As mentioned on p. 344, benzene and most of its derivatives are capable of taking up six atoms of hydro- gen. Benzene itself is only converted into hexa-hydro-benzene, CgHi2, with difficulty, but toluene, xylene and mesitylene com- bine with hydrogen more easily when they are heated with phosphonium iodide, PH^I, to a rather high temperature, the compounds C.^H8.H2, CgH^Q.H^ and CgHjg.Hg being formed. The two former can then be made to take up more hydrogen by energetic reaction. Benzene hexahydride and its analogues, CnHsn, are colourless liquids insoluble in water, and of somewhat lower boiling point than their mother compounds, into which they can be readily retransformed by oxidation, either by heating with sulphur or by means of faming nitric acid, nitration also taking place in the latter case. They are found in petroleum, especially in that from the Caucasus {BeUstein, KwrbaUm). They differ from the isomeric defines by being insoluble in sulphuric acid, and by not forming addition products with bromine (of. B. 20, 1850; A. 234, 89; B. 21, Eef. 570). The partially hydrogenized hydrocarbons, on the other hand, behave more like the defines ; thus, they take up bromine until the point of saturation, OnHan, is reached (B. 21, 836 et seq.; cf. also p. 349). 4. Behaviour with halogens. Chlorine and bromine react differently, according to the conditions. . In direct sunlight they yield with benzene the addition products CgHjClg and CgHgBrg, while in diffused daylight, especially in presence of a little iodine, SbClg or MoClj, they give rise to the substitution products OgHjOl, CjHjBr, etc. (For further details, and for substitution by iodine, see pp. 70 and 366.) 5. Chromium oxyohloride, CrOaClz, converts the methylated benzene hydrocarbons into aromatic aldehydes (p. 433; cf. B. 23, 1070). BENZENE. 361 6. The numerous " condensations " which benzene, etc., can undergo with oxygenated compounds in presence of ZnClj, PgOg of H2SO4, and with chlorinated compounds in presence of Al2Clg, are of great interest; thus benzene yields diphenyl- ethane with aldehyde and sulphuric acid, and benzophenone with benzoic acid and phosphorus pentoxide. 6a. The methyl-benzenes (but not benzene) " condense '' with unsatu- rated hydrocarbons in a similar manner, in presence of sulphuric acid, e.g. xylene with styrene to xylo-phenyl-ethane {Kramer, SpilJcer, B. 23, 3270). The methyl-benzenes react also with allyl alcohol, by the aid of concen- trated sulphuric acid, to form extremely viscous compounds which contain no oxygen. The mineral lubricating oils are probably formed in an anal- ogous manner. 7. In presence of aluminio chloride, oxygen can be introduced into benzene, yielding phenol; sulphur, yielding phenyl sulphide; ethylene, yielding ethyl- benzene ; carbon dioxide, yielding benzoic acid ; and so on. By means of oarbamic chloride, C0(NHj)01, amides of the aromatic acids are produced (which see). Being well crystallized compounds, those amides are of much use for the characterization of the hydrocarbons in question (B. 23, 1190). The Hydrocarbon CgHg. Benzene, CgHg. Discovered by Faraday in 1825, and de- tected in coal tar by Hofmamn in 1845. Benzene is obtained from the portion of coal tar which boils at 80°-85°, by fraction- ating or freezing. It may be prepared chemically pure by distilling a mixture of benzoic acid and lime. The ordinary benzene of commerce usually contains thiophene and thus gives the indophenin reaction, but it may be freed from it by repeated shaking up with small quantities of sulphuric acid. M. Pt. 6°; B. Pt. 79°; Sp. Gr. at 0°, 0-9. It burns with a luminous smoky flame, and is a good solvent for resins, fats, iodine, sulphur, phosphorus, etc. When its vapour is led through a red-hot tube, diphenyl is obtained. Benzene di-hydride ("O.N." dyco-hexadiene), CeHs.Ha. From dlbromo- hexa-methylene (which see). A liquid with an odour of leeks; B. Pt. about 81'5°. It is immediately oxidized by permanganate. It yields a crystalline tetra-hromide (M. Pt. 181°), and gives a blue colouration with alcoholic sulphuric acid. It is nearly related to the terpenes. (Of. Baeyer, B. 26, 230.) 362 XVII. BENZENE HYDROCARBONS. Benzene tetra-hydride (cydo-hexene), CnHe-H,. From quinitol (p-dioxy- hexa-methylene) (which see) . B. Pt. about 82°. This compound also has an odour of leeks, and it yields a liquid dibromide. Benzene hexa-hydride (cyclo-hexwne), CcHs.Hg, also termed "naphthene," is obtained from the earth-oils of the Caucasus (p. 54), and also synthetic- ally from quinitol. B. Pt. 69°; Sp. Gr. at 0°, 0*75. This compound smells like petroleum. It is stable towards permanganate. Benzene hexa-chloride, CsHeOls, is produced by the action of excess of chlorine on benzene in sunlight. It is a solid mass, which is broken up into tri-chloro-benzene and hydrochloric acid on distillation, or when treated with alkalies. Two stereo-isomeric modifications are known. Benzene hexa-hromide, CsHeBrj. M. Pt. 212°. Mercury di-phenyl, Hg(C6H5)j, is an analogue of mercury di-ethyl; it results from the action of mercury upon mono-bromo-benzene. M. Pt. 120°. The Hydrocarbon C^Hg. Toluene, C^Hg, = C|;H5.CH3. Discovered in 1837. Formor Hon: by the dry distillation of balsam of Tolu and of many resins. Synthesis according to Fittig (see above). Prepwroy Hon: from coal tar, in vrhich it is found accompanied by thio- tolene. Toluene is very similar to benzene. It boils at 110°, and is still liquid at - 28°. CrOjClg converts it into benzoic aldehyde, and HNO3 or CrOg into benzoic acid. Toluene di-hydride, C6H6(H2).CH3, and -hexa-hydride, 08H5(H6).CHfc are liquids boiling respectively at 105°-108° and 97°. Hydrocarbons, CgHjQ. (a) 0-, m-, and j7-Di-methyl-benzenes or Xylenes, CgH4(CH3)2. The xylene of coal tar consists of a mixture of the three isomers, ?w-xylene being present to the extent of 70 to 85 p.c. These cannot be separated from one another by fractional dis- tillation, m-xylene is more slowly oxidized by dilute nitric acid than its isomers, and can thus be obtained with relative ease. For the separation of those isomers by means of HjSOi, see B. 10, 1010; 14, 2626; 17, 444; 25, Ref. 315; and for their recognition see B. 19, 2513. Benzene and toluene yield chiefly ortho-, together with a little para-xylene, when subjected to the Friedd-Orafts synthesis (B. 14, 2627). 1. o-Xylene, which can be prepared synthetically from o-bromo-toluene, methyl iodide and sodium, is oxidized to carbonic acid by chromic acid XYLENES, ETC. 363 mixture, and to o-toluic acid, C6H4(CHs)COjH, by dilute nitric acid; it is difficult to nitrate. 2. m.-Xylene or Iso-xylene also results from mesitylene, ^6H3(CH3)g, 1:3:5, when this is first oxidized to mesitylenic acid, C6H3(CH3)2C02H, and the latter then distilled with lime. Dilute nitric acid only oxidizes it at a temperature of 120°, while chromic acid mixture converts it into iso-phthalic acid, CeH4(C02H)2. It yields a Tetra- and Hexa-hydride, CgHio.H^ and CgHj„.Hg; the latter is present in Caucasian petroleum, and boils at 119°. 3. ^-Xylene. Is prepared e.g. from ^-bromo- toluene or, better, ^-dibromo- benzene, methyl iodide and sodium (B. 10, 1356; B. 17, iU). M. Pt. 13°. Dilute nitric acid oxidizes it to ^-toluio acid, CeHilCHsjCOaH, and tereph- thalic acid, C6H4(C02H)a. The Di-hydride, dihydro-p-xylene, CsHm.Hs, can be prepared from suc- cino-suocinio ester. Liquid ; B. Pt. 133°. It has a turpentine odour, and is nearly related to the terpenes. Cf. Baeyer, B. 26, 2122. (J) Ethylbenzene, OsHs— CjHs. Kesults from CcHsBr and CjHsBr by the Pittig reaction; from styrene, CsHj— O2H3 and HI; and from CeHs and C2H5CI by the Priedel-Orafts reaction. Is oxidized to benzoic acid. It is found in small quantity in the xylene from tar. Hydrocarbons, CgHjj (see table). The most important of these are : (a) Tri-methyl-benzenes. 1. Mesitylene, 1:3: 5-trirmethyl-henzene, C6Hg(CH3)3. This is contained in coal tar along with its two other isomeric tri- methyl-benzenes (" tar-cumene " ), and can be prepared from acetone or allylene (p. 353). It is a liquid of agreeable odour. Nitric acid oxidizes the side chains one by one, while chromic acid mixture decomposes it completely. It does not form any isomeric substitution products and has therefore a symmetrical constitution, (Ladenburg, A. 179, 160.) B. Pt. 163°. Mesitylene heza-bydrlde, CgHjj.HB, boils at 138°. 2. tsevido-cuTa.eTa.e, 1 :2: i-tri-methyl-benzene. Present in coal tar. It is separated from mesitylene, not by fractional distillation, but by taking advantage of the sparing solubility of pseudo-cumene-sulphonio acid, (B. 9, 258). Its constitution follows from its formation from bromo-^-xylene, 1:4:2, and also from bromo-m-xylene, 1 : 3 : 4, by the 364 XVII. BENZENE HYDROCARBONS. Fittig reaction. Nitric acid oxidizes the Bide chains successively. B Pt. 169°. Hexahydro-^-cumene, nono-naphthene, C9H1B, is present in Caucasian petroleum. B. Pt. 135°-138°. 3. Hemellithene, X-.'i-.Z-tri-meihyl-henzene (see B. 15, 1853). Present in coal tar (B. 20, 903). (i) Ethyl-toluenes, C6H4(CH3)(CaH5). The m- and p-compounda are known. (c) Propyl-benzenes, CgHj — CgH^. These are oxidized to benzoic acid. 1. N- Propyl -henzene, Cells — CH2 — CH2 — CH3, results from bromo- benzene and normal propyl iodide by the Fittig reaction, and also from benzyl chloride, C6H6.CH2CI, and zinc ethyl. 2. Iso-propyl-benzene or Cumenej CgHj — CH=(CH3)2, is produced by the distillation of cumic acid, C^^{G^^)(pO^), with lime J from benzene and iso- or normal propyl iodide by means of AlgClg, in the latter case with molecular rearrange- ment (p. 74); and from benzylidine chloride, CgHj — CHCl^, and zinc methyl, this last method furnishing proof of its con- stitution. For the transformation of the normal- into the iso-propyl group in cumene and cymene derivatives, see B. 18, Ref. 152; B. 19, 2769. Hydrocarbons, C^qHj^. (See table.) Among these may be mentioned Durene, 1:2:4:5- or s-tetra-methyl-benzene, OgH2(CH3)^, which has recently been found in coal tar, and can be prepared from toluene and methyl chloride by the FriedelrCrafts reaction, or from dibromo-»i-xylene (from coal tar xylene), methyl iodide and sodium (A. 216, 200). It is a solid, M. Pt. 79°, and possesses a camphor-like odour. For its constitution, see B. 11, 31. Both of its isomers are known (see table). Methyl-propyl-benzenes, G^^{GE.^G^^. The most impor- tant of these is cymene or isopropyl-p-methyl-henzene. It is found in Eoman cummin oil (Cuminum cyminum), and results upon heating camphor with PgSj or, better, P2O5, also by heating UNSATURATED BENZENE HYDROCARBONS. 365 oil of turpentine with iodine, etc. It has been synthetically built up from ^-bromo-isopropyl-benzene, methyl iodide and sodium; and also from ^-bromo-toluene, N-propyl iodide and sodium, the N-propyl- changing here into ,the iso-propyl group. It is a liquid of agreeable odour, B. Pt. 175°-176°. Cymene was formerly looked upon as N-propyl-p-methyl-benzene (of. Widmum, B. 24, 439). It yields upon oxidation either j5-toluic, terephthalic, cumio, or oxy-isopropyl-benzoio acid, or ^-tolyl-methyl-ketone, according to the conditions. Bi-Iso-cymene, iscypropyl-m-methyl-benzene, is present in resin oil. Isomeric with the above are the Butyl-benzenes, C5Hs(OiH9), of which three are known, and the Ethyl-xylenes. Cymene di- hydride, CioHu.Ha obtained synthetically from suooino- sucoinic ester, shows exactly the behaviour of the terpenes (B. 26, 233). Hydrocarbon, CjjHjg. Heza-methyl-benzene, mellitene, Ce(CHs)5, crystallizes in prisms or plates which melt at 164°. It can neither be sulphurated nor nitrated (see p. 359). KMnOi oxidizes it to mellitio acid, C6{C02H)s. For the higher homologues see table, p. 356. B. Unsaturated Benzene Hydrocarbons. The benzene hydrocarbons containing less hydrogen comport themselves on the one hand like benzene itself, and on the other like the unsaturated hydrocarbons of the fatty series, combining readily with hydrogen, halogen, halogen hydride, etc. They are derived from the olefines or acetylenes by the exchange of H for GgR^, thus: (C6H5)OH=CH2, styrene or phenyl-ethylene; (06H5)C=CH, phenyl-acetylene. Styrene, 08H5.CH=OH2, occurs along with other compounds in storax (Styrax officinalis), in the juice of the bark of Liquidambar orientale, and in coal tar (being in this last case probably a degradation product of certain acids). It results upon heating cinnamic acid (p. 453) with water to 200°: CHs— CH=CH— COjH = CeHt— CH=CH, + CO* 366 XVIIL HALOID SUBSTITUTION PRODUCTS. For its preparation see A. 19S, 131. Styrene is a liquid like benzene, and of agreeable odour. B. Pt. 146°. It changes on keeping into the polymeric meta-styrene, an amorphous transparent mass, and goes into ethyl-benzene when heated with hydriodic acid. Addition of HBr converts it into a-bromo-ethyl-benzene, CsHs — CHj — CHjBr. By the condensation of styrene with toluene, in presence of concentrated sulphuric acid, and on subsequent superheating, anthracene results (Kra/mer, SpUker, B. 23, 3169). Phenyl-acetylene, CcHs.C^CH, is produced, e.g. by the separation of COj from phenyl-propiolic acid (p. 455) ; CcHs— C=C— CO^H - CeHs— C=CH + COj. It is a pleasant smelling liquid boiling at 142°, and gives proof of its being an acetylene derivative by yielding white and paJe yellow explosive metallic compounds with solutions of silver and cuprous oxides. It com- bines with water to aceto-phenone, C6H5.CO.CHs, when it is dissolved in sulphuric acid and the solution is diluted with water. XVIII. HALOID SUBSTITUTION PRODUCTS. Summary. The numbers in the square brackets [...] indicate melting, and those in the round ones (...) boiling points. CeHjCl Chloro-benzene (132°). C5H4CI2 Di-chloro-benzen es 0- : (179°) ; m- : (172°) ; p- : [56°], (173°). CsHsBr Bromo-benzene (156°). CeH^Br^ Di-bromo-benzenes 0- : (224°) ; m- : (219°) ; p- : [S9°], (219°). CeH,I lodo-benzene (185°). Di-iodo-benzenes (e.g., 285°). CsHjCls, (3), Tri-ehloro-benzenes (208° to 218°). C8H2CI4, (3), Tetra-chloro-benzenes. CjHClj, (1), Penta-ohloro-benzene. CeCls, (1), Hexa-chloro-berzene [226°], (326°). CeH^CKCHs) (3) Chloro-toluenes (156°-160''). C8HsCl2(CH3) (6) Di-chloro- toluenes {e.g., 196°). etc. CsH,— CHjCI Benzyl chloride (179°). CjHj — OHCI2 Benzal chloride (206°). Ce^s — CCI3 Benzo-tri-chloride (21.3°). CeHsCUCHsJj, (6) Chloro-xylenes. C8H4(Cfl3)(CH2Cl),Xylyl chlorides. C8H4(CH2Br)2, (3) Xylylene bromides, etc., HALOID SUBSTITUTION PRODUCTS. 367 Haloid substitution products in immense number are derived from the benzene hydrocarbons by the exchange of hydrogen for halogen. They are either colourless mobile liquids or crystalline solids, insoluble in water but readily soluble in alcohol and ether, which distil unchanged, and are distinguished by their peculiar odour and also, in part, by their irritant action upon the mucous membrane. They are heavier than water. The substitution products of benzene itself and those of its homologues have to be distinguished from one another. In the former the halogen is bound very firmly, far more so than in methyl chloride, ethyl iodide, etc. ; it cannot be exchanged for OH (through AgOH), or for NHj (through NHg), etc., sodium almost alone being capable of bringing it into reaction, (see the Fittig rea.ction, p. 357); for an exception, see B. 25, 1499. The substitution products of toluene, etc., on the other hand, do not all show a similar behaviour. Some of them, e.g., chloro-toluene, contain the halogen bound very fast, while in others of them, e.g., benzyl chloride, the halogen atoms enter into reaction as readily as do those of the haloid sub- stitution products of the methane series. After oxidation, which transforms all the side chains into carboxyl (p. 359), the halogen remains in the former compounds, with formation of chlorinated, etc., benzoic acids, e.g., OgH^Cl — COjH, but it is eliminated in the latter, benzyl chloride e.g. giving benzoic acid, CgHj — COgH. From this it follows that the halogen is present in the one case in the benzene nucleus, and in the other in the side chain. This is in accordance with the conclusion arrived at on p. 360, of toluene being phenylated methane; chloro-toluene, CgH4Cl.(CH3), is quasi-methylated chloro-benzene and is therefore stable, while benzyl chloride, CeHj— CHjOl, is quasi-phenylated chloro-methyl, and is therefore very active chemically. The same relations repeat themselves in xylene and the other homologues of toluene, so that it is always easy to arrive at the con- stitution of a compound from the behaviour of its halogen atoms and from its products of oxidation. Thus a compound C^HgClj, which yields mono-chloro-benzoie acid upon oxidation, has manifestly the formula CgHiCl— CHaCl (chloro-benzyl chloride). 368 XVIII. HALOID SUBSTITUTION PRODUCTS. Foi- the capability of reaction of the chlorinated benzenes, cf, also p. 350. The boiling points of the (position-) isomeric substitution products (o-, m-, and p-compounds), always lie near to one another, and those of the other isomers also are not very far apart from these. Modes of formation. 1. By the action of chlorine or bromine upon aromatic hydrocarbons there result, according to the conditions, either addition or substitution products, the latter class particularly easily in presence of iodine. (Cf. p. 360, also B. 18, 607.) Iodine only substitutes directly under the conditions already detailed at p. 70. From benzene all the chlorinated derivatives up to CgOlg can be obtained in succession, the last named compound resulting with the aid of MoClj, ICI3, etc., at a somewhat high temperature. A hexa-bromo-benzene also exists, but not a hexa-iodo-compound. In the case of toluene and its homologues the halogen enters the benzene nucleus alone, if the operation is performed in the cold, with the exclusion of direct sunlight or with the addition of iodine ; while, if its vapour is led into the boiling hydrocarbon, or if the experiment is conducted in sunlight and without addition of iodine, it goes almost exclusively into the side chain, {Beilstein ; Schramm; see also B. 13, 1216). 2. From compounds containing oxygen (the phenols, aromatic alcohols, aldehydes, ketones, and acids), by the action of phos- phorus pentachloride or bromide : CgHg.OH + PCI5 = CgHjCl + POCI3 + HCl. 3. From the (nitro- or) primary amido-compounds, these being first converted into diazo-compounds (p. 394). Upon boiling the latter with cuprous chloride or bromide, they are transformed into the corresponding chlorine or bromine com- pounds, and upon boiling with iodide of potassium, into iodo- substitution products {Sandmeyer, B. 17, 1633, 2650j Gattermann, B. 23, 1218): OeH,.N=N.Cl = C,H,ei + N^j C6H5.N=N.C1 -1- KI = OgHjI + N^ + KCl. The bromine compounds also result upon boiling the diazo-per- bromides (p. 398) with absolute alcohol, and the fluorine compounds by a similar reaction, ( Wallach, A. 235, 255). CHLOEO- AND BEOMO-BENZENES, ETC. 369 3a. By treating the primary hydrazines with iodine and iodide of potas- sium (B. 20, Eef. 552). 4. By heating the haloid-substitution acids with lime : CeHiCl— COjH = CsHsCl + COa. Mono-ohloro-, bromo-, and iodo-benzene are colourless liquids of peculiar odour. Their boiling points have been given in the summary. Si-chloro- and Bi-bromo-henzenes exist as o-, m-, and ^-compounds. The p-, and also the o-compounds in smaller amount, are obtained directly (see p. 344), while the m-compounds are obtained indirectly from m-dinitro- benzene according to method 3. The para-compounds are solid and the others liquid. The significance of the di- and tri-hromo-heuzenes for the benzene theory has been already indicated at p. 346. The tri-chloro-benzene which results by direct substitution has the (asymmetric) constitution 1:2:4. It may also be formed by the separation of 3HC1 from C(iHo.Cl«. Hexa-chloTO- and -bromo-beuzenes are produced by the thorough chlor- ination or bromination of benzene, toluene, naphthalene, etc., and also from carbon tetrachloride and bromide, as given at p. 354, They are solid and can be distilled. j)-Sibromo-benzene heza-hydride, p-dibromo-hexa-methylene, CeHioBrj, is obtained from quinitol (which see); it exists in two stereo-isomeric forms. Iodo-benzene, Cgllsl, is oxidizable (indirectly) to lodoso-benzene, C6H5.IO, and this latter to the compound, C6H{.I02, solid explosive sub- stances, Fluo-benzene, CsHsF, is a liquid boiling at 85°; the entrance of fluorine into the benzene molecule thus alters its boiling point only in slight degree. Mono-chloro- and -bromo- toluenes, C6H4C1(CH3) and CgH4Br(CH3). These mono-substitution products of toluene likewise exist as di-derivatives of benzene in the 0-, rrir, and y-modijBications. When toluene is chlorinated or brominated, as given on p. 368, the para- and ortho-compounds are formed in approximately equal quantities, m-Chloro-toluene is obtained from chloro-p-toluidine, C6Ha.Cl(NH2)CH3 (from j)-toluidine and CI), according to method 3. The j3-compounds are solid in the cold and the others liquid. Oxidation by HNOs, CrOa, or KMnOi converts them into the haloid-benzoic acids, but chromic acid mixture must only be used in the case of the p- and m-, and not in that of the o-compounds, as it completely disintegrates the latter. Benzyl chloride, CgHs — CHgCl (Cannizaro), results upon chlorinating boiling toluene, and benzyl bromide in an analogous manner; the latter can be converted into benzyl iodide by iodide of potassium. The behaviour of these com- pounds shows them to be the haloid ethers of benzyl alcohol, (606) 2A 370 XIX. NITRO-STJBSTITUTION PRODUCTS. CgHj — CHj.OH, from which they result by the action of halogen hydride, and into which they are transformed by prolonged boiling with water or, better, with a solution of carbonate of potash. Boiling with potassium acetate yields the acetic ether of this alcohol, with potassium, sulph-hydrate the mercaptan, and with ammonia the amine bases. They are colourless liquids, heavier than water, which boil without decomposition and, like o-bromo-toluene, etc., irritate the mucous membrane of the nose and eyes exceedingly. Oxidation converts them into benzoic acid. Benzyl chloride is used on the large scale for the preparation of oil of bitter almonds and also of certain dyes. Benzal chloride, benzylidene chlm-Me, CjHj — CHCLj, and Benzo-tri-chloride, CgHj — CCI3, are produced by the further chlorination of boiling toluene and also by the action of PCI5 upon the corresponding oxygen compounds, benzoic aldehyde, CgHg — CHO, benzoic acid, O5H5 — COjH, and benzoyl chloride, CgHj — COCl. They are liquids resembling benzyl chloride, and are reconverted into the original oxygen compounds by superheating with water, and into benzoic acid by oxidizing agents. For their relations to cinnamic acid and malachite green, see these. Cliloro-bromo-benzenes, CsHiClBr, Cblor-lodo-benzenes and other mixed derivatives also exist in large number. Substitution compounds of unsaturated hydrocarbons are likewise known, e.g. /S-Bromo-styrene, CgHj — CBr=CH2, a-Bromo-styrene, XIX. NITRO-SUBSTITUTION PRODUCTS OP THE AROMATIC HYDROCARBONS. When benzene derivatives (not merely hydrocarbons) are treated with concentrated nitric acid, most of them are easily dissolved, with evolution of heat, and transformed into nitro- compounds which are precipitated on the addition of water. According to the conditions of the experiment and the nature of the compound to be nitrated, one or more nitro-groups enter NITRO-COMPOTTNDS ; PROPERTIES. 371 the molecule (see e.g. phenol). The nitro-groups substitute in the nucleus and only very seldom in the side chain. Summary. Nitro-benzene. Liq. B. Pt. 206°. CeH4(Iir02)3 . 0-, m-, and p-Dinitro- benzenes. Solid. M. Pts. 118°, 90°, and 171°. CeH3(N03)3 «-Trmitro-benzene. Solid. M. Pt. 121° C8H4(CH3)N02 0-, ?»-, p-Nitro-toluenes. B.Pts.218°,230°and234° p-oompound solid. CeHs(CH,)(NOa)j Dinitro-toluenes. 06H3(CH3)i,NO, Nitro-xylenes. e.g. 1:3:4, (NO^ in 4) Liq. B. Pt. 238°. CeHjICHslsNOj, etc. Kitro-mesitylene. Solid. M. Pt. 42°, B.Pt. 255°. CsH^ClINO,) Nitro-chloro-benzenes. etc. CeBr^CNOa), Tetrabromo-dinitro- benzene. Nitro-compounds are also produced by the action of nitrous acid upon diazo-compounds, in the presence of cuprous oxide, (Sandmeyer, B. 20, 1494) : CeHs— N=N— CI + NHOj = CeHj— NOj + HCl + Njj. Diazo-benzcne chloride. Nitro-benzene. The nitro-compounds are for the most part pale yellow liquids which distil unchanged and volatilize with water vapour, or colourless or pale yellow needles or prisms ; some- times they are also of an intense yellow or red colour. Many of them explode upon being heated. They are heavier than water and insoluble in it, but most of them are readily soluble in alcohol, ether and glacial acetic acid. The nitro-group in most aromatic nitro-compounds is bound very firmly, as in the case of the nitro-methanes, and is not exchangeable for other groups. Like the latter compounds also, they are easily reduced in acid solution to the correspond- ing amido-derivatives ; in alkaline solution they are converted into azoxy-, azo- and hydrazocompounds, (see these). 372 XIX. NITRO-SUBSTITUTION PRODUCTS. On the other hand, they cannot be prepared according to mode of formation 1 for nitro-methane (p. Ill), i.e. by the action of AgNOj on CjHjCl etc. Nitro-benzene, CgH5(N02), (Mitscherlich, 1834). Results, with evolution of heat, on the gradual addition of benzene to fuming nitric acid, or on treating it with a mixture of sulphuric and the calculated quantity of nitric acid. It is a yellowish liquid with an intense odour of oil of bitter almonds, which solidifies in the cold ; M. Pt. + 3°- Dinitro-benzenes, CgH^(N02)2. These are produced when benzene is boiled with fuming nitric acid; in this, as in all analogous cases, the two nitro-groups take up the meta-position to one another, very little of the o- and ^-compounds being formed, and, by recrystallizing from alcohol, pure m-dinitro- benzene is obtained in long colourless prisms or needles. The o-compound crystallizes in tables and the j)-compound in needles, both being colourless ; they are prepared indirectly by elimination of NHj from the corresponding di-nitranilines. Upon reduction there result first the three nitranihnes and then the phenylene-diamines (pp. 386 and 393). o-Nitro-benzene exchanges a nitro-group for hydroxyl when boiled with caustic soda, and for amidogen when acted on by ammonia, with the formation of o-nitro-phenol, CsH4(N02)(OH) and o-nitraniline, C8H4(N02)(NH2). The m-compound is oxidizable by KsFeCys to o- and ^-dinitro-phenol. Nitro-toluenes, CgH4(CH3)(N02). When toluene is nitrated, the p- and o-compounds, with hardly any of the TJi-compound, result. The first is solid, crystallizing in large prisms, and the second liquid, the latter being used as a perfume under the name of "oil of mirbane;" both are employed in the colour industry. m-Nitro-toluene can be prepared indirectly from m-nitro-p-toluidine, C6H3(CH3)(N02)(NH2), by the Griess re- action (p. 397). Further nitration gives rise to : Dlnltro-toluenes, C8H3(CH3)(N02)2, of the constitution CHsiNOjiNOj = 1:2:4 and 1:2:6, the two nitro-groups being again in the m-position to one another in both cases. (Cf. p. 348.) NITRO- AND NITROSO-COMPOUNDS. 373 Most of these nitro-compounds are of great technical im- portance, on account of their convertibility into amine bases. Tri-nitro-tertiary butyl-toluene, 06H(CH,)[C(CHa)s](N02)s, is used as " artificial musk." Chloro- and Bromo-nitro-benzenes. When chloro- or bromo-benzeue is nitrated, p-chloro- (or bromo-) nitro-benzenes, and in smaller quantity the o-compounds, result. The m-compounds must be prepared indirectly by replacing an amido-group in m-nitraniline by halogen. The p-derivatives have a higher melting point than their isomers, and the m-compounds for the most part a higher one than the o-derivatives, this law frequently repeating itself in other cases also. The p-derivatives are usually also less soluble in alcohol. The o- and p-compounds, but not the m-, exchange halogen for hydroxyl when boiled with potash, and for amidogen when heated with ammonia. In Tiinltro-cliloro-'beiizene, C8H2(N02)3C1, the chlorine atom has been rendered so easily exchangeable by the acidifying influence of the nitro-groups that the compound behaves as an acid chloride ; hence the name " picryl chloride," the chloride of picric acid (p. 350). Nitro-zylenes, -mesltylene and -pseudo-cumene are also known in many isomeric modifications, (see table). We are further acquainted with nitro-derivatives of styrene, viz., o-, m-, and p-Nitro-styrenes, C5H4(N02)(C2H3), which can be prepared by indirect methods, and also o-Nitro-styrene, C8H50H=CH(N02), which results directly from the nitration of styrene and contains the nitro- group in the side chain, a necessary consequence of its preparation from benzoic aldehyde and nitro-methane by means of zinc chloride, thus : C8H5.CHO -1- CH3NO2 = C8H5.CH=CH(N02) + HjO. This is one of those relatively rare cases in which the nitro-group enters the side chain upon direct nitration. (Cf.'B. 18, 935, 2438; 19, 836.) o-BTltro-plienyl-acetylene, C6H4(NOs)— O^CH, results upon boiling o-nitro- phenyl -propiolio acid with water. It crystallizes in colourless needles. Nitroso-derivatives of the Hydrocarbons. Nitroso-benzene, CeH5(N0), an aromatic compound which contains the nitroso group, NO, in place of a benzene hydrogen atom, is produced by the action of NO.Cl upon mercury di-phenyl dissolved in benzene; it is also obtainable from diazo-benzene. It forms colourless tables, M. Pt. 68", yields green solutions, and possesses a powerful odour similar to that of cyanic acid. Treated with aniline it gives azo-benzene. 374 XX. AMIDO-COMPOUNDS. Hltroso-derlvatlves of tertiary amineB result directly by the action of nitrous acid upon the latter. (See Kitroao-dimethyl-aniline, C6H4(NO)N(CH3)j, p. 388.) XX. AMIDO-DERIVATIVES OP THE BENZENE HYDROCARBONS. (See table, p. 375.) Aniline, the simplest of the aromatic bases, may be regarded (1) as benzene in which a hydrogen atom is replaced by amidogen, ("amido-benzene"), or (2) as ammonia in which a hydrogen atom is replaced by phenyl, CgHj — , ("phenyl- amine"). According to the former view, amido-oompounds are derived from all the benzene hydrocarbons, and not only monamines (containing NHj), but also di-amines (2NH2), tri-amines, etc. ; according to the latter, the phenyl group may enter anew with the formation of secondary or tertiary amines. Secondary and tertiary amines, and even quaternary ammonium compounds may also result from the entrance of alcohol radicles into the above monamines, diamines, etc. NHj, etc., may likewise substitute in the side chain. An extraordinarily large number of aromatic bases are thus theoretically possible and also actually known (see table). They closely resemble in some ways the nitrogen bases of the alcohol radicles, form salts with acids — frequently with evolu- tion of heat — and double salts with chloride of platinum, possess a basic odour, give rise to white clouds with volatile acids, and distil for the most part unchanged, etc. Speaking generally, however, they are weaker bases than the alcoholic amines, since the phenyl group, CgHg, possesses a negative character, and not — like the alcohol radicles — a positive; thus the salts of diphenylamine are decomposed even by water, and triphenylamine no longer possesses basic pro- perties, while dimethyl-aniUne has a strongly marked basic character. [Continued on p. 376 AillDO-COMPOUNDS. 375 Summary. Primary. Secondary, Tertiary. / CeHj-NHj (CeH^j^NH (CsH^JaN ATilllne Dipbenylamlne Trlphenylamlne [-8°] (183°). [54°] (302"). [127°]. CeHJCH3)NHj Alkylated Bases. Toluldines. 0- : m- : p- = ,, CeH5.NH.CH3 CeH..N(CH3)2 (199°), (200°), [45°] (198°). Methyl-aniline (192°). DlmetHyl-anlllne (192°). C6H3(CH3)2NH2 0,H,.NH.C2H„ OeH,.N(C2H5)2 S (6)Xylidmes,(e.sf.217°). Ethyl-aniline (204°). Diethyl-anDine (213°). 55 CA(CH3)3NH2 Nitrosamines. Nitroso-derivativea. sl Pseudo-oumidine [62°]. i\ (CeH^j^N.NO C,H4(KO).N(CH3)2 (!) Nitroso-diphenylamine Nitroso-dimethyl-aniline ^ CeH4(N0,)NHa Nitranilines, [66°] [85°] 0- : m- : n- : Acid Derivatives. [7r][lU°](285°)[147°]. CeH5.NH(0,H30) CeH5.N(CH3)(C2H30) — AcetanmdeL114°]. Methyl-acetanilide [99°]. CeH5(CH2.NH2) C0.(NHCeH6)j CO(N.CsH„) Benzylamine (183°). Carbanilide [235°]. Phenyl cyanate (163°). CgH5(CH2.CH2.NH2) CS(NHC5H5)(NH2) CS(N.C5H,) Phenyl-ethylamine Phenyl-thio-urea [154°] Phenyl-isothiocyanate \ (193°), etc. etc. (222°) etc. / CA(NH,), CeHi(NHj)[N(CH3)j]AmIdo-dimethyl-anmue, Phenylene-diammea, P- : [41°] (257°). (o-: [102°] (252°) - m- : [63°] (287°) 2 p.: [147°] (267°). C6H4(NHj)(NH. CsHj) Amido-diphcny lamine, « C8H3(CH3)(NH2)2 p- : [66°]. l\ Toluylene-diamines e.g. 1 : 2 : 4 [99°] (286°). NH<^«y''-^]^2 p.JDiamido-diphenylamine [158°]. /~l -I -^ C,H3(NH2)3 Triamido-benzenes. C,H,(NH2)4 NH[CeH4. N(0H3)3]2 p-Tetramethyl-diamido- ^ Tetramido-benzene. diphenylamine. 376 ■ XX. AMIDO-COMPOUNDS. The diamines have a more strongly basic character than the monamines and are more readily soluble in water. A. Primary Monamines. Isomers. The isomerism of the aromatic is in part analogous to that of the fatty amines (p. 123), e.g., dimethyl-aniline is isomeric with the methyl-toluidines and the xylidines. Cases of isomerism are also caused by the amido-group being present in the benzene nucleus in the one case and in the side chain in the other. Finally all the isomeric relations of the aromatic hydrocarbons (bi-derivatives, etc.) may also come into play here. Constitution. As already seen at pp. 124 et seq., amines are Tery easy to characterize as primary, secondary, etc. Not only their modes of formation but also their behaviour shows whether the amido- group is present in the benzene nucleus or in the side chain. Modes of formation. 1. The most important mode of pre- paration of the primary aromatic bases, and also of the di-amines, etc., consists in the reduction of the nitro-compounds : C,-H,.m, + SB, = 2H,0 + CeH^.NH^ Nitro-benzene. Aniline. CeH,(NO,)a + 6H2 = 4H2O -1- C,H,(NH2)2 Di-nitro-benzenes. Phenylene-diamines. The reduction of nitro- to amido-compounds goes on espe- cially well in an acid solution, e.g., by the gradual addition of the former to a warm mixture of tin or stannous chloride and hydrochloric acid. On a manufacturing scale iron and a limited amount of hydrochloric acid are used {Bechamp), also frequently zinc dust and hydrochloric or acetic acid. Am- monium sulphide (Zinin), ferrous sulphate and baryta water, etc., also effect the reduction. Sulphide of ammonium acts more mildly than tin and hydrochloric acid and is therefore of special value for the partial reduction of dinitro- compounds (see nitraniline). An alcoholic solution of stannous chloride containing hydrochloric acid may also be used for this purpose, (B. 19, 2161). Amines also result from the reduction of nitroso-compounds, (see nitroso-dimethyl-aniline, ) PRIMARY AMINES ; FORMATION. 377 2. By heating phenols with the compound of zinc chloride and ammonia, or of calcium chloride and ammonia, to 300° (Men), secondary amines being formed at the same time : CsHj-OH + HNHa = CsHj-NHa + HjO. This reaction goes on more easily in the presence of negative groups, t.g. with the nitro-phenols, (B. 19, 1749). 3. By distilling amido-acids with lime, sometimes by merely heating them alone : C6H4(NH2)C02H = CsHs.NHj + COj. 4. By heating secondary and tertiary bases (such as mono- and dimethyl-aniline), which have been formed by the intro- duction of the alcohol radicle into primary aromatic bases, with strong hydrochloric acid to 180°, the alcoholic radicle can be eliminated again in the form of alkyl chloride with repro- duction of the primary bases : C6H5.N(CH3)2 + 2HC1 = CgHs-NHj -i- 2CH3CI. If the temperature is raised higher, the separated CH3CI (i.e. chloro-alkyl) acts further upon the primary amine, causing the replace- ment of hydrogen of the benzene nucleus by alcoholic radicle and the consequent formation of primary bases which are homologous with the original amine ; in this way toluidine hydrochloride results upon heating hydrochloride of methyl-aniline to 335° : C6H6.NH(CHs), HCl = CsHj.NHj + CH3CI = CeH4(CH3)NH2, HCl. The methyl groups which thus enter the nucleus take up the 0- or P; and not the m-position, to the regenerated NHj. In an analogous manner one finally obtains from trimethyl-phenyl-am- monium iodide, C5H5.N(CH3)3l, mesidine hydriodide, C8H2(CH3)3.NHj, HI. Hydrochloride of diphenylamine does not show this reaction. 4». The formation of (e.g. ) amido-isobutyl-benzene, by heating aniline hydrochloride with isobutyl alcohol to 250°, depends upon the same principle, thus : C6H5.NH2, HCl + C4H8OH = CsHiCCiHjj.NH,, HCl + HjO. 5. For the formation of amido-compounds from nitro-haloid-benzenes or o-dinitro-benzenes, see p. 373. 6. By heating the potassium salts of sulphonic acids with sodio- amide, NaNHj, (B. 19, 902). 7. The aromatic amines cannot be obtained by heating chloro-benzene, etc. with ammonia (see p. 367). Benzylamine, however, and all analogously constituted bases, which contain 378 XX. ASIIDO-COMPOUNDS. the NHj-group in the side chain, result by the methods v liich apply in the preparation of amines of the fatty series. Thus benzylamine is formed by the action of ammonia or, better, of acetamide upon benzyl chloride (the latter method giving rise, of course, to the readily saponifiable acetyl-benzylamine), by reduction of benzaldehyde-phenyl-hydrazone (p. 434; B. 19, 1924), etc. The above also holds good for secondary and tertiary bases of this kind. Properties. The primary monamines are partly liquid, partly solid and beautifully crystallizing bases. They are colourless when pure, but readily become brown when exposed to the air, and possess a weakly basic and not disagreeable odour. Aniline is somewhat soluble in water (1 : 31), its homologues less so. Behavwwr. 1. Most of them yield with acids salts which crystallize well and which are usually readily soluble in water. They do not however unite with very weak acids, such as carbonic, and they are therefore separated from their salts in the free state by sodium carbonate. Sodium acetate often acts in the same way (when no acetates exist). They yield double compounds with many metallic salts, especially with platinic chloride [e.g. 2(CgHy]Sr,HCl) + PtCIJ, and with gold chloride; also with stannous and zinc chlorides, etc. The platinum double salts are often sparingly soluble and therefore suited for the isolation of the bases. Besides these there exist the so-called addition salts of those bases, e.g. aniline zinc chloride, 2CgH7N + ZnCl^, aniline mercuric chloride, 206H7N + HgCl2, and so on. 2. When aniline is heated with potassium or sodium, the hydrogen is replaced by metal with formation of the compounds CjHjNHK and CgHjNKj. These yield di- and triphenylamine with bromo-benzene, and decompose immediately with water. 3. For behaviour with sulphuric and nitric acids and with halogens, see pp. 410 and 386. 4. The primary aromatic bases are analogous in every respect to the primary fatty ones, methyl iodide, benzyl chloride etc. transforming them into secondary, tertiary and quaternary compounds : PRIMAKY AMINES; BEHAVIOUK. 379 CeH,.NH, + CH3I = CeH,.NH(CH3), HI ; CeH,.NH(CH3) + CH3I = CeH,.N(CH3)„ HI ; (JeH,.N(CH3), + CH3I = C6H,.N(CH3)3l. The secondary and tertiary bases can be liberated from their hydriodides by soda, but moist oxide of silver must be used in the case of the ammonium bases, (see p. 125). 5. Aldehydes react with the primary bases, with elimination of water, thus : CH3.CHO + 2CeH5.NH5 = CHs.CH(NH.C8H5)j + HjO. ^ ^—- ' Ethylidene-diphenyl-diamiue. Benzoic aldehyde, however, reacts as follows : CjHB.CH0 + NHa.C8HB = CeH5.CH=N— CeHj + HjO. " , ' Benzylidine-aniline. Condensation products of this latter kind can also be obtained with the fatty aldehydes, but they polymerize readily {v. Miller, Plochl, B. 25, 2020). 6. Just as acids yield amides with ammonia, so are they capable of forming "anilides" with aniline, etc., e.g. acetic acid and aniline give acetanilide : C6H,.NH, + C,H30.0H = 0,H,.NH(C2H30) + H,0. These anilides may either be looked upon as acetylated etc. amines or as phenylated etc. amides, the formula 02H30.NH(CgHg) corresponding with the latter view. They are in every respect analogous in their chemical behaviour to the ordinary amides, especially to the alkylated amides (p. 194), being broken up again into their components by alkalies, and being formed by analogous methods, e.g. by heat- ing the acid or, better, its anhydride or chloride with the amine in question, thus: C6H4(CH3)NH2 + OH3.COCl = CsH,(CHg).NH.C2H30 + HCl. Toluidine. Acet-toluide. 7. When warmed with chloroform and alcoholic potash, the primary bases, like those of the fatty series, yield iso-nitriles of stupefying odour. When they are warmed with carbon bisulphide thio-ureas result, and from the latter iso-thiocyan- ates, e.g. on treatment with phosphoric acid, (cf. pp. 124 and 297). 380 XX. AillDO-COMPOUNDS. 8. Nitrous acid converts the primary aromatic amines in acid solution into diazo-compounds (p. 394), and in the absence of acids into diazo-amido-compounds (p. 398). The diazo-com- pounds go into phenols when boiled with water, so that NHj is here indirectly exchangeable for OH, as is the case directly with the amines of the fatty series. When the amines are warmed with ethyl nitrite in alcoholic solution, the amidogroup is eliminated, i.e. replaced by hydrogen (p. 396). 9. The oxidation products of the primary bases are very various, phenols, quinones, azo-compounds, aniline black, etc., resulting according to the conditions; a mixture of aniline and toluidine yields magenta (fuchsine). 10. The bases which contain the amide in the side chain possess, in contradistinction to the purely aromatic amines, the character of the amines of the fatty series. They are thus e.g. not convertible into diazo-compounds. B. Secondary Monamines. We have to distinguish here between purely aromatic secondary amines, such as diphenylamine, and mixed secondary bases which contain an aromatic residue and a radicle of the fatty series. Modes of formation. 1. Mixed secondary bases result from the primary by treatment with methyl iodide, etc. {Hofmann), (see p. 378). This reaction does not usually stop short with the introduction of one alcoholic radicle, but extends further with the formation of tertiary bases. In order to avoid this, the alkyl iodide etc. may be allowed to act upon the acetylated primary bases, e.g. acetanilide [or upon their sodium compounds {Hepp),^ and the resulting acetyl compound be saponified ; CA.NHCCaHaO) + CH3I = CsHj.NCCHsllCaHsO) + HI. The secondary bases are separated from the tertiary by treatment with nitrous acid (see below, under Nitrosamines). 2. The purely aromatic secondary amines result upon heat- ing the primary bases with their hydrochloric acid salts : SECONDARY MONAMINES. 381 CeH^.KHH + C6H5.NH2HOI = c'h'>^H' ^^^ + ^^b- " Unsymmetrical" bases (i.e. those containing two different radicles) have also been prepared in this way. 3. Diphenylamine can further be got by heating phenol with aniline zinc chloride, (B. 17, 2639), and ; 4. By the action of bromo-benzene upon potassium-aniline. Behaviour. 1. The mixed secondary bases have strongly marked basic properties, while the purely aromatic have not, (cf. p. 374). 2. For the breaking up of the mixed bases by hydrochloric acid, see p. 377. 3. The hydrogen of the imido-group is replaceable by an alcoholic or acid radicle, and also by potassium or sodium : (C«H,),NH + CH3I = HI + (OeH,),N(CH3) Methyl- diphenylamine. (CsH5),NH + (G,Bfi)fi = C,H,0, -i- (CeH,),N(C,H30) y Acetyl-diphenylamine. 4. The secondary bases give neither the iso-nitrile nor the "mustard oil" reaction (p. 124). 5. With nitrous acid, nitrosamines are formed, (cf. p. 125): C6H6NH(CH3) + NO.OH = H^O + G^H^^Oy(^) Phenyl-methyl-nitrosamine. These Nitrosamines are neutral oily liquids insoluble in water, which regenerate the secondary bases when heated with stannous chloride or with alcohol and hydrochloric acid, and which yield hydrazines with mild reducing agents. They serve for preparing the secondary bases pure, since they alone are precipitated by sodium nitrite as non-basic oils from the acid solution of a mixture of primary, secondary and tertiary bases. When such nitrosamines are digested with alcoholic hydrochloric acid, a molecular rearrangement takes place and compounds of the nature of nitroso-dimethyl-aniline (p. 374) are formed, the nitroso-group going into the nucleus, (0. Fischer and Hepp, B. 19, 2991; 20, 1247) : CA— N{N0)-CH3 = C5H4(NO)-NH.CH3. 382 XX. AMIDO-COMPOUNDS. 0. Tertiary Monamines. These also are either purely aromatic or mixed (fatty- aromatic) bases. Modes of formation. 1. The latter result upon alkylating the primary or secondary bases (of. p. 378), which, however, may be heated with methyl alcohol and hydrochloric acid instead of methyl chloride or iodide. 2. Tri-phenylamine, a purely aromatic base, is formed by the action of bromo-benzene upon di-potassium-aniliue : CeHjNK^ + 2CsH5Br = (0^n^\lS + 2KBr. Behaviowr. 1. Unlike the mixed (fatty-aromatic) amines, the purely aromatic tertiary amines are incapable of forming salts. 2. They do not yield iso-nitriles with CHClg, iso-thiocyanates with CS2, or acid derivatives with acid chlorides, but they do yield quaternary compounds with methyl iodide. 3. Nitrous acid acts upon the tertiary aromatic bases (which thereby differ from the tertiary bases of the fatty series) with the formation of nitroso-compounds which contain the NO- group linked to the benzene nucleus : C6H5.N.(CH3)2 + NO.OH = C6H,(NO).N(CH3) a + H^O. Nitroso-dimethyl-aniline. Such nitroso-derivatives are, in contradistinction to the nitrosamines already mentioned, changed into amido-com- pounds (diamines) by reduction (see below). For the consti- tution of these nitroso-bases, see also p. 388. D. The Quaternary Bases correspond entirely with the quaternary bases of the fatty series. Trimethyl-phenyl-ammonium hydroxide, C5H|j.N(CH3)3.0H, for in- stance, is a colourless, strongly alkaline, bitter substance which breaks up into dimethyl-aniline and methyl alcohol when heated. Some of the tertiary amines however are not capable of yielding ammonium compounds. DIAMINES AND TRIAMINES. 383 E. Diamines, Triamines, etc. Formation. 1. By reduction of the di- (and poly) nitro- hydrocarbons or of the nitro-amido-compounds. In this way the phenylene-diamines, C8H^(NH2)2, result from the dinitro- benzenes (see table, p. 375). The o- and _p-diamines are best obtained from the o- and p-nitro-amido-compounds (p. 387). Tetramido-benzene results in an analogous manner by reducing the doubly nitrated m-diamido-benzeue. 2. Turther, a new amido-group can be introduced in the p-position into a monamine, especially a secondary or tertiary such as CoHs — N(CHa)i!, by first transforming the latter into an azo-dye {e.g. benzene-azo-dimethyl- aniline), by uniting it with diazo-benzene chloride, and decomposing this by reduction. (See the Azo-oompounds.) Tri-amido compounds can be prepared in a manner exactly analogous. 3. For the preparation of diamines from nitroso-compouuds of tertiary amines, see Amido-dimethyl-aniline, C6Hi(NH2)[N(CHa)a]. Behaviour. The diamines and polyamines are solid com- pounds which crystallize in tables or plates and distil unchanged. They are soluble in water, especially upon warming. Though originally without colour, most of them quickly become brown in the air, their instability increasing with the number of amido-groups present. In accordance with the readiness with which they are oxidized, they frequently yield characteristic colourations with ferric chloride, e.g. o-phenylene-diamine a dark red, and 1:2: 3-tri-amido-benzene a violet and then a brown colour. The three isomeric varieties of diamines differ materially in their be- haviour : (o) Ortho-diamines. 1. Ferric chloride yields a yellowish-red crystalline precipitate of diamido-phenazine hydrochloride with a solution of o-phenylene- diamine. 2. The mono-acyl compounds of the o-diamines change into derivatives of imido-azole (A. 273, 269), the so-called " Benzimido-azoles'' or "Anhydro- basei," through the formation of intramolecular anhydride; thus, by the reduction of o-nitracetanilide by tin and hydrochloric acid, there results methyl-benzimido-azole, which may also be regarded as a derivative of ethenyl-amidine, CH^— O^-j^-g- (i.e. as phenylene-ethenyl-amidine, A. 209, 839); 384 XX. AMIDO-COMPOUNDS. C.H,C-CH3 + HjO. Compounds of this nature are also obtained by heating o-diamines with acids. 3. A similar reaction takes place between aldehydes and diamine hydro- chlorides, with the formation of dihydro-imido-azole derivatives, the so- called " aldehydine bases," HCl being set free (Ladenburg, B. 11, 590 ; 19, 2025). 4. Glyoxal and many of the a-diketones yield quinoxaline and its derivatives with o-diamines, and the a-ketone-alcohols react in an analogous manner, benzoin (e.,7.) yielding dihydro-quinoxaline. With CSNH, isothio- cyanates are formed (A. 221, 1). 5. Nitrous acid converts the o-diamines into the so-called "azimido-com- pounds," compounds which contain three atoms of nitrogen, e.g. o-phenylene- diamine into azimido-benzene, — amido - azo-phenylene, CeHj'^]' jr ^ N (B. 9, 219, 1524; 15, 1878, 2195; 19, 1757). (6) Meta-diamido-bases. 1. These form yellow-brown dyes with nitrous acid, even when only traces of the latter are present (see Azo-colouring matters). 2. They yield azo-dyes with diazo-benzene chloride (see Chrysoidin). 3. With nitroso-dimethyl-aniline, or on oxidation together with para- diamines, blue colouring matters are obtained, and, upon boiling, red (see Toluylene red). 4. With CNSH, phenylene-di-ureas are formed (A. 221, 1). (c) Para-diamido-compounds. 1. When warmed with FeaClj or, better, with MnOz -I- HaSOj, quinone, CeHjOa (or a homologue), results and may be recognized by its odour. 2. All j)-diamines which contain =• primary NHj-group yield violet or blue colouring matters containing sulphur and belonging to the thio- diphenylamine group (p. 389), when FejClj is added to their dilute acid solution containing sulphuretted hydrogen. 3. By oxidizing para-diamines, containing one amido-group, together with a monamine or a meta-diamine, indamines are produced. Aniline, amido-benzene, phenylamine, CgHj.NHj. Was first obtained in 1826 by Unverdorben, from the dry distillation of indigo, and termed by him " crystalline " ; then Runge found it in coal tar in 1834 and called it "cyanol." In 1841 ^WtecAe prepared it by distilling indigo with potash and gave it the name of aniline, while in 1842 Zinin obtained it by the reduction of nitro-benzene and called it "benzidam." It was accurately investigated by A. W. Hofmann in 1843. ANILINE. 386 Occurrence. In coal tar and also in bone oil. Preparation. Since 1864 aniline has been prepared on a manufacturing scale by reducing nitro-benzene with iron filings and a regulated quantity of hydrochloric acid, and distilling with steam. It is a colourless, oily, strongly refract- ing liquid of weak but peculiar odour, which quickly turns yellow or brown in the air and is finally converted into a resin. M. Pt. - 8°, B. Pt. 183°, Sp. Gr. at 0° 1036. It dissolves in 31 parts of water, has no action upon litmus, and is a weaker base than ammonia in the cold, but displaces the latter at higher temperatures. It is poisonous, burns with a smoky flame, and is a good solvent for many compounds which are otherwise difficult of solution, e.g. indigo and sulphur. The salts have an acid reaction. The hehaviowr of aniline has been investigated with the utmost care. Oxidation in alkaline solution leads to azo- benzene, while arsenic acid produces chiefly violaniline, CjgHjg-Ng, a violet colouring matter which also results under the oxidizing influence of nitro-benzene. A solution of free aniline is temporarily coloured violet by one of bleaching powder, this reaction being an extremely delicate one. A solu- tion in concentrated HgSO^ is first coloured red and then blue by a small grain of bichromate of potash. A solution of KgCrgO^ produces in an acid solution of aniline sulphate a dark green and then a black precipitate of aniline black, which finally goes into quinone, CgH^Og. A mixture of aniline and toluidine is oxidizable to magenta, mauveine, etc., and a mixture of aniline and ^-diamines to safranines (p. 641). Chloiine yields trichlor-aniline and iodine mon-iodo-aniline, while chlorate of potash and hydrochloric acid produce chloranil. For the action of TS-fl^, see diazo-oompounda ; of HN.Oj, nitraniline ; and of H2SO4, sulphanilio acid. When aniline is heated with glycerine and concentrated sulphuric acid in the presence of nitro-benzene, quinoline is obtained ; when it is boiled with sulphur, thio-aniline, (C5H4. NH^JaS ; and when it is heated with urea, diphenyl-urea, CO(NHC5Hb)2, with elimination of NH3. Many reactions analogous to the last-named are known. By the action of formic aldehyde upon aniline under certain conditions, there is produced "Anhydro- formaldehyde -aniline" (OsHs — N=CH2)x (BOS) 2B 386 XX. AMIDO-COMPOUNDa (colourless crystals); and this is condensed by hydrochloric acid in presence of more aniline to diamido-diphenyl-methane (which see). Salts. Aniline hydrochloride, CgHj.NHg, HCl: large colour- less tables which become greenish-grey in the air and distil unchanged. Aniline sulphate, (CgHyN)2H2S04 :. beautiful white plates, difficultly soluble in water. The double salt with platinic chloride, (CgH.^N, HC1)2, PtCl^, crystallizes in moder- ately soluble yellow plates. Substitution Prodiicts of Aniline. Aniline is much more readily substituted by halogens than benzene, an aqueous solution of chlorine or bromine causing substitution of as many as three atoms of hydrogen, while iodine produces mono- iodaniline. In the preparation of mono-oMor- (or brom-) aniline, the aniline must be "protected" by using it in the form of its acetyl compound, acetanilide. When this is suspended in water, it is mostly transformed by chlorine into /)-clilor-aoetanlUde, which readily yields p-chlor-aniline on saponification ; the latter forms colourless crystals, M. Pt. 71°, B. Pt. 231°. The o- and m-oompounds, which are both liquid, are prepared indirectly, eg. by the reduction of o- or m-ohloro- (or bromo-) nitro-benzene. The basic character is weakened in the mono-chlor- (and brom-) anilines by the entrance of the halogen, this being the case particularly in the o-compounds. It is still more striking in a-tricMor-anUlne, C5H2Cl8(NH2) (crystals, volatile without decomposition), which no longer combines with acids, o- and p-chlor-anilines are only capable of taking up two more atoms of chlorine with the formation of triohlor- aniline : NHj : CI : CI : 01 = 1.2.4.6 ; m-chlor-aniline, on the other hand, can be further chlorinated to tetra- and penta-cblor-anillne. The Brom-aniUues resemble these in every respect. Aniline is likewise attacked far more violently than benzene by concentrated nitric acid, and therefore, when it is wished to prepare the mono-nitro-compounds, the aniline must again, be "protected," either by using its acetyl compound or by nitrating in presence of excess of concentrated sulphuric acid. In the latter case all three nitranilines result, the ?K-compound preponderating. When acetanilide is nitrated, ^-Nitracetanillde, CgH4(NO2)(NH.02H3O), together with some of the o-compound, result, both of them being easily saponified by potash or hydrochloric acid. NITRANILINES, ETC. 387 The 0- and p-nitranilines are also formed upon heating o- and p-chloro- or bromo-nitro-benzenes, or the ethers of the corresponding 0- and j)-nitro-phenols, C8H4{N02)(O.C2H5), or these nitro-phenols them- selves with ammonia to 180°, (cf. B. 19, 1749). o-Nitraniline may also be prepared by nitrating aoetyl-sulphanilio acid, (B. 19, 985). The nitranilines are further obtained by the partial reduction of the corresponding dinitro-benzenes, e.g. by means of sul- phide of ammonium. The three nitranilines crystallize in yellow needles or prisms, readily soluble in alcohol but only very slightly in water, (cf table, p. 375). The o- and m-compounds are volatile with steam, but not ^-nitraniline. They go into phenylene-diamines on reduction. The o- and j3-nitranilines are converted into nitro-phenols when boiled with alkalies, the former more easily than the latter, thus : C8H4(N02)(NH2) + H.OH = C6H4(N02)OH + NHj. Di- and trl-nitranllines, CsHaCNOjjjINHj) and C6H2(N02)3(NH2), are likewise known; the latter, which is termed Ficramlde, and which crystallizes in yellow needles, M. Pt. 188°, comports itself as the amide of picric acid, since it is readily transformed into the latter compound by saponifying agents, (cf. p. 350). For Aniline-sniphouic acids, see p. 410. Alkylated Anilines. Methyl-aniline, CgH5NH(CH3) (Hofmann), is obtained from the methyl-aniline of commerce (from aniline hydrochloride and methyl alcohol) either by means of its nitroso-compound or as given at p. 380 (cf B. 10, 327, 588). It is lighter than water, and has an odour like that of aniline but stronger and more aromatic. Its sulphate is soluble in ether and non-orystallizable. A solution of bleaching powder colours it violet and then brown. For its transformation into j)-toluidine, see p. 377. Methyl-aniline-nitrosamine, CcH5.N(N0)(CHs), is a yellow oil of aro- matic odour without basic properties, which can be distilled with steam but not alone. It shows the Liebermann (nitroso) reaction, giving an intense " king's-blue " colouration when it is warmed with phenol and sulphuric acid, and the mixture then dUuted with water and saturated with 388 XX. AMIDO-COMPOUNDS. caustic potash. This reaction is characteiistic of all the nitrosamines and of many other nitroso-compounds (see B. 15, 1529). Di-methyl- aniline, OgH5.N(CH3)2 {Bofmarm), is an oil of sharp basic odour, solidifying in the cold. Its salts are not crystallizable. It combines with methyl iodide, even in the cold, to the compound N(C|3H5) (0113)31, which breaks up into its components upon distillation. The corresponding ammo- nium base is mentioned on p. 382. Bleaching powder only colours dimethyl aniline a pale yellow. The H-atom in it, which is in the ^-position as regards the N(CH3)2, is easily exchangeable, e.g. for a nitroso-group, when acted on by NjOg. Dimethyl-aniline consequently yields compounds of somewhat complex composition with acid chlorides, aldehyde, etc.; for example, tetramethyl-diamido-benzophenone or, finally, methyl violet with carbonyl chloride, COClg, leuco-malachite green with benzoic aldehyde, etc. Mild oxidizing agents, such as chloranil, convert it into methyl violet. ^-Nitroso-dimethyl-aniline, C6H4(NO).N(CH8)a, crystallizes in beautiful green plates or tables of M. Pt. 85° ; its HCl-salt forms yellow needles. It is used for the preparation of dyes (methylene blue, indophenol, gallo- cyanine, etc.). It is oxidized by KMnO< or KareCya to y-Nitro-dimethyl- aniline, C6H4(N02).N(CH3)2, M. Pt. 162° (a compound which is also obtained directly together with the m- compound by the nitration of dimethyl-aniline), and is reduced by nascent hydrogen to amido- dimethyl- aniline, C8H4(NH2).N(CH8)2, which belongs to the ^-diamines (p. 393). Boiling with soda converts it into nitroso-phenol and dimethylamine. j3-lTltroao-aniline, C6H4(NO)NH2. For constitution, see above. This is prepared by the action of ammonium acetate upon nitroBO-phend, and crystallizes in blue needles (B. 20, 2471). ^-Nitroso-monomethyl-aniline, C8H4(N'0)(NH.CH3), results by a molecular transformation from the action of hydrochloric acid in alcoholic solution upon methyl-aniline nitrosamine; it forms green plates or steel-blue prisms (cf. p. 381). Nitroso-phenol is a derivative of quinone, viz. : CeHi^C • ; nitroso- ^N.OH dimethyl-aniline therefore probably contains no nitroso- but an isonitroso- group, in accordance with the formulae ; ^N(CHa)2^ ^N(CH5)201. The free base. The hydrochloride. The same applies to nitroso-aniline and nitroso-methyl-aniline. DI- AND TRIPHENYLAMINES, 389 Dir and Triphenyhmines. Diphenylamine, (C8H5)2NH {Hofmann), crystallizes in white plates of flowery odour and burning taste which are almost insoluble in water, but readily soluble in alcohol, ether and ligroin. The hydrochloride, CijHuN, HCl, is a white crystal- line meal which turns blue in the air. A solution of diphenyl- amine in concentrated H2S0^ is coloured an intense blue by traces of nitric acid, this reaction being a very delicate test for the latter. When diphenylamine is heated with formic acid and zinc chloride, it yields acridine. It is used for the pre- paration of diphenylamine blue and aurantia. Diphenyl-nitrosaiuine, (CeHjjaN.NO, is obtained by the use of ethyl nitrite and crystallizes in bright glancing yellowish tables. o-Dinitro- diphenylamine, (CoHi.NOjjjNH, forms red needles, and the analogous p-compound yellow prisms. Hexa-nitro- diphenylamine crystallizes in yellow prisms and has the properties of a weak acid, this being due to the acidifying influence of the nitro-groups upon the imido-hydrogen ; its am- monium salt is a yellow dye, which was formerly used under the name of Aurantia. For the Amido- and Ozy-componnds of diphenylamine, which are tabulated on p. 375, and the colouring matters derivable from them, see also Safranine. Uethyl- diphenylamine, (C6H5)2N.OHj, is a liquid which results on methylating diphenylamine ; it also is employed on a manufacturing scale. Thio-diphenylamiue, O12H9NS, = NH<^p S*%S, is obtained by heat- ing diphenylamine with svdphur. Yellowish plates; M. Ft. 180°. May be distilled unchanged. Trlphenylamine, N(CsHe)8, forms large tables (see p. 374). Indamiues and Indophenols. The compounds designated Indamines (Nietzki) are those green or blue colouring matters which are produced by the action of nitroso-dimethyl ■ aniline upon amines, e.g. dimethyl-aniline, or by the conjoint oxidation of p-diamines and monamines in the cold. 390 XX. AMIDO-COMPOUNDS. The simplest representative of this class is the indamine "Fhenylene r'fi^-MTl' which results from the oxidation of a mixture of aniline and j>-phenylene-diamine, and is converted by reduction into js-diamido-diphenylamine, NH(C6H4.NH2)s (p. 375). " Dimethyl-phenylene Green," tetramethyl-indamine chloride, CioHuNb, is obtained in an analogous manner from ^-amido-dimethyl-aniline and dimethyl-aniline, and yields tetramethyl-^-diamido-diphenylamine, NH[C6H4.N'(CHa)2]2 (p. 375), on reduction. The indamines are unstable compounds, but are of importance as being intermediate products in the manufacture of safranine. Oxygenated compounds, Wittfs " Indophenols," are likewise derived here by the exchange of NHs or N(CHa)a for OH, which is achieved by warming with alkaU; e.g. Phenol Blue (indo-aniline), N<^q«^*'o^'^^°^'' is produced by the oxidation of amido-dimethyl-aniline with phenol. Its analogue, a-Naphthol Blue, N'\ -^° jj" A > prepared by means of naph- thol (p. 505), is a colouring matter which finds technical application. Such compounds exchange N(CHs)2 for OH when boiled with a solution of NaOH; thus, from phenol blue there results Indopheuol ("quinone- /C H OH phenol-imide "), N , compounds as yet but little known, which result from the action of sulphuric oxyohloride or anhydride on the amines in the cold {e.g. in chloroform solution). The free acids are very unstable, like ethyl-sulphuric acid ; but the salts, e.g. the barium salt, are more stable and crystallizable (cf. B. 23, 1653). Formanilide, CsHs.NH.CGHO), from aniline and formic acid, is worthy of note, because its sodium salt reacts according to the formula CeHj.NN'a.lOHO), but its silver salt according to the formula C6H5.N=CH (OAg). (Cf. B. 23, 2274, Kef. 659.) The latter corresponds to those isomers of the amides, the imido-hydrates and imido-ethers (p. 200). Acetanilide, CgH5.]SrH.(C2H30), is most conveniently pre- pared by boiling aniline with glacial acetic acid for several days, or by the action of acetic anhydride upon aniline in presence of caustic soda solution (B. 23, 2962). It crystallizes in beautiful white prisms which are readily soluble in hot water, alcohol, ether and benzene; M. Pt. 115°, B. Pt. 304°. It is easily saponifiable (cf. p. 379). Its imido-hydrogen is replaceable by sodium with the formation of the crystalline Sodium-acetanilide, CgH5.]SI'.Na(02H30), which is again decom- posed by water (see p. 195). Acetanilide is used, under the name of " antifebrine," as a medicine in cases of fever. Thio-acetanilide, CHj — OS.NHCeHs, results upon heating acetanUide with PjSs (analogously to aceto-thiamide, p. 199), and from it Imido-thio- componnds, Amidines, etc. can be prepared. Acetanilide yields the dye Flavaniline when heated with zinc chloride. Methyl-acetanilide, C6H5J!5^(CHs)(C2H80), is used as a specific against headache. In nearly all those compounds of the fatty series which are ammonia derivatives of alcohols, acids or alcohol-acids, and which still contain unreplaced ammoniacal hydrogen, the latter can be substituted either wholly or partially by phenyl, for the most part indirectly. The number of these phenylated 392 XX. AMIDO-COMPOUNDS. (tolylated, xylylated, etc.) compounds is thus extremely large. Among them may be mentioned : ppr "NTT P TT Fbenyl-glycocoU, ^ " ' ° °, from chloracetic acid and aniline ; Phenyl-lmldo-butyric acid, CHj— CINCeHs)— CHa— COjH, from aniline and aceto-acetic ether; CarbaniUde or diphenyl-urea, CO(NHCeH5)2, from aniline and carbon oxychloride, (cf. p. 291) ; Phenyl cyanate, COrN.CjHj, a sharp-smelling liquid exactly analogous to the cyanic ethers, and whose vapour gives rise to tears, from COClj and fused aniline hydrochloride ; Phenyl isotMooyanate, CgHjNrCS, (B. Pt. 222°), a liquid possessing all the characteristics of the mustard oils ; Diphenyl- thio-urea, CS(NHC8H5)2, from aniline and carbon bisulphide, (glancing plates, M. Pt. 154°, decomposed into phenyl isothiocyanate and aniline by boiling with concentrated HCl) ; Mono-, Tri-, and Tetra-phenyl-thio-nreas ; Phenylated guanidines, etc. (cf. table, p. 375). Homologues of Aniline. 1. The three Toluidines, 06H4(CH3)(NH2), result from the reduction of the three nitro-toluenes, ^-toluidine {MvspraU and Hofwann, 1845) being solid, and o-toluidine liquid ; they are also present in coal tar. The crude nitro-toluene of commerce yields a, mixture of o- and p- with a little m-toluidine upon reduction ; the two first may be separated from one another, e.g. by taking advantage of the relatively sparing solubility of y-toluidine oxalate, (cf. B. 16, 908). ni-Toluidine, which is liquid, may be prepared from m-nitro- toluene or »i-nitro-benzaldehyde, (cf. B. 15, 2009). The boiling points of the three isomeric toluidines are almost identical (see table, p. 375), but the melting points of their acetyl compounds differ widely, the o-compound melting at 107°, the p- at 147°, and the m- at 65° ; these are therefore of value for the character- ization of the toluidines. o-Toluidine is coloured violet by a solutiou of chloride of lime, and blue by sulphuric and nitrous acids and also by ferric chloride, but not p-toluidine. For their conversion into fuohsine by oxidation, see p. 490. If, during oxidation, the amido-group be protected by the introduction of acetyl, the methyl can be oxidized to carboxyl and in this way an (acetyl derivative of) amido -benzoic acid obtained, while the amido-compounds are transformed into azo-com- pounds by KMnO^. BENZYLAMINE, ETC. ; DI- AND TELAMINES. 393 Compounds such as Methyl- and dlmetbyl-p-toluldines, acet-tolulde, C5H4(CH3).NH(CjHsO), dl-tolylamlne, (CeHi.CHaJaNH, tolyl-phenyl- amlne, NH[C8H5](CeH4.CH3), nltro-toluidlnes, CjHatCHjJlKOaXNHa), etc., have been prepared in large numbers, and are in every respect similar to the corresponding phenyl compounds. 2. Isomeric with the toluidines is : Benzylamine, CgHg — CHg-NHj, the alcoholic amine of benzyl alcohol, a colourless basic liquid which distils un- changed. It is best prepared, at first as the acetyl com- pound, CgHg — CH2.NH(C2H30), by heating benzyl chloride, CgHg — CHgCl, with acetamide, NH2(C2H30). Its behaviour is entirely analogous to that of methylamine, as the phenyl derivative of which it is to be regarded, (cf. p. 380). 3. Xylidines, C8H3(CH3)2.NHj. According to theory, these may exist in six modifications, all of which are known. Amido-o-zylene (CHsiCHjtNHa = 1:2:4) is solid, melting at 49°, while the other five are liquid. The boiling points lie between 212° and 226°. The xylidine of commerce contains five of these compounds, but principally m-xylldine (CH3:CH3:NHj = 1:3:4), B. Pt. 212°, and p-xylidlne (1:4:2); it is used for the manufacture of azo-dyes. 4. Amido-trimethyl-benzenes, C6H2(CH3)3NH2. The hydrochloride of amido-trimethyl-benzene is formed when HCl-xylidine is heated with methyl alcohol to about 300°. In this way there have been prepared i|»- (Fseudo-)cumidine oiamido-pseudo-cumeneiCH^-.CHg-.CH.^-.NB.^ = 1 :2:4:5), M. Pt. 63°, B. Pt. 235°, and Mesidlne or amido-mesitykne (1:3:5:2), a liquid, B. Pt. 230°. ^-Cumidine is also used for manufacturing azo- dyes. Isomeric with the above bases are amldo- ethyl -benzene C6H4.(NH2)(CjiH6), and amido-propyl-benzene, C6H4(NH2)(C3H,), of which the ^-modifications, for instance, are obtained by heating aniline with the alcohol in question and chloride of zinc. 5. Amido-isobutyl-benzene, CjH4(NH2)(C4H9), has likewise been prepared. Tetrametliyl-amldo-benzenes (amido-dwrene, prehnidine), C8H(NH2)(CH3)4, OT-lsocymidine, CfisQ!f'as)(CS,){OiH.,), and penta- methyl-amido-benzene, Cs(NH2)(CHa)5, are also known. Diamines, Triamines, etc. 1. Of the Phenylene-dlamlnes, C8H4(NH2)2, the meta-compound (Zinin, 1844) is the most easily prepared, by reducing m-dinitro-benzene. It 394: XXI. DIAZO- AND AZO-COMPOUNDS; HYDRAZINES. crystallizes in tables. Nitrous acid converts it into Bismarck brown, the presence of the merest trace of this acid beingshown by the yellow coloura- tion it gives with the diamine (cf. B. 14, 1015). Fara-phenylene-diamine (Hofmann, 1863) crystallizes in plates, and its HCl-salt in white tables; an acid solution of it yields the violet dye thionine (p. 643) with HjS and FejCV A mixture of the p- and «i-compounds ultimately yields a diamido- phenazine upon oxidation. Its unsymmetrical dimethyl-derivative, p-amido- dimethyl-aniline, C6H4{NH2)[N(CH8)2], which may be prepared as given at p. 388, but most easily by the reduction of the azo-dye helianthin (p. 405; B. 16, 2235), gives methylene blue with PeaCls and HjS, this being the most delicate test for sulphuretted hydrogen known, and it is coloured a magnifi- cent purple by PejClc in dilute neutral solution. Ortho-phenylene-diamine (Griess, 1861) is transformed into hydro-phenazine (p. 539) when heated with pyrooatechin, and into a diamido-phenazine upon oxidation with ferric chloride (cf. B. 23, 841). A p-Diamido-hezamethylene is known (B. S2, 2168). 2. o-fi-Toluylene-diamine, 06Ha(OH3)(NH2)2 (1:2:4), is, as a m-diamine, easily obtained by reduction of the common dinitro-toluene (p. 372). It is used for the preparation of toluylene red, etc. m-^-Tolnylene-dlamine, CeH8(OH3)(NH2)2 (1:3:4), is the o-diamine which is most easily prepared, viz., by nitrating aoeto-jp-toluide, saponifying and reducing. 3. The Xylylene-diamines, C6H2(CHs)2(NHj)2, are homologous with the above. 4. The Tetramido-benzenes, CoHsiNHj)! (p. 383; B. 20, 328; 22, 1648; 23, 2815; 25, 283), and Pentamido-benzene, C6H(]S"H2)5 (B. 21, 1541, 1706), are very unstable and easily oxidized. XXI. DIAZO- AND AZO-COMPOUNDS; HYDRAZINES. A. Diazo-OompoUnds. The primary amido-compounds of the benzene series differ characteristically from those of the fatty series in theii behaviour towards nitrous acid. The latter are converted into alcohols by NjOg without the formation of intermediate products, (cf. p. 124): C2H5.NH2 + NO.OH = C2H5.OH -f N2 + HjO. The aromatic amines can indeed undergo an analogous transformation, but there result in their case well-characterized intermediate products, the so-called diazo-compounds, which are of especial interest both scientifically and technically (cf p. 395). They were discovered by P. Griess in 1860 DIAZO-COMPOUNDS ; FORMATION. 395 and were carefully investigated by him, (A. 121, 257; 137, 39) ; their constitution was elucidated by KekulL Formation. When nitrogen trioxide is led into a cream of aniline nitrate and dilute nitric acid, the' aniline salt dissolves and a liquid is obtained from which alcohol and ether precipitate beautiful long white needles of diazo-benzene nitrate, (CgH5N2).N03. These are tolerably stable in dry air but quickly decompose in moist, and they are distinguished by the violence with which they explode when heated or struck. The base itself, diazo-benzene (p. 398), appears to have the formula (CgHj — N2)0H, just as the base KOBE corresponds to the salt KNO3. In a similar manner other salts of diazo-benzene, e.g. the chloride, CgH5N2.Cl, and the sulphate, (OgH5]Sr2).S04H, are obtained from aniline hydrochloride and sulphate in the presence of free acid. Double salts with PtCl^, AuClg, etc., are also known. The homologues of aniline and many diamines show a similar behaviour, e.g. ^-toluidine yields salts of diazo- toluene, e.g. CgH^(CH3)N2.Cl. Most of the diazo-compounds are prepared only in aqueous solution, and not in the solid form, on account of their instability and tendency to explode. One mol. aniline, for instance, is dissolved in two or more mols. hydrochloric acid, and the calculated quantity of a solution of sodium nitrite is allowed to flow into it, the whole being cooled by ice. The liquid must remain clear and no nitrogen to speak of must be evolved. Any excess of nitrous acid can be got rid of by blowing air through the solution. Occasionally the amido-compound dissolved in concentrated sulphuric acid is treated with NjOs; or an alcoholic solution of amyl or ethyl nitrite and a mineral acid are used. The formation of the diazo-compounds is shown by the following equation : N CgH,.N Hj, H 0,H NO, = G«H,.N=N.NO„ + 2H„0. ■^6^^6 Diazo-benzene nitrate. The conversion of amido- into diazo-compounds is termed " diazotizing." The constitution of the diazo-compounds, e.g. OgH5-N=N-Cl or OgH5N=N — SO4H, follows especially from these two re- 396 XXL DIAZO- AND AZO-COMPOUNDS; flYt)tlA2iNES. actions: 1, from their transformation into hydrazines upon reduction; 2, from the formation of azo-dyes by the action of diazo-compounds upon many amines and phenols. Diazo-benzene, CeHj — N=N.OH, also appears frequently to enter into reaction in its "pseudo-form," CsHs— NH — NO (Coro, Ost; of. also B. 26, 495). Behaviour. 1. Towards water. An aqueous solution of a diazo-salt, especially one containing sulphuric acid, gives off all its nitrogen in the form of gas upon warming, and there results a phenol, thus : C«H5;N=N •^^ = CeHj.OH + N2 + HCl. + OHi This reaction, which is of very universal application, there- fore allows of the exchange of amidogen for hydroxyl. The above reaction, as well as the following ones (up to 4), may be included under the term " diazotizing " for the sake of brevity. 2. Towards alcohol. When diazo-compounds, either in the solid state or dissolved in concentrated sulphuric acid, are heated to boiling with absolute alcohol, the diazo-group is generally replaced by hydrogen. In this reaction the alcohol gives up two atoms of hydrogen and goes into aldehyde : OrHj. N=N •^1 = C,He + N, -H HCl. -f H; By this means we are enabled completely to eliminate a diazo- group, and therefore an amido- one from a benzene derivative. Instead of this reaction there occurs in many cases an exchange of the diazo-group for the alcohol radicle, O.CjHj, with the formation of ethyl ethers of phenol; thus chlorinated cresol ethyl ether results, in place of chloro-toluene, from chlorinated toluidines (B. 17, 2703; 22, B.ef. 658). 2a. TJnder certain conditions stannous chloride in alkaline solution acts in an analogous manner (B. 22, Bef. 741), while under others it gives rise to hydrazines (p. 406). In like manner NH2 may be replaced by H, by first converting an amido-compound into a hydrazine, and then decomposing the latter with CuSOi (Baeyer, B. 18, 89). 3. When a diazo-compound is warmed with a concentrated solution of cuprous chloride in hydrochloric acid, the diazo-group is replaced by chlorine {Sandmeyer, B. 17, 1633; 23, 1218, 1628; A. 272, 143); the same reaction takes place on distilling the platinum double salt of the diazo-compound with soda, and sometimes on simply treating the diazo-compound itself with fuming hydrochloric acid, or with hydrochloric acid in presence of copper dust: C4H,.N=N.C1 = CgHjCl-i-Ny DIAZO-COMPOUNDS; BEHAVIOUR. 397 4. Warming with cuprous bromide yields in the same way a bromine compound (Sandmeyer, B. 18, 1482), and treatment with hydriodic acid or potassium iodide an iodine one, while cuprous cyanide effects an exchange of the amido-group for cyanogen (B. 17, 2650): 2C6H5.N2.CI + Cu^Bra = 2C6H5Br + CujClj + N^; C6H5.N2.CI + KI = CgHjI + KCl + Ngj etc. The NHj-group may further be exchanged for Br by boiling the diazo- perbromides (see Diazo-benzene perbromide) with absolute alcohol. 6. Phenyl sulphide results from diazo-benzene chloride and sulphuretted hydrogen (cf. B. 15, 1683); nitro-benzene is formed by the action of nitrous acid in presence of cuprous oxide ; benzene-sulphouic acid from sulphurous acid ; benzene thiocyanate from thiooyanic acid ; and phenyl cyanate from cyanic acid, etc. (cf. B. 23, 738, 1218, 1154, 1628; 25, 1086). The reactions 1 to 4, which are classed together under the name of the Oriess reaction, are invaluable for effecting the exchange of nitro- or amido- groups for OH, H, CI, Br, I and ON, and are constantly made use of in the laboratory. When reactions 3, 4 and 5 take place under the influence of cuprous oxide and its salts, or of copper dust, they are also included under the special name of " the Sandmeyer reaction." 6. Upon oxidation in alkaline solution, diazo-benzene yields — together with other products — nitroso-benzene (p. 373), and much Fhenyl-nitramine, C6H5.NH.NO2 (M. Ft. 46°; explodes at 98°) (see B. 26, 471). 7. Diazo-benzene in alkaline solution unites with compounds containing the group — CH^ — CO — , water being eliminated. It reacts here according to the tautomeric formula CoHj.NH.NO, since hydrazones result, e.g. from acetone the diphenyl-hydrazone of mesoxalic aldehyde, CsHsNH.N^CH — CO— CH=N.NHC6H5 (B. 25, 2793). From diazo-benzene and malonic acid there is produced Formazyl hydride, C5H5N=N — CH=N — NHCeHs, together with azo-compounds and hydra- zone (B. 25, 3175, 3201). 8. When a diazo-compound acts upon a primary or secondary amine, or when NjO, acts upon such an amine in the absence of acid, diazo-amido-compo.unds result, and these readily change into amido-azo-compounds. The latter are formed directly by the action of the diazo-compounds upon tertiary amines : CeH5.N=N.Cl + NH2.C6H5 - HCl + CsH5.N=N— NKCHs ; Dlazo-amldo-benzene. O.H5.N=N.Cl + C,Ha.N(CHs)j = HCl + flHs— N=N— C6H<.]Sr(CH8)^ Dimethyl-amido-azobenzene. Analogous reactions also take place with the m-diamines and with phenols, oxy-azo-compounds being formed in the latter case (see p. 402). The production of an orange-red dye by the action of diazo-compounds upon m-phenylene-diamine or /3-naphthol is a very delicate test for the presence of the former. Diazo-amido-compounds only show this reaction in acetic acid solution. 398 XXI. DIAZO- AND AZO-COMPOUNDSj HYDKAZINES. It has been proposed to use diazo-compounds, sensitive to light, io photo- graphy (B. 23, 3131). The salts of the diazo-compounds are colourless, and frequently crystallize well ; they often decompose with violent explosion in the air or upon being kept. Most of them are easily soluble in water, slightly soluble in alcohol, and insoluble in ether. Diazo-benzene chloride, CeHj — N=N — CI, crystallizes in colourless needles. Biazo-benzene nitrate, CeHj — N=N.(N03) (p. 395). Long needles. Diazo-benzene sulphate, C6Ht.N=N.(S04H), is a syrupy mass which solidifies to prisms; it explodes at 160°. Siazo-benzene perbromide, C8HsN=N.Br.Br2, is a dark brown oil, solidi- fying to yellow crystalline plates, which results upon the addition of HBr or KBr and bromine water to diazo-salts. Two of its atoms of bromine are only loosely linked. Ammonia converts it into diazo-benzene-imide, which is to be regarded as the phenyl derivative of hydrazoio acid, NaH, thus : C6H5.N=N.Br-l-Br2 = CsHs.NBr — NBra [Diazo-benzene-perbromide]. 06Hs.NBr— NBra-1- NHs = 3HBr + C6H5.N< •• [Diazo-benzene-imide]. In accordance with this, dinitro-diazo-benzene-imide (from dinitro-aniline) is broken up by alcoholic potash into dinitro-phenol and hydrazoio acid, — a method of obtaining this latter substance by means of organic compounds (see pp. 228 and 299). When concentrated potash solution acts upon diazo-benzene nitrate, Potassium diazo-benzene, C6H5N=N(OK) (of. B. 23, 3033), is formed. It crystallizes in white glancing mother-of-pearl plates, readily soluble in water and alcohol and easily decomposable, and from its aqueous solution metallic salts precipitate other metaUio compounds. e.g. the very explosive Silver diazo-benzene, CeHsN^N — O.Ag. The free Diazo-benzene, C6H5.N=N.OB[ (?), is precipitated from the potassium salt by acetic aoid as a heavy oil which rapidly decomposes of itself. " Azimido-benzene," C6H4o II I Azoxy-benzene. Azo-benzene. Hydrazo-benzene. CgHj— NHj, Aniline. Of these the azo-compounds are the most important. AZOXY-, HYDKAZO- AND AZO-COMPOUNDS. 401 1. Azoxy-compounds. The azoxy-compounds are mostly yellow or red crystalline substances which result from the action of alcoholio potash, and especially of potassium methylate (B. IS, 865), upon the nitro-oompounds. Many of them may also be obtained by the oxidation of azo-oompounds. They are of neutral reaction, and are very readily changed into azo-compounds, etc. upon reduction. Azoxy-benzene, (CoHsjjNjO (Zinin), forms pale yellow needles of M. Pt. 36°, insoluble in water but easily soluble in alcohol and ether. Concen- trated sulphuric acid transforms it into the isomeric y-oxy-azo-benzene, C6HsN=N— CsHjOH. 2. Hydrazo-compounds. The hydrazo-compounds are colourless, crystalline and of neutral reaction, and — like the azo-compounds — they cannot be volatilized without decomposition; for instance, hydrazo- benzene decomposes into azo-benzene and aniline when heated. They are obtained by the reduction of azo-compounds by sulphide of ammonium or zinc dust. Oxidizing agents such as ferric chloride readily transform them into azo-compounds, into which they also change slowly in the air alone. The stronger reducing agents, e.g. sodium amalgam, convert them into amido-compounds. Strong acids cause them to change into the isomeric deriva- tives of diphenyl (p. 476); thus from hydrazo-benzene and hydrochloric acid there results benzidine chloride (p. 477): CgHs— NH— NH— C.H^ = NH^— CsH,— CsH^— NH^ Benzidine. This molecular rearrangement does not take place if the hydrogen which occupies the para-position to the imido-group is replaced by other groups. In such cases a partial rearrangement only occurs, and derivatives of dipbenylamine are formed (B. 25, 992, 1013,1019); thus ^-hydrazo-toluene, NH— C,H4.CH8 H N- 06Hi.CH3 I , yields o-amido-di-p-tolylamine, \ NH— C6H4.CH, HjN— CeH8.CH,. Hydrazo-benzene, OcHj — NH — NH — CeHj (Hofmann), forms colourless plates of camphor-like odour, which are only slightly soluble in water, but readily soluble in alcohol and ether; M. Pt. 131°. The imido-hydrogen atoms are replaceable by acetyl- or nitroso-groups. 3. Azo-compounds. The azo-compounds are red or yellowish -red crystalline indifferent substances insoluble in water but soluble in alcohol, some of them, e.g. azo-benzene, being capable of distillation (60S) 2C 402 XXI. DIAZO- AND AZO-COMPOXJNDS ; HYDRAZINES. without change. Oxidizing agents convert them into azoxy-, and reducing agents into hydrazo- or amido-compounds. Chlorine and bromine act as substituents. The so-caJled "mixed" azo-compounds, which contain a benzene radicle and an alcoholic radicle of the fatty series, are also known, e.g. Azo-phenyl-etliyl, CjHg — N=N — CjHj, a bright yellow oil. Modes of formation. 1. By the cautious reduction of nitro- or azoxy-compounds, e.g. by means of sodium amalgam, an alkaline solution of stannous oxide (B. 18, 2912), etc. 2. By distilling azoxy-benzene with iron filings. 3. By the oxidation of hydrazo-benzene. 4. By the oxidation of amido-compounds, e.g. together with azoxy-compounds by means of KMn04 : 2C6H,.NH, + 0^ = C^H.-N^N-CeHg + 2H,0. 5. By the action of nitroso- upon amido-compounds. In this way azo-benzene is obtained from nitroso-benzene and aniline acetate : -an. + H,o. Azo-benzene,* CgHj— N=N— OgHg (Mitscherlich, 1834), crystallizes in beautiful large red plates ; M. Pt. 68°, B. Pt. 293°. Azo-toluenes, CeHjICHj) — N=N — CgH^ICHs). All three are known. 4. Amido-azo- and Oxy-azo- compounds. Amido-groups or hydroxyls are capable of entering into azo-benzene etc., whereby amido- and oxy-azo-benzenes are formed, thus : OeHB-N=N-CeH,(NH,) CeH,-N=N-CeH,(OH). Amido-azo-benzene. Oxy-azo-benzene. The former are at the same time bases and azo-compounds, and the latter azo-compounds and phenols {i.e. weak acids, cf, p. 411). * Benzece-azo-benzei^9. AMIDO-AZO- AND OXY-AZO-(JOMPOUNDS. 403 Formation. 1. Amido-azo-benzene is obtained from azo- benzene by first nitrating it and then reducing the resulting mononitro-azo-benzene. 2. Oxy-azo-benzene results from azoxy-benzene by warming it with concentrated sulphuric acid, (cf. p. 401). 3. Amido-azo-compounds are also formed by the molecular rearrangement of the diazo-amido-compounds, according to p. 399, i.e. in a manner indirectly by the action of diazo-benzene etc. upon primary or secondary amines. 4. The corresponding amido-compounds, whose amido- hydrogen is substituted, result directly from the action of diazo- compounds upon tertiary amines (cf. p. 397). The amido-group takes up here the para-position to the azo-group. But if this position is already occupied, a molecular transformation of diazo- amido into amido-azo-compounds becomes much more diflSoult, and the ortho-position is therefore taken up. The o-amido-compounds, thus pro- duced, differ essentially from their isomers of the p-series. With m-diamines, the diazo-compounds yield diamido-azo-benzenes : CeH5.N=N.Cl -I- CsH^INHj)^ - C6H5N=N— CsHs.jNHa), + HCL Chrysoidin. Oxy-azo - compormds result in an analogous manner by the action of diazo-compounds upon phenols in presence of alkali : CeHsN=]Sr.Cl -f OsHsOK = C8H,,N=N— CsH^OH + KCL Keactions of this kind take place especially with resorcin and the phenols of the naphthalene series (which see). The amido- and oxy-azo-compounds are yellow, red or brown in colour and crystalline, and are mostly insoluble in water but moderately soluble in alcohol. They possess the character of dyes (azo-dyes), the chromogenic character of the azo-benzene being developed by the entrance of the salt-forming groups NB^ etc. or of OH (cf. p. 32). Thus faintly acid solutions of amido-azo-benzene colour wool and silk a beautiful yeUow ("Aniline yellow"), and Chrysoidin, C12H12N4, HCl, is an orange-red dye. To this class also belongs Vesuvine or Bismarck brown (see below). Instead of these compounds themselves, their sulphonic acids (p. 408) are generally used as dyes ; thus the so-called " fast yellow " (" Echtgelh ") is the sodium salt of amido-azo- benzene-sulphonic acid. The dyes which are derivatives of amido-azo-benzene are termed 404 XXI. DIAZO- AND AZO-COMPOUNDS ; HYDRAZINES. Ohrysoidines, and those which are derivatives of oxy-azo-benzene, Tropceolines. Of especial importance are those azo-dyes which contain a naphthalene radicle in the molecule. They are formed in a manner exactly analogous to the compounds mentioned above, the two naphthylamines, CioH,.NH2, and the a- and /3-naphthola, CuHy.OH, possessing respectively complete aminic and phenolic characters, and their sulphonic acids being very active chemically. They dye yellow, orange, red, brown, violet and even blue. Worthy of special mention is Orange II., C8H4(S03Na)— N =N — CioHg(OH), which is obtained from diazo-benzen.e-sulphonic acid and ;3-naphthol. The amido-group in p-amldo-azo-benzene may be diazotized, as given above, and the resulting diazo-compound is now capable — like diazo- benzene chloride — of yielding azo-compounds with amines or phenols, Dls-azo- (tetrazo-) compounds, as they are termed, (B. 15, 25) ; e.g. CsHe— ]Sr=N— CeHi— N=N— CeH4. OH, (B. 9, 628). Many of the most valuable azo-dyes,- such as Biebrich scarlet, Crocein scarlet etc. are derivatives of such diazocompounds. Trls-azo-compounds also exist, (B. 16, 2028). In the formation of azo-dyes of this nature, the azo-group always takes up the para-position to the amidogen or hydroxyl if possible. Should this be already occupied, it goes into the ortho-position. This point is elucidated by the examination of the decomposition products which result upon reduction. The azo-dyes are broken up at the point of the double bond by tin and hydrochloric acid and by sulphide of ammonium, two amido compounds resulting, thus j CoHs— N=N-C6H4N(CH3)2 + 2H2 = CoHJnH, + CsH4(NHa)— N(CHa)s. The chemical nature of an azo-dye is thus often easily arrived at by investigating these decomposition products. Upon this reaction also depends the method of introducing new amido-groups into amines and phenols, mentioned on p. 383. In place of the formulse given above for amido- and oxy-azo-oompounda, isomeric formulae have also of late been taken into consideration (especially when the NHj- or OH-group occupies the ortho-position to the azo-group); according to this the amido- and also the free oxy-azo-compounds appear as the hydrazones of quinnnes or quinone-imides. Ojcy-azo-benzene would thus have the formula, CeHs — NHN'=C6H4=0, but its potassium salt the (tautomeric) formula, CsHs — N"=N — CsHi — OK. The behaviour of such compounds upon reduction favours this view (Z?. Ooldschmidt, B. 24, 2300 ; 25, 1324; of., on the other hand, B. 24, 1592). Amido-azo-'benzene, Aniline-yellow, CgHj — N=]Sr— CjH4.NH2(1863). Beautiful yellow plates or needles. The hydrochloric acid salt crys- tallizes in dark violet needles and yields a red solution. METHYL ORANGE ; BISMARCK BROWN. 405 Amido-azo-benzene-sulphonic acid (see p. 410) is prepared by sulphurating amido-azo-benzene, or by the combination of diazo-benzene-sulphonic acid with aniline : C6H,(S03H)— N=N-C1 + CeH^NHg = CeH^lSOgH)— N=N— C6H,-(NH2) + HCl. It has a flesh colour, its salts being yellow. The Di-sul- phonic acid crystallizes in glittering violet needles and its salts are likewise yellow. Dimethyl-amldo-azo-'beiizene, CgHj — Nj — C8H4.N(CH3)2. Golden yellow plates. The chloride crystallizes in violet needles. Its mono- sulpliomc acid, methyl orange, hdianthin, or Orange III., is used instead of litmus as a delicate indicator in alkalimetrical titrations, its yellow solution being coloured red by traces of acids ; it is not affected either by COj or HjS, (B. 18, 3290). It yields amido- dimethyl-aniline and sulphanilic acid upon reduction. Diamido-azo-benzene, CgHg — N=N — CgH3.(NH2)2 (Caw, Witt, 1875); the chloride (chrysmdin) crystallizes in large octa- hedra, built one upon the other. Triamido - azo - benzene, CeH^ (NHj) — N = N — CgHg (NHj)^ (Caro, Griess, 1866), is produced by the action of NjOg upon ??i-phenylene-diamine, one half of the latter being partially diazotized to CgH4{NH2) — N^N.Cl and then acting on the other half, as given at p. 403, It forms brownish-yellow crystals, readily soluble in hot water; the salts are reddish- brown. Its hydrochloride, mixed with complex azo-substances, forms the colouring matter Bismarck brown, Fhenylene brown, or Vesuvine. Amido-azo toluene, from diazo-/>-amido-toluene, has the constitution CsHiCCHs)— N=N— CjHa(CH3)(NH2), (B. 17, 77). It crystallizes in orange-red needles. The alcoholic solution is turned green by hydro- chloric acid. Oxy-azo-benzene, OgH5-N=N— CgH^(OH) {Chiess, 1866), results from the action of diazo-benzene chloride upon phenol and also from the molecular transformation of azoxy-benzene, (cf. p. 401). It crystallizes in brick-red rhombic prisms and is a yellowish-red dye. 406 XXI. DIAZO- AND AZO-COMPOUNDS ; HYDRAZINES. Oiozy-azo- benzene -snlphouic acid, C6H4(SOsH) — N=N — 06H8(OH)2, from diazo- benzene -sulphonio acid and resoroin, forms as sodium salt Chrysom or Tropaeolin 0. D. Hydrazines. The hydrazines of the benzene series {E. Fischer) entirely correspond with those of the fatty, (cf. p. 128). CaH,-NH-NH, (CeH,),N-NH, (CaH,)(C,H3)N-NH,. Phenyl-hydrazine. Dipheny] -hydrazine. Phenyl-ethyl-hydrazine. Hydrazo-benzene results from the entrance of phenyl into the second amidogen of phenyl-hydrazine. Phenyl-hydrazine, CgHj — NH — NHg, forms a colourless crystalline mass, melting at 23° to a colourless oil which quickly becomes brown from oxidation, and which boils at 233° without decomposition. It combines with hydrochloric acid to the chloride, CgHjNjHg, HCl (plates). Like all hydrazines it is characterized by strong reducing power, reducing Fehling's solution even in the cold. It is readily destroyed by oxidation but is stable towards reducing agents ; gentle oxidation of the sulphate by means of HgO converts it into diazo-benzene sulphate. Conversely, phenyl-hydrazine is 'prepared: {a) By reducing diazo-benzene chloride with the calculated quantity of SnOlg and HCl, {V. Meyer and Lecco, B. 16, 2976) : CgHs— N=N.C1 + 2H2 = CgHj— NH— NHj, HCl. (6) By reducing diazo-benzene potassium sulphite, CgHs— N=N.S03K (from CeH^NjCl and KgSOg), with zinc dust and acetic acid to phenyl-hydrazine potassium sulphite, CgHg — NH — NH.SO3K, which is then broken up into phenyl- hydrazine and sulphuric acid upon heating with HCl : CgH^— NH— NH— SO3K + HCl + H^O = CgHg— NH— NHj, HCl -i- SO^KH. PHENYL-HYDRAZINE. 407 By the action of halogen-alkyl upon phenyl-hydrazine, the imido-hydro- gen atom of the latter is replaced hy alkyl; the further action of halogen- alkyl gives rise at once to ammonium compounds, without replacement of the hydrogen of the amido-group. Acid radicles may replace either one or two H-atoms. In the first case Hydrazides are produced, — compounds which correspond to the amides, anilides, etc.; these give a violet-red colouration with sulphuric acid and bichromate of potash, and can be used for isolating acids which are readily soluble (B. 28, 2728). The base is an important and often an exceedingly delicate reagent for aldehydes and ketones, combining with them to hydrazones with elimination of water (cf. pp. 146 and 155; also B. 17, 572; 21, 984). Most of these compounds are solid and crystalline, and are therefore eminently suited for the recognition of aldehydes and ketones, and also of glucoses. Phenyl-hydrazine reacts in the first instance with the latter in the same way as it does with the former, but here (as also in the case of other aldehyde- and ketone-alcohols) a second hydrazine molecule may come into play, whereby osazones (p. 239) result. By the reduction of the hydrazones, primary amines are formed (B. 19, 1924): (OH3)aC=N- NH-CeH5 + 2H^ = (CH3),CH.NH, + NHgCeHg. ** V Y I Acetone-phenyl-hydrazone. Iso-propylamine. Aniline. With aceto-acetic ether, phenyl-hydrazine forms pyrazole derivatives (see Antipyrine). It also reacts with lactones (B. 19, 1706). Phenyl-hydrazine hydrochloride is transformed into chloro-benzene by the action of hydrochloric acid in presence of sulphate of copper (B. 25, 1074). Phenyl-hydrazine-sulphonic acid (B. 18, 2193). Is used for the pre- paration of tartrazine (p. 265). Diphenyl-hydrazine, (C6H5)2N — NHa is an oily base which boils without decomposition and, like phenyl-hydrazine, is easily oxidized; it only reduces Pehling's solution, however, when warmed. It is obtained by reducing diphenyl-nitrosamine, (C6H5)2N — NO, with zinc dust and acetic acid. M. Pt. 34°. Like phenyl-hydrazine, it yields characteristic hydrazones with the sugars. Acetyl-diphenyl-hydrazine results by a peculiar reaction from acetyl- phenyl-hydrazine and acetate of copper (B. 26, 413). 408 XXII. AROMATIC SULPHONIO ACIDS. Appendix. Phosphorus Compounds, etc.; Organo-metals. The phosphorus- etc. compounds of the fatty series have their analogues in corresponding compounds of the aromatic, these latter having been in- vestigated by Michadis and his pupils (A. 181, 188, 201, 312, and 229; B. 2S, 1747); for instance, Phenyl-phosphine, CeHs.PH.; Phenyl-phos- phinic acid, CeHsPOtOHja; Phosphenyl chloride, CeHs-PClj; Phosphino- benzene, CsHsPOj; and Phospho-benzene, C^^=V.G^i (these two last being analogous to nitro- and to azo-benzene). Some of those compounds are solid, and they are less volatile and more stable than the corresponding aliphatic compounds. Phosphenyl chloride is obtained, among other methods, by leading a mixture of benzene and phosphorus trichloride through a red-hot tube. It is a liquid of piercing odour; B. Pt. 225°. We are also acquainted with phenyl compounds of boron, silicon, anti- mony, bismuth, tin, lead and mercury, e.g. mercury diphenyl (p. 362). XXII. AROMATIC SULPHONIO ACIDS. The aromatic sulphonic acids are very similar in properties to the sulphonic acids of the fatty series. Benzene -sulphonic acid, CjHj.SOjH (Mitscherlich, 1834), results upon warming benzene with concentrated sulphuric acid (see p. 338): CgHj + SO.H^ = CeHj.SOjH + H^O. As in the case of ethyl-sulphuric acid, advantage is taken of the solu- bility of its barium, calcium or lead salt to separate it from the excess of sulphuric acid; or its sodium salt is separated by the addition of sodium chloride. Por its formation from diazo-benzene chloride, see p. 397, and B. 23, 1464. Small tables ( + l^HgO), deliquescent in the air and readily soluble in alcohol. The barium salt crystallizes in glancing mother-of-pearl plates. Behaviour. 1. Benzene-sulphonic acid is very stable, not being decomposed when boiled with alkalies or acids, as ethyl- sulphuric acid is. It is, however, broken up into benzene and sulphuric acid when heated with hydrochloric acid to 150°, or with water vapour at a high temperature (of. p. 358) : C,H,.S03H + H,0 = CeH« + SO,H,. BENZENE-SULPHONIO ACID. 409 2. When fused with alkali, it yields phenol: CgHj-SOgK + KOH = C6H5.OH + SO3K2. 3. When it is distilled with potassium cyanide, benzo-nitrile is formed : C6H5.SO3K + ONK = CeHg-CN + SO3K5, 4. When it is acted upon by PCI5, its chloride, Benzene- sulphonic chloride, results: CgH^.SOaOH + PCI5 = CeHj.SOaCl + POCI3 + HCl. The latter is an oil, insoluble in water, M. Pt. 14-5°, B. Pt. 120° (under a pressure of 10 m.m. of mercury); as an acid chloride it is reconverted into Bulphonie acid by hot water, into the corresponding esters by alcohols, and into Benzene-snlphonamide, CeHe.SO2.NH2 (lustrous mother-of-pearl sublimable plates), by ammonia. This compound can be sublimed, and corresponds with other amides in its properties. The amide-group, how- ever, is so affected by the strongly acidifying action of the S02-group that its hydrogen is replaceable by metals, and the sulphone- amides consequently dissolve in solutions of aqueous alJcaZies. Benzene-sulphonic chloride likewise yields sulphone-amides with primary and secondary amines, CeH5.SO2.NHE and C6H6.SO2.NKR', the former of these being soluble in alkali, but the latter insoluble. Tertiary amines do not of course give sulphone-amides. Upon this fact a good method for separating primary, secondary, and tertiary bases is founded (Sinsherg, B. 23, 2962). 5. When benzene-sulphonic chloride is treated with zinc dust, benzene- sulphinate of zinc is formed : 2C„H5.S02C1 + 2Zn = (C6H5S02)2Zn -f- ZnClj. An alkaline sulphinate is also produced (along with phenyl disulphide as by-product) when benzene-sulphonic chloride is treated with thio-phenol in presence of alkali. Benzene-sulphinic acid crystallizes in large glancing prisms, readily solu- ble in hot water, alcohol, and ether. It possesses reducing properties and is itself converted into thio-phenol by nascent hydrogen : CeH5.S02H -I- 2H2 = CeHjSH 4- 2H2O. The sulphone, Snlpho-benzide, (CeH5)aS0z, results from the action of SOs upon benzene, and also from the oxidation of phenyl sulphide, (OgHe)2S. It crystallizes in plates, is only sparingly soluble in water 410 XXII. AROMATIC SULPHONIC ACIDS. but more readily in alcohol, and distils unchanged. In properties it is analogous to diethyl-sulphone. Mixed aulphones are also known, e.g. Phenyl-etliyl-sulphone, (CgHjXCaHjjSOa. Isomeric with the sulphones are the (easily decomposable) ethers of benzene-sulphinic acid, e.g. CeH5.S02(C2H5); of. B. 24, 1147. Substitution may be effected in benzene-sulphonic acid by chlorine, bromine, and tbe groups NOg and NHg. The NUro-benzene-sulphoiilc acids, C8H4(N02).SOsII, result upon nitrating benzene-sulphonic acid or upon sulphurating nitro-benzene, the m-compound preponderating. Reduction converts them into the : Amido-benzene-sulphonic acids, 08H4(NH2).S03H. The p-compound, which is termed Sulphanilic acid, is obtained by heating aniline with fuming sulphuric acid, or from aniline sulphate at 180° to 200° (Gerhardt, 1845); also by reducing p-nitro-benzene-sulphonic acid. It forms rhombic plates ( + H2O), rather difficultly soluble in water, which weather in the air. It combines with bases, e.g. with soda to sodium sulphanilate, CgHiNHaSOsNa + 2H2O (large plates), but not with acids. The ■W"TT formula C8H4<^ qq ^^ possibly expresses the constitution of sulphanilic acid. The m-acid, also termed MetaniUc acid, is employed in the preparation of azo-dyes; e.g. metaniline yellow ; it crystallizes in fine needles or prisms. Diazo-benzene-sulphonic acid, C^H^^ ^ ^ (the an- hydride of OgH^^g^-rr' j, is obtained by adding a mixture of sulphanilate and nitrite of sodium to dilute sulphuric acid. White needles, sparingly soluble in water. It shows all the reactions of the diazo-compounds and is of great importance for the preparation of azo-dyes (p. 403). Benzene-dlsulphonic acids, CsH4(S03H)2 (principally meta-), and Benzene-trisulphomo acids, C5H3(S08H)3, result from the energetic sulphuration of benzene. The former exist, of course, in three isomeric modifications. When they are distilled with KCN, they yield tbe com- pounds C6H4(CN)2, the nitriles of the phthalic acids; when fused with KOH, the m-disulphonic acid changes into resoroin (m-dioxy-benzene), CcHi(OH)s. A Di-8ulphanilic acid, C5Hj(NH2) (SOsH)j, has also been prepared. PHENOLS. 411 Almost all the homologuea of benzene, with the exception of hexa- methyl-, etc., benzene, are likewise capable of yielding sulphouic acids. From toluene are obtained the Tolueue-sulphonlc acids, C8H4(CH3)S03H, which — as di-derivatives — exist in three different modifications. Of these it is the ^j-acid which is formed in largest quantity directly ; its potassium salt crystallizes beautifully. The sulphonic acids of the three xylenes, the Xylene-sulphonlc acids, C5H3(CH3)2S03H, serve for the separation of these isomers from each other ; and the power of crystallization of the salts or amides of the sulphonic acids of the higher benzene homologues is frequently made use of for the recognition and separation of these hydrocarbons. As an example of a complicated aromatic sulphonic acid may be mentioned o-Bromo-m-nitro^-toluene-sulphonic acid, CeH,(CH3)Br(NO,)(S03H). The above instance is sufficient to show that sulphonic acids may be obtained from the most complicated aromatic compounds. This is of especial importance if the latter are dyes whose application is hindered by their insolubility in water or by other circumstances, as in the case e.g. of indigo, amido-azo-benzene, etc. ; it is true that the sulphonated dyes are usually inferior to their originals in colouring power and purity, e.g. they do not stand the effects of light so well (indigo, for example). Por sulphonic acids of the azo-dyes, see p. 404. XXIII. PHENOLS. Phenols are oxygenated derivatives of benzene which stand midway in chemical character between alcohols and acids. They are derived from the benzene hydrocarbons in the same way as the alcohols of the fatty series are from the paraffins, i.e. by the replacement of hydrogen in the benzene nucleus by hydroxyl. The phenols are either liquid or solid compounds and are often characterized by a peculiar odour, e.g. carbolic acid and thymol. Most of them can be distilled without decomposition and are readily soluble in alcohol and ether; some dissolve easily in water, others with more difficulty. Many of them are antiseptics, e.g. phenol, creosol and resorcin. 412 XXIII. PHENOLS. Summary of the most important Phenols. Monatomio i Diatomic : Triatomic : CeHs-OH Phenol [42°] (181°) CeH4(CH3).OH Cresols o- : m- : p-t (Sn (188') [3'] (201*) [36°] (198') C6Hs(CH3)2.0H Xylenols e.g. [74°] (211°) Cj, ^-Cumenols Cio, Durenols C,H3(CH3)(C3H,).OH Thymol [51°] (222°) Carvaorol [0°] (237°) Cu, Penta-methyl-phenol C6H,(0H), Dioxy-benzenes o = Pyrocateohin [104°] (245°) m=Resorcin [118°] (280°) p=Hydroqninone [169°] QuinoneJ CeHaCOHJs Trioxy-benzenes » = Pyrogallol [115°] (210°) a=Oxy-hydroquinone s=Phlorogluoin (217°) G C6H,(CH3)(OH)3 Methyl-pyrogallol Tetratomlc : CeH3(CH3){OH)j l:3:5=Orcm[107°] (288°) 1 :3 :4 = Homo- pyro- cateohin C6H,{OH)4 Tetroxy-benzene Hexatomic ; Cg, Xylorcin, etc. Ce(OH)e Hexoxy-benzene 1. The phenols behave like alcohols in that they are capable of forming ethers such as anisol, CgHj.O.CHg, saponifiable ethers such as phenyl-sulphuric acid, CgHg.O.SOgH, thio-compounds, etc. They can only be compared with the tertiary alcohols, since they cannot, like the primary or secondary, yield acids or ketones containing an equal number of carbon atoms in the molecule upon oxidation. Unlike the alcohols, however, the phenols are very stable as regards oxidizing agents, undergoing only substitution and not oxidation by halogens and nitric acid, and not going into hydrocarbons with elimination of water, etc. 2. The phenols possess the character of weak acids; they form salts with alkalies, etc., most of which are readily soluble in water, and which correspond with the alcoholates but are far more stable than these. Thus, the phenols dissolve in the alkalies to salts; the latter are usually decomposed, PHENOLS; BEHAVIOUR AND CONSTITUTION. 413 however, by carbonic acid. The acid character of the phenols is considerably increased by the entrance of negative groups, especially NOg, into the molecule. (See picric acid.) 3. The phenols are true derivatives of benzene. They are capable of yielding all those varieties of derivatives which have been described as derivatives of benzene, e.g. chloro-, bromo-, nitro-, amido-, diazo- and sulpho-phenols. The ease with which chlorine, bromine, nitric acid, etc., produce such derivatives is characteristic of the phenols ; thus the former substitute even in very dilute aqueous solution, and nitro- phenols also result from the action of dilute HNOg, the concentrated acid giving rise at the same time to di- and trinitro-compounds. From the phenols having the character of weak acids, it follows that the group C5H5 (phenyl) is of a negative nature, i.e. that it acts as an acid radicle. Occurrence. Many individual phenols are found in the vegetable and animal kingdoms. Constitution. The hydroxyl in phenol, CgHj.OH, and in the dioxy- and trioxy-benzenes, etc., containing six carbon atoms, is linked to the benzene nucleus. That this is also the case in the homologues of those compounds follows : (a) from their completely analogous reactions ; (6) from their behaviour upon oxidation. The products which hereby result from the trans- formation of the side chains into carboxyl are oxy-acids, i.e., still contain the hydroxyl. The entrance of the hydroxyl into the side chain of the benzene homologues is also theoretically possible, but in this case it is not phenols which result but true aromatic alcohols, (cf. p. 431) A. Monatomic Phenols. Modes of fffrmatim. 1. Many phenols result from the destructive distillation of the more complex carbon com- pounds, especially of wood and coal; they are therefore present in wood and coal tars. The latter contains especially 414 XXIII. PHENOLS. phenol and its homologues, cresol, etc. ; the former, among other products, the methyl ethers of polyatomic phenols, e.g. guaiacol, 06H^.(OH)(O.CH3), and its homologue creosol, C6H3.CH3(OH)(O.CH3). The phenols are isolated from coal tar etc. by shaking up with potash, in which they dissolve, saturating the solution with hydro- chloric acid, and purifying the precipitated phenols by fractional distillation. 2. The phenols result together with a sulphite upon fusion of the sulphonic acids with potash or soda, {Kekuli, Wmtz, Dusart, 1867) : CgH^-SOsK + 2K0H = CgHg-OK + SOgK^ -^ H,0. In the laboratory nickel or silver basins are used for this fusion, and on the large scale iron boilers, etc. The chlorinated sulphonic acids and the chlorinated phenols also exchange the halogen for hydroxyl upon fusion with potash : C8H4.C1(S03K) + 4K0H = CeHiCOK)^ + SO3K2 + KCl + •m.fi. 3. By boiling the diazo-compounds with water (Griess; cf. p. 396). In this case a very dilute sulphuric acid solution is employed : C6H,C1(N:N.C1) + H^O = CeUfil{OB.) + N^ + HCl. 4. Phenol is produced from benzene by the action of ozone or hydrogen peroxide, and also by that of the oxygen of the air in presence of caustic soda solution or of aluminium chloride. In an analogous manner di- and even tri-oxy-benzene may be obtained by fusing phenol with potash : CSH5.OH + O = C8H4(OH)j. 5. The phenols cannot be prepared from chloro-, bromo- or iodo- benzene as the alcohols can from chloro-, bromo- or iodo-alkyl, the halogen being bound too firmly to the benzene nucleus. If, however, nitro-groups are present at the same time, an exchange of this kind can be effected by heating with potash or soda solution; trinitro- chloro-benzene indeed reacts with water alone : CeHjCl.dTOi,), + HOH = C8H2(OH)(NOj)3 -I- HGl. 6. Similarly the amido-group in amido-compounds may be replaced by hydroxyl upon boiling with alkalies, provided nitro-groups are MON ATOMIC PHENOLS; BEHAVIOUR. 416 also present; thus o- and p- (not m-) dinitro-anUine yield dinitro- phenols, a reaction which corresponds with the saponification of the amides, (of. pp. 350-351). 7. Phenols result from the dry distillation of the salts of the aromatic oxy-acids with lime, or from that of their silver salts, e.g. CeH,(0H)3.C0,H = CO, + C,H3(OH)3. Gallic acid. Pyrogallol. 8. Homologues of the phenols are produced by heating phenol with alcohols and zinc chloride, e.g. ethyl and butyl phenols, (B. 14, 1845 ; 15, 150). 9. Phenols also result from the putrefaction of albumen, especially ^-cresol, CgH4(CH3)OH. Behaviour. 1, 2, and 3. For the alcoholic and acid characters of the phenols and for their substitution, see above and also on p. 417 et seq. Bromine water precipitates even very dilute aqueous solutions of phenol, with the formation of tribromo- pheuol. 4. Many phenols give characteristic colourations with ferric chloride in neutral solution, e.g. phenol and resorcin violet, pyro-catechin green, and orcin blue-violet; while pyrogallol yields a blue colour with ferrous sulphate containing a ferric salt, and a red one with ferric chloride. Chloride of lime and iodine also sometimes give particular colourations. 5. When the phenols are mixed with concentrated H2SO4 and some NaNOa, they yield intensely coloured solutions which turn to king's blue on saturation with potash, (the Liehermann reaction, p. 387). 6. The sodium and potassium salts of the phenols react with CO2 (Kolbe) or with COClj, with formation of aromatic oxy- acids, e.g. salicylic acid : CeHj.OH -1- CO2 = C6H^(OH).C02H. The oxy-acids are also formed when CCI4 and NaOH are used, (B. 9, 1285), and their aldehydes by the action of CHClg and NaOH upon phenol, (B. 9, 824). 7. The phenols combine with diazo-compounds to form azo-dyes (p. 403); when heated with benzo- trichloride, CbH5.C=C13, they yield yellow-red dyes (see aurin), and with phthalio acid, the phthaleina. 416 XXIII. PHENOLS. 8. When heated with zinc dust, the phenols are converted into the corresponding hydrocarbons {Baeyer) : C,H,.OH + H^ = CeH, + H^O. 9. TJpon heating with zinc or calcium chloride and ammonia, the OH is replaced by NH2 (cf. p. 377; also B. 19, 2901). 10. Heating with PCI5 partially converts the phenols into chlorinated hydrocarbons, and heating with P2S5 into thio-phenols (p. 418). H. For the breaking up of the phenols by chlorine, see p. 355. 12. For the oxidation of phenol by permanganate of potash to i-tartario acid, see B. 24, 1753. Phenol. Phenol, carbolic acid, phenyl alcohol, Cf^HjOH. Discovered in 1834 by Bimge in coal tar. Occurs in the urine of the herbivora and in human urine as phenyl-sulphuric acid, in castoreum and in bone oil. It forms a colourless crystalline mass consisting of long needles. M. Pt. 42°; B. Pt. 181°; Sp. Gr. at 0°, 1-084. It is soluble in 15 parts of water at 16°, and itself dissolves some water, a small percentage of the latter sufficing to liquify the crystalline phenol; alcohol and ether dissolve it readily. It is hygroscopic and acquires a reddish colour in the air, possesses a characteristic odour and burning taste, is poisonous, and acts as a splendid antiseptic. It exerts a strongly corrosive action upon the skin. Soluble in caustic potash but not in the carbonate. Ferric chloride colours the aqueous solution violet, while a pine shaving moistened with hydrochloric acid is turned greenish-blue by phenol. Phenol-potassium, CeHs.OK, results upon heating phenol with KOH. It crystallizes in white needles which are readily soluble in water and which redden in the air. Pheuol-calcium or carbolate of lime, (C6H5.0)2Ca, is employed as a disin- fectant. The corresponding Mercury compound, (C6H5.0)2Hg, which crys- tallizes in colourless needles, is used in skin diseases. For the reactions of phenol and its homologues, see B. 14, 2306; IS, 1207. Hexa-hydro-phenol, CoHs.Hj.OH, prepared from quinitol as given iu B. 26, 229, is a liquid with an odour resembling that of fusel oil. PHENOLIC ETHERS. 417 Summary of the most important derivatives of Phenol. Substitution Products. Ethers. Compound ethers. C6H,(0H)01 (3) Chloro- phenols. p- : [37°] (217°) CeH5.0(CHs) Anisol. Liq. (155°) 06Hg.O(SO3H) Phenyl-sulphurio acid. C«H4(0H).N0, (3) Nitro-phenola. o-:[45°](214°);p-:[114°] CeH5.0(C,H,) Phenetol. Liq. (172°) Aoetyl-phenol. (193°) C8H3(OH)(N02)3 Trinltro-phenola. ie.g. 123°] C8H5.0.CeH5 Diphenyl ether. [28°](253°) Thio-compounds. C6H,(0H).NH, (3) Amido-phenola. o.:[170°];i)-:[184°] C6H4(NH2).OCH3 (3) Anisidines. p- : [56°] (245°) CsHj.SH Thio-pheuol, (172°) CeH4(OH).S03H (3) Phenol-sulphonic acids. C8H3(NH2)(OCH8)(S03H) Aniaidine-sulphonic acid. (06H,),S Phenyl aulphide. (272°) Ethers. Anisol* or phenyl-mefhyl ether, CgH5.0(CH3), and Phenetol or phenyl-ethyl ether, C6H5.0(C2H5), are best got by heating phenol-potassium (or phenol and caustic potash) with methyl or ethyl iodide in alcoholic solution : CgHs.OK + CH3I = C6H5.0(GH3) + KI; the former is also obtained by distilling anisic acid with Ume. They are liquids of ethereal odour which boil at a lower temperature than phenol, just as ether boils at a lower one than alcohol. As regards behaviour, they are very stable neutral compounds of hydrocarbon character; when heated with HI to 140°, or with HCl to a higher temperature, or with aluminium chloride, they are decomposed backwards, thus : C6H5.O.CH3 + HCl = CA-OH + CH3OL Thia reaction servea for the quantitative determination of the number of methoxy-groupa (— O.CH3), in phenolic ethers (cf. e.g. B. 28, Kef. 710). Phenyl ether, di-phenyl oxide, (OeHsjA is formed upon heating phenol with ZnCls or AljCle, but not with HjSO,. Long needles. Not split up by HI. ... • Benzene-oxy-methane. ^^ 418 XXIII. PHENOLS. Con/pound ethers of Phenol. Phenol reacts as an alcohol with inorganic and organic acids to form compound ethers. Phenyl-sulphurie acid (also termed phenol-sidphuric acid), C|;H5.0(S0gH), is only capable of existence in the form of salts, being immediately saponified into phenol and sulphuric acid when attempts are made to isolate it. The potassium salt, OgH5.0.(S03K) (plates, sparingly soluble in water), is found in the urine of the herbivora and also in human urine after the consumption of phenol, and it may be prepared synthetically by heating phenol-potassium with potassic pyro- sulphate in aqueous solution, (Baumann). It is very stable towards alkalies, but is saponified by hydrochloric acid. The other phenol-sulphuric acids, e.g. cresol-sulphurio acid, which occur in urine, are exactly analogous to the above. PIienol-carl)onlc ether, phenyl carbonate, COCO.CjHb)^, is prepared from COClj and CjHgONa. It crystallizes in glancing needles, M. Pt. 78°, and is convertible into salicylic acid. Sodium phenyl-carbonate, CgHj.O.COaN'a, results from COj and CjHj.ONa, and goes into sodium salicylate upon heating. Acids decom- pose it into CO2 and phenol. Acetyl-phenol, OgHjO.OjHgO, obtained from phenol-sodium and acetyl chloride, or from phenol, acetic acid and sodium acetate, is an easily saponifiable liquid which boils at 193°. Thio-phenols. Thio-'phenol, phenyl hydrosulphide, C5H5.SH, is prepared from benzene-sulphonic chloride, CgHg — SOgCl, as given at p. 409, or by heating phenol with PgSjj also by the exchange (best eff'ected indirectly) of the diazo-group in diazo-benzene chloride for — SH (see B. 23, 738, Eef. 327). It is a liquid of most unpleasant odour and of pronounced mercaptan character (see p. 104). It yields, for instance, a mercury compound, (C5H5S)2Hg, crystalliz- ing in glancing needles, and also salts with other metals. When warmed with concentrated HjSO^, a cherry-red and then a blue colour- ation is produced. It is readily oxidizable to phenyl disulphide. NITROSO-PHENOLS. 419 Closely related to the above are (a) Phenyl sulphide, (05115)28, which results, among other methods, by the action of diazo- benzene chloride upon thio-phenol (B. 23, 2469) : — C0H5— N=N— 01 + H— S— CgHj = CeHj— S— CeHj + N^ + HCl. It is a liquid smelling of leeks and is oxidizable to Phenyl sulphoue, (CeHiljSOa ; (6) Phenyl disulphide, (CsHsjA (glancing needles, M. Pt. 60°), which is very easily prepared by the action of iodine upon the potassium compound of thio-phenol, or by exposing an ammoniacal solution of the latter to the air. It is readily reducible to thio-phenol, and is indirectly oxidizable to Benzene di-sulph-oxide, (CsHsjjSaOz. (Of. the corresponding compounds of the fatty series, p. 102 et seq.) Chloro- and Bromo-phenoh. When chlorine is led into phenol, 0- and jp-Chloro-phenols are formed. These also result, together with the m-compound, by reducing and diazotizing the haloid-nitro-benzenes. Of the isomeric bi-derivatives, the p-compounds have the highest melting point and the 0- the lowest ; thus o-chloro- and bromo-pheuols are liquid and the p-compounds solid. When fused with caustic potash they yield dioxy- benzenes (p. 423), often with a molecular rearrangement. The Shloro-phenols have a sharp persistent odour. All the five hydrogen atoms of phenol have been replaced by chlorine and bromine. Nitroso-phenols. Nitroso- phenol, C15H5O2N, is prepared from phenol and nitrous acid {Baeyer, B. 7, 964), by boiling nitroso-dimethyl- aniline with caustic soda solution (see p. 388), and by the action of hydroxylamine upon quinone (p. 427). It crystallizes in fine colourless needles which readily become brown, or in large greenish-brown plates, and detonates when heated. It yields a soda salt crystallizing in red needles and amorphous dark- coloured salts with the heavy metals. Potassio ferrioyanide in alkaline solution oxidizes it to ^-nitro-phenol, while tin and hydrochloric acid reduce it to p-amido-phenol. It gives the Liebermann reaction with phenol and concentrated sulphuric acid. It was formerly given the formula C6H4(NO)(OH), but is really an tso-niiroso-compound, an oxime of quinone, with the formula r. rr /NOH ^N.OH C6H4<_^ • or CsHj^Q (see Quinone; also B. 17, 213, 801). This follows from its formation from quinone, and also from the fact that hydroxylamine converts it into quinone-dioxime (p. 429). 420 XXIII. PHENOLS. Nitro-phenols. On mixing phenol with cold dilute nitric acid, o- and p-nitro- phenols are formed, the latter preponderating if the liquid is cold, and the former if it is warm. Upon distilling with steam, the 1 : 2 compound (strongly smelling yellow prisms) volatilizes, while the 1 : 4 (colourless tables) remains behind. For their formation, see also pp. 414 and 387 m-Nitro- phenol results from m-nitraniline by diazotizing the latter. The acid character of phenol is so strengthened by the entrance of the nitro-group that its salts are not decomposed by COj but result from the nitro-phenols and alkaline carbonate. o-Nltro-phenol-sodium, C5H4(N02)ONa, crystallizes in dark red prisms, and p-Nitro-phenol- potassium in golden needles. Halogens and nitric acid readily substi- tute further in these (or in phenol itself), yielding two isomeric Dinitro- phenols, C6H3(N02)20H, (OH : NOj : NOj = 1 : 2 : 4 and 1 : 2 : 6, i.e. the two NOj-groups are always in the m-position to one another). Further nitration gives : Picric acid, trinitro-pkenol, 0gH2(NO2)3.OH, (OH : NO^ NO2 : NO2 = 1:2:4:6). This compound was discovered in 1799. It may also be prepared by the direct oxidation of s-trinitro-benzene with KgFeCyg, and is produced by the action of concentrated nitric acid upon the most various organic sub- stances, e.g. silk, leather, wool, resins and aniline. It is a strong acid and forms beautifully crystallizing salts which explode violently upon heating or when struck. Very spar- ingly soluble in water. Crystallizes from alcohol or water in yellow plates or prisms, M. Pt. 122°. Can be sublimed with- out decomposition, but is explosive also. It is used for the preparation of explosives, and is also an important yellow dye. Picryl chloride, G8H2(]Sr02)3Cl (from picric acid and PCI5), resembles the acid chlorides (p. 350) in behaviour. Picric acid forms beautifully crys- tallizing addition-compounds with many hydrocarbons, e.g. CsHj, CioHj, etc. With KCN it yields Iso-purpuric acid, CsHjIfsOi,, whose potassium salt dyes a garnet-brown like orchilla. Isomers of picric acid are also known. AMIDO-PHENOLS. Amido-phenols. 421 The nitro-phenols go into amido-phenols upon reduction ; CsH4(OH)NH2 CeHs(OH)(NH2)2 06H8(OH)N02(NH2) CeHs(OH)(NH2)3. 0-, m-, p- Di-amido- Nitro-amido- Tri-amido- Amido-phenols. phenols. phenols. phenol. In the Amido-phenols {Hofmann, 1857) the acid character of the phenols is neutralized by the presence of the amido-groups, so that they only yield salts with acids ; but, as phenols, they are still capable of yielding derivatives (see anisidine), while on the other hand their amido-hydrogen is exchangeable in the most various ways, as in the case of aniline, but chiefly for acid radicles. The Hydrochlorides of the amido-phenols are relatively stable in the air, and are often capable of being sublimed; the free bases (colourless plates) on the other hand, especially if they are impure, are very readily oxidized in the air, with blackening and the formation of resin. o-Amido-phenol, C6H4(OH)(NB[2), M. Pt. 170°, yields with acids (like an o-diamine) so-caUed "anhydro-bases" instead of normal derivatives, e.g. with formic acid the compound Methenyl-o-amido- phenol, C6Hi<^q^CH. This last is crystalline and boils without decomposition. ^-Amido-phenol, M. Pt. 184°, is easily oxidized to quinone, CeHiO^, and is converted by chloride of lime into quinone ohlor-imide, 06HiO(N01) (which see). m-Amido-phenol, and Diethyl-m-Amido-phenol, C6H4(OH)[N(02Hs)j], result upon fusing m-amido-benzene-sulphonic acid or its diethyl derivative with alkali. Diethyl-m-amido-phenol is used for the preparation of the red dye Rhodamine. Amido-thio-phenols, 06H4(SH)NH2, are also known, of which the o-com- pound is again characterized by the ready formation of anhydro-compounds, such as Methenyl-amido-tMo-phenol, 06H4<['g^0H, isomeric with phenyl isothiocyanate [Hofmann, B. 13, 1226). The yellow cotton dye, Frimnline, a more complex compound of this nature, is obtained by heating ^-toluidine with sulphur and then sulphur- ating the product. The Anisidines, amido-anisols, methoxy-wnUines, CeH4(O.OH3).NH2, and the Phenetldines, C6H4(O.C2H5).NH2, are bases similar to aniline, and are used in the colour industry (azo-dyes). Aceto-^-phenetidine, C6H4(O.C2H6).(NH.C2HsO), which forms colourless crystals, is used as an anti-pyretic and a remedy for neuralgia, under the name of " Phenacetine," 422 XXIII. PHENOLS. The Oxy-diphenylamines, e.g. Cells — NH — CoHj.OH, are phenylated aiuido-phenols, and react accordingly (see also p. 389). Salts of diamido-phenol 1:2:4 are used under the name of Amidols as photographic developers. Phenol-sulphonic Acids. Phenol-sulphonic acids, GgH^(0H)(S03H). The o- and p- acids are obtained from phenol and concentrated HgSO^ at a moderate temperature, that is, with much greater ease than the benzene-sulphonic acids; the ortho-acid changes into the para- on warming, even when in aqueous solution. The m-compound can be prepared indirectly by fusing m-benzene- disulphonic acid with potash. All three are crystalline. The 0- and m-acida yield o- and m-dioxy-benzenes when fused with KOH, but the p-acid does not react in this way, being attacked only at temperatures over 320°, and no resorcin then resulting; the same applies to caustic soda. o-Phenol-sulphonic acid is used as an antiseptic under the name of "Aseptol" or "Sozolic acid" (B. 18, Kef. 606); similarly, Di-iodo- p-phenol-sulphonic acid, C6H2.l2(OH)(S03H), is "■ Sozo-iodol," an antiseptic like iodoform. Phenol-di- and tri-sulphonic acids are also known. Homologvss of Phenol. The homologues of phenol resemble the latter very closely in most of their properties, form perfectly analogous deriva- tives, and possess likewise a disinfectant action and a peculiar odour (the cresols an unpleasant fsecal-like odour, the higher homologues one which is less marked). They differ from phenol mainly by the presence of side chains which, as in the case of toluene etc., may undergo certain transformations. In especial, when they are used in the form of alkyl or acetyl derivatives or sulphonic acids, they can be oxidized in such a manner that the side chains (methyl groups) are transformed into carboxyl, with the production of oxy- carboxylic acids. The cresols themselves cannot be oxidized even by chromic acid mixture, but are completely destroyed by permanganate of potash. Negative substituents, especially if they are present in the o-position, render such oxidation more difficult in acid, but facilitate it in alkaline solution. The Cresols, OgH4(CH3)OH, are all three present in coal CRESOLS; THYMOL; PYROCATECHIN. 423 tar and are also contained in the tar from pine and beech wood; they can be prepared from the corresponding toluidines. o-Cresyl-sulphuric acid (analogous to phenyl-sulphuric acid) is found in the urine of horses, and the ^-compound in human urine. m-Cresol is conveniently prepared by heating thymol with phosphoric anhydride and then with potash. i?-Cresol, CeH^(CH3)0H, is produced by the decay of albumen. Its dinitro-compound is a golden-yellow dye which is used as ammonium or potassium salt under the name of Victoria orange. Crude cresol is rendered soluble in water by the addition of resin soap or of oil soap ; the preparations so obtained are termed CreoUne and Lyaol, and are employed as antiseptics. Thymol, CjoHi^O, (CHgtCgH^tOH = 1:4:3) is found together with cymene, CjqH^^, and thymene, CjqHjj, in oil of thyme. Thymus Serpyllum, and is used as an antiseptic. m-Xylenol, CsHijO, (CH3 : CHa : OH = 1 : 3 : 4) is found in the creosote of beech-wood tar. Carvacrol, CioH„0, (CH, : OsH? : OH =: 1:4:2) present in Origanum hirtum, is prepared either by heating camphor with iodine or from its isomer, carvol, and vitreous phosphoric acid. Carvol, CioHuO, the chief con- stituent of oil of cumin (from Carvum Carvi), appears to be a Iceto-dihydro- cymol (B. 19, 12 ; 24, 3985), since it yields carvoxime with hydroxylamine, Carvoxime, like carvol, exists in three optically diflferent modifications. For other homologues of phenol, see table, p. 412; Ethyl-, Propyl- and Bntyl-phenols and also Feuta-methyl-phenol (B. 18, 1825) have likewise been prepared. B. Diatomic Phenols. By the entrance of two hydroxyls into benzene and its homologues, the diatomic phenols are produced. These are analogous to the monatomic compounds in most of their relations, but differ from them in the same way as the diatomic alcohols do from the monatomic. They are likewise formed by methods completely analogous to those for the monatomic phenols, especially by fusion with potash (p. 414); instead, however, of the compound expected, an isomeride which is stable at that high temperature frequently results (see Eesorcin). The ^-dioxy-compounds are characterized by their close connection with the quinones. Many of the poly- atomic phenols are strong reducing agents. {a. ) Dioxy-henzenes. Pyrocatechin, G^^{QiH.)^ (1 : 2), which was first obtained by the distillation of catechin (Mimosa Catechu), 424 XXIII. PHENOLS. is present in raw beet sugar and results from the fusion of many of the resins as well as of o-phenol-sulphonic acid with potash. It crystallizes in short white rhombic prisms, which can be sublimed, and are readily soluble in water, alcohol and ether. It is prepared by heating its mono-methyl ether, Guaiacol, CcHi(OH) (O.CHs), a constituent of beech-wood tar, with hydriodic acid (see Anisol, p. 417). Like most of the polyatomic phenols it is very unstable in an alkaline solution, which quickly becomes green and then black in the air. The aqueous solution is coloured green by PejCls and then violet by NH3 (reactions of the o-dioxy-compounds). It possesses reducing properties, causing separation of the metal from a solution of silver nitrate even in the cold. By the continued action of chlorine upon it, derivatives of penta- methylene and finally of the fatty series result [Zinclce and Kilster). By boiling it with potash and potassic methyl-sulphate, it may be reconverted into guaiacol, which likewise shows the ferric chloride reaction and possesses reducing powers. Guaiacol is employed medicinally as an expectorant. Veratrol, C6H,(OCHs)2, is its di-methyl ether. Resorcin, 0^114(011)2, (1:3) {Hladwetz, Bwrth, 1864), is obtained on fusing many resins (Galbanum, Asafoetida), also wi-phenol-sulphonic acid, all three bromo-benzene-sulphonic acids, and m- and ^-benzene-disulphonic acids with potash. The last mentioned compounds are employed for its prepara- tion on the technical scale. It also results from the distillation of the extract of Brazil wood. White rhombic prisms or tables which quickly become brown in the air, dissolve easily in water, alcohol and ether, and reduce an aqueous solution of silver nitrate when warmed with it, and an alkaline solution even in the cold. With FcjClg resorcin gives a dark violet colouration. It acts therapeutically like carbolic acid, only more mildly. It yields dyes with NgOj. When heated with phthalio anhydride it ia converted into fluorescein (see eosin ; test for m-dioxy-benzenes), and it is therefore prepared on the large scale. Diazo-compounds transform it into azo-dyes, (of. p. 403). Its trinitro-derivative is Styphnlc acid, C6H(OH)2(N02)3, which is formed by the action of nitric acid upon many gum-resins. Hydroquinone, G^Ii.^{OR)^ (1:4), {Wohler, 1844). Formation. By the oxidation of quinic acid, C^HjjOj, by means of PbOj, by the saponification of arbutin, and from succino-succinic ether as given at p. 354, etc. Preparation. By the oxidation of aniline with chromic acid HYDEOQUINONE. 425 mixture, and also by the reduction of quinone with sulphur dioxide. Small monoclinic plates or hexagonal prisms, of about the same solubility as its isomers and capable of being sublimed. Ammonia colours it reddish-brown, while chromic acid, ferric chloride, and other oxidizing agents convert it into quinone and eventuaDy into quin- hydrone (p. 428). B. Ft. 285°. Being a strong reducing agent, it is used as a developer in photography (of. also B. 25, Eef. 432). Acetate of lead yields a white precipitate with a solution of pyrocatechin, but none with resoroin, while hydroquinone is only precipitated in presence of ammonia. Prom the observed heat of neutralization, resorcin and hydroquinone behave towards soda as dibasic acids, and pyrocatechin as a weak monobasic acid. (6.) Sioxy-tolnenes, C6H3(CH3) (0H)2. Among the various isomerides which have been prepared (see B. 15, 2995), there may be mentioned : 1. Orcin, (OHaiOHiOH = 1:3:5), which is found in many lichens (KoceUa tinctoria, Lecanora, etc.). It results from orsellinic acid with separation of CO2, e.g. upon fusing extract of aloes with potash, and it can also be prepared synthetically from toluene (B. 15, 2992). Of especial interest is its synthesis from acetone-dicarboxylio ether (p. 265) and sodium (B. 19, 1446). It crystallizes in colourless prisms of sweetish taste which tend to become red, and whose aqueous solution is coloured bluish-violet by FejClo. It does not yield a iluoresoeJn with phthalic anhydride. By the oxidation of its ammoniacal solution in the air. Orcein, CzsHaNaOj, the chief constituent of the commercial orchil dye, is formed, a compound which ia also prepared directly from the lichens named above. Belated to it is the weU-linown colouring matter litmus. 2. Homo -pyrocatechin, C6H3(OHa)(OH)s, (CHarOH: OH = 1 :3:4) deserves mention on account of its mono -methyl ether Greosol, C8H8CH3(OH)(O.OH3), occurring in beech-wood tar. Creosol is a liquid similar to guaiacol, boiling at 220°, and, as a derivative of pyrocatechin, giving a green colouration with Fe^Clj. 3. Among the other isomers are Cresorcin, Toln-hydroqninoue, etc, (c.) Homologous with the above are e.g. Xylorcin {CH3: CH3: OH: OH = 1:3:4:6) and Beta-orcinol (m-dioxy-ji-xylene), C8H|!(CH8)2(OH)2; Mesorcin, CeB(GB.i)i (OH)j, (CHj : CH3 : CH3 : OH : OH = 1 : 3 : 5 : 2 : 4) (see table, p. 412) ; Thymo-hydroquinone, OioHuOa which is present in Arnica montana, etc. (d.) Eugenol, OioH^aOj, = C6H8(OH)(OCH3)(CH2.CH=CH2), the chief constituent of oil of cloves, is a derivative of an unsaturated diatomic phenoL {e.)Q,uinitol{l,i-Cyclo-}ieocane-diol),p-J)ioxj/-7iexamethylene,GeELi.lIi.(OII)2, a diatomic phenol of reduced benzene, is obtained synthetically by the reduction of p-diketo-hexamethylene. It crystallizes in crusts and has a sweet taste with a bitter after-taste; M. Pt. 144°. It is the simplest repre- sentative of the Inosite-sugar group (p. 427). From quinitol a series of derivatives of reduced benzene can be prepared {Baeyer, B. 25, 1037; 26, 229). 426 XXIII. PHENOLS. O. Triatomic Phenols. iTyrogallol = 1 : 2 : 3 = » ] C6Ha(0H)aK Phloroglucin = 1 : 3 : 5 = » >See table, p. 412. V Oxy-hydroquinone = 1 : 2 : 4 = o / 1. Pyrogallol, pyrogallic add (Scheele, 1786), is the most important of these three isomers. It is obtained, apart from synthetical reactions, by heating gallic acid, COj being split off: CeH,(0H)3.C0,H = C.HjCOH), + CO,. It crystallizes in white plates, M. Pt. 132°, readily soluble in water and capable of subliming without decomposition. It is an energetic reducing agent, e.g. for silver salts, and its alkaline solution rapidly absorbs oxygen from the air, hence it is used in gas analysis, as a developer in photography, and so on. The aqueous solution is coloured bluish-black by a solution of ferrous sulphate containing ferric salt, and purple-red by iodine. It does not react with hydroxylamine (cf. phloroglucin). Pyrogallol dimethyl ether, C6H8{OH) (0CHa)2 {Sofmarm), is contained in beeoh-wood tar, aa are likewise the dimethyl ethers of the componnds C6H2(CH3){OH)s and CsHjCOsH,) (0H)8, homologous with pyrogallol. 2. Phloroglucin (Hlasiwetz, 1855) results from the fusion of various resins and of resorcin with potash or soda, by the action of alkali upon phloretin, and by fusing its tricarboxylic ether (whose synthetical formation is given on p. 354) with potash. Large prisms which weather in the air and sublime without decomposition; M. Pt. 218°. Gives with FegClg a dark violet colouration. Its reactions (analogous to those of succino-sucoinic ether) partly agree with the formula C6Hs(OH)3, e.g. it forms metallic compounds and a Tri- methyl ether, C6Hj{O.CHs)3, insoluble in alkali; but, on the other hand, it yields with hydroxylamine, like the ketones, a Trioxime, C6H6(N,OH)s, and therefore appears readily to build up the atomic group CHa— CO— CHj— CO— CHj— CO, = Tri-keto-hexa-methylene, which is termed the secondary or pseudo-iorm, in contradistinction to the first-named (the tertiary). (Cf. pp. 286 and 349; also B. 19, 159, 2186; 23, 1272. For the special constitution of the benzene ring in tertiary phloroglucin, see p. 349.) The action of chlorine upon phloroglucin yields, among other products, Hexachloro-triketo-hexamethylene, CeClsOa, which can be split up into dichloro-acetic acid and tetrachloro-acetone, and further into chlorinated acetyl-acetone, etc. (ZincJce and Kegel, B. 23, 1467; 28, 230). QTJINONE. 427 3. Oxy-hydroc[uinone results from the fusion of hydroquinone with potash (B. 16, 1231). Like pyrogallol it does not react with hydroxyl- amine. D. Tetra-, penta- and hexatomic Phenols. Tetr-oxy-benzene, 06H2(OH)4 (1:2:4:5), can be prepared from dinitro- resorcin (B. 21, 2374). It crystallizes in small gray plates with a silvery lustre; M. Pt. 215°-220°. Its chloro-derivative, Diohloro-tetroxy-benzene, CsCl2(OH)4, is readily oxidizable to chloranilio acid (see p. 429). Hez-oxy-benzeue, C6(0H)e, forms as potassium salt the so-called Potas- sium carboxide, CsOsKs. It crystallizes in colourless readily oxidizable prisms, and can be converted into its quinone (tri-quinoyl), CsOs (p. 430). It has also been prepared synthetically (B. 18, 499, 1833). The following are perhaps to be regarded as polyatomic phenols of reduced benzene: — Quercite, C6H(Il6)(OH)5 (in Quercus), and Inosite or Phaseo-mannite, C5H8(OH)6, a. substance resembling sugar, which is found in the animal organism (the muscles of the heart) and in many plants (unripe beans, peas, and lentils). It forms large crystals which weather in the air, and exists in a dextro-, a laevo-, and an inactive modification. Finite, C7H14O6, which occurs in Pinus Lambertiana, and which also resembles sugar, likewise belongs to this class, seeing that hydriodic acid reacts with it to produce methyl iodide and inosite. E. Quinones. Quinone, GeH^Og (1838). Quinone is produced when chromic acid is added to a solution of hydroquinone. It crystallizes in yellow needles or prisms of a characteristic pungent odour something like that of nut shells, sparingly soluble in water but readily in alcohol and ether, and capable of sublimation; M. Pt. 116°. Corresponding to it we have a large number of higher homologues, etc. These also are solids mostly of a yellow colour and volatile with steam ; they result from the oxidation of the corresponding para-dioxy-com- pounds or of the higher atomic phenols, which contain two hydroxyls in the para-position. The isomeric dioxy-benzenes do not show this formation of quinone. Quinone is also produced by the oxidation of many aniline and phenol derivatives belonging to the para-series, e.g. p-amido-phenol, sulphanilic acid and ^-phenol-sulphonic acid ; further, by the oxidation of aniline itself by means of chromic 428 XXIII. PHENOLS. auid, (see B. 19, 1467). It was first obtained by distilling quinic acid with manganese dioxide and sulphuric acid. Quinone readily volatilizes with steam, but at the same time much of it is decomposed. Exposure to light causes it to turn brown, and it colours the skin yellow-brown. It is easily converted into hydroquinone by reducing agents such as SOj, HI, SnClj and HCl etc., and can therefore act as an oxidizer. In solution in chloroform it takes up two or four atoms of bromine to form a di- or tetra-bromide (CsHiOj-Br,). Under other conditions chlorine and bromine act upon it as substituents, while hydrochloric acid forms Mono-chloro-hydroquinone: CeHiOj + HCl = C6Hs01(OH)2. It yields sparingly soluble crystalline compounds with primary amines and also (coloured) compounds with phenols. It is soluble in alkalies, the solution decomposing rapidly. With hydroquinone it forms an addition-compound termed Quliihydrone, C8H402-l-CgH4(OH)2, crystallizing in green prisms with a metallic glance, which also results as an intermediate product in the oxidation of hydroquinone or in the reduction of quinone. Constitution. Quinone is derived from benzene by the exchange of two atoms of hydrogen for two of oxygen which, from the close connecti«n between quinone and hydroquinone, must be in the j7-position. The constitution of quinone may be explained either by assuming that these two oxygen atoms are linked together as in peroxide of hydrogen, H — — — H, so that the benzene nucleus remains unchanged, or that the latter experiences a partial reduction, with the formation of a derivative of OgHg, a " diketo-dihydro-benzene " : C CO /O HC/3\CH ^0 HO/\CH CeH/ |, = I J , or erf , = II II . \0 HCV^CH \-o HC^/CH C CO According to the first of these two formulae quinone would be a peroxide, according to the second, a ketone (quinone on = C2H2<^pX^C2H2). In favour of the latter view (which was brought forward by Fittig, and is now almost universally accep- ted) are (1) the fact that quinone can be converted into an oxime, C.,H2<^^q"q ^^>C2H2 (identical with nitroso-phenol, p. 419), CHLORANIL. 429 and into a dioxime, Quinone dioxime, CjHg^^Q^jr'QTTC^CjHj (B. 20, 613)j (2) its power of forming addition-compounds with bromine; and (3) its relations to the analogously consti- tuted anthraquinone. (Cf. B. 18, 568; A. 223, 170; J. pr. Ch. 42, 161.) The formation of succino-sucoinic ether, which was spoken of on p. 354, involves a synthesis of quinone. Suocino-succinic acid is the diearboxylic acid of a hypothetical dioxy-dihydro-benzene, C6H4.H2.(OH)2, and it can be transformed into the diearboxylic acid of hydroquinone, CsH^OHja, by the elimination of two atoms of hydrogen, and into bromanil (tetra-bromo- quinone) by bromine (of. A. 2U, 306: B. 16, 1412; 19, 429, 1977; 23, 1273). Quinone tetra-hydride, C6H4.H4.(02), can be prepared by eliminating the carboxyls from succino-succinio ether, being thus obtained instead of the tautomeric hypothetical dioxy-dihydro-benzene (see above). It pos- sesses the constitution of a p-DiJoeto-hexamethylene {Cyclo-hexane-dione), CHo-CO— CHj I I . Colourless prisms; M. Pt. 78°. It yields quinitol upon CH2 — CO — CHa reduction. Cf. B. 22, 2168; 23, 1272. Quinone dioxime, CeHj^j^'^-rr, results from the action of hydroxyl- amine upon nitroso-phenol (B. 20, 613; 21, 428). Chlorinated, etc., products are derived from hydroquinone as well as from quinone. Chloranil, tetracMoro-quinme, CgCl402, which crystallizes in lustrous yellow plates, is obtained by chlorinating quinone and also by oxidizing many organic compounds, e.g. phenol, with HCl and KCIO3. It goes into tetra-chloro-hydroquinone, a colourless compound, upon reduction, and acts as an oxidizing agent, converting e.g. dimethyl-aniline into a methyl violet. A. dilute solution of potash transforms it ifito potassium chloranilate, CgCl202(OK)2 + H.p (dark red needles), corre- sponding to which there is also an analogous nitrocompound, potassium nitranilate, C6(N02)202(OK)o. The latter salt is distinguished by its sparing solubility, hence its formation may be made use of as a test for potassium compounds. For its constitution, see B. 19, 2398. By the action of chlorine upon chloranil and ohloranilic acid, there result a series of complex chloro-products of the hexa- and penta-methylene series, and finally chlorinated fatty compounds. Tor a tabular summary, see Hcmtzsch, B. 22, 2841; cf. also B. 25, 827, 842. 430 XXIII. PHENOLS, As homologues of quinone may be mentioned Tolu-quinone, C«H3(0,)(CH3), Xylo-quinone, C,H,(0,)(CH3)„ Thymo- quinone, CeH,(02) (CH3) (CgHj), etc. Several of these can be prepared synthetically by the condensation of 1 : 2 di-ketones, for instance di-acetyl yields xyloquinone under the influ- ence of alkali (of. B. 21, 1411) : CHs— CO— CO— CHHa CH3— 0— CO— CH = 11 II + 2H2O. + H2CH— CO— CO— CHj HC— CO— C— CHs Dioxy-quinone, CeH2{03)(OH)2, which corresponds to tetroxy- benzene (p. 427), forms dark yellow needles (B. 21, 2374). It is the mother sub- stance of chlor- and nitranilic acids, mentioned above. From hexoxy- benzene there can be prepared Tetroxy - quinone, (CciOj) (0H)4, Dioxy-diquinoyl or rhodisonio acid, C6(02)(02)(OH)2, and iinally Tri-quinoyl, C6(02)(Oj)(02) + 8H2O. In both the latter compounds the formation of quinone has taken place more than once (cf. B. 18, 499, 1833; 23, 3136, etc.). P. Quinone-aniles and Anilido-quinones. Aromatic bases, especially aniline, can so act on certain quinones that — with the aid of a simultaneous oxidation pro- cess — the group (NHCjHj)' replaces hydrogen in the nucleus once or twice. There are thus formed "Anilido-quinones," which are mostly red or dark-coloured crystalline compounds. On the other hand, the quinonic oxygen may be replaced by the group (NCgH,)", in which case "Quinone-aniles" result. Both of these changes are represented (e.g.) in Azo-phenine or Dianilido- quinone-dianUe, C8H2 (NHC6H5)a' ( NCeHsja". This results from aniline, more especially by heating it with azo-, amido-azo-, or nitroso-compounds in presence of hydrochloric acid. Small red plates. On further heating with aniline it yields induline dyes (0. Fischer and E. Hepp, A. 262, 247). G. Quinone Ohlor-imides. Eelated to the quinones are the quinone chlor-imides, which result from the oxidation of the^-amido-phenols or^-phenylene- diamines by means of chloride of lime. Quinone chlor -imide, C8H4(0)(NC1), results from HCl-p-amido-phenol, and qninone dichlor-imide, C6H4(NC1)2, from HCI-^-phenylene-diamine. The first named crystallizes in golden yellow crystals which are volatile with steam; reduction converts it into amido-phenol, and boiling with AROMATIC ALCOHOLS. 431 water into quinone, the diohloro- compound behaving in an analogous man- ner. Tor these compounds the following constitutional formulae are assumed : °«=Cci °' ««°*-'■ Saligenin. oH o-' Salicylic aldehyde. ^«^, Benzoic anhydride ; CsHb.CO.CI, Benzoyl chloride; CcHb.CO.NHj, Benzamide; etc. But they are at the same time benzene derivatives and, as 438 XXV. AROMATIC ACIU3. such, can undergo most of the transformations of which benzene itself is capable. Thus chlorine, bromine and iodine substitu- tion products and nitro-, amido- and sulphonic acids, etc. can be prepared from them, the amido-acids can be diazotized, and, upon the entrance of oxygen into the benzene nucleus, there result phenolic acids (i.e. compounds which possess the characters of phenols and of acids), quinone acids, (i.e. com- pounds at once a quinone and an acid), etc. Alcohol-acids, ketone-acids, etc., are likewise capable of existence in the aromatic as well as in the fatty series. We have, for instance, the following derivatives : C5H4CI.CO2H, chloro-benzoic acids ; C6H4(N02). COjH, nitro-benzoic acids ; C5H4(NH2).C02H, amido-benzoio acids ; C8H4(S03H). COjH, sulpho-benzoio acids ; C8H4(OH).C03H, oxy-benzoic acids ; 06H6.CH(0H),C02H, mandelic acid, etc. Their modes of formation are likewise partly analogous to those of the fatty acids, (cf. p. 440 et seq.). The homologous acids however do not here show the gradual changes in physical properties which the homologous fatty acids do. Constitution. Corresponding to the aromatic acids there are again nitriles, e.g. to benzoic acid benzo-nitrile, C5H5.CN, which may also be regarded as cyanogen derivatives of the hydro- carbons (in the above case, cyano-benzene), and which are converted into the acids upon saponification. From this it follows that their constitution must correspond exactly with that of the fatty acids ; like the latter they are characterized by the presence of carboxyl, CO. OH, in the molecule. There are monobasic, di-, tri- and up to hexabasic aromatic acids, according to the number of hydrogen atoms in the molecule which are readily replaceable by metal, i.e. according to the number of carboxyl-groups : CeH,(CO,H), CeH3(CO,H)3 CgCCO.H),, Phthalic acids. Benzene-tri-carboxylic acids. Mellitio acid. Unsaturated aromatic acids also exist in large number. They chiefly differ from the saturated acids in that, as un- CONSTITtTTION; NOMENCLATURE. 43d saturated compounds, they readily form addition-compounds with H2, Clj, HCl, etc., going thereby into the saturated acids or their substitution products. In most of these additions the benzene nucleus remains unaltered (cf. p. 344, 3). Their con- stitution is therefore entirely analogous to that of the acids of the acrylic or propiolic series; they contain a side chain with a double or triple carbon bond: CeHs— OH=OH— CO2H OeHs— O^C-COjH Ginnamic acid. Fheuyl-propiolic acid. For the special constitution of the benzene ring in the aromatic acids, see p. 349. Besides the aromatic acids proper, which have just been spoken of, other acids have recently become known, which are derivatives either of a com- pletely reduced or a partially reduced benzene. The acids of the former series, e.g. the hexahydro-benzoic acids, behave in exactly the same manner as the saturated fatty acids ; while those of the latter, e.g. the di- and tetra- hydro-benzoic acids, resemble the unsaturated fatty acids. Cf. p. 349. The aromatic oxy-acids, e.g. the oxy-benzoic acids, which possess at the same time phenolic and acid characters, mani- festly contain phenol-hydroxyl {ie. hydroxyl which is linked directly to the benzene nucleus) in addition to the carboxyl group or groups; they are capable of yielding salts either as acids or as phenols, but otherwise they correspond in many points with the alcohol-acids of the fatty series. The true aromatic alcohol-acids, such as mandelic acid (phenyl-glycoUic acid), which correspond completely with the latter, manifestly contain their alcoholic hydroxyl not in the benzene nucleus, but in the side chain, as is also the case with the aromatic alcohols. Nomenclature. The most rational nomenclature* is the desig- nation of the aromatic acids as carboxylic acids of the original hydrocarbons in question, e.g. phthalic acid is benzene-dicarb- oxylic acid. Many names, such as xylic acid, are taken from those of the hydrocarbons into which the carboxyl has entered, while others, such as mesitylenic acid, indicate the hydrocar- bons from whose oxidation the acids result. An important principle as regards nomenclature depends upon the fact that aromatic acids can be derived from almost every fatty acid of any consequence by the exchange of H for C5H5, e.g. : CHg-COjH, acetic acid; CgH5-CH2-C02H, phenyl-acetic acid. There thus exist phenylated acids analogous to the acids of the acetic, glycollic, succinic, malic and tartaric series, etc. OH Atropic acid, CgHg — CJ^nO H' ^'^^ example, may be designated a-phenyl-acrylic acid, and so on. *For "official names" see p. 28. 440 XXV. AKOMATIC ACIDS. Properties. Most of the aromatic acids are solid crystalline substances, generally only sparingly soluble in water and therefore precipitable by acids from solutions of their salts, but often readily soluble in alcohol and ether. The simpler among them can be distilled or sublimed without decomposi- tion, while the more complicated, especially phenolic and poly-carboxylic acids, give up carbon dioxide when heated; e.g. salicylic acid, GgS^{0IL).C02H., breaks up thus into phenol and COg. Such a separation of carbonic anhydride is effected in the case of those acids which are volatile without decom- position bj'^ heating e.g. with soda-lime ; in polybasic acids the carboxyls may be split up in succession : OeH,(C02H)2 = 06H,(C02H) + CO, = C.U, + 200,. Occurrence. A large number of the aromatic acids are found in nature, e.g. in many resins and balsams, and also in the animal organism in the form of nitrogenous derivatives such as hippuric acid. Modes of formation. A. Of the saturated acids. 1. By the oxidation of the corresponding primary alcohols or aldehydes ; e.g. benzoic acid from benzyl alcohol. 2. By the oxidation of the benzene homologues and of all the compounds which are derived from these by substitutions in the side chain; also of all the derivatives of those com- pounds which contain halogen, nitro-, sulpho-, etc. groups, hydroxyl or carboxyl in place of benzene hydrogen : CeH5(CH3) yieldi 8 CbHsCCOsH) CeH^ICO.H)^ C^3(CH3)2(CA) CeH3(C02H)3 C8H,-CH,(NH,) CeH^-COsH CeH^CKCHs) CeHiCKCOjH) C,K,(NO,){C,U,) CeH4(N0i,)(C0jH) CeH3(OH),(CH3) CeH3(OH)2(CO,H) CeH,(CH3)(C0,H) C6H,(C0,H), C8H5-CH=CH-C03H CsH^-COjH. Should there be several side chains in the molecule, they are usually all converted directly into carboxyl by chromic acid, whereas by GENERAL MODES OF FORMATION. 441 using dilute nitric acid, this transformation can be eifected step by step, e.g. -. C6H4(CH3)2 yield first CeH4(CH3)(COjH) and then CeH^lCOaH)^ The xylenes Toluic acids Phthalic acids. Nevertheless the three classes of isomeric benzene derivatives with two side chains comport themselves differently. The para-compounds are the most readily oxidized to acids by chromic acid mixture and then the meta-, whereas the ortho-compounds are either completely destroyed by it (p. 359) or not attacked at all. The last-named may however be oxidized in the normal manner by nitric acid or perman- ganate of potash. The entrance of a negative group (and also of hydroxyl) renders more difficult the oxidation of an alkyl-group having the o-positiou with regard to it (cf. p. 422). 3. By the saponification of the corresponding nitriles (p. 438). CgHj-CN + 2B.p = CgHg.COaH + NHg. These Nitriles, which can be prepared from the ammonium salts of the acids in the same manner as those of the fatty series, result from the following syntheses : (a) By distilling the potash salts of the sulphonic acids with potassium cyanide or ferrocyanide (Merz), just as the nitriles of the fatty acids are formed from the alkyl sulphates (p. 117): CgHg.SOgK -f KCN = CgHj.CN -f SOgK^. Nitriles cannot as a rale be prepared from chloro-benzenes, etc. and KCN, (cf p. 367); the halogen is more readily replaced by cyanogen if sulpho-groups are likewise present. Or nitro-groups (in presence of halogens) can also be replaced, as in the case of the bromo-nitro-benzenes, (B. 8, 1.418). Benzyl chloride, CgHg — CH2CI, and all the haloid hydro- carbons which are substituted in the side chain, on the other hand, show the normal ready exchangeability of halogen for cyanogen : CgHs— CH2CI + KCN = KCl -t- CgHg— CH2.CN Benzyl cyanide. (6) By heating the mustard oils with copper or zinc dust ( Weith) : CeH5.NCS -I- 2Cu = CbHjCN -t- Gu^S. (c) By the molecular transformation of the isomeric iso-nitriles at a 442 XXV. AROMATIC ACIDS. somewhat high temperature: (C8H5.NO = C5Hs.CN). (d) By diazotizing the primary amines, and replacing the diazo-group by cyanogen, according to the Sand/meyer reaction (p. 396); or by first con- verting them into iso-thiooyanates or iso-nitriles, and treating these as given in (6) or (c). (e) By eliminating the elements of water from the oximes of the alde- hydes by means of acetyl chloride : Benzaldoxime, CeH5.CH=N.0H = CcHj.ON + H2O. 4. Syntheses effected by the action of carbonic acid or its derivatives : (a) Benzoic acid, etc. is produced by the action of carbon dioxide upon mono-bromo-benzene, etc. in presence of sodium, {KehiU) : CgHsBr + CO2 + 2Na = CgHj.COaNa + NaBr. (S) By the action of phosgene, COClj, or also of COj, upon benzene and its homologues in presence of AlgClg {Friedel and Crafts) : CgHs + COCI2 = CeHg.COCl + HCl. Acid chlorides are first formed here, which are then to be decomposed by water. By the further action of these chlorides upon benzene in presence of ALjClg, ketones result (see benzophenone.) GOCI2 acts with particular ease upon tertiary amines ; CsH5.N(CH3)a + COCI2 = CsH,[N(CH3)2].COCl + HCl. (c) By the action of carbamic chloride, CI — CO.NH2, upon benzene (or phenol) in presence of AIjCIb, there result in an analogous manner the amides of the aromatic acids, which are readily saponified {Oatterman, A. 214, 29) : CcHe + CI— CO.NH2 = CsHs— CO.NH2 + HOI. (d) By the action of sodium upon a mixture of brominated benzenes and chloro-carbonic ether (Wmtz); in this case the compound ethers are first formed, but these are easy to saponify : CeHgBr + C1.C02(C2H5) -t- 2Na = C6H5.C02(C2H5) -1- NaBr + NaCl. («) The phenolic acids are produced by passing carbon dioxide over heated sodium phenate, (Kolbe ; see p. 455) : CgHj.ONa -I- CO2 = C6H^(0H).C0jNa. GENERAL MODES OF FORMATION. 443 In the case of the phenols of higher atomicity, e.g. resorcin, it often suffices merely to heat with a solution of ammonium carbonate or potassium bicarbonate, (B. 13, 930). Chlorocarbonic ether acts in a similar way. (/) i^-Oxy-acids are formed by the action of carbon tetra- chloride upon phenols in alkaline solution, (B. 10, 2185) : CgHjONa + CCli = C6H^(OH).CCl3 + NaCl. C6H^(OH).CCl3 + 4NaOH = C6H^(OH).C02Na + 3NaCl + 2TI2O. When chloroform is employed, the aldehydes of these (o- and p-) oxy-acids result in an analogous manner : CgHg.OH + CHCI3 + SNaOH = CoH^.(OH)CHO + SNaCl + 2H2O. Methylene chloride, CH^Clj, also shows a similar behaviour, with the formation of aromatic oxy-aloohols. (3) By heating the sulphonates with sodium formate ( V. Meyer) : C5HJ.SO3K + HCO2K = C6H5.CO2K + HSO3K. 5. Aceto-acetic ether and malonic ether syntheses, etc. (a) For the formation of phloroglucin-trioarboxylic ether from sodio- malonio ether, see p. 354. Sodio-aceto-acetio ether yields a complicated benzene derivative in an analogous manner (B. 18, 8460). (6) For the production of hydroquinone - dicarboxylic ether, etc. from ethyl succinate or from brom-aceto-acetic ether, see p. 354. (c) For the action of aceto-aoetio ether upon phenols, see p. 444. (d) Aceto-acetic ether acts upon the haloid derivatives which are substituted in the side chain, e.g. benzyl chloride, exactly as in the fatty series, with the formation of the more complicated ketonic acids, which again are capable of undergoing either the "acid decomposition" or the "ketone decomposition" (p 244), e.g. : CeHg— CH2CI + CH3— CO— CHNa— CO2R = CH3— CO— CHCCyH^)— CO2R + NaCL > , ' Eenzyl-aceto-acetic ether. CH3— CO— CH(C,Hy)— CO2R + H2O = CgH^- CH2— CH2-CO2R + CH3.CO2H. Phenyl-propionic ether. 444 XXV. AROMATIC ACIDS. 6. Alcobol-acids and ketone-acids are formed by exactly the eame methods as in the fatty series (p. 222), e.g. mandelio acid by the com- bination of hydrocyanic acid with benzaldehyde, and saponification of the resulting nitrile, (B. 14, 239, 1965) : CeHj— CHO + HON = CsHs— CH(OH)— CN ; or, from o-chlorophenyl-acetic acid, (B. 14, 239) : CsHj-CHCl— COjH + KOH = CsH^— CHlOHj-COjH + KCl. 7. Hydro^-cumaric acid, hydrocinnamic acid, ^-oxyphenyl- acetic acid, etc. are produced by the decay of albumen, (B. 16, 2313). B. Of the unsaturated acids. 1. From the mono-haloid substitution products of the saturated acids in the normal manner (p. 178); similarly from the corresponding nitriles, primary alcohols, etc., as in the case of the saturated compounds. 2. According to the so-called Perhin reaction, by the action of aromatic aldehydes upon fatty acids. Thus, when benzalde- hyde is heated with acetic anhydride and sodium acetate, cinnamic acid is formed : C6H5.CHO-l-CH3.C02lSra = CeHg— CH=CH— COaNa -f HjO. The acetic anhydride only acts as a dehydrating agent in this instance, the reaction taking place between the sodium acetate and the aldehyde (cf. A. 216, 101). Oxy-acids are formed as intermediate products here by a reaction similar to "aldol condensation" (p. 14.5) ; in the above case, for instance, ;8-phenyl- hydraorylic acid, CeHj— CH(OH)— CH^— OO^H. This reaction also takes place with the oxy-aldehydes, with the homo- Icgues of acetic acid, and also with dibasic acids, e.g. malonic. Cinnamic acid is similarly produced by the action of sodium upon a mixture of benzoic aldehyde and ethyl acetate (B. 23, 976). 8. Cinnamic acid results in an analogous manner by the action of benzal chloride upon sodium acetate (Caro) : CsHs-CHClj -I- CH,— COaH = CeHj— CH=CH-COs,H + 2HC1. 4. By the action of aceto-acetio ether upon the phienols in presence of concentrated H2SO4, there are formed unsaturated phenolic acids or their anhydrides (B. 16, 2119; 17, 2191), e.g.: CeH,(OH) H- (OH).C(CH,)=CH ^ C(CH3)=CH ° " HO— CO ° ^0 —CO (Pseudo-torm.) Methyl-cumarin. MONOBASIC AEOMATIC ACIDS. 445 4a. Malic acid acts upon phenols ia presence of H2SO4 in an analogous manner, reacting here probably as the half-aldehyde of malonie acid, CHO-CH3— CO2H (=malic acid, C2H3(OH)(COaH)2, -COjHa [see p. 240]), {v. Pechmann, B. 17, 929) : 0=CH-CH2 _ ^CH=CH HO. CO ~ ^'6^4Vq _^q CA.OH + "=^^-^^» = 0,H, j 0-, m-, p-Toluio acids, Hydrocinnamic acid, Hydratropic acid, . a-Xylic acids, . . . Ethyl-benzoic a (^l etc. CeH,(OH)- CH=CH-C02h| 1:3:5, etc, ; CO3H in position 1. SUliaiARY. 447 Aromatic Acids. 3. Diatomic saturated Phenolic Acids. M.Pt. O f Salicylic acid (1:2) l o" Im-, p-Oxybenzoic acidsj [Anisic acid (1 : 4), Cs {Oxy-toluie acids, etc. Hydro-para-cumaric acid (1 :4), (Tyrosine (1:4), etc. C6H,(0.CH3).C02H] C6H3(CH3)<^Q jg- CsHKcH.— CH„- CO.H C6H4CO + HjO. Such a. formation of intramolecular anhydride is of very frequent occurrence in ortho-compounds of this kind, in contradistinction to the m- and ^-compounds (see Indole). Theoretically it may take place in the above instance in two different ways, viz., either by the elimination of a hydrogen atom of the amidogen together with OH, or of both of the amidogen H-atoms with 0. These two cases are distinguished by Baeyer aa " Lactame formation " and " Lactime formation." Oxindole is a lactame, while isatin, CgH4<^pj^C.0H (p. 471), is a lactime of o-amido-phenyl-glyoxylio acid (p. 460). Both lactames and lactimes contain hydrogen which is readily replaceable ; in the former case it is present in the amido-group and in the latter in the hydroxyl. If the compounds which result from the replacement of hydrogen by alkyl are very stable, the alkyl in them is linked to the nitrogen and they are derivatives of the lactames ; if on the contrary they are easily saponifiable, the alkyl is linked to oxygen and they are ethers of the lactimes. 1. Dimethyl-benzoio acids, xylene-carboxylie adds, CgH3(CH3)2(C02H). Of these six are possible and four are known. Mesitylenlc acid, (COgH : CHj : CHj = 1:3:5), results from the oxidation of mesitylene, and Xylio and Para-xylic acids from that o£ pseudo-oumene. Isomeric with them are : 2. The Phenyl-propionic acids, GJl^—G^^—GO^R. These may be either a- or ;S-derivatives of propionic acid. ^-Phenyl -propionic acid or Hydrocinnamic acid, HYDROCINNAMIC ACID; CINNAMIC ACID. 453 CgHg — CH2 — CHg — OOjH, results from the action of sodium amalgam upon cinnamic acid and from the decay of albuminous matter. Fine needles; M. Pt. 48°, B. Pt. 280°. Many substitution products etc. of this acid are known, among which may be mentioned o-mtro-cinnamlc dlbromlde, *-'6H4<^pTiTj PHBr CO H' * compound nearly related to indigo (p. 470) ; further, Fhenyl-a-amido-proplonic acid (phenyl-alanine), CsHj— CHj— CH(NH2)— COjH, and Phenyl-^-amido-propionic acid, CjHb — CH(NH2) — CHj — COjH, both of which can be prepared syntheti- cally, the former being likewise produced by the decay of albumen and by the germination of {e.g.) Lupinus luteus. NTT The isomeric o-Amido-liydroclimamlc acid, CsH^"^^, -^^qq ct is not stable, but goes immediately into its lactame, hydro-carbostyril, CgHgON, a quinoline derivative. Hydratropic acid, a-Phenyl-propionie acid, OeHs — CH(CHs) — COjH, is obtained — as its name implies — by the addition of hydrogen to atropic acid. It is liquid and volatile with steam. Adds, CiqHijOj. Among these may be mentioned Cumic acid or p-isopropyl- benzoic add, CgH4(C3H^)(C02H), which is obtained by oxidizing Eoman oil of cumin with permanganate of potash; (this oil contains — in addition to cymene — its aldehyde, cumic alde- hyde). It also results from the oxidation of cymene in the animal organism, the propyl group being here changed into the isopropyl one. It crystallizes in plates, boils without decomposition, and yields cumene when distilled with lime. The isomeric normal Propyl-benzoic acid has also been prepared (see p. 364). 2. Monatomic unsaturated acids. 1. Cinnamic acid, CgHgO^, = CfiHs— CH=CH— COgH, (Trommsdorf, 1780), occurs in Peru and Tolu balsams and also in storax, and may be prepared as given at p. 444. It crystal- lizes- in needles or prisms, readily soluble in hot water; M. Pt. 133°, B. Pt. 300°. When fused with potash, it is split up into 454 XXV. AROMATIC ACIDS. benzoic and acetic acids, going into the former also upon oxidation. It yields salts, compound ethers, etc.; also HC1-, HBr-, HI-, C10H-, Brj- etc. addition compounds, e.g. cinnamic dibromide (phenyl -dibromo- propionic acid), CgHj — CHBr — CHBr — OOjH. Further, the hydrogen in the benzene nucleus may be replaced by CI, Br, NOg, NHj, etc. Theoretically, a second stereo-isomerio cinnamic acid should exist, accord- ing to the formulae : — • H — G — Cells CeHfi — C — H (I.) II and (II.) II H— C— COaH H— C— CO2H (cf. pp. 24 and 180). As a matter of fact an AUo-cinnamic acid (M. Pt. 68°; present in coca-leaves) is known, which is readily convertible into ordinary cinnamic acid, and which can be prepared from phenyl-propiolic dibromide; it probably corresponds therefore to formula (I.) and cinnamic acid to formula (II.). Besides these there is a dimorphous (physically isomeric) form, " Iso-cinnamic acid," M. Pt. 57°, which changes slowly into allo-cinnamic acid on standing {IMermann, B. 33, S4, 2S, 89, 950; also B. 23, 3130). 0- and ^-Nitro- cinnamic acids, C5H4<^pTT?_pTT pQ rr the first of which is of importance on account of its relation to indigo, result from the nitration of cinnamic acid. On reduction the former yields - Amido - cinnamic acid, CgH4<^Qjj|_Qjj QQ TT (fine yellow needles), which readily gives up water and goes into its lactime carbostyril (a-oxy- • T \ nvr /CH=C(OH) qumolme), CgH^^ j^^gg • The radicle of cinnamic acid, i.e. (CeHj — CH=CH — CO), is termed "cinnamyl," and the group (CeHs — CH=CH), " cinnamenyl." 2. Atropic acid, CgHsOu, is a decomposition product of atropine. It crystallizes in monoclinio tables and can be distilled with steam. It breaks up into formic and o-toluic acids when fused with potash, this decomposition taking place at the point of the double bond, as in the cases of cinnamic acid and the unsaturated acids of the fatty series. 3. (7)-Phenyl-isocrotonio acid, CeHs— CH=CH— CHj— COjH, results upon heating benzaldehyde with sodium succinate and acetic anhydride {W. H. Perhin, sen.) : CHj— CO2H ^C— CO2H CeHs— CHO -1-1 - H2O = C„H— CH | CHj— COjH CHs— CO2H Intermediate product. = C0H5— GH I + COa. CHj— COsH PHENYL-PROPIOLIC ACID; PHENOLIC ACIDS. 455 It is of interest on account of its conversion into o-naphthol upon boiling (see p. 473). 4. Phenyl-propiolic acid, CgH^O^, = C5H5— C=C— COjH (Glaser, 1870), is formed by the addition of bromine to ethyl cinnamate and subsequent heating of the dibromide, CgHj— CHBr=CHBr— CO2C2H5, so obtained with alcoholic potash (just as ethylene is converted by bromine into ethylene bromide, and the latter decomposed into acetylene by potash). It crystallizes in long glancing needles which can be sublimed; M. Pt. 136-137°. When heated with water to 120°, it breaks up into COg and phenyl-acetylene (p. 366). It can be reduced to hydrocinnamic acid and transformed into benzoyl-acetic acid. o-Nitro-phenyl-propiolic acid,C(;H^<^^ ^^ qq jt (Baeyer), is prepared in a manner analogous to that just given, viz., by the addition of Br^ to ethyl o-nitro-cinnamate and treatment of the resulting bromide with alcoholic potash, (A. 213, 240). It is employed technically on account of its relation to indigo (see p. 470). It breaks up into CO^ and o-nitro-phenyl-acetylene upon boiling. 3. Diatomic (saturated) Phenolic Acids. For modes of formation, see p. 442. These acids may also be obtained by the oxidation of the homologues of phenol and of the oxy-aldehydes, which is effected, among other methods, by fusing with alkalies. The phenolic acids form salts both as carboxylic acids and as phenols, salicylic acid, for instance, the two following classes : C6H4 which is isomeric 460 XXV. AROMATIC ACIDS. with mandelio acid, is unstable in the free state; as an orthc-com- pound, it readily goes into its intra -molecular anhydride Phthalide, C8H4<^I^Q^^O. The latter is a S-Iactone (see p. 233), and results from the reduction of phthalio acid or its chloride. It crystallizes in needles or plates and can be sublimed unaltered. 3. Tropic acid, CsHi„Os, = OoH5-CHCa,) .CH=CH-CH=CH-COjH, a decomposition product of piperine (p. 528), which crystallizes in long needles. 464 XXV. AROMATIC ACIDS. Trioxy-dnnanvic adds. £sculetln, C8H2(OH)2<[p__A_., and its isomeride Daphnetin are dioxy-cumarins, their gluoosidea (^soulin and Daphnin) ooeurring respectively in the horse chestnut and in Daphne varieties. Like the dioxy-cinnamic acids they may also be prepared synthetically (B. 16, 2119; 17, 2187, etc.). B. Dibasic Acids. The dibasic acids occupy exactly the same position in the aromatic series as the dibasic acids G^B.^_J3t do in the fatty; they form two series of each derivative (compound ethers, chlorides, amides, etc.). The two carboxyl groups, which according to theory they contain, may either both be in the nucleus or in the side chain or chains, or be divided between them. Dibasic phenolic acids can of course occur here also. Benzens-dicwrboxi/lic acids, C8H4(C02H)2. 1. Phthalic acid, C6H4(C02H)2 (1 : 2), {Laurent, 1836), results when any o-di-derivative of benzene, which contains two carbon side chains, is oxidized by HNO3 or KMnO^, but not CrOg (cf. p. 359); it is formed in especial by the oxidation of naphthalene by nitric acid, and also of anthracene derivar tives. In preparing it on the large scale the naphthalene is iirst converted into its tetra-chlor-addition product, CiqEjCI^, and this then oxidized. It crystallizes in short prisms or plates, M. Pt. 213°, readily soluble in water, alcohol and ether. When heated above its melting point, it goes into the anhy- dride (see below). It loses one mol. COg when heated with a little lime, and two mols. when heated with excess, yielding benzoic acid or benzene. Chromic acid disintegrates it com- pletely, while sodium amalgam converts it into dihydro-, tetrahydro-, and finally hexahydro-phthalic acid (see below). Its barium salt, CeH^(C02)2Ba, is difficultly soluble in water. PHTHAUO AND HYDRO-PHTHALIC ACIDS. 465 Phthalio anhydride, CeH4<^QQ^0, crystallizes in magni- ficent long prisms whicji can be sublimed; M. Pt. 128°, B. Pt. 284°. It is used in the preparation of eosin dyes (see Fluorescein). Fhthalimide, G^Si<^„Q^NTI, corresponds to auccinimide in many respects. The chloride, Phthalyl chloride, which results from the action of PCI5 upon the acid, appears strangely enough not to have the constitution Gq1I^{C0G1)2 but that of GBE^<^^Q^yO, as it yields, for instance, phthalo-phenone, G^'E^C=CCeH^. The following are isomerides of indigo : indigo red (in the indigo of commerce), indirubin (also called indigo-purpurin), and indin ; the last two of these have been prepared synthetically. There have also been prepared dichlor-, dibrom-, tetrachlor-, diethyl-, etc. substitution products of indigo, also indigo-dicarboxylic acid, (B. 1!^.. 458). ISATIN. 471 Derivatives of Indigo. CsHjNOj CsHjNOj CsH^NO J C8HtN(C0i!H) { CsHslCHaJN Isatin Dioxindole .... Oxindole .... Indoxyl Indole Indole - carboxylio acid («.Sr./3-) Skatole . . . . (and its isomers) CeH,C0 C.H4<^^^>C0 C6H4^^ 1. Isatin, C5H4<^pQ^C(OH), is easily prepared by oxidizing indigo with nitric acid {Erdmann and Lament, 1841 ; of. also B. 17, 976). It likewise results from the oxidation of dioxindole, of oxindole (indirectly), and of indoxyl (Baeyer) ; also by boiling o-nitro-phenyl-propiolic acid with alkalies. It crystallizes in reddish-yellow monoclinic prisms, which are only sparingly soluble in cold water, but more readily in hot water and in alcohol to a brownish-red solution. Caustic potash dissolves it at first to a violet solution, with the formation of the compound OgH^NO.OK, but this changes into potassium isatate, CgH4(NH2) — CO — COOK, upon warm- ing (p. 460). Isatin is the lactime of isatic acid (o-amido- benzoyl-formic acid) (p. 452); for arguments in favour of the lactame formula, however, cf. B. 23, 253. For its synthesis from o-nitro-benzoyl-formio acid, see p. 460, and for its reaction with thiophene, p. 331. Chloro-, Bromo- and Nitro- isatins are also known. As a ketone, isatin forms with ammonia Imesatin, CsHsNOlNH)", by the exchange of O for NH; and with 472 XXVI. INDIGO GROUP. hydroxylamine, Isatoxime, CgH4<^p, -vr q-tt^^COH (yellow needles), which also results from oxindole and nitrous aoid. The homologous Methyl-isatin can be obtained from p-toluidine and diohlor-aoetio aoid, a tolyl derivative of Methyl-imesatin being formed here in the first instance, (B. 18, 190). Chromic acid oxidizes isatin to Isatolc acid (anthranll-carboxylio acid), CjHjNOj, = C6H4 it (''^- P- ^^^)- JN — OOgil Isatin yields a methyl ether, Methyl-isatin, C8H4<_qq>C.O.CH3, which is prepared from isatin-silver (a red powder) and methyl iodide, and forms blood-red crystals ; it dissolves in alkali to isatic acid and methyl alcohol, i.e. the water abstracted in the formation of lactime is again taken up, and the methyl ether is saponified. From this reaction the above constitutional formula of isatin follows. An isomeric compound, Methyl-pseudo-isatin, is derived from an unknown isomer of isatin, pseudo-isatin, C5H4<^p,-. ^CO, the lactame of amido-benzoyl-formic acid. This results e.g. by the action of sodium hypobromite upon methyl-indole and subsequent boiling with alcoholic potash ; since it dissolves at once in alkali to Methyl- isatic aoid, C6H4(NH.CH3) — CO — CO2H, it has the constitution C,H4cO, (B. 17, 559). Isatin chloride, C5H4<^^ ^C. CI (from isatin and PCls), crystallizes in brown needles which are soluble in alcohol and ether with a blue colour. It goes into indigo when treated with hydriodic acid, or with zinc dust and glacial acetic acid (synthesis of indigo, Baeyer) ; 2C8H4NOCI + 2H2 = CisHioNjOj + 2HC1. 2. Dioxindole, C5H4<^ -ji-rT '^CO, is the intra-molecular anhydride of the unstable o-amido-mandelic acid (p. 459). It is obtained from the reduction of isatin (into which it is again easily oxidized) with zinc dust and hydrochloric acid. Readily soluble colourless prisms, M. Pt. 180°. It possesses both basic and acid properties (two H-atoms being replaceable), and forms a nitroso-compound, acetyl derivative (the acetyl being joined to the N), etc. NTT 3. Oxindole, CgH^^pTj ^00, the lactame of o-amido- plienyl-acetic acid, is formed by the reduction of o-nitro-phenyl- acetic acid (p. 451); also by that of dioxindole with tin and hydrochloric acid. Colourless needles, M. Pt. 120°, readily OXINDOLE ; INDOXYL. 473 oxidizable to dioxindole, and therefore of faintly reducing character. Oxindole is at the same time an acid and a base, dissolving both in alkalies and in hydrochloric acid. Baryta water at a somewhat high temperature transforms it into o-amido-phenyl-acetate of barium. The imido-hydrogen is exchangeable for ethyl, acetyl, the nitroso-group, etc. 4. Isomeric with oxindole is : Indoxyl, CgH4<^Q,QTT>^CH, which is obtained by the separation of COg from indoxylic acid, from phenyl-glycocoll (p. 470), and by fusing indigo with potash, and which is often present in the urine of the carnivora as potassium indoxyl- sulphate or urine-indican, C8H|jN.O.(S03K). It is a thick liquid, moderately soluble in water with yellow fluorescence, and not volatile with steam. It dissolves in concentrated hydrochloric acid to a red solution. It is very unstable, quickly becoming resinous, and readily changing into indigo when its alkaline solution is exposed to the air, or when ferric chloride is added to its solution in hydrochloric acid. It yields a Nltroso-compound, CeH4<^j-,,VjTT>'^CH, of the same character as the nitrosamines, and therefore it contains an imido- group ; further, its relation to indoxyl -sulphuric acid shows that it contains an alcoholic hydroxy!, from which its constitution follows. Potassium Indoxyl-sulphate is prepared synthetically by warming indoxyl with potassium pyrosulphate ; it crystallizes in glancing plates and breaks up again backwards when warmed with acids. Ethyl-indoxyl results from indoxyl by the exchange of the hydroxylio hydrogen for C2H5. Derivatives of the hypothetical Fseudo-indoxyl, ^^i^CO ^^^2' ^""^ *'^° known, some of them being convertible into indigo derivatives {e.g. diethyl-indigo). NTT Indoxylic acid, CgH4<^Q,Q-CT,^C — COjH, the carboxylic acid of indoxyl, forms white crystals, is converted into indigo by ferric chloride, and breaks up into indoxyl and COj when fused. It is obtained from its ether : Ethyl indoxylate, by fusing with soda. The latter compound, which crystallizes in thick prisms, M. Pt. 120°, also results — among other methods — from the reduction of ethyl-o-nitro-phenyl-propiolate with ammonium sulphide. The mother substance of the whole indigo group is : 474 XXVI. INDIGO GROUP. 5. Indole, C6H^<^g>CH {Baeyer, 1868), which is ob- tained by distilling oxindole with zinc dust; by heating o-nitro-cinnamic acid with potash and iron filings ; by the action of sodium alcoholate upon o-amido-chloro-styrene (from o-nitro-cinnamic acid -f CIOH - CO^) (B. 17, 1067) : C6H4<^HLcjjCi-l-NaO.Ci,H5 = C^4<^^>CH-HNaCl-HC2H50H; by the pancreatic fermentation of albumen; together with skatole by fusing albumen with potash; and by passing the vapours of various anilines, e.g. diethyl-o-toluidine, through red-hot tubes, etc. It crystallizes in glancing plates, M. Pt. 52°, volatilizes readily with steam, and has a peculiar faecal- like odour. It is weakly basic, colours a pine shaving which has been moistened with HCl cherry-red, gives a red pre- cipitate, which consists partly of the so-called nitroso-indole, [C8H|5N(NO)]2, with NgOg (a delicate reaction, seeB. 22, 1976), and yields acetyl-indole when acetylated. These last reactions show that indole contains an imido-group. Indole may be looked upon as pyrrol which has two C-atoms in common with a benzene nucleus, as in the case of naphthalene: (n)NH CH (a) Ch/\°/\cH ^„ (^) CnLJi^^cH • = CeH'^CB., results from phenyl -methyl - hydrazine (p. 406) and pyroracemio acid, at first in the form of the car- boxylio acid. It is an oil, B. Pt. 239°. Indole-carbozylic acids, C8H6N(C02H), can be synthetized, e.g. the ^-acid (together with the a-), CaHi<[^p,pQ tti^OH, from indole by ^oZJe's method, i.e. by acting on the latter with sodium and carbon dioxide. The homologous Skatole-oarboxylic acid, C9H8N(C02H), and also Skatole- acetic acid, CgHsNICHa — CO2H), are produced by the decay of albuminous substances. For the transformation of indole into quinoline derivatives, see B. 20, 2199, 2608; 21, 1940; 23, 2302, 2628; 25, Kef. 111. Cumarone and Indazole groups. For these see Appendix, p. 567. The compounds of the aromatic series which have been treated of up to now are derived, with the exception of indigo, from one molecule of benzene, i.e. they contain one benzene nucleus. There are however a vast number of compounds known which contain two or more benzene nuclei. 1. When two phenyl groups are joined together directly, there results Di-phenyl, CgHg— CgHj (Group XXVII.). 2. When a methylene group, i.e. a carbon atom, connects two phenyl groups, we obtain Diphenyl-methane,CgH5 — CHg — CgHj (Group XXVIII. ). 3. Should three benzene residues be joined in a similar manner to methine, Triphenyl-methane, CII(OgH5)3, is formed (Group XXIX.). 4. Benzene nuclei may likewise be connected through two or more carbon atoms, as in Di-benzyl, CgHg — CHg — CH^ — CgHg (Group XXX.). 5. Lastly, the benzene nuclei may be so grouped together that two carbon atoms are common to two of them, as in anthra- cene and naphthalene, etc. (Group XXXI. etc.). From all the hydrocarbons mentioned under the above para- graphs 1-4, homologues are derived j all of these with the exception of diphenyl (which possesses the benzene character only) have like toluene partly a benzene and partly a 476 XXVII. DIPHENYL GROUP. methane character, and yield completely analogous derivatives, like the benzene hydrocarbons in the narrower sense of the term. XXVII. DIPHENYL GROUP. Summary. t. Diphenyl, CeHj— CeHj, = CijHu p-Chloro-diphenyl . 0-, p-Nitro-diphenyl Amido-diphenyl Diphenylol , Cyano-diphenyl . . Diphenyl-carboxylic acid CuHg(OH) CijHsCCOsH) p-p-Diohloro-diphenyl ^a = p-p-XDmitvo- ^P = o-^-j diphenyl ip-p-) = Benzidine l( o-P-) = Dipheuyline Carbazole Diphenols . . . Diphenylene oxide Dicyano-diphenyl Diphenyl-dicarboxylic acid C12H3CI2 C^HslNOj), C5H4- C„H, '>NH C„H8(0H), C5H4 Cl2Hg(C02H)3 2. Phenyl-tolyla, CsHj— CeH4.CH3. 3. Ditolyls, CsH4(CH3)-C6H4(CH3), etc. 4. Diphenyl-benzene, €5114(05115)2. 5. Triphenyl-benzene, OeH3(CcH5)3. Diphenyl, C^jHio {Fittig, 1862). When bromo-benzene in ethereal solution is treated with sodium, a synthesis of diphenyl, analogous to the Fittig reaction (p. 357), is effected : 2C6H5Br + Naj C„H5-CbH, + 2NaBr. Diphenyl also results when the vapour of benzene is led through a red-hot tube, this being the most convenient mode of preparing it. It is contained in coal tar. Large colourless DIPHENYL; BENZIDINE. 477 plates, readily soluble in alcohol and ether; M. Pt. 71°, B. Pt. Chromic acid oxidizes diphenyl to benzoic acid, one of the two benzene nuclei being destroyed, thus leaving only one carbon atom joined to the other benzene residue. From this and from its synthesis, the constitutional formula of diphenyl follows as CjHj — CgHj. Derivatives. (See Summary; also Schultz, A. 207, 311). Like benzene, diphenyl is the mother substance of an extended series of derivatives. Even the entrance of only one substituent produces isomers, since the latter may stand either in the o-, m-, or ;>-position to the point of junction of the two benzene residues. The same thing applies in still greater degree to isomeric di-derivatives, of which o-o-, p-p-, o-p- etc. compounds can exist. The constitution of these is elucidated either from their syntheses or from their products of oxidation ; thus a chloro- diphenyl, C12H9CI, which yields /j-chloro-benzoio acid when oxidized by chromic acid, is obviously p-chloro-diphenyl. The substituents take up the p-position for choice ; in di-derivatives the p-p- (and to a lesser extent the o-p-) position. Di-j'-diamido diphenyl, benzidine, Ci2Hg(NH2)2, = p^tt* -vrTT^ (Zinin, 1845), results from the reduction of di-ji-dinitro- diphenyl (the direct nitration product of diphenyl); also, together with diphenyline, by the action of acids upon hydrazo-benzene, the latter undergoing a molecular transfor- mation : CgHj— NH— NH— CeHj = NH^— CeH^— CgH^— NH^ ; it is consequently formed directly from azo-benzene by treating it with tin and hydrochloric acid. Benzidine is a diatomic base which crystallizes in colourless silky plates, readily soluble in hot water and alcohol and capable of sublimation ; M. Pt. 1 22°. It is characterized by the sparing solubility of its sulphate, Ci2Hm(NH2)2.S04H2, and by various colour reactions. Like its homologues (tolidine. 478 XXVIL DIPHENYL GROUP. etc.), it is of special importance in the colour industry, since, by coupling its diazo- compound (tetrazo-diphenyl chloride) with naphthol-sulphonic or naphthylamine-sulphonic acids, etc., colours are produced which dye unmordanted cotton directly, the so-called "substantive" or cotton dyes. To this class belongs the dye Congo, 0«H,-N=N-C,„H,(NH,)(S03Na) ^ J' 8 . CgH,— N=N— Ci„H5(NH2)(S03Na)' prepared by means of naphthionic acid (p. 504), and the dye Chrysamiue Gt, prepared with salicylic acid. (I) The isomerio Sipheuyline, | (i) (2) , results from o-p-dinitro-diphenyl, CsHj— NHj and also as a by-product in the preparation of benzidine from azo-benzene. Needles, M. Pt. 45°. Its sulphate is readily soluble. Carbazole, OkHsN, = •" *J>NH, the imide of diphenyl, is contained in coal tar and in crude anthracene. It is formed e.g. by distilling o-amido- diphenyl over lime at a low red heat, or by passing the vapour of diphenyl- amine or of aniline through red-hot tubes, just as diphenyl is obtained from benzene: (C8H5)2]SrH - (CeHJjNH -t- H2. It crystallizes in colourless plates sparingly soluble in cold alcohol, M. Ft. 238°. It distils unchanged and is characterized by its great capability of sublimation. Concentrated sulphuric acid dissolves it to a yellow solution, and it forms an acetyl- and a nitro-compound, etc. The nitrogen in it occupies the di-ortho-position; it thus appears, like indole, to be a pyrrol derivative, and it shows, in fact, most striking analogies to the latter (B. 81, 3299). It is convertible into : p-Diamido-carbazole, Ci2H7N(NHj)2. For constitution, see B. 25, 128. The substantive dye Carbazole yellow is formed by the union of this com- pound with salicylic acid. Benzidine-niono-, di-, etc. Sulphonio acids, e.g. Ci2H8(NH2)2(S03H)2, are of technical importance in some cases, as are also Benzidine-sulphone, Ci2H|j(NH2)2(SOs), and its Sulphonio acids, the sulphone resulting from the action of sulphuric acid upon benzidine. The Dioxy-diphenyls, CuHaCOHjj, of which four isomeric modifications are known, result partly by diazotizing benzidine, partly by fusing diphenyl- disulphonic acid with potash, and partly by fusing phenol with potash or by oxidizing it with permanganate; in the last case hydrogen is separated and two benzene residues join together. Dipheuylene oxide, ■ >0, is obtained by distilling phenol with oxide CaUj^ COERULIGNONE; DIPHENIC ACID. 479 of lead; it ciyatallizes in plates which distil without decomposition (cf. e.g. B. 25, 2745). Hezozy-diphenyl, Ci2H4(OH)8 (silvery glancing plates), which dissolves in potash with a beautiful violet-blue colour, is the mother substance of Coernligiioue or Cedriret, CioHieOs, a violet-coloured compound which is formed when crude pyroligneous acid is purified with ohromate of potash, and also from the oxidation of the dimethyl-pyrogallol of beech-wood tar by means e.g. of potassic ferricyanide; in the latter case there is not only a joining together of the two benzene nuclei, but also a separation of hydro- gen, with the production of a linking of somewhat the same nature as that in peroxides : C H ^(^•^•^3)a 2CeH3 Coerulignone crystallizes in fine steel-grey needles soluble in concentrated sulphuric acid with a blue colour. Tin and hydrochloric acid convert it into Hydro-coerulignone, = tetramethyl-hexoxy-diphenyl, which is split up into methyl chloride and hexoxy-diphenyl on warming with concentrated hydrochloric acid (Lieiermann). The carboxylic acids of diphenyl are obtained (1) from the corresponding cyanides, which on their part are prepared by distilling the sulphonic acids of diphenyl with KCN, e.g. Di-p-diphenyl-dioarboxylic acid, Ci2Ha(COjH)2, a white powder insoluble in water, alcohol and ether; (2) by the oxidation of phenanthrene and similar compounds, e.g. Diphenlc acid, • , CaH^.COaH a di-ortho-compound, crystallizing in needles or plates which are readily soluble in the solvents just mentioned; M. Pt. 229°. Both of these are dibasic acids, which yield diphenyl when heated with soda-lime. The homologues of diphenyl are, like the latter, obtained by means of the Fittig reaction. Analogous to benzidine is o-Tolidine, Ci2Hg(CHs)2(NH2)2, M. Pt. 128°, whose diazo-compound unites with naphthionic acid to the red substantive dye, Benzo - purpurine 4 B. Similarly Sl-anisidine or dimethoxy- benzidine, C,2H6(O.CH3)2(NH2)2, combines with a-naphthol- a-sulphonic acid (which see) to form a blue substantive dye, Benzaznrine G. Appendix. By the action of sodium upon a mixture of j3-dibromo- benzene and bromo-benzene, there is formed Diphenyl-benzene, C6H4(C5Hs)2 (flat prisms, M. Pt. 205°), which is oxidizable to diphenyl-monocarboxylic and terephthalic acids. When hydrochloric acid gas is led into acetophenone, C6H6.CO.CH3, a reaction analogous to the formation of mesitylene from acetone ensues, and there is produced Triphenyl- benzene, C6Hs(C6Hs)3 (1:3:5; rhombic 480 XXVIII. DIPHENYL-METHANE GROUP. XXVIII. DIPHENYL-METHANE GROUP. Summary. Diphenyl-methane. (C6H5)j=CH.OH Benzhydrol. (CeH5)i=C0 Benzophenone. (CeH5),=CH-CH3 Diphenyl-ethane. (CeH^l^H-CO^H Dlphenyl-acetio acid. (CeH5)^C(0H)-C02H Benzylic acid. CflHg-CH2-CgH4-CH3 ToIyl-phenyl-methaneB. CeH5-CH(OH)-C6H4-CH3 Tolyl-phenyl-oarbinols. CeHj-CO-C6H4-CH3 Tolyl-phenyl-ketones. C^Hs-CHj-CeHi-COsH Benzyl-benzoio acids, etc. C^Hs-CHiOHj-CeHi-COaH Benzhydril-benzoic acids. CeHg-CO-CsH^-COjH Benzoyl-benzoic acids. Pluorene. Fluorenyl alcohol. Diphenylene ketone. Diphenyl-methane is derived from methane by the substitu- tion of two hydrogen atoms by two phenyl-groups, just as toluene is by the substitution of one. It consequently resembles the latter hydrocarbon in most of its relations, with this important difference that, as it no longer contains a CHj-group, it cannot yield an acid containing an equal number of carbon atoms in the molecule upon oxidation; combination with oxygen produces benzhydrol and benzo- phenone. As soon, however, as more carbon atoms are made to enter the molecule, the same conditions repeat themselves as in the case of toluene, xylene, etc., and the most various acids, alcohol-acids, ketone-acids, etc. can be obtained from the resulting homologues. Formation of diphenyl-methane and its derivatives. 1. Diphenyl-methane is produced by the action of benzyl MODES OF TfORMATION. 481 chloride upon benzene, in presence of zinc dust (Zincke, A. 159, 374), or of aluminium chloride (Friedel and Crafts) : CgHg — CHgCl + CgHj = CgHg — CHg — CgHj + HOI. The homologues of benzene, and also the phenols and tertiary amines, may be used here instead of benzene itself. In an exactly analogous manner diphenyl-methane results from the action of methylene chloride, CHjClj, upon benzene in presence of chloride of aluminium : CHijCIa + 2C6He = CH2(C6H5)2 + 2HC1. 2. Diphenyl-methane hydrocarbons are formed by the action of the fatty aldehydes, e.g. acetic or formic aldehyde, upon benzene, etc. in the presence of concentrated sulphuric acid {Baeyer, B. 6, 221) . Diphenyl-ethane. CH3— OHO + 2C6Hg = OHg— CH(CeH5); + H^O. . The acetic and formic aldehydes are employed here in the form of para- aldehyde and methylal. Formic aldehyde itself condenses with aniline to diamido-, and with dimethyl - aniline to tetramethyl - diamido - diphenyl- methane (which see). When aromatic aldehydes are used, triphenyl- methane derivatives result (p. 485). 2*. Aromatic alcohols react with benzene and sulphuric acid in an analogous manner ( V. Meyer) : CsHj-CH^.OH + CeHj = O^-B.^-CE^-O^H^ + H^O. Similar reactions have also been brought about by means of ketones, aldehyde-acids and ketone-acids on the one hand, and phenol and tertiary anilines on the otter. 3. Benzophenone is produced by the action of benzoic acid upon benzene in presence of PgOg {Merz, B. 6, 536) : CgHs-CO.OH + CgHg = CgHs-CO-CgHj + H,0. 4. Benzophenone and the analogous ketones result upon heating the mixed calcium salts of the aromatic acids, accord- ing to the general mode of formation 2 of the ketones; thus calcium benzoate heated alone yields benzophenone : CgH,.C02ca + CgH5.C0,ca = CgHg.CO.CgHg + CaCO,. Mixed ketones (p. 152) can be prepared in the same way. (606) 2H 482 XXVIIL DIPHENYL-METHANE GROUP. 5. Ketones are likewise produced by the action of benzoyl- chloride, CgHjCO.Cl, etc. upon benzene, etc. in presence of AljCIg {Friedel and Orafls; also Ador, B. 10, 1854): CgH5.CO.Cl + CfiHs = CeH5.CO.C6H5 + HCl. In this case also, as in method 3, phenols (or, better, phenolic ethers) or tertiary amines may be employed in place of the benzene hydrocarbons. &\ Since the acid chlorides are formed from the benzenes with carbonyl chloride and zinc chloride, these reagents may be used directly for the pro- duction of ketones, under suitable conditions. 6. The above ketones are, like all others, converted into their correspond- ing hydrocarbons by distilling over zinc dust, or by heating with hydriodic acid and phosphorus, etc. (cf. p. 46). 1. Diphenyl-methane, (C|3H5)2CH2, is most conveniently prepared from benzyl chloride, benzene and AljClg. It crys- tallizes in colourless needles of very low melting point (26°), is readily soluble in alcohol and ether, has a pleasant odour of oranges, and distils unaltered; B. Pt. 262°. It yields nitro-, amido-, and oxy- derivatives. ^ - Diamido - diphenyl- methane, CH2(C6H,NH2)2, is obtained by heating anhydro-tormaldehyde- aniline, 06Hs.N=OH2 (which see), with aniline and aniline salt. Lustrous silvery plates; M. Pt. 87°. It may be used for the preparation of fuchsine. By the action of bromine, aided by warming, Siphenyl-bromo-methane, (C6Hs)2CHBr, is obtained, and when this latter is heated with water to 150°, it passes into: Benzhydrol, diphenyl-carbinol, (CoHsjaCH.OH, which also results from benzophenone and sodium amalgam. It crystallizes in glancing silky needles, possesses in every respect the character of a, secondary alcohol (forming compound ethers, amines, etc.), and is readily oxidizable to the correspond- ing ketone: Benzophenone, diphenyl-ketone, (CgH5)2CO. This compouna is prepared by distilling benzoate of lime (Pdligot, 1834), and also results directly from the oxidation of diphenyl-methane with chromic acid. It is the simplest pure aromatic ketone, and possesses the ketonic character in its entirety, being reducible to benzhydrol, yielding with PCI5 a dichloride, (03H5)2C=Cl2, and combining with phenyl-hydrazine, etc. It is characterized by being dimorphous, crystallizing in large rhombic prisms, M. Pt. 49° (stable), and also in rhombohedra, M. Pt. 27° (unstable) ; B. Pt. 267°. Fused potash decomposes it into benzoic acid and benzene, while red-hot zinc dust regenerates diphenyl-methane. Among its derivatives may be mentioned Di-p-diamido-benzophenone, CO(C6H4.NH2)2, which is obtained by boiling fuchsine with hydrochloric acid; M. Pt. 2-37°. The tetra-methyl compound, Tetramethyl-diamido- BENZOPHENONE DERIVATIVES; BENZILIC ACID. 483 benzophenone, CO[06H,N(CHa)2]2, results from the action of COClj upon dimethyl-aniline : COCI2 + 2C6H5.N(CHs)j = CO[C5H4N(CH,)Ja + 2HC1. It is nearly related to certain dyes, being converted into methyl violet (p. 491) upon further treatment with dimethyl-aniline, and into Auramine or its derivatives (beautiful yellow dyes) by ammonia or amine bases respec- tively (B. 20, 3260). The ^-position of the amido-groups has been proved. p-Dioxy-beuzophenone, [C6Hi(0H)a]C0, results among other methods from the decomposition of complicated benzene dyes, such as rosaniline and aurin, by heating these with water or with alkalies. It can be prepared synthetically from anisaldehyde (B. 14, 328), and therefore contains the hydroxyls in the ^-position ; see also B. 24, 1340. A derivative of o-dioxy- benzophenone is : Siphenylene-ketone oxide, Xanthone, C6H4<^ ^ ^CgH, (Oraebe, A. 254, 265), which is readily formed by abstracting the elements of water from phenyl-salicylic acid by strong sulphuric acid. Its dioxy-compound is Euxanthone, (HO)CjHs<^ ^ ^C6Hs(0H),whichispreparedfrom the yellow pigment Indian yellow or " Piuri," and which has also been synthetized. Bright yellow needles; M. Pt. 240°. A Trioxy-benzophenone is obtained on warming an alcoholic solution of pyrogallol with benzene trichloride or benzoic acid. It is a yellowish dye, which is used with a mordant (in the same way as alizarin). B. 24, 967, Ref. 378. Homologues of Diphenyl-methane; Fliurrene, 2. Diphenyl-ethane, (C6H5)2CH — CHj (unsymraetrioal, see p. 496), is obtained from benzene and para-aldehyde as given on p. 481. It is a liquid which boils without decomposition and which is oxidized to benzophenone by chromic acid. From it is derived : Benzilic acid, diphenyl-glycolUc add, (06H6)2=C(OH) — CO2H, which results by a molecular transformation upon fusing benzile (p. 497) with potash. It crystallizes in needles or prisms, soluble in H2SO4 with a blood- red colour, and is reduced by hydriodic acid to : Diphenyl-acetic acid, (C8H5)2=CH— CO2H (needles or plates), which on its part is obtained synthetically from phenyl-bromacetic acid, CeHj — CHBr — CO2H, benzene and zinc dust, according to mode of formation 1, p. 480; this yields proof of its. constitution. Both substances give benzophenone upon oxidation; here, therefore, as in the simpler cases, all the carbon is separated which is not directly linked to the benzene nuclei. ' 3. Tolyl-phenyl-metlianes, CbHs— CH2— CeH,— CHs. The p- and 0- compounds are obtained from benzyl chloride and toluene, as given at 484 XXVIII. DIPHENYL-METHANE GROUP. p. 480. They yield on oxidation the corresponding Tolyl-phenyl-ketones, and finally the Benzoyl-benzoic acids (see below). Tolyl-phenyl-ketones, Cells — C0^05H4 — OHs (see summary, p. 480). For preparation, see above. Of the ^-compound there exist two stereo- isomerio ^-Tolyl-phenyl-ketozimes, the investigation of which has contri- buted materially towards the development of the theory of nitrogen- iaomerism (see p. 158; also Eantzsch. B. 23, 2325, 2776): — CHa— CeHi— C— CsHj CHs— 0— CeH^— CH, (I.) II and (II.) II N-OH N— OH They yield structurally isomeric anilides by the Bechmcmn molecular transformation, the stable aii<»-tolyl-phenyl-ketoxime (formula L) giving toluio anilide, CH3 — CsH, — CO — NHCsHj (which is decomposable into toluio acid and aniline); while the unstable «y»-tolyl-phenyl-ketoxime (formula II.) gives rise to benzp-toluidide. Cells — CO — NHC6H4CH3 (decomposable into benzoic acid and toluidine), together with toluic anilide, because the conditions of the reaction are such that it partly changes into the anfi-modi- fication. (N.B. — ^The Bechmann transformation, jost alluded to, is brought about by treatment with a solution of hydrochloric acid gas in glacial acetic acid and acetic anhydride, or treatment in etheresil solntion with phosphorus pentaohloride, and then with water; cf. B. 20, 2581; 24, 52, 4028). Benzoyl-benzoic acids, CeHs— CO— CeH,— CO2H (B. 6, 907). Of these the o-acid, for example (M. Pt. 127°), has also been prepared synthetically by heating phthalio anhydride with benzene and AlaCle. They are reducible to benzhydril-benzoio acids (or anhydrides) and benzyl-benzoic acids (see summary). When the o-aoid is heated with P2O5 to 180°, it yields anthra- quinone, various transformations into the anthracene series having been effected from o-tolyl-phenyl-methane and -ketone. CeH4\ . 4. Fluorene, dipTienylene-methane, ■ >CH2, stands m the same rela- CeHi--^ tion to diphenyl-methane as carbazole (p. 478) does to diphenylamine; it is at the same time a diphenyl and a methane derivative. It is contained in coal tar, and is produced when diphenyl-methane is led through red-hot tubes (like diphenyl from benzene), and also by passing the vapour of diphenylene-ketone over red-hot zinc dust. It crystallizes in colourless plates with a violet fluorescence; M. Pt. 113°, B. Pt. 295°. The corres- ponding ketone, Biphenylene-ketone, CisH8=C0 (yellow prisms, M. Pt. 84°), is obtained e.g. by heating phenanthrene-quinone with lime, and is converted into Flnorenyl alcohol (p. 480; colourless plates, M. Pt. 153°) by nascent hydrogen, and into diphenyl-carboxylic acid, CeHj — CeHj — COjH, by fusion with potash. 5. Tolyl-phenyl-ethane, (C6H5)(C7H7)CH — OHj, results from the con- densation of styrene with toluene (B. 24, 2785). Styrene condenses with phenols in an analogous manner (!B. 25, 3889). XXIX. TRIPHENYL-METHANE GROUP. 485 XXIX. TRIPHENYL-METHANE GROUP. Triphenyl-methane, CH(C8H5)3, results from the entrance of three phenyl groups into the methane molecule; among its homologues are e.g. Tolyl-diphenyl-methane, CHC^^??^)?^ , Ditolyl-phenyl-methane, CH0 and CAo)\0; Phenol-phthalein. Fluorescein. in the latter case a molecule of water is split off from two hydroxyls of the two resorcin residues. Phthaleins of this kind (being oxy-phthalophenones) are converted by reduction into the oxj'-derivatives of triphenyl-methane-carboxylic acid, which are termed "Phthalines;" e.g. phenol-phthalein into dioxy-triphenyl-methane-carboxylic acid {i.e. phenol-phthaline), CH^k |t ^pq XT- The phthalines are colourless, and are to be looked upon as leuco-compounds of the phthaleins. The phthaleins include among themselves many dyes which are of technical value, e.g. the eosins {Can, Baeyer, 1871). For constitution, cf. also Bernthsen, Chem. Zeitung for 1892, p. 1856. fluorescein; eosin, etc. 495 Fhenol-phthalein, C20H14O4, is prepared by heating phthalic an- hydride with phenol and sulphuric acid or, better, stannic chloride (or oxalic acid) to 115-120°. It also results upon nitrating diphenyl- phthalide, reducing the two substituting nitro-groups to amido-ones, and transforming these into hydroxyl by diazotizing (A. 202, 68). It crystallizes from alcohol in colourless crusts ; in water it is nearly insoluble, but it dissolves in alkalies with a beautiful red colour which vanishes again on the addition of acids ; it is thus a valuable indicator (B. 17, 1017, 1097). It yields a Dl-acetyl derivative and is reduced by potash and zinc dust to : Fhenol-phthallne (colourless needles), which dissolves in alkali to a colourless solution, but is readily reoxidized in this solution to phthalein. Flaorane, OjoHuOa, which was formerly looked upon as being phenol- phthalein anhydride, results as by-product in the phenol-phthalein melt, and is the mother substance of fluorescein. For constitution, see B. 25, 1385, 2118. Pluoreseein or resorcivrphthalein, CjoHjgOj + H^O, is prepared by heating phthalic anhydride and resorcin to 200°. It forms a dark red crystalline powder, and dissolves in alcohol with a yellow-red colour, and in alkalies with a red colour and splendid green fluorescence. It is reducible to the phthaline "Fluorescin," and yields with bromine red crystals of tetrabromo-fluoresce'in, whose potassium salt, G^oR^Bifi^K,^, is the magnificent dye £j0Sin. Fluorescing dyes are likewise formed in an analogous manner from aU the derivatives of 1 :3-dioxy-benzene, in which position 5 is unoccupied. Instead of phthalic acid itself, chlorinated or brominated, etc., phthalic acids may be employed, so that, by gradually increasing the amount of halogen present, a whole series of yeUow-red to violet-red eosins can be prepared, e.j'.tetrabromo-di-iodo-eosin ; these are known under the names of Erythrosin, Rose de Bengale, Phloxin, etc. It is worthy of note here that many other dibasic acids {e.g. succinic) and also benzoic acid are capable of yielding fluorescing compounds. If the two hydroxyls of the resorcin residue in fluorescein are replaced by group N(C2Hs)2, (Tetra-ethyl-) Ehodamin, OimHi80s[N(C2H5)2]ij, results. This is a splendidly fluorescing red basic dye. It is produced by heating phthalic anhydride with diethyl-m-amido-phenol (p. 421; of. also Formo-rhodamin). Gallein, O20H10O7, is obtained in an analogous manner from pyrogallol and phthalic anhydride; it dissolves in alkalies with a blue colour. Gallein contains two atoms of hydrogen less than the normal phthalein of pyro- gallol; as in the case of coemlignone, two "peroxide" oxygen atoms are assumed here. Its phthaline, Gallin, CjoHuO:, is transformed by concentrated 496 XXX. DIBENZYL GROUP. sulphuric acid into the " phthalidine " CoeruUn, CjjHijOj, which yields the " phthalideiin " Coerulein, CjoHjOs, a valuable olive-green dye, upon oxidation. The mother substance of both the latter compounds is phenyl-anthranol (p. 511). For details, see A. 209, 249. XXX. DIBENZYL GROUP. The modes of formation, etc. of the members of the dibenzyl group show that the two benzene nuclei in them are connected together by two carbon atoms ; all of them are transformed into benzoic acid up©n oxidation. Summary. C„HB-CH2-CH2-CeH5 C8H6-CH=CH-C8H, C5H,-C=C-CeH, Dibenzyl. Stilbeue. Tolane. CsHj-CHa-CO-CeHj C8H5-CH(OH)-CH(OH)— OjHj Desoxy-benzoin. Hydrobenzoin. C8H5-CH(OH)-CO— CjHj CsHj— CO-CO— CeHj Benzoin. Benzile. Dibenzyl may be designated as symmetrical diphenyl-ethane (for the unsymmetrical compound, see p. 483), stilbene as s-diphenyl-ethylene, and tolane as diphenyl-acetylene. Dibenzyl, C14H14. When benzyl chloride (2 mols.) is treated with sodium, the two liberated residues OjHj — CH2 — (benzyl) join together with the formation of dibenzyl, a hydrocarbon which is isomeric with ditolyl and with tolyl-phenyl-methane. It crystallizes in needles or small plates, M. Pt. 52°, and sublimes unchanged. Stilbene, diphenyl-ethylene, OuHu, forms monoclinic plates or prisms, M. Pt. 125°, which also boil without decomposition. It may be prepared e.g. by the action of sodium upon benzal chloride or oil of bitter almonds, or by passing the vapour of toluene or dibenzyl over heated oxide of lead, and possesses the full character of an olefine, giving — for instance — a dibromide, CsHs — CHBr — CHBr — CsHj, with bromine, and being con- verted into dibenzyl by hydriodic acid. jp-Siamido-stilbene, CuHio(NH2)2, and its disulphonio acid (obtained by reducing jp-nitro-toluene or its sul- phonic acid in alkaline solution) are, like benzidine, mother substances of TOLANE, BENZOIN, BENZILE, ETC. 497 "cotton dyes" (see p. 478), Just as ethylene bromide yields acetylene when boiled with alcoholic potash, so does stilbene dibromide yield: Tolane, OuHm, which crystallizes in prisms or plates, M. Pt. 60°. Tolane corresponds with acetylene in its properties in so far that it combines with chlorine to a dichloride and a tetrachloride, and so on, but it does not yield metallic compounds since it contains no " acetylene hydrogen." When stilbene dibromide is treated with silver acetate, two di-acetic esters are formed; and when these are saponified by aloohollo ammonia, two isomeric substances of the composition: CuHuOa, =; CeHs — CH(OH) — CH(OH) — OsHs, Hydro-benzoin and Iso-hydrobenzoin or s-diphenyl-glycol, are produced. These likewise result from the action of sodium amalgam upon oil of bitter almonds. The former crystallizes in rhombic plates, M. Pt. 138°, and the latter in four-sided prisms, M. Pt. 119°, which are the more soluble of the two. These two compounds are stereo-isomeric, as are also their diaoetyl esters (A. 198, 115, 191). The compounds Benzoin, Benzile and Sesozy-benzoiii, which have already been referred to in the summary, are closely related to one another as their formulae show, and can also be prepared from bitter almond oil. The latter "condenses" (p. 144) in alcoholic solution, under the influence of potassium cyanide, to benzoin (2C7HsO, = C14H12O2), which forms beauti- ful glancing prisms ; nascent hydrogen reduces it to hydro-benzoin, from which it also results upon oxidation. It reduces Fehling's solution even at the ordinary temperature, with the formation of benzile. Benzile, ObHs — CO — CO — Cells, is obtained by oxidizing benzoin by means of nitric acid. It crystallizes in large six-sided prisms, M. Pt. 95°. It is oxidized to benzoic acid by CrOg, and reduced by nascent hydrogen — according to the conditions — either to benzoin or to desoxy-benzoin. It reacts with hydroxy lamine to produce: — Benzile-monoxime, OeHj — CO — C(N.OH) — CeHs, and Benzile-dioxime, (CeH5)2=[C(N.OH)]ij, both of which exist in stereo- isomeric modifications. Cf. Avwers. V. Meyer, B. 21, 3510; 22, 705, 1996; 23, 3589; 24, 3267; Eantzsch and Werner, B. 23, 1, 3589; 24, 3267. Desoxy-benzoin. The latter forms large plates, M. Pt. 55°, and may be sublimed or distilled unchanged. It can be prepared by the action of benzene and aluminic chloride upon the chloride of phenyl-acetic acid (OeHs — CH2 — CO.Cl), which is a proof of its constitution, and yields di-benzyl with hydriodio acid. Desoxy-benzoin can also be prepared from benzile and benzoin (B. 25, 1728). One of its methylene hydrogen atoms is readily plaoeable by alkyl, just as in aceto-acetic ester. The residue, CeHs— CH— CO— CsHs, is termed "Desyle." Benzillc acid, (C6H6)ii=C(OH) — CO2H (p. 483), results upon heating benzile with alcoholic potash, by a peculiar molecular transformation similar to that by which pinaooline is formed (p. 157). A series of compounds homologous with di-benzyl, stilbene, etc., is also known. Carboxyl groups can likewise substitute in di-benzyl and stilbene, with the formation of phenyl-cinnamic acid, diphenyl-succinio acid, stilbene- dicarboxylic acid, etc. (606) 81 498 XXX. DIBENZYL GROUP, Appendix. Further, two or more benzene nuclei may be connected together through more than two carbon atoms. In indigo, for example, the two benzene residues are linked together by four carbon atoms, and the same holds good for the hydrocarbon which is its basis, viz., Dlphenyl-dlacetylene, CsHj— C=C— C=C— CeHj {Baeycr). This last compound results from the oxidation of copper phenyl-acetylene, CgHj — C=C — Cu, with a solution of potassium f errii yanide, crystallizes in long needles which melt at 88°, and combines with eight atoms of bromine to an ooto-bromide. Its o-Dlnitro-derivative, which is pre- pared in an analogous manner from o-nitro-phenyl-acetylene, yields indigo when treated first with sulphuric acid and then with sulphide of ammonium (see p. 470; also B. 16, 5.3). In Dlbenzoyl-acetlc acid, (CgH5.CO)2=CH— CO^H, a di-ketonio acid, whose ether is obtained by treating benzoyl-acetio ether with benzoyl chloride, two benzene residues are connected together by three carbon atoms. The free acid, which crystallizes in needles, M. Pt. 109°, is split up into COj and the di-ketone Dlbenzoyl-methane, (C8H5CO)2=CH2, when boiled with water. In the latter, a solid substance which boils without decomposition, the hydrogen of the methylene group is re- placeable by metals (through the influence of the two oarbouyls), so that the compound dissolves in alkalies and is again thrown down by acids. By the further action of benzoyl chloride upon its sodium compound, we obtain Tribenzoyl- methane, (CsHj.COjjCH. VulplG acid, C19H14O5, a lichen acid, is related to the above compounds. Tetraphenyl-ethane, (C6H5)2=CH— CH=(CsH5)5 (large prisms), and Tetraphenyl-ethylene, (C|5H5)2=C=C=(C5Hj)2 (fine needles), are also related to dibenzyl ; both of these go into benzophenone upon oxidatidn. COMPOUNDS WITH CONDENSED BENZENE NUCLEI. That portion of coal tar which boils at a high temperature contains a number of higher hydrocarbons, among which majr be especially mentioned naphthalene, CjqHj, anthracene, NAPHTHALENE. 499 Cj^HjQ, and its isomeride phenanthrene, Cj^Hk,. The first- named is found in the fraction between 180-200°, and the two latter in that between 340-360°. These compounds are of more complex composition than benzene, the molecule of naphthalene differing from that of the latter by C^Hj, and those of anthracene and phenanthrene from that of naphthalene by the same increment. They show however the most complete analogy to benzene as regards behaviour, so that almost exactly the same varieties of com- pounds may be derived from them as from benzene itself. As a matter of fact they are undoubtedly benzene deriva- tives, anthracene yielding benzoic acid upon oxidation, naphthalene phthalic acid, and phenanthrene diphenic acid. From their modes of formation and behaviour it follows that in the building up of their molecules the benzene residues combine together in such a manner that 2 or (2 x 2) contiguous carbon atoms are common to both. For further details see pp. 500 and 509. XXXI. NAPHTHALENE GROUP. Naphthalene. Naphthalene, Oj^Hg, was discovered by Garden in 1820. It is contained in coal tar and crystallizes out from the fraction which distils over between 180-200°. Formation. 1. By exposing a large number of carbon com- pounds to a red heat; thus, together with benzene, styrene, etc., by passing the vapours of methane, ethylene, acetylene, alcohol, acetic acid, etc. through red-hot tubes. 2. By leading the vapour of phenyl-bntylene dibromide, C5H5 — CH2 — CH2 — CHBr — CHaBr, over quick-lime raised to a low red heat {Aronheim) : CioHijBrj = CjoHg + 2HBv + H^. 3. By the action of o-xylylene bromide (p. 366) upon the sodium com- pound of the aymmetrioal ethane-tetracarboxylic ether (p. 268), there results " Hydronaphthalene-tetracarboxylio ether," thus: P „ ^CH,Br , Na-C(CO,R), _ .CH,-C(CO,E), 500 XXXI. NAPHTHALENE GROUP. and from this latter, by the separation of the carboxyl groups and the excess of hydrogen, naphthalene (Batyer and Perkin, B. 17, 448). 4. a-Naphthol, CiqHj.OH, is produced by the separation of water from phenyl-isocrotonic acid (Fittig and Erdmann, B. 16, 43), and yields naphthalene when heated with zinc dust. For further details, see below. Constitution. That naphthalene contains a benzene nucleus, in which two hydrogen atoms occupying the ortho-position are replaced by the group (O^HJ", follows not only from its oxidizability to phthalic acid, but also {e.g.) from its formation from o-xylylene bromide. And that the four carbon atoms of this group are linked to one another without branching is shown by the formation of a-napthol (as given above), from which it follows at the same time that the end C-atom of the side chain takes hold of the benzene nucleus already present, with the production of a new six-cornered ring : CH CH CH CH — HiO HC M HC H OiC (OH) HC CH H HC CH CH HC C (OH) o-Naphthol. Phenyl-isoorotonio acid. That there are actually two so-called " condensed " benzene nuclei present in the naphthalene molecule is a necessary con- sequence of the fact that phthalic acid or its derivatives ensue on the breaking up of the compound, not only from one but from both of the six-cornered rings. For instance, a-nitro-naphthalene (p. 503) allows itself to be oxidized to nitro-phthalio acid, C5H3(N02)(C02H)3 ; consequently the benzene ring to which the nitro-group is linked remains intact. But, on reduc- ing the nitro-naphthalene to amido-naphthalene and oxidizing the latter, no amido-phthalic acid nor any oxidation product of it is obtained, but phthalic acid itself, a proof that this time the benzene nucleus which binds the amido-group has been destroyed, and that the other has remained intact (Oraebe, 1880 j for an analogous proof by him, see A. 149, 20). NAPHTHALENE, CONSTITUTION OF. 501 Naphthalene therefore receives the constitutional formula {Erlerwneyer, 1866) : This union of two benzene nuclei is accompanied by a modifi- cation of their properties, so that naphthalene and its derivatives differ characteristically from benzene in many respects. Such differences show themselves, for instance, between the naph- thylamines and aniline, the naphthols and phenol; and also especially in the greater readiness with which the naphthalene derivatives are hydrogenized, the latter taking up as many as four atoms of hydrogen easily. After such addition the hydrogenized nucleus is found to have entirely lost the characteristics of the benzene nucleus, and to have become very similar in properties to a radicle of the fatty series, whereas the (other) non-hydrogenized nucleus assumes the character of a benzene nucleus in its entirety {Bamberger). See the tetrahydro-naphthols, p. 505. Properties. Naphthalene crystallizes in glancing plates which are insoluble in water, sparingly soluble in cold alcohol and ligroin, but readily soluble in hot alcohol and ether; M. Pt. 80°, B. Pt. 218°. It has a characteristic tarry smell, and is distinguished by the ease with which it sublimes and volatilizes with steam. It yields a molecular compound, crystallizing in yellow needles, with picric acid, and takes up hydrogen far more readily than benzene does to form Naphthalene dihydride, CioHa.Hz, and -tetrahydride, CioHs-Hi, both of these being liquids of pungent odour which regenerate naphthalene again when heated. By the powerful action of hydriodic acid and phosphorus, the second benzene nucleus can also be made to take up hydrogen, so that a hexahydride, CioHs.He, and finally a dekahydride, C,oH8.Hio, result. It likewise yields addition-products with chlorine more readily than benzene does, e.g. Naphthalene dichloride, CioHs.Cl^, and -tetrachloride, CioHs.Cli (M. Pt. 182°); the latter is oxidized to phthalio acid more easily than naph- thalene itself, hence that acid is prepared from it on the large scale. Naphthalene is principally used for the preparation of phthalic acid (for eosin, etc.), and of naphthylamines and naphthols (for azo-dyes); also for the carburation of illuminating gas. It is a powerful antiseptic, and is employed therapeutically. 502 XXXI. NAPHTHALENE GROUP. Derivatives of Naphthalene. The substitution products etc. of naphthalene may be mono- or di-derivatives, etc. The mono-derwatives invariably exist in two isomeric forms, the a- and P-compounds, thus : CloHyCl g' Ichloro-naphthalene. CjoHyNHj „] VNaphthylamine. CioHyOH g"|Naphthol. CioH^CHj °;| Methyl-naphthalene. As in the case of the benzene compounds, the existence of two series of mono-derivatives here has not only been established empirically, but it has also been proved (in a manner similar to that given on p. 340 et seq.) that in the naphthalene molecule two sets of hydrogen atoms (viz. a, o', o", a'" and j3, ^', /3", j3"') have an equal value as regards one another (but the atoms of the one set differ from those of the other), so that the a- and the ^-positions occur severally four times, i.e. twice in each benzene nucleus (Atterbcrg). The above constitutional formula for naphthalene satisfies these con- ditions admirably, since, according to it, the positions 1, 4, 5 and 8 are severally equal and also the positions 2, 3, 6 and 7, but not the positions 1 and 2. The conception that in the a-compounds the position 1, 4, 5 or 8 is occupied : a a a" a' is due to Liebermarm (A. 183, 225), Reverdim, and NoUing (B. 13, 36), and Fittig and Erdmamn (cf. the formation of a-naphthol given above). With regard to the di-derivatives of naphthalene, a considerable number of isomerides of a good many are known; according to the naphthalene formula, ten are theoretically possible in each case when the two substituents are the same, and fourteen when they are different. The position 1:8 (i.e. o:o"') is termed the "peri-" position; it resembles the ortho- position to some extent. Bromo-naphthalenes. o-Bromo-naphthalene, which can be prepared directly, goes partially into the ;8-eompound when heated with chloride of aluminium. Its bromhie atom is somewhat more easily exchangeable than that of bromo-benzene. NAPHTHYLAMINES. 503 Nitro-naphthalenes. a Nitro-naphthalene, OjoHy.NOg {Laurent,1835), results from the direct nitration of naphthalene. It forms yellow prisms, M. Pt. 61°, boils without decomposition, and goes into di-, tri- and tetra-nitro-naphthalenes upon further nitration. On reduction it is converted into a-naphthylamine. The isomeric /S-Nltro-naphthalene can be obtained indirectly by diazotizing j3-naphthylamine, and acting on the product with sodium nitrite in presence of cuprous oxide (see p. 371); it crystallizes in bright yellow needles. Naphfhylammes ; Naphthalene-sulphonic adds. a-Naphthylamine, CiqH^.NH2 (Zinin), forms colourless needles or prisms readily soluble in alcohol; M. Pt. 50°, B. Pt. 300°. It can also be easily prepared by heating a-naphthol with the double compound of chloride of calcium and ammonia (while aniline can only be got from phenol in a similar manner with difficulty) : O10H7.OH + NH3 = O10H7.NH2 + H2O. It possesses a disagreeable fsecal-like odour, sublimes readily, and turns brown in the air. Certain oxidizing agents, such as ferric chloride, produce a blue precipitate with solutions of its salts, while others give rise to a red oxidation product; chromic anhydride oxidizes it to a-naphthoquinone. In other respects it is very like aniline. For the differences from aniline shown by it and by /3-naphthylamine, cf. B. 23, 1124. The isomeric /3-Naphthylamine, GioHyNHj (Liebermann, 1876), is most conveniently prepared by heating /3-naphthol either in a stream of ammonia or with the double compound of zinc chloride and ammonia. It crystallizes in glancing mother- of-pearl plates, M. Pt. 112°, B. Pt. 294°, and has no odour. It is more stable than a-naphthylamine and is not coloured by oxidizing agents. Both of these naphthylamines can be converted into tetrahydro-com- pounds by the action of sodium and alcohol (i.e. nascent hydrogen) upon 504 XXXI. NAPHTHALENE GROUP. them. The resulting Tetrahydro-a-naphthylamine resembles its mother substance closely in most of its properties, e.g. it can be diazotized and has entirely assumed the character of aniline; the hydrogen atoms have entered the nucleus •which does not contain the NHj-group. It is termed wromatic or "ar-" tetrahydro-a-naphthylamine. Tetrahydro-j8-naphthylamine, on the other hand, is not diazotized by nitrous acid but transformed into a very stable nitrite. Here It is the benzene nucleus containing the NHj-group which has become hydrogenized ; the compound has assumed the properties of an amine of the fatty series, and is termed alicyclic or "ac- " tetrahydro-;8-naph- thylamine. The a-compound is oxidizable to adipic acid (p. 247), and the /3-compound to o-hydrooinnamo-oarboxylic acid, C6H4C,B, + H,0. 3. Together with dibenzyl, by heating benzyl chloride with water to 200° (B. 7, 276): iCsHs-CHjCl = CuHio + O14H14 + 4HC1. 4. From o-bromo-benzyl bromide and sodium in ethereal solution ; here hydro-anthracene is at first formed, and this is converted by oxidation (which is partly spontaneous during the above reaction) into anthracene (B. 12, 1965) : CeHKcH^Br + ^"^^f ^>CeH4 + 4Na = CeH4C6H4 + 4NaBr ; CeS,<^^>C,-H, - H, = CeH,C«H,. 5. By heating benzene with symmetrical tetrabromo-ethane and aluminic chloride (B. 16, 623) : ^"^' + 13^ + ^«^« = CeH,CeH, + 4HBr. 8. When phthalic anhydride is heated with benzene and ANTHRACENE. 509 chloride of aluminium, o-benzoyl-benzoic acid results, and from this, on heating with phosphoric anhydride, anthraquinone (^Behr and v. Dorp, B. 7, 578); the latter goes into anthracene upon reduction with zinc dust: C.H,CoH4 + 3Hs = CeH,<^^>CeH4 + 2HjO. 7. When a mixture of m-xylene and styrene is treated with concentrated aulphurio acid, there is formed tolwjl-phenyl-propwne, OHs — CoHj — CHj pjT- , which decomposes almost quantitatively into methane, hydro- gen and methyl-anthracene on being strongly heated (B. 23, 3272). 8. From alizarin by means of zinc dust (see p. 513). Constitution. From the above modes of formation and from its relation to anthraquinone, whose constitution follows e.g. from mode of formation 6, the anthracene molecule is seen to contain two benzene nuclei, C5H4, joined together by a middle group, CgHg. The carbon atoms of this middle group are like- wise linked together, as is seen from mode of formation 5, and take up the o-position with regard to each other on one or other of the benzene nuclei (on one nucleus according to methods of formation 2 and 6, and on the other according to method 4; for further proofs of this, see e.g. v. Pechmann, B. 12, 2124). The constitution of anthracene is thus the follow- ing (Graebe and Liebermann, A. Suppl. 7, 313): HC HC The two carbon atoms of the middle group thus form a new hexagon- ring with the carbon atoms of the benzene nuclei to which they are linked, so that anthracene may «,1bo be looked upon as being built up by the con- junction of three benzene nuclei. Besides the formula CaHj-C^ • ^CbH,, the " quinoid " formula 06H4^p-rT/>C6H4 has also to be taken into con- sideration {Armstrong, Proc. Chem. Soc. for 1890, p. 101). As regards combination with hydrogen, the same applies here as to naphthalene, two hydrogen atoms being readily added on at 9 and 10 (see H C H C H C A y \ A CH 7 /N ^ k/^ \ A \J CH or V \o/ w c H c I [ c H 510 XXXII. ANTHRACENE AND PHENANTHRENE GROUPS. fig. above) ; the middle or " meso " ring thus shows a more or less aliphatic character, whUe both outer rings have entirely the character of benzene. Properties and Behaviour. Anthracene crystallizes in colour- less plates which show a magnificent blue fluorescence. It is insoluble in water and only sparingly soluble in alcohol and ether, but readily so in hot benzene; M. Pt. 213°, B. Pt above 351°. With picric acid it yields an addition-compound crystallizing in beautiful red needles. Anthracene is transformed by sunlight into (the polymeric) Fara-anthra- cene, (CuHio)2. It takes up in the first instance two atoms of hydrogen when reduced (e.g. by hydriodlc acid and phosphorus), with the formation of Anthracene dihydride, CuHio-Hu (see above, mode of formation 4). This latter crystallizes in white plates, readily soluble in alcohol, M. Pt. 107°; it sublimes easily and distils without decomposition, but goes back into anthracene at a red heat or when warmed with concentrated sulphuric acid. It has the constitution : Further addition of hydrogen yields the hydrides CuHie and, finally. Derivatives of Anthracene. Theoretically three isomeric mono-derivatives are possible in each case, viz., the a-, j8- and 7-compounds: since, in the graphical formula given on the preceding page, l = 4 = 5 = 8 = a, 2 = 3 = 6 = 7 =)8, and 9 = 10=5.7. The observed facts are in complete accordance with this. The position of the substituting group can usually be determined either by the behaviour of the substance in question upon oxidation, e.g. if it be in the 7-position it will be eliminated with the formation of anthraquinone; or it is arrived at from the synthesis of the compound, e.g. in the case of alizarin, whose formation from pyrocatechin and phthalio acid shows that its two hydroxyls are contained in one and the same benzene nucleus. Anthraquinone, 0|jH4(CO)2CgH4, in which the hydrogen atoms 9 and 10 are replaced by two atoms of oxygen, only yields two isomeric mono-derivatives in each case. Isomeric di-derivatives may exist in very large number. DERIVATIVES OF ANTHRACENE. 511 Summary of the most important derivatives of Anthracene. CuHgCl 1 Chloro-, Diohloro-, and CuHaCla > Dibromo-Anthracenes Ct,HaBr, \ (y) CHH9.NO2 \Mono- and Dinitro- CuH8(NOj)5/ anthracenes (7). C14H9.NH2, Anthramine (j3). C H SO Ti//3-Anthracene-sulph- " '■ ' \ onic acid. n Ti /an tt\ /"" ^^^ /3-Anthracene- Oi4H8(&Ustl)2^ disulphonic acids. Ci4H5(OH), Oxy-anthracenes : CeH4<^^>CeH3.0H ^jAnthrol. G,Ki<^^^'yGMA, Anthrone. OH p XT ^CHj ^.^pi TT Hydranthra- ^6^4<,CH(OH)/''"6"-i' nol (7). Ci4H8(OH)2, Dioxy-anthracenea : ^«^^<^-'^*' Anthra-hydroqumone (isomers : chrysazol. ) CiiHjOa, Anthraquinone : 06H4^6^i' Oxanthranol. n Tt n lan xr\ fAnthraquinone- Ci4H702(OH), Oxy-anthraquinones ; C8H4(CO)jC8Hj(0H) : a = Erythro-oxy-, /S = Oxy-anthraqninone. Ci4H80j(OH)2, Dioxy-anthraquinones : C8H4(CO)aC8H2(OH)2 : a/3 = AUzarln, oa' = Quinizarin, o;8' = Purpuro- xanthine, etc. C8H3(OH)(CO)2C5Hj(OH): Anthraflavic acid, Iso-anthraflavic acid, Anthra- rufin, Chrysazin, etc. Ci4H502(OH)3, Trioxy-anthraquinones : CeHjCCOlaCeHCOHls : a/3o' = Purpurta. Isomers : Plavo-purpurin, Anthra-purpurin, etc. Tetroxy-anthraquinones: Anthrachrysone, Rufiopin, Quinalizarin. Hexoxy-anthraquinones: Hexoxy-anthraquinone, Bufigallic acid. Ci4H9(CH3), Methyl-anthracenes. CiiHglCeHs), Phenyl-anthracene, etc. p„^CH2-.og- Alkyl-hydro- ^e'^4.<^CnB^^ *' anthracenes. CJSa<^^^^^^ >C»H., anthranol CwHglCHjjj, Dimethyl-anthracenes. C H (CO HI /Anthracene-carboxylic 14 s\ 2 ^■^ acids (a, /3, 7). r IT ^CHj \p -rr Alkyl-hydr- ^6^4CjH4, oxanthra- C(CeHj).0H-^"^«"4' nol ( Phthnlideins). 512 XXXII. ANTHRACENE AND PHENANTHEENE GKOXTPS. Substitution products are obtained directly from these compounds ; they yield anthraquinone upon oxidation, and therefore contain the halogen in the 7-position. j8-Anthramine, C14H11N, is obtained from ;8-anthrol, C]4Hi|,0, and ammonia, anthrol from anthraoene-sulphonic acid and potash, and the last-named acid by the reduction of ^-anthraquinone-mono-sulphonic acid, a- and /3-Dioxy-anthracenes are prepared by fusing the sulphonio acids with potash, and the following substances, which stand midway between hydro-anthracene and anthraquinone, viz. hydranthranol, oxanthranol, anthranol and anthra-hydroquinone {Liebermann), by the more or less energetic reduction of anthraquinone. The oxy -anthracenes appear to be also present in coal tar. The phthalidines result from the action of concentrated sulphuric acid upon the phthalines (p. 494; cf. also B. 18, 2150), thus : C«HC,H, Triphenyl-methaue-carboxylic acid. Phenyl- anthranol ; they are oxidizable to the phthalideins, e.g. Coerulein (p. 496). 7-Alkylated anthracenes are also produced by the elimination of the elements of water from the alkylated hydranthranols, which in their turn are obtained from hydranthranol by acting upon it with alkyl iodide and potash ; while 7-phenyl-anthracene is got by heating phenyl- anthranol (a phthalidine) with zinc dust. For isomeric alkyl-anthra- cenes, see below. Anthraquinone and its oxy-compounds are of especial importance. Anthraquinone, Cj^HgOg (Laurent, 1834). Formation as given above. It is easily obtained by oxidizing anthracene with chromio acid mixture (which is the method followed on the large scale), or with chromic anhydride and glacial acetic acid, and is also produced when calcium benzoate is distilled. It crystallizes in yellow prisms or needles which are soluble in hot benzene, sublime with great readiness, and are ex- ceedingly stable as regards oxidizing agents; M. Pt. 285°. Hydriodic acid at 150° reduces it either to anthracene or its di-hydride, while fusion with potash converts it into benzoic acid. It possesses more of a ketonic than of a quinonic character [Zincke, Fittig), not being reduced by sulphurous acid, and it gives an oxime with hydroxylamine. ALIZARIN. 513 It yields (mono- and di-) bromo-, nitro- and sulpho-compoundB. Antliraqiilnone-/3-mono-sulphonlo-aold crystallizes in yellow tablets ; of the Di-sulpho-acids we are acquainted with two which are formed directly from anthraqulnone, and two which are produced by the oxidation of the anthracene-disulphonic acids. Fusion of the sulphonic acids with potash does not generally yield the analogous oxy-compounds in theoretical quantity, oxygen being usually absorbed from the air at the same time; thus the mono-sulphonic acids yield mono- and dioxy-, and the di-snlphonic acids di- and trioxy- anthraquinones. In practical working the amount of chlorate of potash required is added to the "melt." Prolonged fusion with potash gives rise to decomposition into (oxy-) benzoic acids. Various Oxy-anthraciuinoueB can also be prepared by the synthetical mode of formation 6, p. 508, which applies in the case of authraquinone, viz. , from phthalic anhydride and the mono- or dioxy-benzenes {Baeyer and Garo, B. 7, 792 ; 3, 152), e.g. : C,H40 + CeH^OH), = C,li,<^^-:>C,n,{OK), + HjO ; phenol yields by this method the two oxy-anthraquinonea (yellow needles), pyro-cateohin (1 : 2) yields alizarin, hydroquinone yields quinizarin, and so on. They are further produced by fusing ohloro- and bromo-anthraquinones with potash, while m-oxy-benzoic acid can be converted directly by sulphuric acid into anthraflavio acid, water being separated (see Summary). Cf. A. 240, 245. Alizarin, Cj^HgO^, is the most important constituent of the beautiful red dye of the madder root (Rubia tinctorum), which has been known for ages, being present in the latter as the readily decomposable glucoside, Euberythric acid, CjgHggOi^ (p. 560); in addition to alizarin, madder also contains purpurin. The preparation of alizarin from anthracene, with the inter- mediate formation of anthraquinone-mono-sulphonic acid (men- tioned above), which was first introduced in 1871 (Graebe and Liebermcmn, Garo, PerMn, B. 3, 359; A. 160, 130), depends upon an observation made by Graebe and Liebermann in 1868 (B. 1, 49; A. Suppl. 7, 297), that alizarin is reduced to anthra- cene when strongly heated with zinc dust. It crystallizes in magnificent red prisms or needles of a glassy lustre, which melt at 289° and can be sublimed, dis- solves readily in alcohol and ether, only sparingly in hot water, but, as a phenol, very easily in alkalies to a violet-red solution. It yields insoluble coloured compounds — the so-called "lakes" (606) 2K 514 XXXII. ANTHRACENE AND PHENANTHEENE GROUPS. — with metallic oxidea, the alumina and tin lakes being of a magnificent red colour, iron lake violet-black, and lime lake blue. In the Turkey Red manufacture, for instance, the materials to be dyed are previously mordanted with acetate of alumina or with " ricinoleic-sulphuric acid "(see p. 233). Anthrarobin, dioxy-anthrcmol, C6Hi<\ • _^C6Hs(OH)2, ia obtained by reducing alizarin with ammonia and zinc dust. It is a yellowish-white powder which is reconverted into alizarin on oxidation; on account of its reducing properties it is used in skin diseases. Nitrogen tetroxide, N2O4, converts alizarin into jS-BTitro-alizariu or Alizarin orange, Ci4H;(N02)04, a yeUowish-red dye; and this latter, when treated with glycerine and sulphuric acid (the Skraup reaction, p. 531), yields Alizarin, bine, CirHgNOj (see Quinoline), which is likewise a valuable blue dye, being used chiefly in the form of the NaHSOj-compound. Purpurin, Anthrapurpurin, and Flavopurpurin are also valuable dyes which are manufactured on a large scale; the same applies to the isomeric compound Anthragallol or "anthracene brown," C6H4<^p(-.^C6H(OH)3, which is prepared by acting on a mixture of gallic and benzoic acids with concentrated sulphuric. Alizarin-bordeaux, quinalizarm or tetroxy-antJi/raquirume, Ci4H402(OH)4 (of. B. 33, 3739), results from alizarin as an' easily saponifiable sulphuric ester by the action of fuming sulphuric acid of high percentage. On oxida- tion it yields : Penta- and Hexozy-authraqniuones ("alizarin cyanines"), colours which dye a violet -blue with a chrome mordant (cf. J. pr. Ch. 43, 237, 246). Kelated to these are the : Anthracene Blue dyes, which are produced from o-a"-dinitro-anthra- quinone by treating it successively with fuming and then with ordinary sulphuric acid ; they yield blue tints with chrome mordants. A hexoxy- anthraquinone can also be prepared directly from anthraquinone by oxida- tion with sulphuric anhydride. According to v. Kostamecki the colouring power of these compounds is connected with the presence of two hydroxyls in the ortho-position to one another. Closely related to the anthracene dyes in properties is the yellow dye Galloflavin, CuHsOg, which is obtained by exposing an alkaline solution of gallic acid to the action of the air {Bohn and Qraebe, B. 20, 2327). Eomologues of Anthracene. (See e.g. mode of formation 7.) There are also present in coal tar : 1. Methyl-anthracene (either a- or j8-), CuH9.CHa, which resembles anthracene and is oxidizable to methyl-anthraquinone; M. Pt. 199°. 2. Dimethyl-anthracene, OuH8(CH8)2, M. Pt. 224''-225°; isomers of this compound have been prepared synthetically. The three Anthracene-monocarboxylic acids which are theoretically possible and also some Anthracece-dicarboxylic acids are likewise known. PHENANTHRENB. 515 B. Phenanthrene. Phenanthrene, Ci4Hi„ [Fittig and Ostermeyer (1872), A. 166, 361]. This hydrocarbon is found accompanying anthracene in coal tar. It crystallizes in colourless glancing plates, and dissolves in alcohol more readily than anthracene (with a blue fluorescence); M. Pt. 103°, B. Pt. 340°. It may be separated from anthracene by partial oxidation, the latter being the first to be attacked, and subsequent distillation. Oxidizing agents convert it into diphenic acid (p. 479). It is employed in the manufacture of printer's black. ■Formation. 1. By leading the vapour of toluene, stilbene, dibenzyl or o-ditolyl through a red-hot tube, thus : C5H4— CH3 ^ CsHj— CH ^ 2^ C(jH4 — CH3 CgH4 — OH o-Ditolyl. Phenanthrene. 2. Together with anthracene from o-bromo-benzyl bromide and sodium. 3. By distilling morphine with zinc dust. Constitution. The formation of phenanthrene from o-ditolyl, and its oxidation to diphenic acid, -^ * nr\Ti> show that it is a diphenyl O51I4 — L/Ugii derivative and that it contains one C-atom linked to each benzene nucleus ; this carbon atom is joined to the corresponding one by a double bond, as is shown e.g. by its formation from ' stilbene, O TT CH ' ' ■■ a reaction completely analogous to the preparation of CjHj — CH diphenyl from benzene. Since diphenic acid is a di-ortho-diphenyl- dicarboxylic acid (Schvltz, A. 196, 1 ; 203, 95), phenanthrene is also a di-ortho-derivative and possesses the following constitution ; Hc/AcH ^°\J^ CHi-CH or c/Nch HCk yCH CH According to the above formula, the two CH-gioups form a new hexagon ring with the two carbon atoms of both benzene nuclei of the 616 XXXII. ANTHRACENE AND PHENANTHRENE GROUPS, diphenyl to which they are linked, so that phenanthrene — like anthra- cene — may be looked upon as the product of the coalition of three benzene nuclei, or of one naphthalene and one benzene nucleus. We are likewise acquainted with addition and substitution products of phenanthrene, e.g. a tetrahydride, nitro-, amido-, cyano- and oxy- compounds, and sulphonic and carboxylic acids. Phenanthrol, Ci4H9(OH), is an oxy-phenanthrene, and Fhenantlirene-hydrooiuinone, Ci4H3(OH)2, a dioxy-compound which goes upon oxidation into : C,H,-CO Phenanthrene-quinone, \^ * i , which latter may also OgH^ — CO be prepared directly from phenanthrene and chromic acid. It crystallizes in odourless orange needles which distil un- changed, but are not volatile with steam; M. Pt. 200°. Phenanthrene-quinone possesses the character of a di-ketone, reacting with hydroxylamine, sodium bisulphite, etc., but it can be reduced to the corresponding hydroquinone by sul- phurous acid. It gives a bluish-green colouration with toluene containing thio-tolene, glacial acetic acid and sulphuric acid, which changes to violet after dilution and addition of ether, i.e. the ether becomes violet-coloured; this is the Laubenheimer reaction (see p. 327, also B. 17, 1338). 0. Hydrocarbons of more complex nature. Fluoranthene, CjsHio, Pyrene, CisHi,,, Cbiysene, CijHu, and Betene, Ciglljg, are hydrocarbons which have been isolated from that portion of coal tar which boils at above 360°. Phenanthrene, pyrene and fluoranthene are also found in " Stupp " fat, i.e. the fat obtained as a bye-product from the working up of mercury ores in Idria. They all crystallize in white plates, sublime without decomposition, and are converted into the corresponding ketones upon oxidation. Their constitution is expressed by the following formulae (with regard to that of pyrene, see Bamberger, A. 240, 147) ; CgB[4.s^^ Cg H4 — CH CgS^ — CS CoHj^Qjj^CH CioHg — CH q j|^CjHj — CH Fluoranthene. Chrysene. Retene. Ferhydro-retene, CuHas, is found native as FieJUdite, along with retene. TRANSITION TO THE PYRIDINE GROUP. 517 PYRIDINE DERIVATIVES, ALKALOIDS AND COMPOUNDS RELATED TO THEM. The aromatic compounds which have been described up to now are derived from the mother hydrocarbons : Benzene, CgHg, Naphthalene, OjoHg, Anthracene, Ci^Hjq, etc. But alongside of them we have to place several groups of very important nitrogenous compounds, which are derived from the mother substances : Pyridine, C5H5N, Quinoline, CgHjN, Acridine, CuH^N, etc. in precisely the same manner as the former are from benzene, etc., i.e. through the replacement of hydrogen by halogen, NO2, NHg, SO3H, OH, CH3, CO2H, etc. The difference in composition between these bases (among one another) is C^Hg, this being the same as the difference between the mother hydrocarbons, from which they may be considered as being derived by the exchange of CH for N, thus: CgHg - CH + N = O5H5N. Just as naphthalene and anthracene are benzene derivatives, so are quinoline and acridine derivatives of benzene on the one hand and of pyridine on the other ; the latter is thus the mother base of all the classes of compounds which are now about to be described. It may be compared with benzene in many points : 1. It is even more stable than benzene, and is further distinguished from the latter by a greater indifference towards the substituting reagents sulphuric and nitric acids and the halogens. The first of these sulphurates only at very high temperatures ; nitro-pyridines are as yet unknown, as are also iodo-pyridines ; while chloro- and bromo-pyridines have so far only been prepared in small number. Neither pyridine nor its carboxylic acids are affected by nitric acid, chromic acid, or permanganate of potash. 518 TRANSITION TO THE PYRIDINE GROUP. 2. The behaviour of its derivatives is on the whole very like that of the derivatives of benzene. Thus its homo- logues (and also quinoline, etc.) are transformed into pyridine- carboxylic acids upon oxidation, and these acids yield pyridine when distilled with lime, just as benzoic acid yields benzene. 3. The isomeric relations are also precisely similar to those of the benzene derivatives. Thus the number of the isomeric mono-derivatives of pyridine is the same as that of the isomeric bi-derivatives of benzene, viz., three ; and the number of the bi-derivatives of pyridine, with two atoms of one and the same substituent, the same as that of the benzene derivatives CgHgXXX', viz., six, and so on. 4. The products of reduction are likewise analogous. Just- as hexahydro-benzene results from benzene, so do we obtain from pyridine (but more easily) hexahydro-pyridine or piperi- dine, CjHjjN ; further, just as naphthalene yields tetrahydro- naphthalene, so does quinoline (readily) tetrahydro-quinoline, CgHjiN, and acridine (readily) (di-) hydro-acridine, CjjHuN, which last is analogous to' anthracene di-hydride. Here also, as in the case of the hydrides of the benzene series, further combination with hydrogen may take place, but there is like- wise here a tendency to the reproduction of the original bases. Consequently the constitution of these compounds is very similar to that of the benzene hydrocarbons. (For further details, see pp. 622 and 533.) In contradistinction to the neutral benzene hydrocarbons, pyridine and its homologues, etc., are strong bases, most of them having a pungent odour ; pyridine is readily soluble in water but quinoline only slightly so. They distil or sublime without decomposition, and form salts with hydrochloric and sulphuric acids which are for the most part readily soluble, while those with chromic acid, though often characteristic, are usually only sparingly soluble; also double salts with the chlorides of platinum, gold and mercury, most of which dissolve with difficulty, and so on. TRANSITION TO THE PYRIDINE GROUP. 519 Summary of several Pyridine and QmnoUne Derivatives. Pyridine .... CjHsN Quimoline OiS,N Ohloro-pyridine, etc. Fyridine-snlphonio acid 03-) . . . . OjHiNCl 05H^(S0,H) Chloro-quinoline, etc. Amido-quinolines . . Quinoline-snlpbonic acids CaFoNCl CsHjNINHs) CsHjNCSOsH) Oxy-pyridines (3) . . C5H,N(0H) Oxy-quinoUnes . . . CjHsNtOH) Methyl-pyridinet . . (Picolines) (3) Dimethyl-pyridines . (Lutidines) Trimethyl-pyridines . Propyl-pyridines . . OjH.N(CH,) OjHaN(OHs)2 CsHaNCCHa), CAN(O.H,) Methyl-quinolines . . (Quinaldine, etc.) Dimethyl-quinolines . Trimethyl-quinoliues . etc. CsH,N(CH.) 0,H«N(OH,). ■CjHtN(CH,). Pyridine-carboxylic acids {3) . . . . Pyridine-dicarboxylio acids (6) . . . . Picoline-carboxylic acids C,H4N(C0jH) CtH,N(0OjH)2 CjF,N(0H,)(C02H) Quinoline-c^H + nh, Piperidine therefore contains a hexagon ring made up of one imido- and five methylene groups, and is a complete analogue of hexa- methylene; it may be designated penta-methylehe- imine. This constitution of piperidine receives further support from the products which are obtained from its decomposition, viz. (1) 8-amido-valeric acid on treating its benzoyl derivative with valeric acid (B. 24, 3687), and (2) glutaric acid and ammonia by the action of hydrogen dioxide on piperidine itself (B. 25, 2777). The constitution of pyridine follows: 1. from its near rela- tion to piperidine; 2. from the formation of pyridine-dicarboxylic acid by the oxidation of quiholine (see above): CsHjN-l-O, = CsHsNICO^H), -(- HjO -1- 2C0j, in conjunction with which are to be taken the proofs of the constitution of quinoline (p. 533) ; THE PYRIDINE GROUP. 523 3. from the perfect agreement with theory of the observed isomeric relations (see below) ; 4. from the transformation of ethyl-pyridine into ethyl-benzene upon heating pyridine with ethyl iodide (A. 247, 14). The above constitutional formula of pyridine was first proposed by Kdrner. The formation of coUidine-dicarboxylic ether (p. 521) thus proceeds as follows (B. 18, 1744) : COjR— CHj HjC— CO2R COjR— C— COjE I I = I II H-SHjO + Hj. CH3— CO OC— CH3 H,C— C C— CHj Three isomeric mono-derivatives of pyridine are known in each case (p. 518). This agrees with the view that pyridine IS a kind of mono-derivative of benzene in which, instead of H, a CH-group is replaced by N; the mono-derivatives of pyridine are thus comparable veith the bi-derivatives of benzene, and are therefore three in number. They are designated as a-, )8- and 7-derivatives of pyridine, as is shown in the following graphical formula : 7 (11.) rCf W In order to determine the position of any given group, it is sought to exchange it for carboxyl; should picolinic acid result, it fills the a-poaition, and should nicotinic or iso-nicotinio, then it fills the ^- or 7-position respectively, since in these acids the a-, ;8- and 7-positions of the carboxyl have been determined by special means. (See Monatsh. f. Chemie, 1, 800; 4, 436, 453, 595; B. 17, 1518; 18, 2967; 19. 2432). Di-derivatives of pyridine containing in the molecule two atoms of one and the same substituent can exist theoretically in six isomeric forms. As a matter of fact the six dicarboxylic acids, for example, are known (00'-, o(3-, 07-, aj3'-, py- and j3/3'- ; see (p. 527). The above pyridine formula (II. ) has the advantage over (I. ) that it gives expression to the linking in ring form of the five carbon atoms and of the nitrogen, without rendering it necessary to take specially into 524 XXXIII. PYRIDINE GROUP. account the mode in which the fourth affinity of each carhon and the third affinity of the nitrogen are used (analogously to the hexagon formula of henzene, p. 344). Besides Komer's formula another is frequently taken into consideration which, like Dewar's benzene formula (p. 348), shows a ^ora-bond connect- ing the nitrogen atom with the 7-carbon atom, besides two double bonds between the carbon atoms o:j3 and a':/3' {Riedd, Bernthsen). Of late, too, central Unkings (three ^ara-bonds) have been assumed in pyridine, this being in analogy with daus'a benzene formula (cf. p. 348; B. 24, 3151). The isomerism of picoline, CjHjN, with aniline, CjHj.NHj, which repeats itself in their homologues, is also worthy of notice. Pyridine. Pyridine, C5H5N [Anderson, 1851), may be prepared from bone oil, and can be obtained chemically pure by heating its carboxylic acid with lime ; the ferrocyanide is especially applicable for its purification, on account of its sparing solu- bility in cold water. It is also found in the ammonia of com- merce. Pyridine is a liquid of very characteristic odour, miscible with water and boiling at 115*. When sodium is added to its hot alcoholic solution, hydrogen is taken up and piperidine, CgHuN, formed (Ladenburg and Both, B. 17, 513 ; see also p. 528). Pyridine is used as a remedy for asthma, and also in Germany for mixing with spirit of wine in order to render the latter duty-free. When heated strongly with hydriodio acid, pyridine is converted into normal pentane. The ammonium iodides, e.g. CjHjN, CH3I, give a characteristic pungent odour when heated with potash, a fact which may be made' use of as a test for pyridine bases ; it depends upon the formation of alkylated dihydro-pyridines, e.g. Dlhydro-metliyl-pyridliie, C5H4.H2.N(CHs) (Hofmann, B. 14, 1497). Pyridine is polymerized by the action of metallic sodium to Dipyrl- dine, CioHuNj (an oil, B. Pt. 286-290°), with the simultaneous production ofp-Dlpyridyl, CioHjNj, = C5H4N— CeH^N (long needles, M. Pt. 114°), a compound corresponding to diphenyl (p. 476); both of these yield iso-nicotinic acid upon oxidation. An isomeric m-Dlpyrldyl has also been prepared, which gives nicotinic acid when oxidized. Pyridine can be brominated but not nitrated ; it can also be sulphur< HOMOLOGUES OF PYRIDINE. 525 ated, with the formation of /3-pyridine-sulphonio acid, CjHjNXSOsH), from which potassium cyanide produces /3-Cyano-pyridine, CsHiN.CN, and fusion with potash ;8-oxy-pyridine. The three Oxy-pyridines, CtHiNIOH) (a-, j3-, 7-), are best prepared by the separation of CO2 from the respective oxy-pyridine-carboxylic acids. a-:M. Pt. 107°; ;3-:M. Pt. 124°; 7-:M. Pt. 148°. They possess the char- acter of phenols and are coloured red or yellow by ferric chloride. As in the case of phloroglucin, so here also there is a tertiary as well as a sec- ondary form to be taken into account, the former reminding one of the lactames and the latter of the laotimes; for instance, 7-oxy-pyridine may either have the " phenol " formula C2H2<^ ^jj '^CjHj or the "pyridone" formula CaHs-C^^TT^CaHj, the latter of the two representing a keto-di- hydro-pyridine. Both of the methyl derivatives, Methoxy-pyridine and Methyl-pyridone, which result from these two forms by the exchange of H (of the OH or NH respectively) for CHj, are known (Monatsh. f. Chemie, 6, 307, 320; B. 24, 3144). Trioxy-pyridlne, CjHbNOj. By the condensation of acetone-dicar- boxylic ether with ammonia there is produced Glutazine, CsHjNaOj (colourless plates soluble in alkali), which is converted by boiling hydrochloric acid into ammonia and trioxy-pyridine (yellowish micro- scopic prisms or needles). For its constitution see B. 19, 2694 ; 20, 2655.) Homologues of Pyridine. (Cf. Ladenhurg, A. 247, 1.) Methyl-pyridines or Picolines, C5H^N(CH3). All the three picolines are contained in bone oil and probably also in coal tar. The y8-compound results from acrolein-ammonia (p. 150) and also upon heating strychnine with lime. They are liquids of unpleasant piercing odour resembling that of pyridine, and they yield o-, yS- or y- pyridine-carboxylic acid when oxidized. 0-: B. Pt. 129°; ;8-: B. Pt. 142°; 7-: B. Pt. 142°-144''. Ethyl-pyridines, CsHiNCCaHs), are also known, o-Ethyl-pyridine (B. Pt. 148°) being obtained by the breaking up of tropine. Propyl- and Isopropyl Pyridines, C6H4N(C8H7), have been carefully in- vestigated on account of their near relation to conine. They are prepared as given at p. 522, 13. Conyrine, CsHuN (liquid, B. Pt. 166°-168°), which results upon heating conine, CsHwN, with zinc dust, and which goes into conine again when treated with hydriodic acid, is a-normal propyl-pyridine. 526 XXXIIT. PYRIDINE GROUP. a-Allyl-pyridine, C5H4N(CjH5), ia produced when o-picoline is heated with aldehyde : C5H4N.CH3 + OHO-CHs = CsH4N.CH=CH— CH3 + Ufi. Eeduotion transforms it into inactive conine (B. Pt. 189-190°). DimetHyl-pyridlnes or Lutldlnes, 05113^(0113)2. The presence of the three lutidines has been proved in bone oil and coal tar. For their synthetical formation see p. 521.» a-7-Lutidine boils at 157°, the a-a'-oom- pound at 142°-li3°, and the j3-/S'-compound at 169°-170°. The CoUidines, CaHuN, are isomeric with the propyl-pyridines. Some of them are present in bone oil and can be prepared from cinohonine by distilling the latter with caustic potash (p. 521). The coUidine {a-a'-y) which is obtained from aoeto-acetio ether and aldehyde-ammonia (p. 521), boils at 171°-172°. "Aldehydine" (from aldehyde, p. 521) is /S'-ethyl- a-methyl-pyridine (B. 21, 294). o- and /3-Phenyl-pyridines, 05H4N(CoH5), are analogous to diphenyl. (See Monats. f. Chemie, IV., 456, 472.) Pyridine-carboxylic acids. (See Summary, also A. 241, 1.) The Pyridine-mono-carboxylic acids, C5H4N(C02H), result from the oxidation of all the pyridine derivatives which con- tain only one (carhon-containing) side-chain, i.e. from methyl-, propyl-, phenyl-, etc. pyridines; also from the pyridine-dicar- boxylic acids by the breaking up of one of the carboxyls, just as benzoic acid results from phthalic. It is the carboxyl which stands nearest to the nitrogen which is first eliminated here. Nicotinic acid is also produced by the oxidation of nicotine. They unite in themselves the characters of the basic pyridine and of an acid, and are therefore comparable with glycocoU. They yield salts with HCl, etc. and double salts with HgClj, PtCl^, etc. ; on the other hand they also form salts as acids, those with copper being frequently made use of for the separa- tion of the acid. For Constitution see SJiraup and Cohenzl, Monats. f. Chemie, 4, 436. The a- acid is Picolinic acid; needles, M. Pt 135°. The /8- „ Nicotinic acid; needles, M. Pt 231°. The 7- „ Iso-nicotinic acid; needles, M. Pt (in sealed ■tube) 309°. PYKIDINE CARBOXYLIC ACIDS, ETC. 527 It is noteworthy that all three aoida (and also e.g. the 18-7-dicarb- oxylie aaid) readily yield up their nitrogen as ammonia when acted upon by sodium amalgam, being thereby transformed into unsaturated acids of the fatty series ( Weidd, Monats. f. Chemie, 11, 601). Pyridine-dicarboxylic aoids, CsHsNICOaHjj. 0-/3- = Qainolinic acid M. Pt. about 190°. a-y- = Lutidinic acid, M. Pt. 235°. o-a'- := Dipieolinic acid M. Pt. 226°. a-p'- = Iso-cinchomeronic acid, ...M. Pt. 236°. |8-j3'- = Diniootinic add, M. Pt. 323°. 18-7- = Cinchomeronie acid, M. Pt. 249°. Quinolinio acid (short glancing prisms), the analogue of phthalio acid, results from the oxidation of quinoline, just as phthalic acid does from naphthalene; cinchomeronie and iso-cinohomeronio aoids from the oxida- tion of cinchonine and quinine. The constitution o-j3- follows for quinolinic acid from its mode of formation. The pyridine-mono- and di-carbozylic acids, which contain a carboxyl in the a-position, give a reddish-yellow colouration with ferrous sulphate. Pyridine-tricarboxylic acids, C6H2N(C02H)8, are obtained in a similar manner by the oxidation of quinine, cinchonine (Carbo-cinchomeronlc acid), berberine (Berberonic acid), etc. Fyridine-pentacarbozylic acid (from collidine-dicarboxylic acid) has no longer basic properties ; it readily gives up CO2. Oxy-pyridine-carboxylio adds result from the action of ammonia upon many vegetable acids, especially upon carboxylic acids of pyrone derivatives (p. 529). Thus cnmalic acid (from malic) is transformed by ammonia into: a-Oxy-;8-nieotinio acid, CjHsN(OH)(COjH) ; colourless erystals, M. Pt. 803°. 7-Oxy-dipioolinie acid, C5H2N(OH)(C02H)2, is obtained from chelidonio acid (p. 529) in an analogous manner. It is possible that similar reactions take place in the genesis of alkaloids from vegetable acids. Citraziuic acid or a-a-dioxy-isonicotinio add (see p. 522). Hydro-derivatives of Pyridine. •According to theory, Hexa-, Tetra-, and Di-hydro-pyridines may exist. The first of these receive the generic name of "Piperidines," e.g. Pipeooline, CjHioNiCHs), Lupetidine, CsH,N(CH,)s, and Copellidine, C^H8N(CH8)3; while the tetra- hydro-compounds are termed " Piperideins." Dihydro-methyl-pyridine (see p. 524). > Dihydro-coliidine-dicarboxylic acid (see p. 521). Tetrahydro-pyridins or piperidem. ]?or synthesis, see B. 25, 2782. o-f ipecolein, CeHuN, results from the action of bromine and soda solution upon piperidine ; for a direct synthesis, see also p. 522. 528 XXXIII. PYRIDINE GROUP. o- Ozyethyl - n - methyl - tetrahydro - pyridine, CHs-NCsHj-CHj-OHaOH (obtained from a-pipeoolein and formic aldehyde), is isomeric with tropine, although totally different from the latter. Piperidine, CjHuN {JVertheim, Bochleder, 1850), is a colour- less liquid of peculiar odour slightly resembling that of pepper, and of strongly basic properties, readily soluble in water and alcohol; B. Pt. 106°. It forms crystalline salts. It occurs in pepper in combination with piperic acid, CuHmOi (p. 463), in the form of the alkaloid Piperine, CigHuNOs, = CsHioN — CijHsOa, i.e. piperyl-piperidine, which crystallizes in prisms, M. Pt. 129°; from this latter it may be prepared by boiling with alkali. For its formation from pyridine and from penta-methylene-diamine, see pp. S24 and 521. Piperidine is a secondary amine; its imido-hydrogen is replaceable by alkyl and by acid radicles. When its vapour, mixed with that of alcohol, is led over zinc dust, homologous (ethylated) piperidines are formed. As a secondary base piperidine yields, in the first instance, tertiary n-methyl-piperidine, C5HioN(CH3), on methylation, the latter then uniting further with methyl iodide to an ammonium iodide. The corresponding hydroxide does not decompose backwards upon distillation, but the ring is broken and a base of the fatty series results,— the so-called "dimethyl- piperidine," C^HigN. If this in its turn is treated with methyl iodide, an ammonium iodide is produced which, on distillation, gives off its nitrogen as tri-methylamine, and yields the hydrocarbon piperylene, CjHs (p. 66). Cf. ffofmatm, B. 14, 660; Ladenburg, B. 16, 2058; also A. 264, 310. Conine, dextro-rotatory a-normal-propyl-piperidine, CgHj^N, = C5Hi(,N(C3H^), is the poisonous principle of hemlock (Conium maculatum). It is a colourless dextro-rotatory liquid of stupefying odour, slightly soluble in water; B. Pt. 167°. Hydriodic acid at a high temperature reduces it to normal octane, while nitric acid oxidizes it to butyric acid, and potas- sium permanganate to picolinic acid (hence the a-position). Ladenbwrg has prepared it synthetically by reducing o-allyl-pyridine in alcoholic solution by means of sodium (B. 19, 2578) : CsHiNlCaHs) -I- 4Hj - CjHioNICaH,). In this reaction there is first formed the optically inactive a-normal- propyl-piperidine, which is broken up, by crystallization of the tartrate, into Conine (dextro-conine) and a Isevo-conine which resembles the other closely. The relations of these two bases to one another and to the inactive modification are the same as that of dextro- to Isevo-tartaric acid and of NICOTINE J PYRONE; ETC. 529 both of these to raoemio acid (cf. B. 19, 2574). Analogous relations hold good with regard to other o-alkyl-piperidines (A. 247, 64, 80). When treated thoroughly with methyl iodide, oonine behaves similarly to piperidine (see above), the final product being oonylene, CsHu (p. 66). 0-, j3- and 7-Conlceiiis, CsHisN, are peculiar bases which result from the (indirect) separation of hydrogen from conine. Conydriue, CisHiyNO, an oxy-derivative, occurs along with oonine in hemlock; it crystallizes in plates, M. Pt. 120°, B. Pt. 240°. Nicotine, C^^Hi^Ng, = CioH3(H5)N2, is the poisonous con- stituent of tobacco and the tobacco plant. It is a strong di- atomic base, oily, readily soluble in water, alcohol and ether, and of a stupefying odour. It can be distilled unchanged in an atmosphere of hydrogen, but becomes rapidly brown in the air; B. Pt. about 250°. Permanganate of potash oxidizes nicotine to nicotinic acid, whence it follows that the former is a /S-pyridine derivative. It was formerly looked upon as hexahydro-dipyridyl, but according to Pinner (B. 26, 292; cf., however, B. 26, 628), it appears to be a pyridyl-n-methyl-pyrrolidine, C5HiN.C4H;(NCHa), in which the methyl-pyrrolidine is united tothe;8-oar- bon atom of the pyridine. For Tropine and Ecgonine, two more complex pyridine deriva- tives, see p. 543. Appendix: Pyroue; Pyrazine; Pyrimidine; Morpholine, etc. CO N CH O HC(j^.CH HCj/\cH HC/^\CH B.iO/^pB.^ Hol^^'cH HcL IcH ^\/^ Hzc'sJcHa N CH ^NH Pyrone. Pyrazine. Pyrimidine. Morpholine. 1. Pyrone, pyro-comane, CsHjOj (a neutral compound, M. Pt. 32°, B. Pt. about 212°), and its position-isomer Cumaline, a-pyrone, CsH402 (whose CO and O are next to one another in the ring, hence it is to be regarded as a S-lactone), are the mother substances of the following compounds: Comanic and Cumalic acids, CsH302(C02H), Ghelidonic acid, CeHjO^ (C02H).2, Meconicaoid, CaH02(0H)(C02H)2, Pyro-meoonio acid, C6H80a{OH), etc. Ghelidonic acid is found in celandine, and can be transformed into comanic acid and pyrone by the separation of carbon dioxide. Meoonic acid occurs in opium and passes into pyro-meconic acid through loss of car- bon dioxide. Cumalic acid results from malic acid, as given at p. 258. (S06) ill 530 XXXIV. QUINOLINE AND ACRIDINE GROUPS. When they are treated with ammonia these compounds exchange an oxygen atom for nitrogen, with the formation of pyridine derivatives (see e.g. B. 17, 2384). Por syntheses, of. among others B. 20, 154; 24, 111, Kef. 575; A. 257, 263; 262, 89; 273, 164. 2. Fyrazlne, aldme, CiHiNj (colourless prisms, M. Pt. 55°, B. Pt. 115°), possesses a basic character (B. 26, 721) and is the mother substance of the ketines, e.g. Ketine or dvmethyl-pyrazine, C4H2(CH3)2N2, which is obtained by the reduction of isonitroso-acetone or the condensation of amido-acetone (p. 157; B. 19, 2524; 21, 19). " Piperazine " is formed by the addition of six hydrogen atoms to pyra- zine. It is identical with dietbylene-diaimine (p. 210), and is employed in cases of gout and stone diseases on account of its solvent action on uric acid. 3. Fyrimidine, miazme. From this (unknown) mother substance there are derived the so-called Cyan-metMnes, which result from the polymeriza- tion of the nitriles, and a series of compounds which are produced by the action of aceto-acetio ester upon the amidines ; also alloxan (p. 303). Cf. E. V. Meyer, J. pr. Ch. 39, 188, 262; Pinner, B. 18, 759, 2845; 23, 3820. A similar hexagon ring to that of pyrimidine, but with three symmetric- ally distributed nitrogen atoms, appears to form the basis of certain: 4. Tricyanides, e.g. CyapTienine, CsNa. (OsHsja, which is formed from benzo-nitrile, benzoyl chloride, and sal-ammoniac in presence of chloride of aluminium (B. 25, 2263; cf. also the cyanogen compounds). 5. Morpholine, C4H9NO. A methyl derivative of this base, Methyl- morpholine, (CHa)N<[^QTx'' nn!/^' "^^^"^'^ "P°" methylating dioxy- CeH, + H,0. Formyl-diphenylamine. Acridine. It consequently appears as an anthracene in which the middle group ('H is replaced by N. Acridine is a tertiary base. Methyl- and Butyl-acrldlnes, Phenyl-acrldlne, C8H40 \CeHs— N(OHb), . '^C6H,=N(CHs)jCl Leuco-compound. Formo-rhodamine hydrochloride. Benzo-, succino-, and phthalo-rhodamines (p. 495) are also derived from this dye. Fluorane (p. 495), and its derivatives fluorescein, etc., likewise belong to the same group, C. Azines, Oxazines, and Thiazines. In anthracene and hydro-anthracene two benzene nuclei are joined together by two (CH)- and (CH2)-groups respectively, in acridine by one (CH)-group and one nitrogen atom in an analogous manner, and in hydro-acridine by one (CHj)- and one (NH2)-group, these being always in the orfAo-position to one another. A similar junction of two benzene nuclei can A2INES; OXAZINES; THIAMINES. 539 be brought about by two nitrogen atoms or imido-groups (like- wise in the o-position to one another), thus: C«H,<^>C«H, 0,H,<^^>CeH, (L) Phenazine. (II.) Hydro-phenazine. Also by an imido-group and an oxygen or sulphur atom, thus : CaH,<^(f>CeH,. CeH,<^gH>C«H,. (III.) Phenoxazine. (IV.) Phenthiazine (thio-diphenylamine). In these compounds the benzene nuclei may be replaced by those of naphthalene, with the formation {e.g.) of — C,oH6<^^>Ci„H5 OioHe<;^>C6H„ etc Kaphthazine. Naphtho-phenoxaziue, The compounds (II.) to (IV.) of the type of hydro-anthracene pass into the leuco-compounds of dyes upon the entrance of amido- (alkyl-amido-) or of hydroxyl groups holding the pa/ror position to the nitrogen. The colours themselves are then obtained from these by oxidation (i.e. abstraction of Hj), so that the dyes derived from (II.) appear likewise as amido- (or oxy-) phenazines. In this way the (mono-amidated) eur- hodines and the (di-amidated) toluylene red dyes are derived from phenazine and hydro-phenazine, and also the safranines and indulines; Nile blue springs from naphtho-phenoxazine; and the thionine dyes from phen-thiazine. 1. The Azines. Phenazine, or azo-phenylene, CijHjNz, results from the distillation of barium azo-benzoate, upon leading the vapour of aniline through red-hot tubes, and by the oxidation of its hydro-compound (see below). It crystal- lizes in beautiful long bright yellow needles, M. Pt. 171°, which can be readily sublimed, is only sparingly soluble in alcohol, but easily in ether, and soluble in concentrated sulphuric acid with a red colour; the alcoholic solution yields a green precipitate on the addition of stannous chloride. When reduced with sulphide of ammonium it goes into a colourless hydro- compound, Hydro-phenazine, C6Hi^»^* = C«Hi<^g>C,Hi + 2HsO. In accordance with the formula diH-^^Kr^Celli, phenazine may also be regarded as a derivative of (the unknown) or«Ao-Benzo-quinone, CgHt^J;, in which the two oxygen atoms are linked to neighbouring carbon atoms of the ring (of. Quinone, p. 427). Phenazine is also closely related to quinoxaliue (p. 537). Naphtho-phenazine, CioH6C8H4, results from the action of acids upon the azo-dyes derived from phenyl-;8-naphthylamine (B. 20, 571). It forms lemon-yeUow crystals which can be sublimed. Naphtho-tolazine, CiciH6C6H3(CH3), is very similar. ForisomericlTaphthazineSjCKiHiaNacf. A. 237, 327; 272,307; B.26,183. Eurhodine, amido-naphtJio-tolazine, H2N.CioHjC6Hs(CHa), is obtained by warming a-naphthylamine with o-amido-azo-toluene dissolved in phenol. Lustrous golden crystals, soluble in ether with a yellowish- green fluorescence and in dilute hydrochloric acid to a red solution (B. 19, 441; 21, 2418; 24, 1337). When heated with acid it is converted into the basic and at the same time phenolic compound: Eurhodol, HO.CioH5<]Sr2>C8H8(CH8) (yellow crystals) ; cf. B. 24, 1337. o-Siamido- phenazine, Ci2H6N8(NH2)2, results from the oxidation of o-phenylene-diamine with ferric chloride (B. 22, 355); and a hetero-nucleal isomer, analogous to toluylene red, from a mixture of m- and ^-phenylene diamines (B. 23, 1862). Toluylene red, CisHisN, {Witt). When ^-amido- dimethyl -aniline is oxidized in the cold along with m-toluylene-diamine, the beautiful blue compound Toluylene blue, an indamine (p. 389), results, which gives up hydrogen and goes into toluylene red when boiled: /NHa (CH.,)jN— CeH,/ + /CoH8(CH3)(NHj) -1- O, NH/ Amido-dimethyl-aniline. Toluylene-dlamine. = (CH8)2N— C.H8<^j^^06Hs(CH8)— NHa + SH^O. Toluylene red. Other similar compounds can be prepared in an analogous manner. The simplest toluylene red, which results from ji-phenylene -diamine and m-toluylene-diamine and which contains NHj in place of N(CH8)si yields Methyl-phenazine, CoHifNjjCaHafCHs), when diazotized. Toluylene red is used on the technical scale as " Neutral red," I'or Iri- and Tetramido-phenazlne, cf. B. 22, 3039. SAFEANINES; INDULINES. 541 Safranines. The Safranines are related to toluylene red. They are produced by oxidizing an aqueous solution of a mixture of the sulphates of ^-phenyl ene-diamine (1 mol.) with a primary monamine (I mol.) and a second monamine in which the p-position is unoccupied (1 mol.). The simplest safranine is Pheno-safranine, CigH^N^Cl [from CeH^(NH2)2 + 2O6H5.NH2], while the ordinary safranine of commerce consists principally of Tolu-safranine, C^iHioN^ HCl [from C6H3(CH3)(NH2)2 (1:2:4) and 2CaH^(CH3)NH2]. See B. 16, 472, etc. The requisite mixture of mono- and diamines is attained in practical working by the reduction of amido-azo-compounds (see p. 404). The safranines are beautiful crystalline compounds of a metallic green lustre, readily soluble in water, which dye yellowish-red, red and violet. The solution in concentrated sulphuric acid is green, becoming blue, violet, and iinally red on dilution with water. Eeduction gives rise to leuco-com- pounds, which are diamido-compounds of the as yet unknown substance OgH^^^S, jj y>G^B.i (B. 19, 2690, 3017, 3121, etc.). The safraniDes are therefore probably diamido-compounds of a still un- known "azonium" base, CsHi^^.p -o- .J^CsHj. OH Mauveine, phenyl -safranine, CiiHj!(i(08H5)N4Cl, was the first aniline dye to be prepared on the technical scale (by Perhm in 1856, from crude aniline, bichromate of potash and sulphuric acid). Magdala red, CaoHjiNiCl, is the safranine of the naphthalene series. Indulims. The dyes of this group contain the peculiar induline ring; I 1 fS~J 1 ; this appears on the one hand as a derivative of a \/ I \/ pseudo-form of phenazine (the latter base being E obtained e.g. from benziuduline), while on the other it is derived from (yara)-quinone, seeing that two atoms or groups in the yaro-position to one another are linked to one benzene ring by double bonds {i.e. in " quinoid " linkage). 542 XXXIV. QUINOLINE AND ACRIDINE GROUPS. The benzindulines are direct derivatives of this induline ring, while the rosindulines and naphthindulines are referable in the same way to corre- spondingly modified naphtho-phenazines and naphthazines respectively. The indulines are violet-blue to grey-blue dyes which result upon heating amido-azo-benzene with the aniline hydrochlorides, and sulphurating the product so obtained. Pora-quinone-anilides are formed here as intermediate products, e.g. Azo-phenine or diamilido-qumone-dianile (p. 430, B. 21, 676; Witt, B. 20, 2659); the formation of these from the amido-azo-compounds is explicable from the latter acting to a certain extent as oxidizing agents, and also at the same time as the source of the jsara-diamines which result by their reduction (0. Fischer and Hepp, B. 2S, 2731; cf. also p. 403). Fhenyl-indnline, CmHuNs, = "5.1^=0^^^^^,^ -^ .^CsHj, is the sim- plest benzinduline. M. Pt. 125°. It yields reddish-violet salts which are soluble in water. The more complex and bluer indulines, C24Hi8N4, CseHaNj, etc., whose sulpho-salts constitute the Fast Blue, etc. of commerce, are derived from phenyl-induline by the further entrance of phenyl- and amido- phenyl groups into the molecule. When phenyl-induline is warmed with hydrochloric acid, Benzene-indone, CisHiaNaO (in which the imido-group of the phenyl-induline is replaced by oxygen) is obtained among other products. It crystallizes in small plates with a metallic lustre, and yields phenazine when distilled with zinc dust. Fhenyl-rosinduline, OjaHigNs, an induline of the naphtho-phenazine series, results upon heating (e.g.) benzene-azo-a-naphthylamine with aniline and aniline hydrochloride. Its disulpho-aoid is the valuable oroein-red dye, Azo-carmine. For the literature on this subject, see 0. Fischer and Hepp, B. 23, 838; A. 256; 262; 266; 272, 306. Aniline black (CS0H27N5?), obtained by acting upon aniline with (e.g.) potassium chloride in presence of copper or vanadium salts, is produced directly upon the fibre; it is a dark green amorphous powder, insoluble in most menstrua. 2. Oxaziues. Fheuozazine, C{Hi<^ q ^CeHj, is obtained by heating pyrocatechin with o-amido-phenol ; sublimable plates. Nile Blue, HN=C,oH,^q^C6H,— NCCjHsjs, HCl, whose leuco-base is a di-ethylated diamido-naphtho-phenoxazine, results upon converting diethyl-m-amido-phenol into its nitroso-compound, and heating the latter with a-naphthylamine. It is a magnificent greenish-blue ba^io dye. 6allo-cyaii,ine, djHuNaOjCI, a blue-violet dye which, like alizarin, re- quires a mordant, is prepared by the action of nitroso-dimethyl-aniline upon gallic acid ALKALOIDS OF COMPLEX CONSTITUTION. 543 3. Thiazines (Thionine dyes). Fheu-thiazine, thio-diphenylamme, C6H4<^? ^dHi. Of. p. 389. When nitrated and then reduced, this compound yields : Diamido-tMo-diphenylamine, leuco-thumine, CbH,NS(NHj)2, the leuco- compound of the less hydrogenized : Thionine, CuHgNaS, whose hydrochloride is Lanth's Violet. /CeH3-N{CH,)j Methylene Blue, CmHisNsSCI, = n/ >S (Caro, 1876), a ^C,Ha=N(OHs)sCl blue dye which ia particularly valuable for cotton, results from the action of ferric chloride upon amido-dimethyl-aniline, in presence of sulphuretted hydrogen; also by oxidizing the latter base in presence of thio-sulphurio acid to Amido-dimethyl-aniline-thioBTilphonic acid, C6H3(N[CH3]2) (NHj) (S.SO3H), joining this (by oxidation) with dimethyl-aniline to the corre- sponding indamine, and boiling the latter with chloride of zinc. Cf. Bemthsen, A. 230, 73; 251, 1. XXXV. ALKALOIDS OP COMPLEX OR UNKNOWN CONSTITUTION. Some of the alkaloids which occur in nature are free from oxygen, liquid, and volatile without decomposition; while others contain oxygen, are (usually) solid and crystalline, and are not volatile without decomposition (strychnine volatilizes in a vacuum). They are precipitated by certain reagents such as tannic acid, phospho-molybdic acid, platinic chloride, the double iodide of mercury and potassium, potassic iodide, etc. Many of them give intense colour reactions with nitric acid, chlorine water, concentrated sulphuric acid, etc. A. The Tropine Group. The degradation products of the important alkaloids atropine and cocaine probably contain a peculiar and but slightly stable combination of a piperidine- with a hexahydro-henzene ring, in which four carbon atoms are common to both systems {Merling, 1891) : CH CH CR H2C /^ CH2 UiCrcso] enI chJcBj cHjnI CH2 JcBj ch3:s\ch JCH2 CH2 H2C/CH /^s \j/ \l7 CHz CH CH CH Hypothetical Tropine. Tifopidine. mother substance. 544 XXXV. ALKALOIDS OF COMPLEX CONSTITUTION. These formulae explain in an especial degree how the formation of the most varied decomposition-products is brought about, in that the hexa- hydro-benzene ring ia sometimes broken and derivatives of hydro-pyridine ensue, while in other cases the piperidine ring is split up and hydrogenized benzene derivatives result (see below; also B. 24, 3108; 25, 1391). The formula of tropine, given above, receives further support from a beautiful synthesis of that compound from dihydro-benzyl-dimethylamine (Chem. Ztg. for 1892, p. 319). The above compounds were formerly held as derived from a tetrahydro- pyridine with a long side-chain, e.g. tropine was regarded as a-oxyethyl-n- methyl-tetrahydro-pyridine. But this latter compound (p. 528) has been synthetized and found to he quite diflterent from tropine (Lvpp, B. 25, 2197). Tropine, CaHisNO, is obtained by decomposing atropine by means of baryta water. It is a tertiary base crystallizing in plates; M. Pt. 62°, B. Pt. 220°. When it is oxidized with chromic acid, the hexa-methylene ring is broken and Tropinic acid, CsH8N(CHs)(C02H)2, — the dicarboxylio acid of a methylated piperidine in which the methyl group is attached to the nitrogen — is formed. Concentrated hydrochloric acid converts tropine into: Tropidine, CsHisN, an oily base, B. Pt. 162°, which likewise results on the separation of carbon dioxide from anhydro-ecgonine. Ecgonine, CsHuNOs, = CsHuNO.COjH. White prisms; laevo-rotatory. Ecgonine is a carboxylio acid of tropine {Binhom), and therefore an oxy- acid. As an alcohol it forms a benzoic ester and as an acid a methyl ester, from a mixture of which cocaine can be synthetized (see below). Anhydro-ecgonine, C9H13KO2, stands in the same relation to ecgonine as tropidine does to tropine. When its dibromide is treated with soda the piperidine ring is broken up, with the production of dihydro-benzaldehyde (p. 435) and methylamine {Einhorn, B. 26, 451). Cocaine, CiyHjjNO^, is the active constituent of the coca leaf (Erythroxylon coca), and is well known for its property of deadening pain. Lsevo-rotatory. Its hydrochloride crystallizes in white prisms. Hydrochloric acid breaks it up into benzoic acid, ecgonine and methyl alcohol, and it may be conversely reproduced by benzoating ecgonine and then methylating the resulting benzoyl-eogonine. Homologous cocaines have been prepared in a similar manner. Several of the compounds of this group are known in different optically active modifications (B. 83, 979; 26, 927). B. Opium Bases. Opium (Papaver somniferum) contains: 1. Morphine, CjyHjjNOj, = Cj7Hi7NO(OH)2, a monatomic OPIUM AND CINCHONA BASES. 545 and tertiary base. It crystallizes in small prisms ( + HjO) of bitter taste, and is a valuable soporific. When distilled with zinc dust it yields phenanthrene in addition to pyrrol, pyridine and quinoline, and it is also convertible into phenanthrene derivatives in another way (A. 222, 235). It appears to be a derivative of morpholine (p. 630). For its constitution, of. Knorr, B. 28, 181, 1113; Shraup, Monats. f. Chemie, 10, 101. 2. Codeine, methyl-morphine, CigHjiNO., can be prepared by methylating morphine. 3. Thebaiae, O19H21NOS. 4. Ifarceine, CssHjsNO,. 5. Papaverine, CaiHjiNOi, and 6. Berberine, CsoHbNOi, are derivatives of iso-quinoline. For their constitution, see Monats. f. Chemie, 9; B. 24, Kef. 157. 7. Narcotine, C22H23NOy, crystallizes in glancing prisms. It is decomposed by the action of water into Meconine, CjqHjjO^ (cf. p. 467, the anhydride of meconinic acid), also present in opium, and Cotarnine, CijHigNOg (prisms, + H^O), which latter is convertible by bromine into dibromo-pyridine. Like papaverine it is a derivative of benzyl-isoquinoline. For constitution, see Roser, A. 254, 351, 356. O. Cinchona Bases. Quinine barks {i.e. the Cinchona varieties) contain: 1. Quinine, C20H24N2O2 + 3H2O, a diatomic base of intensely bitter taste and alkaline reaction, whose sulphate and chloride are universally used as febrifuges. It crystallizes in prisms or silky glancing needles; M. Pt. 177°. The quinine salts in dilute solution are characterized by a magnificent blue fluor- escence. As a base quinine is a tertiary diamine, but it contains in addition — as its reactions show — a hydroxyl and a methoxyl, and seems to be built up of two different ring-systems, in accordance with the following formula: — (CH30).Ci,H5N— Ci„Hm(OH)N. The first of these represents the radicle of a p-methoxy-quinoline, this latter compound being obtained on fusing quinine with potash (p. 535). The second system probably possesses a ring similar to that of tropine, since it yields as decomposition-products sometimes a pyridine derivative (e.g. /3-ethyT pyridine on fusion with alkali), and sometimes benzene derivatives containing no nitrogen (e.g. a phenolic compound, CioHuOH, together with (606) 2M 546 XXXV. ALKALOIDS OF COMPLEX CONSTITUTION. ammonia, on succeBsive treatment with phosphorus pentachloride, potash, and hydrobromio acid). It yields quininic acid, C9H5N(OOH8)COjH (p. 536), and Ciucho-loiponic acid, CisHisNOi, upon oxidation; and Apo-qninine, Ci9H2oN2(OH)2, when warmed with hydrochloric acid, methyl being separated. Of. B. 14, 1852; A. 204, 90; Shraup, Monats. f. Chemie, 10, 220; Koniga and Comstoch, B. 25, 1539 (where a riswrrUoi the literature on the subject is given); 26, 713. 2. Ciuchonine, CigHmNjO, = Ci9H2iN2(OH), is derived from quinine by the exchange of (OCHs) for H. It forms white sublimable prisms or needles, is a weaker febrifuge than quinine, and yields cinchoninic acid upon oxidation and quinoline on fusion with potash. 3. Conchinine, G^oB-^A, and 4. Ciuchonidine, CuH^^NsO, are isomeric with quinine and cinchonine respectively, and milder in their action. D. Strychnine Bases. Strychnos nux vomica and certain other beans, etc. contain: 1. Strychnine, C^^^^^O^, and 2. Brucine, C2gH28N204. The former, which is excessively poisonous (producing tetanic spasms) crystallizes in four-sided prisms and yields quinoline and indole when fused with potash, and /8-picoline, etc., when distilled with lime. (For recent literature on this subject, see A. 264, 33; 268, 229.) Brucine (prisms) is converted into homologues of pyridine on fusion with potash. E. Solanine Bases. Atropine, Hyoscyamine and Hyoscine are three isomeric bases of the formula OJ.7H23NO3, which can be respectively prepared from Atropa Belladonna, Datura Stramonium and Hyoscyamus niger, and which are remarkable for their mydriatic action (power of dilating the pupil of the eye). Atropine crystallizes in colourless prisms or needles, possesses an extremely bitter taste, and is broken up by baryta water into tropic acid and tropine, CgHjjNO (p. 544), being therefore the tropic ester of the latter. Tropic acid and tropine reunite again to form atropine when their dilute hydrochloric acid solutions are evaporated together. When optically active (d- and 1-) tropic acids are used, a dextro- and a Isevo-rotatory atropine result (B. 22, 2590). And if, instead of tropic acid SOLANINE BASES, ETC. 547 itself, a homologue is employed, homologous bases, the " Tropei'ues " are obtained; thus mandelio acid yields Homatropine, CioHiaNOs, which exerts like atropine a mydriatic action, although a less lasting one {Ladenburg, A. 217, 82). Hyoscyamine (needles or plates, M. Pt. 109°) resembles atropine closely, and is readily transformed into the latter, e.g. under the influence of alcoholic potash (WiU, B. 21, 1725, 2777). Its components are very possibly Mropic acid and i-tropine, in which case it would be stereo-isomerio with atropine (B. 22, 2590). Hyoscine, M. Pt. 55°, is likewise decomposed by baryta water into tropic acid and tropins (?), and is perhaps stereo-isomerio with the above com- pounds (B. 25, 933, 2388; A. 271, 100). P. Among other alkaloids may be mentioned: Corydaline, CjoHzgNOj, from Corydalis cava. Plat colourless prismatic crystals, M. Pt. 134-5°. Yields the hydriodide of a base, dgHaiNOi, with hydriodio acid, four methoxy-groups being split oflf, and Corydalinie acid, CisHjiNOis, when oxidized with permanganate {Bobbie and Lauder, Ch. Soc. J. for 1892, pp. 244, 605 ; 1894, p. 57). Veratrine, Ci;HtjN08, from Veratrum album. Sinapine, CieHasNOs (from the seed of white mustard), is a derivative — not of pyridine — but of choline on the one hand and of gallic acid on the other. Sparteine, CisH^eNs (in Spartium sdoparium). For the alkaloids produced by the decomposition of dead bodies, which are termed Ptomaines, see p. 563. 548 XXXVI. TERPENES AND CAMPHORS. XXXVI. TERPENES AND CAMPHORS. The terpenes are hydrocarbons of the formula CjjHj,, [or (CjHg)^], some of which are nearly related to cymene (p. 364), and others to other benzene derivatives. The camphors, e.g. Japan Camphor, CjQHjgO, contain oxygen in addition, but are closely allied to the terpenes. Both classes of compounds are widely distributed in nature. Ethereal oils. Many plants contain, especially in their blossoms and fruits, oily substances to which they owe their peculiar fragrance or odour, and which can be obtained from them e.g. by distillation with steam. These, which are termed ethereal oils, were formerly grouped together in a special class, but now they are recognized as being more or less hetero- geneous ; thus oil of bitter almonds is benzoic aldehyde, and Roman oil of cumin is a mixture of cymene and cumic aldehyde, etc. Many of these ethereal oils contain terpenes, e.g. oil of thyme consists of thymene (a ter- pene) together with cymene and thymol; in fact the terpenes are often among their chief constituents, as in the case of turpentine, citron, and orange oils, etc. We further meet in some with olefinio alcohols, aldehydes, or ketones (for instance linalool and dtral) which are isomeric with certain varieties of camphor, and which readily allow of ring-formation, and thus pass into terpenes (see appendix, p. 558). Many oils deposit solid substances, the " stearoptenes," when exposed to cold, the liquid portions being termed "Elseoptenes." The camphor varieties resemble the ethereal oils in their occurrence and modes of preparation, but they are solid. A. Terpenes. (Cf. especially 0. Wallach, B. 24, 1525, where references to the literature on the subject are given; A. 268 et seq.; 272, 99; Baeyer, B. 26, 232, 820.) The terpenes are widely distributed in the vegetable king- dom, especially in the Coniferse (Pin us, Picea, Abies, etc.), in the varieties of Citrus, etc. The products which are isolated in the first instance from the individual plants, and which according to their source are designated terpene, citrene (from oil of citron), hesperidene (from oil of orange), thymene (from thyme), carvene (from oil of cumin), eucalyptene, olibene, etc., have for the most part the formula CjjHjg and approximately equal boiling points (160°-190°); they are not, however, chemical individuals but mixtures of isomeric compounds. With the exception of camphene they are all liquid, but it is hardly TERPENES; PROPERTIES OF, ETC. 549 possible to separate them completely by fractional distillation (see table, p. 550, for boiling points). The terpenes can, however, be obtained chemi- cally pure from crystalline derivatives. Quite recently, too, compounds belonging to this class have been synthetized (see below). Many terpenes are nearly related to cymene, C-^f^'H.-^^•, thus oil of turpentine goes directly into cymene when heated with iodine, and it yields, like the ^ara-dialkyl-benzenes, terephthalic acid, CgH4(C02H)2, upon oxidation, etc. They are therefore to be regarded in part as di-hydrides of cymene, CjqHj^.Hj (see p. 364). Some show a close relation to o-xylene (see Can- tharene), and others to m-xylene (see Cineol). The terpenes are also capable of forming addition-compounds which frequently lead as far as to derivatives of CiqHjq, i.e. to compounds whose benzene nucleus is completely reduced. They unite with hydro- chloric acid to di-hydrochlorides, CjjHj80l2, or — in the case of the pinenes and camphenes — to mono-hydrochlorides, CjqHj^CI, only. They often form with bromine characteristic tetra- bromides, CigH^gBr^. They readily yield compounds with nitrosyl chloride, of the formula CmHg.NOCl, on treatment with ethyl nitrite, glacial acetic acid and hydrochloric acid. Lastly, two of the terpenes — terpinene and phellandrene — com- bine easily with nitrous acid to form " Nitrosites," CiqEEj^Nj^s- The combination with bromine and with halogen hydride is readily effected in an acetic acid solution. When the solution of the halogen hydride addition-product in glacial acetic acid is heated vrith sodium acetate, the halogen acid is split oS. The nitroso-chlorides, which are solid compounds melting at about 100°, react readily with organic bases — e.g. piperidine, ethylamine, aniline, etc. — to produce other well-characterized bases, the NUrolamines, OioHi6(NO)(NE.E.') : CioH8"C^(-jj + NHjE. = Cii}Hi8<\j^g-E, + HCl. Among those the nitrol-benzylamines (prepared from benzylamine) may be instanced as specially well suited for the recognition and characterization of the terpenes. Many terpenes show a great tendency to pass into more stable isomers under certain conditions, e.g. when acted upon by acids. They also polymerize readily. When in solution in acetic anhydride or alcohol, they give (yellow) red or blue colour-reactions with concentrated sulphuric acid. 550 XXXVI. TERPENES AND CAMPHORS. Optical hehaviour of the terpenes. The behaviour of the terpenes with regard to polarized light is very interesting. They are almost all optically active, and most of them exist both in dextro- and in lasvo-rotatoiy modifications. While no appreciable alteration in properties (with the exception of the resulting optical inactivity) is as a rule apparent upon mixing equivalent amounts of these modifications, there results, oddly enough, when dextro- and Isevo-limonene are mixed together, a peculiar "raoemic compound," inactive dipentene, the derivatives of which differ materially from those of its components in boiling point, in melting point, and in solubility. The terpenes are divisible into three main groups: (a) Those which are capable of combining with one molecule of halogen hydride only, provided they do not in the meantime change into isomers : — pinene and camphene ; (6) Those which can unite with two molecules of halogen hydride, but not with nitrous acid : — dipentene, sylvestrene and terpinolene; (c) Those which form nitrosites with nitrous acid : — terpinene and phellandrene. They differ further in the boiling points, melting points, and properties of the mono- and di-hydrochlorides, and of the bromine addition-products (mainly tetrabromides), etc. Swinmary, M.Pt. B. Pt. Bromides, M. Pt. Hydrochlorides, M. Pt Nitrites, M-Pt 1. Pinene 2. Camphene - 3. Fenchene Liq. 60° Liq. 159°-160° 160°-1.61° 158°-160° Bra: 170° Bra: liq. + HCl : 125° „ : decomp. — i. + Limonene ia, Dipentene - 5. Sylvestrene - 6. Terpinolene - Liq. 1 175° 175°-176° 185°-190° Br, : 104° „ 125° „ 135° „ 116° 1 -1-2HC1:50° :72° [ „ :50°] — 7. Terpinene - 8. Phellandrene 180° about 170° — — 155° 102° In addition to the "Terpenes proper," CjoHie, we have Hemiterpenes, CjHj (see Isoprene), which polymerize to terpenes (dipentene); Sesqui- PINENE. 551 terpenea, (OsHjjj (Cedrene, Cardinene, CaryophyUeue, and Clovene, B. Pt. 250°-260°); and Polyterpenes (OjH,)i, [Colophene, dMsi (B. Pt. above 300°), and Caoutchouc {CioHis)i]. Constitution. The conception that the terpenea are dihydro-cymenes is apparently warranted in the case of many of them. The frequently observed transformation of certain terpenea into cymene (which, however, does not usually go quantitatively), and the formation of terephthalio acid by their oxidation, are in favour of this assumption. Further, carvol (carvone) yields oximes {oanioximes) which, according to S. Goldschmidt (B. 18, 1733), are identical with the nitroao-limouenea prepared from limon- ene; carvone also yields dihydro-carveol upon reduction, and this passes into terpinene when warmed with dilute sulphuric acid (B. 24, 3991). Again, corresponding to the (aldehyde) citral, CwHisO, which can yield up the elements of water and thus pass into cymene, we have as alcohol the com- pound linalool, OioHijO, which goes over into terpinene together with dipentene when water is abstracted from it (cf. e.g. J. pr. Oh. 45, 596). Lastly, A. Baeyer has quite recently synthetized a, dihydro-cymene which shows the terpene character in its entirety (B. 26, 233). Dihydro-cymenes with two ethylene Unkings in the benzene nucleus can exist in various isomeric modifications according to the relative position of these linkinga, being thus analogous to the dihydro-phthalio acids. Ter- penes of section (6) probably come under this category, since their capacity for taking up four monovalent atoms ia readily intelligible on the above assumption. For the terpenes of section {a) only one ethylene linking is to be assumed, so that their molecule perhaps contains a diagonal {para-) linking in addition. The side-chain may also contain the group CaHs instead of CjH?, and therefore an ethylene- linking (terpinene ? ). 1. Pinene, CjflHjg, is the chief constituent of German and American oil of turpentine, oil of juniper, of eucalyptus, of sage, etc. It forms, together with sylvestrene and dipentene, Eussian and Swedish turpentine oiL Oil of turpentine is obtained by distilling turpentine, the resin of pines, with steam, colophonium (fiddle resin) remain- ing behind. It is a colourless strongly refracting liquid of characteristic odour, almost insoluble in water but readily soluble in alcohol and ether. It dissolves resins and caoutchouc (being therefore used for the preparation of oil paints, lakes, etc.), also sulphur, phosphorus, etc. It absorbs oxygen from the air with the formation of ozone and production of resin, 552 XXXVI. TERPENES AND CAMPHORS minute quantities of formic acid, cymene, etc. being formed at the same time. Dilute nitric acid either gives rise to tereph- thalic acid in addition to fatty acids, or — under other condi- tions — to terpenylic acid, C8HJ2O4 (which belongs to the fatty series), etc. Heating with iodine transforms it into cymene, the action being violent, and heating with hydriodic acid into the compounds CjjHjg and CuHjq. It acts as an antiseptic and arrests the secretions {e.g. that of the kidneys). Oil of turpentine shows physical differenoes, according to the source from which it is derived, the German, French, and Venetian oils being Isevo- and the Australian dextro-rotatory. These differences depend upon the existence of Isevo- and dextro-pinenes, etc. (cf. the tartaric acids). B. Ft. 158°-161°; Sp. Gr. 0-86-0-89. Inactive pinene can be obtained pure by heating pinene nitroso-chloride vrith aniline, NOCl being separated. B. Pt. 155°-156°; Sp. Gr. 0-86. Pinene hydrochloride, CjoHiyCl (see table, p. 550), M. Pt. 125°, is a solid white crystalline mass with a camphor-like odour, whence its name of " artificial camphor,'' insoluble in water but readily soluble in alcohol. If its hydrochloric acid is separated by weak alkali, e.g. by heating it with soap, camphene is obtained (see below). Pinene hydrochloride is incapable of further combination with HCL Prom this it may be concluded that pinene has only one double bond in the molecule, and the same applies to camphene. The mono-hydriodide of pinene yields the same reduction product as bornyl iodide, viz. dihydro- camphene. Finene nitroso-chloride, C10H18.NOCI, results, together with cymene and pinol, by the action of ethyl nitrite, glacial acetic acid and hydrochloric acid upon pinene. Crystals; M. Pt. 103°. When heated with aniline it changes back into pure inactive pinene. 2. Camphene, CiqHj^, of which there are two modifications, dextro- and Isevo-, is a solid terpene. It is obtained by heating pinene mono-hydrochloride with alcoholic potash or with dry soap, and is more stable than pinene. M. Pt. 50°. It also results in an analogous manner from Bornyl chloride, C10H17CI (see Borneo camphor). It has an odour like that of oil of turpentine and camphor, and is oxidized to camphor by chromic acid mixture. With DIPENTENE, ETC. 553 bromine it does not yield a tetrabromide but a mono-substitution product, and it combines with only one molecule of hydrochloric acid. 3. Fenchene, CioHm, This is obtained from fenchone or fenchyl chloride as camphene is from camphor or bornyl chloride. It is a liquid, but is in other respects very like camphene. 4. d-Limonene, hesperidene, citrene, or carvene. The oil of the orange rind consists almost entirely of dextro-limonene, which is likewise the chief constituent of carvene, oil of dill, oil of erlgeron, etc.; together with pinene it forms oil of citron. It boils at 175°, and forms a dextro-rotatory tetra- bromide, CioHisBri, which melts at 104°, and it therefore probably contains two double Unkings. The H- and - tetrabromides are identical, except that their crystals are the mirror images of one another. Dextro-limonene is very easily rendered inactive, i.e. converted into dipentene. The "racemio" tetrabromide melts at 125°. 2-Limouene is present together with Isevo-pinene in the oil of fir cones. Its tetrabromide has the same M. Pt. as that of the cJ-compound, viz. 104°. Z- and cJ-limonenes yield nitrosyl chlorides, CioHmNOCI, of corresponding rotatory powers; and, on the separation of hydrochloric acid from these, I- and (i-IfitroBO-Umoneues, CioHuNO, which are identical with the carv- oximes (p. 423). Dihydro-dipentene, from dipentene-di-hydriodide, is exceedingly like carvo-menthene (p. 555). 4a. Dipentene, cinene, inactive limonene, OjqHjj, is found {e.g.) together with cineol in Oleum cinae, and is prepared by heating pinene, camphene, sylvestrene or limonene to 250°-270° for several hours, and also by the abstraction of 2HC1 from its di-hydrochloride. It is further produced from pinene under the influence of dilute alcoholic sulphuric acid, from terpin hydrate and terpineol by the separation of water, by the poly- merization of isoprene, and, together with the latter substance, on distilling caoutchouc. It is a liquid of pleasant odour like that of oil of citron, B. Pt. 175°-176°, and is more stable than pinene, although it can still be "isomerized" to terpinene by acids. It readily forms dipentene dihydrochloride with hydro- chloric acid, and a crystalline tetrabromide with bromine, M. Pt. 125°. Its (inactive) nitroso-chloride yields, on separation of hydrochloric acid, the so-called Nitroso-dipentene (inactive carvoxime), M. Pt 93°. Dipentene di-hydrochloride, CioHibCIj, crystallizes in rhombic tables, M. Pt. 50°, and is very readily soluble in hot aloohoL It is formed by the 554 XXXVI. TERPENES AND CAMPHORS. addition of hydrochloric acid to dipentene, limonene, etc., and also from moist pinene, this latter first undergoing conversion into its isomer, dipen- tene. Terpin hydrate, CioHis(OH)2 + HaO, is formed when the solution of di- pentene di-hydrochloride in aqueous alcohol is allowed to stand, and also from pinene under the influence of alcohol and nitric acid. It crystallizes in large rhombic colourless crystals, M. Ft. 117°, which lose their water at 100°. The compound thus formed, Terpin, CioHi8(OH)2 (needles, M. Pt. 105°), possesses the character of glycol and yields the above dichloride again with hydrochloric acid. By the separation of HjO it goes into Terpineol, CioHi7(OH), an unsaturated monatomic alcohol which is transformed by bromine into dipentene tetrabromide. Further elimination of HjO from terpineol (by boiling it with dilute acids) gives rise to dipentene, terpinene, or terpinolene as the principal product, according to the conditions of the experiment. 5. Silveetrene, B. Pt. 175°, is the (dextro-rotatory) chief constituent of Swedish and Bussian oil of turpentine. Its Si-hydrochloride is isomeric with dipentene di-hydrochloride and is dextro-rotatory. Sylvestrene is one of the most stable of the terpenes. It gives a magnificent blue colour reaction with acetic anhydride and concentrated sulphuric acid. 6. Terpinolene, which is very like dipentene, and : 7. Terpinene both result from the " isomeration " of pinene and limonene (see Terpin hydrate). Terpinene yields a nitrosite. 8. Fhellandrene, which occurs as dextro-pheUandrene in water dropwort (Fhellandrium aquaticum) and as Isevo-phellandrene in eucalyptus oil, yields a solid nitrosite readily with nitrous acid. Phellandrene is among the most easily altered of the terpenes; it is readily converted into dipen- tene, while alcoholic hydrochloric acid changes it into terpinene, 9. Synthetized Sihydro-cymene (see above), B. Pt. 174°. This com- pound, prepared from sucoino-succinio ester (B. 26, 233), shows the complete terpene character, has » turpentine odour, becomes resinous on exposure to the air, decolorizes permanganate at once, and takes up bromine. It resembles the terpenes in many of its properties. 10. Caoutchouc (CjQHjg)„ is the hardened milky juice of the tropical euphorbiaceae, apocyneae, etc., especially Siphonia (ficus) elastica, which grows in Brazil, etc. It can be obtained pure, in the form of a white amorphous mass, by dissolving the crude material in chloroform and precipitating with alcohol. For its behaviour on distillation, see Dipentene. It absorbs oxygen from the air and is converted into vulcanite on treat- ment with sulphur. CAMPHOR. 555 Gutta percha (from Isonandra Gutta, which grows in India) differs from caoutchouc in that it contains oxygen. Cantharene, CjIIij, appears to be a lower homologue of the terpenes. It is obtained by acting on oantharidin with phosphorus pentasulphide, smells like turpentine, and resinifies in the air. B. Pt. 135°. When oxid- ized it yields o-toluio and phthalic acids, and is therefore probably o-dihydro- xylene. The following are to be regarded as dihydro-terpenes : — Menthene, OwHis, can be synthetized from menthol (p. 557) by converting it into the bromide and then splitting ofi hydrobromic acid. B. Ft. 167°. Carvo-mentliene, CioHis, likewise obtainable synthetically from carvone. B. Pt. 176°. Isomeric with menthene. Both these hydrocarbons are tetrahydro-cymenes (for constitution, see B. 36, 824). B. Oampliors. The most important variety of camphor is : 1. Common or Japan Camphor, CioHjgO, which is found in the camphor tree (Laurus Camphora) and can be obtained from the latter by distillation with steam. It forms colourless transparent and readily sublimable glancing prisms of charac- teristic odour; M. Pt. 175°, B. Pt. 204°, Sp. Gr. 0-985. It is dextro-rotatory in alcoholic solution, the amount of rotation varying with the source of the camphor. When distilled with phosphoric anhydride it goes into cymene, zinc chloride having the same effect, though in the latter case the reaction is less simple: ^^^^^^^ ^ (.^^H^^ ^ jj.O. Heated with iodine it yields oarvacrol, i.e. oxy-cymene (p. 423), just as oil of turpentine yields cymene. Nitric acid oxidizes it to the dibasic Camphoiic acid, C8Hn(COjH)2, which somewhat resembles phthalic acid, and which is perhaps a tetramethylene-dicarboxylic acid derivative (see B. 23, 218, and 2S, 267, 2087; but also B. 25, 920), and then to Camphoronic acid, CbHhOs, etc. Camphor reacts with hydroxylamine to produce Camphor-ozime, CtoHi8(NOH), and therefore contains a carbonyl group. The oxime can give up water and thus go into the Cyanide, CjHis.CN, which yields Campholenic acid, CjHis.COaH, on saponification, and Camphylamine, Ci^i5(CH2.NH2), on reduction (B. 21, 1125). Camphor may be prepared artificially by oxidizing camphene (p. 552). 556 XXXVI. TERPENES AND CAMPHORS. Two Dichlorides, CioHisCls, result upon treating camphor with phos- phorus pentachloride. Chloro-, Bromo-, Xitro-, and Amido-camphors are also known; likewise (e.^.) Ethyl-camphor. Pinol, CioHieO, is an isomer of camphor which is obtained as a by- product during the preparation of pinene nitroso-chloride. B. Pt. 183°-184°. It has an odour like that of cineol, yields terebic acid on oxidation, and is indifferent to hydroxylamine. It yields a characteristic dibromide, CioHisO.Brj, M. Pt. 94° (from which the bromine may be again split off), and a hydrobromide, CioHuO.HBr. In this latter compound the bromine may be exchanged for hydroxyl, with the formation of : Fiuol hydrate, CioHi70(OH), a monatomic alcohol crystallizing in needles, M. Pt. 131°. It is reconverted into pinol when warmed with dilute sul- phuric acid, and ia oxidizable (quantitatively) to terpenylic acid, CsHigO^. Borneol or Borneo Camphor, CjQHigO, occurs in nature (in Dryobalanops Camphora), and is produced by the action of nascent hydrogen upon Japan camphor: ^10^16^ + H2 = Cj„HigO. It is very like the latter, but has at the same time an odour of pepper. It crystallizes in hexagonal plates, M. Pt. 208°, B. Pt. 212°. Oxidation converts it in the first instance into camphor. Borneol possesses the character of a secondary alcohol, yielding compound ethers, etc., and giving with PCls Bornyl chloride, C10H17CI (M. Pt. 148°), isomeric with pinene hydrochloride; bornyl chloride goes into camphene when warmed with alkalies. Borneol comports itself as a saturated com- pound, but at the same time it forms unstable addition-products with bromine and halogen hydride. Cineol, eucalyptol, the chief constituent of Oleum cinae, and which is frequently found accompanying the terpenes, is iso- meric with borneol; M. Pt. - 1°, B. Pt. 176°. It is formed, among other methods, by the action of sulphuric acid upon pinene. It yields an unstable HCl-compound and readily goes into dipentene, and subsequently dipentene dihydrochloride. Oxidation converts it into the beautifully crystallizing Gineolic acid, CijHjgOj (M. Pt. 196°). Acetic anhydride transforms this into Cineolic anhydride, CiqHj^O^, which gives up carbon monoxide and carbon dioxide on being heated, with the forma- tion of a ketone, OgHj^O, apparently containing an open chain, — mefhyl-hezylene ketone. This last compound melts at 173°- MENTHOL. 557 174°, and has a penetrating odour like that of amyl acetate; when heated with chloride of zinc, it passes into m-Hydroxylol, CgHio-Hj (A. 258, 319; 271, 20). 1. Terpineol, which is also isomeric with borneol and'is present in certain ethereal oils, results together with cineol from terpin, water being elimin- ated. M. Pt. 35°, B. Pt. 215°-218°. It behaves as a monatomio unsaturated alcohol, yields dipentene tetrabromide with bromine, and is converted into cineol by sulphuric acid. Dipentene or isomers result from terpineol by water being split off. 2. Fenchone, CioHuO, is present as d-fenchone in many fennel oils, and as ?-fenchoue in oil of Arbor vitse; when these two are mixed, an inactive racemio compound results. It is a ketone and shows a similar behaviour to camphor; it may also be transformed into a terpene, fenchene (p. 553), but does not yield a compound corresponding to camphoric acid. 3. Thujone, CioHuO, present together with Z-fenohone in Thuja oil (oil of Arbor vitse), possesses the properties of an unsaturated ketone. The base obtained from it by the action of ammonium formate breaks up on heating into ammonia and a hydrocarbon, CioHu, whose properties are totally dif- ferent from those of the known terpenes (A. 878, 109). 4. Pulegone, CioHuO (from oil of Penny-royal), an unsaturated ketone, is isomeric with camphor (A. 272, 122; B. 25, 8515). 5. Dihydro-carvone, OioHmO, an unsaturated ketone, results upon reduc- ing oarvone, CmHhO, to the corresponding alcohol " Dihydro-carveol," CioHijO, and oxidizing the latter. When warmed with dilute sulphuric acid, dihydro-carveol is converted quantitatively into terpinene (B. 24, 3984). Tetrahydro-carvone, CmHisO, a saturated ketone, is formed by the oxidation of the corresponding alcohol " Tetrahydro-carveol," CioHajO, which in its turn is got by reducing dihydro-carveol. For constitution, see B. 86, 824. 6. Uenthone, CjoHieO, is a saturated ketone obtained by oxidizing menthol. Liquid (B. Pt. 207°), with a soft peppermint odour. Exists in two optically different modifications {Seelcmann, A. 850, 322). For con- stitution, see B. 26, 824. Menthol, mint-camphor, CioHg^O, is the principal constituent of oil of peppermint (Mentha piperita). It is a monatomic alcohol and forms a crystalline mass; M. Pt. 42°, B. Pt. 213°. Heated with sulphate of copper it is converted (quantitatively) into cymene. It is used as an antiseptic and anaasthetic. Constitutian of the Camphors. The compounds included in the above group are either ketones or alcohols, and — further — are either saturated or 558 resins; glucosides; etc. unsaturated. The ketones can be reduced to the alcohols by treatment with sodium, while the alcohols may be reoxidized again to- the ketones (A. 250, 825). The ketones yield oximes, and can be transformed into bases by heating with ammonium formate (LeucJcart, B. 20, 104), e.g. camphor, CwHisO, Into Bornylamine, OioHir.NHj, a compound of charac- teristic behaviour (of. B. 24, 3993). For further details, see e.g. Bredt, A. 226, 261; WaUach, A. 269, 326; Baeyer, B. 26, 824). Appendix. Oleflnio Camphors. On p. 548 some unsaturated alcohols, aldehydes, and ketones of the fatty series are mentioned, which are isomeric with the camphors and very similar to these, and which can be transformed into terpenes (see p. 551; of. Bertram and Walbcmm, J. pr. Ch. 45, 596; SemmUr, B. 23, 1098; 24, 201; 25, 1180, 3343). Among these may be mentioned : Linalool, CuHuO, an unsaturated alcohol, is present in the oils of linaloes (German, Lmaloe), lavender and geranium, and its acetic ether in oil of bergamot. Citral, geranial, CioHisO, the aldehyde of linalool, and therefore obtain- able from it by oxidation, is found in oil of citron. Tanacetone, CioHieO, found in oil of Fansy, is a ketone. XXXVII. RESINS; GLUCOSIDES; VEGETABLE SUBSTANCES (of unknown constitution). A. Besins. Many organic compounds, the terpenes in particular, possess the property of becoming " resinified " by oxidation in the air or under the influence of chemical reagents, i.e. of being converted into substances very similar to the resins which occur in nature. These natural resins are solid, amorphous, and generally vitreous brittle masses of conchoidal fracture, insoluble in water and acids, but soluble in alcohol, ether and oil of turpentine. They are found naturally in abundance, partly also as balsams, i.e. dissolved in terpenes or ethereal oils, from which they can be separated by distilling with steam. The resins dissolve in alkalies to form compounds of the nature of soap (resin soaps), being again precipitated GLUCOSIDES. 659 from the aqueous solutions of these on the addition of acids ; most resins must therefore consist of a mixture of somewhat complicated acids (the so-called resin-acids). Abietic acid (C^oHggO^?) is an individual acid which has been isolated from colophonium (the residue from the distilla- tion of turpentine, see below) ; it crystallizes in small plates, M. Pt. 165°, and is soluble in hot alcohol. Pimaric acid, C25H39O2, has been prepared {e.g.) from galipot resin (Pinus maritima) in a similar way; M. Pt. 148°. It closely resembles abietic acid, is crystalline and forms crystalline derivatives, and exists in two modifications, dextro- and Isevo-pimaric acids. The resins show their relation to the aromatic compounds by being converted into hydrocarbons of the benzene or naphthalene series when distilled with zinc dnst, and by the formation (e.g. ) of dioxy- and trioxy- benzenes when they are fused with potash. In addition to Colpphoninm, there may be mentioned among other resins Shellac (from East Indian Ficus varieties), and Amber, a fossil resin which contains succinic acid in addition to resin-acids and a volatile oil. The resins are largely used for the manufacture of lacs, varnishes, etc. B. Glucosid.es. (Cf. 0. Jacohsm's "Die Gluooside," Breslan, Trewendt.) As glucosides are designated a series of vegetable substances which are so broken up by alkalies, acids, or enzymes, that one of the products of this decomposition is a glucose, usually grape sugar. They are thus ethereal derivatives of the sugar varieties in question. Some of them have been mentioned already. Amygdalin, CgoHj^NOu (p. 433), is found in bitter almonds, in the leaves of the cherry laurel, in the kernels of the peach, cherry and other amygdalaceae. It crystallizes in colourless prisms, M. Pt. 200°, is readily soluble in water, and breaks up 560 XXXVII. RESINS; GLUCOSIDES; ETft into oil of bitter almonds, dextrose and hydrocyanic acid under the influence of emulsin (p. 322), or when saponified. Among others there may be mentioned : Salloin, CijHjgO,, found in varieties of Salix, which breaks up into saligenin (o-oxy-benzyl alcohol) and dextrose ; Hellcin, CijHjjO, + HgO, which results from the action of N2O3 upon salicin and is decomposable into salicylic aldehyde and glucose, from which it can again be obtained synthetically; Populin or henzoyl-salicin, OioHajOj (in varieties of Populus), which can be prepared artificially from benzoyl chloride and salicin. Arbutin, CisHigO;, and Methyl-arbntin, CisHisO^, present in the leaves of the bear-berry, etc., break up into glucose and hydroquinone or methyl- hydroquinone respectively. Arbutin is used in medicine. Hesperidin, CmHisOij, which is contained in unripe oranges, etc., can be decomposed into glucose, hesperetic acid (isomeric with ferulio acid, p. 463), and phlorogluoin. Fhloridzin, OjiHmOio (fine prisms), found in the bark of fruit trees, can be split up into grape sugar and Fhloretiu, CuHuOs, and this latter — in its turn — into phloretic acid and phloroglucin (p. 426). Both induce glycosuria (i.e. a functional derangement of the liver, giving rise to temporary diabetes) in animals. Aesculin, OuHigOg (prisms), present in the bark of the horse-chestnut, is decomposed by acids into grape sugar and Aesculetin (dioxy-cumarin, p. 464), CsHisOi. Saponin, Cs2Hs20i; (in the soapwort). Digitonin, CaH«0i4, Digitalin, CmH^Om, and Digltalem, are three glucosides which, together with digitoxin, CjiHsaOv (the most important constituent from a pharmacological point of view), are present in the digi- talis of commerce (cf. B. 24, 339 ; 25, Kef. 680). ftuercitrin, OssHaaOao, found in Quercus tinctoria, chestnut blossoms, etc.; yellow needles. Coniferin, Oi6H220a -I- 2H20 (in the cambium sap of the coniferae), breaks up into glucose and coniferyl alcohol, and serves for the preparation of vanillin, which results from it upon oxidation (p. 437). Myronic acid, C10H10O10NS2, is present as potassium salt, CioHisKOmNSj (glancing needles), in black mustard seed. It is broken up into grape sugar, potassium bisulphate and allyl isothiocyanate by baryta water or by the enzyme Myrosin, which likewise occurs in the mustard seed. Bnberythric acid, see p. 513. For synthetized glucosides, see B. 18, 1960, 3481. 0. Vegetable substances of unknown Constitution. Aloi'n, CiyHisO? (in the aloe plant), crystallizes in fine needles and is a powerful purgative; it is a derivative of anthracene. VEGETABLE SUBSTANCES OF UNKNOWN CONSTITUTION. 561 Cantharldln, CioHjjjO^ (in Spanish fly), forms sublimable plates ; it blisters the skin. Ficrotozln, C30II34O13 (in the seeds of Cocoulus indious). Santonin, CijHijOj (in worm seed), is derived from naphthalene (B. 16, 2686 ; 24, Eef. 908). Among natural dyes of unknown constitution we have : Brasilin, CmHuOs, the red dye of Brazil and Fernambuco woods. Colour- less glancing needles ; it appears to be a derivative of resoroin (B. 25, 18). CuTcumln, C14H14O4 ?, the yellow dye of the turmeric root, is turned brownish-red by alkalies, for which it forms a delicate test. Hsematoxylin, C18H14O8, is the colouring matter of logwood (Hsema- toxylon Campechianum). It forms yellowish prisms, which dissolve in alkalies with a violet-blue colour. Carmlnic acid, Ci^HijOio, the active principle of cochineal (Coccus Cacti), is a red amorphous mass which is split up by acids into a sugar (not glucose) and Carmine red, CuHijO,, the latter forming a purple-red mass with a green reflection; bromine converts carminio acid into a dibromo-derivative of a methylated and hydroxylated phthalic acid (B.-18, 3180). Harmlu, C13H12N2O, and Harmalln, CjaHj^NjO, are the colouring matters of Peganum Harmala (B. 18, 400). Chlorophyll or leaf green, is the green colouring matter of plants, and contains iron in its molecule. Together with starch, wax, etc., it forms the chlorophyll granules of the cells, but, notwithstanding that it has been the subject of numerous investigations, its nature is not yet accurately known. Litmus is a blue dye obtained from Roccella tinctoria and other lichens ; it is related to orcein (p. 425), and is turned red by acids, the blue colour being restored by alkalies. Hence it is much used as an indicator in alkalimetry. XXXVIII. ALBUMINOUS SUBSTANCES; ANIMAL CHEMISTRY. An extended description of the substances (other than those akeady mentioned) which are found in the animal organism and which are therefore of importance for physiological chemistry, will not be attempted here, since they are for the most part better known from a physiological than from a chemical point (BO6) «N 562 XXXVIII. ALBUMINOUS SUBSTANCES; ANIMAL CHEMISTRY. of view. Only the albumens and albuminoids, both of which are .classed as proteids, and some of the substances which are produced during metabolic processes, will be treated of. A. Albumens. (Of. Drechsd's article " Eiweiss " in Ladenburg's Neuea Handworterbuoh. ) The albumens make up the chief part of the organism, being present partly in the soluble and partly in the solid state; they are found in protoplasm and in all the nutritive fluids of the body. In solution they are opalescent, optically ( - ) active, and do not diffuse through parchment paper, i.e. are colloids; but they are thrown down when the solution is warmed, or upon the addition of strong mineral acids, of many metallic salts [e.g. copper sulphate, basic lead acetate and mercuric chloride], of alcohol, tannic acid, acetic acid together with a little potassium ferrocyanide, etc. When boiled: (a) with nitric acid, they are coloured yellow (the xantho-protein reac- tion); (b) with a solution of mercuric nitrate containing NjOg (Millon's reagent), red; (c) with caustic soda solution and a very little cupric sulphate, violet. The albumens combine both with acids and alkalies to acid- and alkali-albuminates (see below). Many of the albumens have been prepared pure, although this is a very difficult operation. With the exception of the crystalline albumen which occurs in hemp, castor oil, and pumpkin seeds (B. 15, 953), and the recently isolated crystal- line egg albumen (B. 24, Eef. 469; 25, Eef. 173), they do not crystallize. The different albumens vary only slightly among themselves in percentage composition; they contain: = 52-7 to 54-5 p.c; H = 6-9 to7-3p.c.; N = 15-4 to 16-5p.c; = 20-9 to 23-5 p.c.; and S = 0-8 to 2-0 p.c. It is impossible at present to construct a formula from these numbers. The fact that albumen contains sulphur is worthy of note, though the mode in which it is combined in the molecule is unknown; warming with a dilute alkaline solution is sufficiejit albumens; constitution of. 563 to eliminate it partially, e.g. when white of egg is boiled with an alkaline solution of lead oxide, sulphide of lead is separated (the test for sulphur in albumen). Albumen preparations usually leave a very considerable amount of ash, i.e. inorganic salts, on incineration. It is not yet certain in how far this mineral matter forms an integral constituent of these substances ; but the properties of " egg albumen free from ash " are materially different from those of ordinary albumen (B. 25, 204). Constitution. The way in which albumen is split up by acids (especially in presence of stannous chloride), or by baryta water, gives some indication of its constitution. Here, in addition to ammonia and carbonic acid, amino-acids are the principal products, and these belong not only to the fatty series [e.g. glycocoll, leucine, aspartic acid, glutamic acid and "leucein," (C^H^NOa),, (B. 19, Ref. 30), "lysine," OgHi^N^O^ (probably di-amino-caproic acid, B. 25, 3504)], but also to the aromatic {e.g. phenyl-amino-propionic acid and tyrosine). Loew's hypothesis that albumen is essentially a condensation product of aspartic aldehyde, CiHyNOj, i.e. of leucein, is worthy of mention. The putrefaction of albumen gives rise not only to amino- acids but also to other aromatic and fatty acids {e.g. butyric acid), indole, skatole, and cresol; further, to the alkaloid-like Ptomaines (the tpxines or poisonous alkaloids produced in dead bodies), of which neurine and pentamethylene-diamine (or "Cadaverin," B. 19, 2585) have been isolated (cf. p. 211). For a compilation of the ptomaines, see Brieger, Archiv. f. patholog. Anatomie, 115, 483. Albuminous matters undergo change when acted upon by the juices of the stomach at a temperature of 30°-40°, pepsin converting them in the first instance into Anti- and Hemi-albumoses, both of which then pass into peptone ; trypsin, the enzyme of the pancreas, likewise gives rise to the two above albumoses, but then transforms the anti-compound into peptone and the hemi-compound into leucine, tyrosine, aspartic acid and glutamic acid (the pancreatic digestion; for details, see Kuhne, B. 17, Kef. 79). The peptones are readily soluble in water, diffuse quickly through vegetable parchment, and they are neither coagulated upon heating nor by most of the reagents which coagulate albumen, e.g. sulphate of ammonium. The albumoses are thrown down by ammonium sulphate. 564 XXXVIII. ALBUMINOUS SUBSTANCES; ANIMAL CHEMIbTRy. When soluble salts of iron are allowed to act upon white of egg and upon peptone, Iron albuminate and Iron peptonate are respectively produced, these being employed in medicine as iron preparations for internal use under the names of liquor ferri albwminati and peptonati. Classification of the albumens. 1. Coagulahle aZhumens: A. Those which are soluble in water and not preoipitable by, common salt, but which become insoluble, i.e. coagulate, when the solution is heated to 70°-76'' ; to this class belong Egg albumen (in the white of birds' eggs), Serum albumen (the chief constituent of all nutritive fluids, of the blood, chyle, etc.), and Phyto-albumen (in plants). B. Those which are insoluble in water, but soluble in a dilute solution of common salt, being thrown down however by an excess of the latter, and which coagulate upon warming (fibrinogene at 56°, and the others at 70°-75°). These include the glohulines, viz. Globnline (in the crystalline lens of the eye), Fibrinogene or meta-globuline (in blood, chyle, etc.), Para-globuline (in blood), and Phyto-globuline (in plants). Vitellin (in the yolk of egg) is related to the last-named, but is not preoipitable by common salt. 2. Coagulated albumens, etc. Insoluble in water : A. Coagulated albumens: Fibrin (an essential constituent of clotted blood, which separates at once when the blood leaves the organism). Myosin (which separates from the plasma of living muscle), and Phyto-myosin (the coagu- lated albumen of flour paste). The two last dissolve in a 10 per cent solu- tion of common salt, and coagulate in this solution at 56°-57°. B. Coagulates. In this class we have Syntoniu or acid albumen, which is insoluble in a solution of common salt, but readily soluble in dilute acids or alkalies, from which it is thrown down on neutralization, but not by heat. C. Alkali albuminate. Soluble in alkali and preoipitable from thi» solution by acid ; insoluble in water and in solutions of salts. The Legumin of plants perhaps belongs to this class. 3. Compound albumens (Nucleo-aZbumens) : A. Caseins. These are found in milk only. They are insoluble in water and in a solution of sodium chloride, but readily soluble in dilute hydro- chloric acid or carbonate of potash ; they are not thrown down from solution upon boiling. Casein is kept in solution in milk by alkali, is separated on the addition of acid, and is coagulated by the addition of rennet (an infusion of the stomach of the calf) as a sparingly soluble cheese. B. Nucleo-albnmens (see under "Nuoleins"). C Hcemoglobins. Hsemoglobin is the colouring matter of the red blood corpuscles. It can be broken up into albumen and haematin (see below). THE ALBUMINOIDS. 565 Haemoglobin combines very readily with oxygen, e.g. in the lungs, to Oxy- hoemoglobin, which yields up its oxygen again, not only In the organism but also in a vacuum and when exposed to the action of reducing agents. With carbon monoxide it combines to the compound, Carbon monoxide- hsemoglobin. All three compounds can be obtained crystallized in the cold, and they possess characteristic absorption-spectra. Hsematin (C8sH32N4Fe04?), a, dark brown powder containing 8 p.c. of iron, results even from the spontaneous decomposition of hsemoglobin. Its hydrochloride, Hsemin. (CajHaoNiFeOa, HCl ?), is obtained in the form of characteristic microscopic, reddish-brown crystals by the action of glacial acetic acid and some common salt upon oxy-hsemoglobin ; this is a delicate test for the presence of blood. ITucle'iils. The nucle'ins are important constituents of the cell nucleus, e.g. of pus cells, of nucleated blood corpuscles, of yeast cells, etc. They form white masses insoluble in water or dilute mineral acids but readily soluble in alkalies, and contain phosphoric acid in ethereal combination. Some of them, the nucleo-albumens, break up when boiled with water or dilute acids into albumen, hypoxanthine and the acid just named. Certain varieties of nuole'ii> are free from sulphur while others contain it, the latter yielding tyrosine when decomposed. The product which is obtained when the albumen of hens' eggs is coagulated by m-phosphoric acid resembles nuclein. B. Albuminoids. The albuminoids are to be regarded as the nearest derivatives of the albumens, being closely related to these; they are mostly organized, and are important constituents of the tissue. Some of them are converted into glue when boiled with water, and hence are termed glue-yielding substances. They give " bone oil" (p. 519) on destructive distillation. To this group belong : 1. Glutin or Bone glue, known as gelatine in the pure state, which is characterized by its solution solidifying to a jelly on cooling; it is obtained by boiling bone cartilage, connective tissue, s.tag's horn, calves' feet, etc. (the so-called " collogenes ") with water. Unlike the albumens, glutin is not precipitated from aqueous solution by nitric acid or potassium ferrocyanide. Tannic acid throws down gelatine from solution, and unites with the glue-yielding substances of the organism to form compounds insoluble in water (the tanning of hide; leather). For glutin-peptone salts, see B. 2^ 1202. 566 SUBSTANCES PRODUCED DURING METABOLIC PROCESSES. Bone glue yields glycoooll and leucine when boiled with acids, but no tyrosine. 2. Mucin or Mucus, found in slime secretions, is free from sulphur. 3. Keratin or horn suhstanee goes to build up the epidermis, nails, hair, etc. ; it contains sulphur. Is not attacked by the gastric juice. i. Elastin is the chief constituent of the elastic ligaments of the organism. It does not contain sulphur, and yields leucine with sulphuric acid. 5. The enzymes {unorganized ferments) diastase, ptyalin, pepsin, trypsin, etc., already mentioned at p. 322, also belong to this group. 6. Chitin, the principal constituent of the cuticular covering of the articulata, e.g. of the shell of the crab, differs from horn substance in being insoluble in alkalies; it yields glucosamine (p. 312) when boiled with acids (B. 17, 241). D. Substances produced during Metabolic processes. 1. Acids of the hile. Bile contains the sodium salts of Olycocholic acid, OasHuNOs, and Taurocholic acid, CjsHisNSOf, both of which are decom- posed byalkaUes into Cholic acid, CmHwOs, = C2,H3j(OH)(C02H)(CH2.0H)2, on the one hand, and glyoocoU and taurine respectively on the other. 2. The bile also contains various colouring matters: Bilirubin, Biliverdin, Bilifnscin, etc. These apparently bear some simple relation to the colour- ing matter of blood, the formula of bilirubin being CasHssNiOg (see B. 17. 2267). 3. The Cholesterins, C26H43(OH), of which numerous varieties are now known, are present in blood, bile, nerve substance, vegetable fats, etc. They are monatomic alcohols, and crystallize in small plates with a mother- of-peail lustre. i. Lanolin or wool fat consists of fatty esters of cholesterin. It is a valuable salve, and is distinguished from other fats by the readiness with which it is absorbed into the skin and by its power of taking up water. 5. Cerebrin, OuHasNOs, is an important ingredient of the medullary sub- stance of the nerve. 6. Lecithin, OijHmNOsP, is a characteristic constituent of nerve substance, brain, yolk of egg, etc. It forms a waxy mass capable of crystallization, which dissolves in alcohol and ether, and swells up to an opalescent liquid with water. It breaks up on saponification into choline, glycerine-phos- phoric acid, stearic and palmitic acids, and is therefore to be regarded as glycerine in which the three hydroxyl hydrogens have been replaced by the palmitic, stearic and phosphorio acid residues, the last of which still remains in ethereal combination with choline. CTJMAEONE AND INDAZOLE GROUPS, 567 APPENDIX A. (to p. 475). Oumarone and Indazole Grroups. Just as furfurane and thiophene are related to pyrrol, so there are com- pounds analogous to indole which contain oxygen or sulphur in place of the imido-group. Cumarone, C6H4<^pjT^CH, is a compound which closely resembles the benzene hydrocarbons, especially pseudo-cumene; it is found in coal tar, from which it can be isolated by means of its compound with picric acid. It is a liquid of very negative properties (B. Pt. 170°-171°), being resinified however by mineral acids, with the production of a red colour. When its vapour, mixed with that of benzene (or naphthalene), is led through a red- hot tube, phenanthrene (or chrysene) is produced. Of. B. 23, 78; 28, 2i09. Por analogous compounds, see B. 19, 1290, 1432, 1617, 1667, and 2927. There exist still other compounds, the Indazolea, derived from the indoles, but differing from these in that they contain a nitrogen atom instead of a nucleus-carbon atom. Corresponding to indole we have Indazole, CeHeNj, = C6H4<^ -^NH or C6H4<^pTT^N, a weak base, which can be pre- pared indirectly from p-nitro-o-toluidine by transforming this into the diazo- compound, boiling the latter with glacial acetic acid, and then eliminating the uitro-group (B. S3, 3635; 2^ 2370; 2S, 3149; 26, 216, etc.). APPENDIX B. (to p. 504, after line 30). The two Naphthalene-mono-sulphonic acids, OioH,(SOsH), are formed when naphthalene is warmed with concentrated sulphurio acid, and are crystalline hygroscopic compounds ; the a-acid undergoes a molecular trans- formation into the /3- when heated with sulphuric acid. They yield the two naphthols on fusion with alkalies, and the two Cyano-naphthalenes, Oio H7 . CN (crystalline compounds which can be distilled without decom- position), when heated with cyanide of potassium. INDEX. A. rt=ana-position, 534. ic=asymmetric, 345. Of =alicycUc, 504. ar==aroinatic, 504. Abietic acid, 559. Acenaphthene, 507. Acetal, 148. Acetals, 143. Acetamide, 198. Acetamidine, 200. Acetamido-chloride, 198. Acetanilide, 379, 391. Acetenyl-benzene, 365. Acetic acid, 8, 170. Acetic aldehyde, 147. Acetic anhydride, 193. Acetic ether, 189. Acetic fermentation, 170. Acetimido-chloride, ig8. Acetimido-hydrate, 200. Acetimido-thio-ethyl, 200. Acetimido-thio-hydrate, 20a Acetins, Z13, 317. Aceto-acetic acid, 243. Aceto-acetic acid, alkyl derivatives of, 245. Aceto-acetic aldehyde, 239. Aceto-acetic anilide, 532. Aceto-acetic ether, 243. Aceto-acetic ether syntheses, 164, 443 Aceto-brom-amide, 198. Accto-butyl alcohol, 237. Aceto-isopropyl alcohol, 237. Aceto-mallc acid, 258. Aceto-malonic ether, 246' Aceto-nitrile, 118. Aceto-phenetidine, 421. Aceto-phenone, 435. Aceto-phenone-acetone, 43b. Aceto-propionic acid, 240. Aceto-propyl alcohol, 237, Aceto-succinic ether, 246. Aceto-tartaric acid, 263. Aceto-thiamide, 199. Acetol, 237. Acetone, 156, 353. Acetone-alcohol, 237. Acetone-amines, 154. Acetone-chloride, 152, Acetone cyanhydrin, 208. Acetone-diacetic acid, 265. Acetone-dicarboxylic acid, 265, 522. Acetone-phenyl-hydrazone, 156, 474. Acetonic acid, 232. Acetonyl-acetone, 238,^ 328. Acetonyl-acetone-dioxime, 33a. Acetoxime, 155, 158. Acet-toluide, 393. Aceturic acid, 228. Acetyl, 167. Acetyl-acetone, 238. Acetyl-amido-benzoic acid, 533. Acetyl bromide, 192. Acetyl-carbinol, 237. Acetyl chloride, igi. Acetyl cyanide, 191. Acetyl-diphenylamine, 581. Acetyl-diphenyl-hydrazme, 407. Acetyl-glycocoU, 228. Acetyl-mdole, 474. Acetyl iodide, 192. Acetyl-naphthols, 505. Acetyl peroxide, 193. Acetyl -phenol, 418. Acetyl-sulphanilic acid, 387. Acetyl-thio-urea, 298. Acetyl-toluidines, 379, 392. Acetyl-urea, 294. Acetylene, 65, 353. Acetylene-dicarboxylic acid, 256 Acetylene series, 62. Achroo- dextrine, 322 Acid albumen, 564. Acid anhydrides, 192. Acid bromides, 192. Acid chlorides, ipo. "Acid decomposition", 244, Acid derivatives, 187 Acid fuchsine, 491. Acid green, 48S. Acid violet, 492. Acids, aromatic, 437. Acids, fatty, 160. Aconitic acid, 267. Acridine, 533. 537. Acridine-carboxylic acid, 538. Acridine yellow, 538. Acridinic acid, 533. Acridyl aldehyde, 538. Acrolein, 149. Acrolein-ammonia, 150, 521. Acrolein-aniline, 531. «-Acrosazone, 316. «-Acrose, 309, 316. »-Acrosone, 316. Acrylic acid, 179. Acyls^ 167. Adenine, 306. Adipic acid, 247, 324, 504. iSsculetin, 464. iEsculin, 464, 560. Affinities, free, 17, 59. Alanine, 331. Albumenoids. 565. 570 INDEX. Albumens, 562. Alcohol, 88. Alcohol, constitution of, iS. Alcohol-acids, fatty, 220, 221 Alcohol acids, aromatic, 458. Alcohol of crystallization, 87. Alcohols, aromatic, 405. Alcohols, fatty, 79. Aldehyde, 147. Aldehyde-acids, 220, 239, 354. Aldehyde alcohols, 220, 237, 307. Aldehyde-ammonia, 1^3, 148. Aldehyde "condensations", 144. Aldehydes, aromatic, 433. Aldehydes, fatty, 139. Aldehydes, the fucfisine test for, 146, 491. Aldehyde sugars, 318. Aldehydine, 526. Aldehydine bases, 384, Aldehydo-benzoic acid, 460. Aldine, 530. Aldol, 237. Aldol "condensations", 145, 444. Aldoses, 313. Aldoximes of the fatty series, 15a Aliphatic series, 160. Alizarin, 511, 513. Alizarin blade, 507. Alizarin blue, 514. Alizarin-bordeaux, 514. Alizarin cyanines, 514. Alizarin orange, 514. Alkali-albuminate, 564. Alkaloids, 520, 543. Alkaloids from dead bodies, 547, 563. Alkarsin, 135. Alkines, 209. Alkyl, 30j 45. _ Alkyl-arsine dichloride, 136. Alkyl-hydro-anthracenes, 511. Alkyl-hydro-anthranols, 511. Alkyl-hydroxylamines, 128. Alkyl-malonic acids, 253. Alkyl sulph-hydrates, 103. Alkyl sulphides, 103. Alkyl thio-ureas, 298. Alkylenes, 30. AUantoin, 304. Allanturic acid, 300. Allene^ 66. Allo-cinnamic acid, 454. AUo-isomerism, 22. Allophanic acid, 294. Alloxan^ 303^ 334. Alloxanic acid, 304. Alloxan tin, 304. Allyl alcohol, g6. AUyl aldehyde, 149. AHyl-aniline, 533. Allyl bromide, 69, 79. Allyl chloride, 69, 79. Allyl cyanide, 118. Allyl ether, loi. Allyl iodide, 69, 79. Allyl " mustard oil", 284, Allyl-pyridine, 526, 528. Allyl sulphide, 107, Allyl thiocyanate, 384. Allylene, 60, 353. Aloin, 560. Alpha-compounds (see individually). Aluminium chlorjde, action of, 357. Aluminium methide, 139. Amalic acid, 304. Amber, 559; "Amidatmg", 376. Amides of the fatty series, 194. Amidines, 187, 200. Amido; see also Amino, Amido-acetic acid, 227. Amido-acetone, 157. Amido-acids, 227. Amido-anisols, 421 Amido-azo-benzene, 402, 404. Amido-azo-benzene-sulphonic acid, 405. Amido-azo-compounds, 397, 402. Amido-azo-naphthalene, 504. Amido-azo-phenylene, 384. Amido-azo-toluenes, 405. Amido-benzaldehyde, 435. Amido-benzene, 375, 384, Amido-benzene-sulphonic acids, 410, Amido-benzoic acids, 340, 392, 450. Amido-benzoyl-formic acid, 460. Amido-butync acids, 232. Amido-camphor, ^56. Amido-caproic acid, 232. Amido-chlorides, 187, ig8. Amido-chloro-styrene, 474. Amido-cinnamic acids, 454. Amido-cinnamic aldehyde, 531. Amido-derivatives, aromatic, 374. Amido-dimethyl-aniline, 375, 394. Amido-dimethyl-aniline-thiosulphonicacid, 543- Amido-diphenyl, 476. Amido-diphenylamine, 375. Amido-ditolylamine, 401. Amido-durene, 393. Amido-ethyl-benzenes, 39^. Amido-ethyl-sulphonic acid, 212. Amido-guanidine, 299. Amido-hydrocinnamic acid, 453. Amido-isobutyl-benzene, 377, 39^ Amido-ketones, 156. Amidols, 422. Amido-mesitylene, 393. Amido-naphthalenes, 500, 504. Amido-naphthols, 505. Amido-naphthol-sulphonic add, 506. Amido-naphtho-tolazine, 540. Amido-phenols, 421. Amido-phenyl-acetic acids, 452. Amido-phenyl-glyoxylic acid^ 452. Amido-phenyl-meth^l-quinohne, 536. Amido-propionic acid; see Alanine, 231. Amido-propyl-benzene, 393. Amido-pseudo-cumene, 393. Amido-quinolines, 535. Amido-succinic acid, 258. Amido-thiazole, 333.^ Amido-thio-lactic acid, 243. Amido-thiophene, 331. Amido-thio-phenolSy 421. Amido-trimethyl-benzenes, 393. Amido-triphenyl-methane, 487. Amido-valeric acids, 232, 523. Amidoximes, 201. INDEX. 571 Amido-xylenes, 393. Aminiides, 200. Amines, aromatic, 375. Amines, fatty, 120. Amino-acids, 227. Amino-ethanoic acid, 227. Ammelide, 286. Ammeline, 286. Ammonium bases, 120, 125. Ammonium cyanide, 275. Ammonium thiocyanate, 282. Amygdalin, 273, 433, 559 Amy! acetate, 189. Arayl alcohols, 94. Amyl-benzene, 356. Amy! bromide, 75. Amyl chloride, 75. Amylene hydrate, 95. Amylene glycols, 206. Amylenes, 61. Amyl nitrite, 110. Amylo^dextrine, 322. Amyloid, 321. Amylum, 321. Analysis, qualitative, z. Analysis, quantitative, 4. Analysis, elementary, 4. Ana-position, the, 534. Angelic acid, 180. Anhydrides of the fatty acids, 192. Anhydride sugars, 318. Anhydro-bases, aromatic, 383. Anhydro-ecgonine, 544. Anhydro-formaldehyde-aniline, 385, 482. Anihdes, 379, 391, 484. Anilido-quinones, 430. Aniline, 384. Aniline black, 542. Aniline blue, 492. Aniline red; see Fucksine or Magenta, 490. Aniline violet; see Methyl violet, 491. Aniline yellow, 404. Animal chemistry, 561. Anisic acid, 457. Anisic alcohol, 436. Anisic aldehyde, 436, 437. Anisidines, 421. Anisidine-fiulphonic acid, 417. Anisol, 417. Anthracene, 366, 508. Anthracene blue, 514. Anthracene brown, 514. Anthracene-carboxylic acids, $1.1., 514. Anthracene hydrides, 510. Anthracene-sulphonic acids, 5x1, 5x2. Anthrachrysone, 511. Anthraflavic acid, 511, 513. Anthragallol, ^x^ AnthKi-hydroquinone, 511, 512. Anthramme, 511, 536. Anthranil, 451. Anthranilic acid, 450, 451. Anthranol, 511^ 512. Anthra-purpunn, 511, 514. Anthra-quinoline, 536. Anthraquinone, 509, 511, 512. Anthraquinone-sulphonic acids, 5x1, 513* Anthrarobin, 514. Anthranifin, 5x1. Anthrol, 511, 512. Anthrone, 511. Anti-albumoses, 563. Anti-aldoximes, 158. Anti-febrine, ^gx. Antimony ethide, 136. Antimony methide, 136. Antipyrine, 333, 407. Apo-quinine, 546. Appendix, 567. Arabin, 323. Arabinose, 30S. Arabinose-carboxylic acids, 237. Arabonic acid, 235. Arachidic acid, 175. Arbutin, 560. Aromatic compounds, 335. Aromatic hydrocarbons, 356. Aromatic hydrocarbons, isomers and con- stitution, 358. Arsenic compounds, 133. Arsines, 133. Arsonium compounds, X33. Aseptol, 422. AsparaginCj 258. Aspartic acid, 258, 563. Aspartic aldehyde, 563. Asphalt, 54. Asymmetric benzene derivatives, 345. Asymmetric carbon atoms, 22, 40. Atoms, law of even numbers of, 29. Atro-lactinic acid, 460. Atropic acid, 454, Atropine, 546. Auramine, 483. Aurantia, 389. Aurin, 487, 493. Avogadro and Ampere's theory, 10. Azimido-benzene, 384, 398. Azines, 530, 538. Azo-bcnzene, 373, 402. Azo-carmine, 542. Azo-compounds, aromatic, 400, 401. Azo-dicarboxylic amide, 299. Azo-dyes, 384, 393, 403. Azo-dyes of the naphthalene series, 506. Azoles, 332. Azo-naphthalene, 504, Azoniiun base, 541. Azo'phenine, 430, 542. Azo-phenyl-ethyl, 402. Azo-phenylene, 539. Azo-toluenes, 402. Azoxy-benzene, 401. Azoxy-compounds, 40X, B Backward substitution, 45. Barbituric acid,^ 303. Basset's carbonic ether, 218. Bassorin, 323. ^ Beckntann molecular transformation, the, X51, 484. Beer, c)o. Behenic acid^ 175. Behenolic acid, i8x 572 INDEX. Benzal chloride, 366, 370. Benzaldehyde, 433. Benzaldehyde-cyanhydrin, 459, Benzaldehyde-phenyl-hydrazone, 434. Benzaldoxime, 434. Benzal violet, 487. Benzamide, 449. Benzamide-silver, 450. Benzanilide, 449. Benz-anti-aldoxime, 434. Benzjizurine, 440. Benzene, 353, 301. Benzene, constitution of, 343, 348. Benzene, formation, 353. Benzene, properties and behaviour, 361. Benzene-azo-benzene, 402. Benzene-azo-dimethyl-aniline, 383. Benzene-azo-naphthylamine, 506. Benzene-carboxylic acid, 431. Benzene derivatives^ 335. Benzene derivatives, formation, 353. Benzene derivatives, occurrence, 352. Benzene derivatives^ summary, 335. Benzene-dicarboxylic acids, 464. Benzene dihydride, 361. Benzene-disulphonic acids, 410. Benzene disulphoxide, 479. Benzene formulae, ^43, 348. Benzene hexabromide, 362. Benzene-hexacarboxylic acid, 468. Benzene hexachloride, 362. Benzene hexahydride, 362. Benzene hydrocarbons, 356. Benzene-indone, 542. Benzene-methylal, 433. Benzene-methylol, 431. Benzene of crystallization, 420, 486. Benzene-oxy-methane, 417. Benzene-pentacarbo:^lic acid, 468. Benzene-sulphinic acid, 409. Benzene sylphonamide^ 409. Benzene-sulphonic acid, 337, 338, 397, 408. Benzene-sulphonic chloride^ 409. Benzene-tetracarboxylic acids, 468. Benzene tetrahydride, 362. Benzene thiocyanate, 397. Benzene thio-hydrate ; see Phenyl tkio- hydrate. Benzene-tricarboxylic acids, 468. Benzene-trisulphonic acids, 41a Benzhydrol, 482. Benz-hydroxamic acid, 202. Benzhydryl-benzoic acids, 48a Benzidam, 384. Benzidine, 401, 477. Benzidine-sulphone, 478. Benzidine-sulphonic acids, 478. Benzile, 497. Benzile-oximes, 497. Benzilic acid, 480, 483, 497. Benzimido-azoles, 383. Benzoic acid, 337, 446, 448. Benzoic anhydride, 449. Benzoic ethers, 449. Benzoin, 4^6, 497. Benzo-nitnle, 451. Benzo-phenone, 482. Benzo-pUT3)urine 4 B, 479, Benzo-toluidide, 484. Benzo-trichloride,^ 366, 370. Benzoyl-acetic acid, 460. Benzoyl-acetone, 436. Benzoyl-azimide, 4^0. Benzoyl-benzoic acids, 484. Benzoyl-carbinol, 437. Benzoyl chloride, 449. Benzoyl cyanide, 449. Benzoyl-ecgonine, 544. Benzoyl-formic acid, 46a Benzoyl-glycocoll; see Hippuric acid, 4sa Benzoyl-hydrazine, 450. Benzoyl-salicin, 560. Benzoyl-sulphone-imide, 451. Benz-syn-aldoxime, 434. Benzyl-aceto-acetic ether, 443. Benzyl-alcohol, 432. Benzylamine, 393. Benzyl-benzene; see Diphsnyl-metkane. Benzyl-benzoic acids, 480. Benzyl bromide, 369. Benzyl chloride, 369, 508. Benzyl cyanide, 451. Benzyl hydrosulphide, 433. Benzyl hydroxylamines, 433, Benzyl iodide, 369. Benzylidene-aniline, 379. Berberine, 527, 545. Berberonic acid, 537. Berlin blue, 277. Betai'ne, 228. Beta-orcinol, 425. Betol, 505. Biebrich scarlet, 404, 506. Bile, 566. Bile, acids of the, 566, Bilifuscin, 566. Bilineurine, 211. Bilirubin, 566. Biliverdin, 566. Bioses, 317. Bismarck brown, 402, 405. Bitter almond oil, 433. Bitter-almond-oil green, 488. Biuret, 204. Blood colouring matter, 564. Blood fibrin, 564. Boiling point, laws regulating, 33. Bonds, change in; see Desmoiropism, 287. Bone glue, 565. Bone oil, ^zg. Boradc ethers, 416. Borneo camphor, 556. Bomeol, 556. Bomylamine, 558. Bomyl chloride, 356- Bomyl iodide, 552. Boron compounds, 136. Brain, 566. Brandy, go. Brasilin^ 561. Brassyhc acid, 247. BranI wood, 561. Brilliant black, 506. Brilliant green, 488. Brom-aceto-acetic ether, 354. Bromanil, 429. Bromanilic acid, 355. Bromo-acetyl bromide, 191. INDEX. 573 Bromo-acetylene, 79, 353. Bromo-allyl alcohol, 96. Bromo-anilines, 386. Bromo-anthraquinones, 513. Bromo-benzene, 369, 382, Bromo-benzoic acids, 340. Bromo-benzyl bromide, 508. Bromo-butyl-methyl ketone, 52a. Bromo-camphorj 556. Bromo-crotonic acids, 186. Bromo-ethylamine, 211. Bromo-ethyl-benzene, 366. Bromo-ethylene, 79. Bromoform, 78. Bromo-isatin, 471. Bromo-naphthalene, 502. Brorao-nitro-benzenes, 373, 387. Bromo-nitro-toluene-sulphonic acid, 411, Bromo-phenols, 41^. Bromo^hthalic acids, 467. Bromo-propionic aldehyde, 150. Bromo-styrenes, 370. Bromo-succinic acids, 254. Bromo-toluenes, 369. Brucine, 546. Butadiene, 66. Butadiine, 66. Butane di-acid, 253. Butane-diamine, 210. Butane-diol di-acid, 259, Butane-dione, 238. Butane hexacarboxylic acid, 268. Butanes, 49. Eutane-tetrol, 218. Butane-triolic acid, 235. Butanoic acid, 173. Butanols, 93. Butanol di-acid, 257. Butanolone, 237. Butanone, i57-, Butanone di-acid, 265. Butanone-nitrile, 157. Butanonic acid, 240. Butene, 61. Butene di-acid, 256. Butenic acid, 180. Butine, 66. Butine di-acid, 256. Butyl-acridine, 537, Butyl alcohols, 93. Butyl-benzenes, 365. Butyl bromides, 75. Butyl chlorides, 75. Butylene glycols, 206. Butylene hydrate, 93. Butylenes, 6x. Butyl iodides, 69, 75. Butyl-methyl ketone, 157. Butyl-phenol, 423. Butyric acid, 173. Butyric ether, 189. Butyric fermentation, 173. ButjTO-lactone, 233, Butyrone, 157. Butyro-mtrile, 118. Butyryl chloride, igz. Cacodyl, 135, 136. Cacodyl chlorides, 136. Cacodyl compounds, 133-136. Cacodylic acid, 136. Cacodyiic oxide, 135. Cadaverin, 210, 563. Cai/ei's liquid, 135. Caffeic acid, 463. Caffeine, 306. Caffetannic add, 463. Cairolin, 535. Campechy wood, 561. Camphene, 550, 552. Campholene cyanide, 555. Campholenic acid, 555. Camphor, 548, 555. Camphor^ artiiicial, 552. Camphoric acid, 555. Camphoronic acid, 555. Camphor-oxime, 555. Camphylamine, 555. Cane sugar, 319. Cane sugar group, 317. Cantharene, 555. Cantharidin, 561. Caoutchouc, 554. Capric acid, 175. Caprilic acid, 175. Caproic acid, 175. Caproyl alcohol, 95. Caramel, 319. Carbamic acid, 291. Carbamic chloride, agz, 361, 44a. Carbamic compounds, 295. Carbamic ethers, 291. Carbamide, 292. Carbamines, 119. Carbanilide, 375, 392. Carbazole, 476, 478. Carbazole yellow, 478. Carbimide, 270, 290. Carbinol, 86. Carbo-cinchomeronic acid, 527. Carbo-di-imide, 285, 278. Carbohydrates, 307. Carbohydrates, reaction with «-naphthol and sulphuric acid, 308. Carbolate of lime, 416. Carbolic acid, 416. Carbon, estimation of, 4. Carbon, nature of, 20. Carbon bisulphide, z8S. Carbonic acid, derivatives of, 287, Carbonic acid, etbers of, 288, 289. Carbon monoxide-hEemoglobin, 565. Carbon oxychloride, 289, 491. Carbon oxy-sulphide, 288. Carbon tetrabromide, 78. Carbon tetrachloride, 78, 4^2, 488. Carbon tetrafluoride, 78. Carbon tetra-iodide, 78. Carbonyl compounds, 295. Carbonyl di-urea, 295. Carbo-pyrrolic acid; see Pyrrol-carboxy^ lie acid. Carbostyril, 454, 535> 574 INDEX. Carboxyl group, 166. Carboxylic acids, aromatic, 437. Carboxylic acids, fatty, 160, 221, 246. Carboxyl-phenyl-glyoxylic acid, 505. Carbyl sulphate, 212. Cardinene, 551. Carmine red, 561. Carminic acid, 561. Carnine, 306. Carrophyllene, 551. Cartilage glue, 563. Carvacrol, 423, 555. Carvene, 548. Carvol or Carvone, 423, 555. Carvo-menthene, 555. Carvone, 423, SSS- Carvoxime, 423, 551. Case'ins, 564. Catechu-tannic acid, 462. Cedrene, 551. Cedriret, 479. Celluloid, 321. Cellulose, 320. Central formula of benzene, 348. Cerebrin, 566. Ceresine, 54. Cerotene, 61. Cerotic acid, 161, 177. Cerotin, 95. Ceryl alcohol, 95. Cetme, 62, Cetyl alcohol, 95. Cetyl bromide, 75. Cetyl cerotate, 189. Cetyl iodide, 75. Cetyl palmitate, 189. Chains, closed, 20. Chains, open^ 20. Chain isomerism, 102. Chelidonic acid, 529. Chemical theories, 14. Chitin, 566. Chlor-acetanilide, 386. Chloral, 149. Chloral alcoholate, 149. Chloral-amide, 198. Chlor-aldehydes, 149. Chloral hydrate, 77, 149. Chloral-imide, 144. Chloranilj 385, 429. Chloranilic acid, 429. Chlorhydrins, 203, 215-216. Chlorinated alcohols, 92. Chloro-acetamide, 19B, Chloro-acetic acids, 182, z86, 227. Chloro-acetic ethers, 189. Chloro-aceto-acetic ether, 246. Chloro-acetone, 157. Chloro-acetyl chloride, 192. Chloro-acetyjene, 79. Chloro-acrylic acids, 183, 448. Chloro-amylamine, 2ii, 522. Chloro-aniline, 386. Chloro-anthracenes, 511. Chloro-anthraquinone, 513. Chloro-benzene, 366, 369, 377, 407. Chloro-benzoic acid, 450. Chloro-benzyl chloride, 367. Chlora-bromo-benzenes, 370. Chloro-butenic acid, 186. Chloro-butylamine, 211, 330. Chloro-camphor, 556. Chloro-carbonic acid, 289. Chloro-carbonic ether, 290. Chloro-crotonic acids, 186. Chloro-derivatives of benzene, 366. Chloro-diphen^l, 476, 477. Chloro-ethanoic acid, 186. Chloro-ethylene, 69. Chloro-ethyl-sulphonic acid, 212. Chloroform, 77, 379. Chloro-formic ether, 290. Chloro-hydroquinone, 428. Chloro-iodo-benzenes, 37a Chloro-isatin, 471. Chloro-isocrotonic acid, 186. Chloro-malonic ether, 253. Chloro-methane-oxy-methanol, 147. Chloro-methanol, 147. Chloro-methyl alcohol, 147. Chloro-naphthalenes, 502. Chloro-nitro-benzaldehyde, 437. Chloro-nitro-benzenes, 371, 373, 387. Chloro-phenols, 41^, 419. Chloro-phenyl-acetic acid, 444. Chloro-propane-diol, 216. Chloro-propene, 79. Chloro-propylenes, 79. Chloro-phthalic acids, 467. Chlorophyll, 561. Chloro-picrin, 113. Chloro-propionic acids, 182, 186. Chloro-pyridine, 519. Chloro-quinoline, 519. Chloro-toluenes, 366, 369. Chloro-xylenes, 366. Cholesterin, 566. Cholestrophane, 303. Cholic acid, 566. Choline, 2zi, 566. Chromogenes, 32. Chrysamine, 478. Chrysaniline, 538. Chrysazin, 511. Chrysazol, 511. Chrysene, 516. Chrysoi'din, 384, 403, 405. Chrysoi'dines, 404. Chrysoi'n, ^06. Cincho-lepidine, 536. Cincho-loiponic acid, 546. Cinchomeronic acid, 527. Cinchona bases, 545. Cinchoninic acid, 503, 512. Cinchonidine, 512. Cinchonine, 520, 531, 51a. Cinene, 553. Cineol, 556. Cineolic acid, 556. Cinnamenyl compounds, 454. Cinnamic acid, 365, 453. Cinnamjc alcohol, 433. Cinnamic aldehyde, 435. Cinnamic dibromide, 454. Cinnamo-carboxylic acid, 467, 505. Cinnamon, oil of, 435. Cinnamyl compounds, 454. Cinnoline compounds, 537. INDEX. 575 Crcular polarization, 38. "_Cis-" form, 25, Citraconic acid, 255. Citral, 548, SSI, 558. Citramalic acid, 2S9. Citramides, 268. Citrazinic acid, 268, 522, 527. Citrene, 548, 553. Citric acid, 267. Citric ethers, 268. Citron, oil of, 548. Classification of organic compounds, 30. Closed chains (rings), 21, 55, 210, 323, 343. Clovene, 551. Cloves, oil of, 425. Coagulable albumens, 564. Coagulated albumens, 564. Coagulates, 564. Cocaine, 544. Coccerylic acid, 233. Codeine, 545. CoeruleVn, 496. Coerulignone, 479. Coerulin, 496. ColUdine, 520, 521, 526, CoUidipe-dicarboxyfic ether, 523. Collodion, 321. Collogenes, 565. Colophene, 551. Colophonium, 551, 559- Colour^ 31. Colounng matters, natural, 561. Comanic acid, S29. Combustion, heat of, 37. Combustion, organic, 4. Conchinine, 546. "Condensation", 144-145, 500, 533. Condensed benzene nuclei, 49B ei seq. Configuration, spacial, 22. " Congo" (dye), 478. Conic acid, 233. Coniceins, S^P* Coniferin, 437, 560. Coniferyl alcohol, 437, 560. Conine, 528. Constitution of organic compounds, 17 tf^ seg. Conydrine, 529. Conylene, 65, 529. Conyrine, S2S- Copellidine, 527. Copjjer-zinc couple, 48. Conndine, S2o. Corydaiine, 547. Cotamine, 545. Cotton dyes, 478, 497. Cream of tartar, 262. Creatine, 299. Creatinine, 299. Creoline, 423. Creosol, 425. Cresol ethyl ether, 396. Cresols, 422, 563. Cresorcin, 425. Cresyl-sulphiiric acid, 423. Crocein scarlet, 404. Croconic acid, 325. Crotonic acids, 178, 180. Crotonic aldehyd.e, 150. Crotonylehe, 66, 353. Cryoscopic methods, 11. Crjrptidme, ^6. Crystalline, 384. Crystal violet, 492. Cumalic acid, 258, 529. Cumaline, 529. Cumaric acids, 446, 463. Cumarin, 44s, 463. Cumarone, 3S2, 567, Cumene, 356, 363, Cumenols, 412. Cumic acid, 364, 453. Cumic alcohol, 432. Cumic aldehyde, 435. Cumidine, 375, 393, Cumin, oil of, 423, 548. Cuminol, 435, Cupric ferrocyanide, 276. Curcumin, 561. Cyamelide, 279. Cyan-acetic acid, 186. Cyanamide, 285. Cyanates, 279. Cyan-etholine, 280. ' Cyanic acid, 278. Cyanic ether, 279. Cyanides, metallic, 275 ei seg. Cyanides of the alcohol radicles, 117, Cyanines, 53s. Cyanmethine, 530. Cyano-acetone, 157. Cyano-benzene, 451. Cyano-carbonic ether, 252. Cyano-diphenyl, 476. Cyano-fatty acids, 185. Cyano-naphthalenes, S04, 567. Cyano-propionic acids, 186. Cyano-pyndine, 525. Cyano-quinoline, S3S- Cyanogen, 272, Cyanogen bromide, 278. Cyanogen chloride, 278, 285. Cyanogen compounds, 269 et seg. Cyanogen iodide, 278. Cyanogen sulphide, 283. Cyanol, 384. Cyanuramide, 286. Cyanuric acid, 280. Cyanuric chloride, 278. Cyanuric ethers, 280. Cyaj^henine, 530. Cyclic compounds, 308. Cyclo-butane, 61, 323. Cyclo-hexadiene, 361. Cyclo-hexane, ^5, 362. Cyclo-hexane-dione, 429. Cyclo-hexene, 362. Cyclo-pentane, 61. Cyclo-propane, sSt 323- Cymene, 364, 548, S49. 55^- Cymene dihydnde, 365, 551, 554. Cymidine, 393. Cymogene, 52. Cystein, 243. Cystine, 243. 576 INDEX. D. . (f= dextro-rotatory, 309. Daphnetin, 464. Daphnin, 464. Decane, 52. Deca-tetrine di-acid, 257. Decomposition of hydrocarbons, 53. Decomposition of optically inactive com- pounds by ferments, 39. Decyl alcohols, 95. Decylene, 55. Desmotropism, 287. Desoxalic acid, 268. Desoxy-benzoin, 497. Developers, photographic, 251, 422, 425, 426, 506. DewaPs benzene formula, 348. Dextrine, 322. Dextrite, 323. Dextro-limonene, 553. Dextrose, 314. Dextrose-phenyl-hydrazone, 315. Dextro-tartaric acid, 259 et seg. Diacetamide, 198. Diaceto-acetic ether, 246. Diaceto-succinic acid, 263. Diaceto-succinic ether, 246. Diacetyl, 238. Diacetyl-dinydrazone, 239. Diacetylene, 66. Diacetylene-dicarboxylic acid, 67, 257. Diacetylene-monocarboxylic acid, 182. Diacetyl-osazone, 239. Diagonal formula of benzene, 348. Di-aldehydes, 220, 238. Dialkyl-succintc acids, 255. Dialkyl-thio-ureas, 297. Di-ally_l, tt.^ Dialuric acid, 303. Diamide, 130, 228, 299. Djamido-azo-benzene, 403, 405. Diamido-benzenes, 393. Diamido-benzoic acids, 346, 451. Diamido-benzophenone, 482. Diamido-dimethyl-acridine, 538. Diamido-diphenyl, 4:^7. Diamido-diphenylamine, 390. Diamido-diphenyl -methane, 386, 482. Diamido-hexamethylene, 394. Diamido-naphthalenes, 504. Diamido-phenazine, 394, 540. Diamido-phenols, 422. Diamido-phenyl-acridine, 538. Diamido-stilbene, 496. Diamido-triphenyl-methane, 487. Diamines, 208. Diamines, aromatic^ 383. Diamino-caproic acid, ^63. Dianilido-quinone-dianile, 430, 542. Di-anisidine, 479. Diastase, 321, 566. Diaterebic acid, 259. Diazo-acetic ether, 228. Diazo-amido-benzene, 400. Diazo-amido-compounds, 380, 398 et seq. Diazo-amido-naphthalene, 504. Diazo-amido-toluene, 405. Diazo-benzene, 287, 395, 396. Diazo-benzene chloride, 398. Diazo-benzene imide, 398. Diazo-benzene nitrate, 398. Diazo-benzene perbromtde, 398. Diazo-benzene-potassium, 398. Diazo-benzene-potassium sulphite, 406. Diazo-benzene-sJlver, 398. Diazo-benzene sulphate, sgS, 406. Diazo-benzene-sulphonic acid, 410. Diazo-benzoic acids, 450. Diazo-compounds, 380, 394, 414, Diazo-compounds, fatty, 129. Diazo-compounds, isomers of, 400. Diazo-ethane-sulphonic acid, X29. Diazo-ethoxane, 113, Diazo-guanidinc, 299. Diazo-naphthalenes, 504. Diazo-probromides, 397. Diazotising, 39^. Dibenzoyl-acetic acid, 49S. Dibenzoyl-methane, 498. Dibenzyl, 475, 496, 508. Dibromo-anthracenes, 511, Dibromo-acrolein, 150. Dibromo-benzene hexahydride, 369. Dibromo-benzenes, 346, 369. Dibromo-furfurane, 326. Dibromo-hexa-methylene, 369. Dibromo-indigo, 47a Dibromo-nitro-ethane, X12. Dibromo-propionic acids, 182. Dibromo-pyndine, 545. Dibromo-succinic acid, 254. Dibromo-thiophene, 326. Dibromo-»2-xylene, 364. Djcetyl, 41. Dicetyl ether, loi. Dicetyl-malonic acid, 247. Dichlor-hydrins, 215, 216. Dichloro-acetic acid, 186. Dichloro-aceto-acetic ether, 246 Dichloro-acetone, 268. Dichloro-aldehyde, 149. Dichloro-anthracene, 511. Dichloro-anthraquinone, 513. Dichloro-benzenes, 366, 369, Dichloro-diphenyl, 476. Dichloro-ethane, 76. Dichloro-ether, loi. Dichloro-indigo, 470. Dichloro-methane, 75. Dichloro-propane, 77. Dichloro-quinoline, 531. Dichloro-tetroxy-benzene, 427. Dichloro-toluenes, 366. Dicyan-diamide, 286. Dicyano-benzenes, 410. Dicyano-dipheuyl, 476, Diethyl; see Normal butane^ 49. Diethylamina, 127. Diethyl-aniline, 375. Diethyl-benzenes, 356. Diethyl-cyanamide, 285. Diethyl disulphide, 106, Diethylene-diamine, 210, 530. Diethylene glycol, 208. Diethyl ether, 100. Diethyl-hydrazine, 129. INDEX. 577 Diethyl-hydrazine, urea derivatives of, 129. Diethyl-indigo, 470. Diethyl ketone, 157. Diethyl-phosphinic acid, 132. Diethyl-semi-carbazide, 129. Diethyl sulphide, 106. Diethyl sulphone, zo6, 410. Diethyl sulphoxide, 106. Diethyl-thio-urea, 297. Diethyl-toluidine, 474. Diethyl-urea, 129. Differentiating action, 357. Digallic acid; see Tannin. Digitalein, 560. Digitalin, 560. Digitonin, 560. Digitoxin, 560. Di-glycollamic add, 227. Di-glycollic acid, 227. Di-glycoUic anhydride, 227. Di-hydrazones, 238. Dihydro-benzaldehyde, 435, 344. Dihydro-benzoic acids, 449. Dihydro-carveol, 557. Dihydro-carvone, 557. Dihydro-coUidine-dicarboxylic ether, 521. Dihydro-cymenes, 365, sSi> 554- Dihydro-dipentene, 553. Dihydro-imido-azole, 384. Dihydro-methyl-pyiidine, 524, 527, Dihydro-phthalic acids, 349, 465-466. Dihydro-p3rridines, 527. Dihydro-quinoline, 535. Dihydro-quinoxaline, 384. Dihydro-terephthalic acids, 349, 465-466. Dihydro-terpenes, 555. Dihydro-xylene, 363. Di-iodo-benzenes, 366. Di-iodo-phenol-sulphonic acid, 422. Di-isobutyiene, 61. Di-isocyanic acid, 281. Diketo-butane, 238. Diketo-dihydro-benzene, 428. Diketo-hexamethylerie, 429. Diketo-hexamethylene-dicarboxylic acid= Dioxy-dihydro-terephthalic acid^ 467. Diketo-hexamethylene-dicarboxylic ether, 354- Diketo-hexane, 238. Diketones, 220, 238. Di-Iactic acid, 231. Dill, oil of, 553. Dimethoxy- benzidine, 479. Dimethyl-acetamide, 194. Dimethyl-acetic acid, 174, Dimethyl-aceto-acetic ether, 245. Dimethyl-alloxan, 304. Dimethyl-amido-azo-benzene, 405. Dimethyl-amido-azobenzene-sulphonic acid, 405. Dimethylamine, 126. Dimethyl-aniline, 375, 382, 388, Dimethyl-anthracines, 511, 514. Dimethyl-arsine compounds, 133, 135- Dimethyl-benzenes; see Xylene, 362. Dimethyl-benzoic acids, 452. Dimethyl-butane-diol, 207. Dimethyl-butanone, 157, Dimethyl-carbinol, 93. (506) Dimethyl ether, loi. Dimethyl-ethyl-henzenes, 356. Dime thy l-furfurane, 326, 329. Dimethyl-ketol, 237. Dimethyl ketone, 156, Dimethyl-malonic acid, 253. Dimethyl-naphthalenes, 507. Dimethyl-naphthylamines, 504. Dimethyl-nitrosamine, 125. Dimethyl-oxamic ether, 123, 252. Dimethyl-oxamide, 123, 252. Dimethyl-parabanic acid, 303. Dimethyl-phenylene green, 390. Dimethyl-phosphine, 131. Dimethyl-phosphinic acid, 131. Dimethyl-piperidine, 528. Dimethyl-propane, 52. Dimethyl-pyrazine, 530. Dimethyl-pyridine, 526. Dimethyl-pyridine-carboxylic ether, 521. Dimethyl-pyrrol, 326, 330. Dimethyl-quinolines, 519. Dimethyl sulphide, 106. Dimethyl-thiazole, 333. Dimethyl-thiophene, 326, 328. Dimethyl-toluidine, 393. Dimethyl-uric acid, 305. Dimorphism, 26. Dinapnthols, 505. Dinaphth^ls, 507. Dinicotimc acid, 527. Dinitranilines, 387. Dinitro-anthracene, 511, Dinitro-benzenes, 372. Dinitro-cresol, 423. Dinitro-diazo-benzene-imide, 398. Dinitro-diphenyl, 476. Dinitro-diphenyl-diacetylene, 498, Dinitro-diphenylamines, 389. Dinitro-ethane, 113. Dinitro-naphthalene, 503. Dinitro-«-naphthol, 50s. Dinitro-fl6-naphthol-sulphonic acid, 505. Dinitro-phenols, 420. Dinitro-toluenes, 348, 372. Dioximes, 238. Dioxindole, 459, 472. Dioxy-acids, 179, 235. Dioxy-anthracenes, 511. Dioxy-anthranol, 514. Dioxy-anthraquinones, 511. Dioxy-azobenzene-sulphonic acid, 406. Dioxy-benzenes, 412, 423. Dioxy-benzoic acids, 461. Dioxy-benzophenone, 483. Dioxy-cinnamic acids, 463. Dioxy-dihydro-benzene, 429, Dioxy-diphenylamine, 390. Dioxy - diphenyl - phthahde ; see Phenol- phthale'in, 495. DiQxy-diquinoyl, 430. Dioxy-ethylamine, 211, 530. Dioxy-hexamethylene, 425. Dioxy-malonic acid, 265. Dioxy-naphthalenes, 506. Dioxy-naphtho-quinones, 507. Dioxy-pyndine-carboxylic acid, 522, 527. Dioxy-quinone, ^30. Dioxv-stearic acid, 235. 20 578 INDEX. Dioxy-tartaric acid, 264, 265, 355. Dioxy-terephthalic acid, 467. Dioxy-terephthalic ether, 354, 438. Dioxy-toluenes, 425. Dioxy-xylenes, 425. Dipentene, 550, 553. Dipentene dihydrochloride, 553. Diphenic acid, 479, 515. Diphenols, 423, 476. Diphenyl, 401, 476. Diphenyl-acetic acid, 480, 483. Diphenyl-acetylene, 496. Diphenylamine, 381, 389. Diphenylamine blue, 492. Diphenyl-benzene, 476, 479. Diphenyl-bromo-methane, 482. Diphenyl-carbinol, 482. Diphenyl-carbo-di-imide, 285. Diphenyl carbonate, 416. Diphenyl-carboxylic acid, 476, 479. Diphenyl-diacetylene, 498. Diphenyl-dicarboxylic acid, 476, 479. Diphenylene ketone, 484. Diphenylene-ketone oxide, 483. Diphenylene-methane, 484. Diphenylene-methane oxide, 538. Diphenylene oxide, 476, 478. Diphenyl-ethane, 483. Diphenyl-ethylene, 496. Diphenyl-glycol, 497. Diphenyl-glycollic acid, 483. Diphenyl group, 476. Diphenyl-hydrazine, 407. Diphenyliue, 476, 478. Diphenyl ketone, 482. Diphenyl-methane, 475, 482. Diphenyl-nitrosamine, 389. Diphenylol, 476. Diphenyl oxide, 417. Diphenyl-phthaJide, ^g^. Diphenyl-succinic acid, 497. Diphenyl-thio-urea, 392. Diphenyl-urea, 385. Dipicohnic acid, 527. Di-potassium-aniline, 378. Dipropargyl, 67. Dipropyl-ketone, 157. Dipyndine, 524. Dipyridyl, 524. Diquinoline, 535. Diquinolyline, 535. Disazo-compounds, 404. Distillation, fractional, 34, 90. Disulphanilic acid, 410. Disulphides, 104. Disulph oxides, 104. Dithio-acids, 1^3. Dithio-carbamic acid, 297, Dithio-dicyanic acid, 284. Dithio-urethane, 297. Ditolylamine, 393. Ditolyl-phenyl-methane, 485. Ditolyls, 476. Di-ureides, 301. Docosane, 42. Dodecane, 42. Dodecyl alcohol, 95. Dodecylene, 55. Dodecylidene, 6s. Double bond^ 58-59' Double cyanides, 275, Dualistic formulae, 14. Dulcite, 219. Durene, 364. Durenols, 4x2. Dyes; see (e.g.) Triphenyl-ntetkcme' and Azo-dyes. Dyes, sulphonates of, 41X. Dynamite, 217. Earth oil, 53, 353. Earth pitch, 54. Ecgonme, 544. Egg albumen, 563, 564. Egg, white of, 564. Eicosane, 42. Eicosylene, S5' Eikonogen, 506. Elaeoptenes, 548. Elaidic acid, 181. Elastin, 566. Elayl; see Ethylene^ 60. Electrical behaviour, 36. Electrolysis, 48, 58. Elementary analysis, 4 Empirical formulae, 7. Emulsin, 273, 322, 434. Enzymes, 322, 566. Eosm, 495. Eosin group, the, 494. Epichlorhydrin, 216. Ei^ui-molecular solutions, 11. Engeron, oil of, 553. Erucic acid, z8i. Erythrin, 218, 461. Erythrite, 218. Erythritic acid, 235. Erythro-dextrine, 322. Erythro-oxy-anthraquinone, 511. Erythrosin, 495. Esters, 188. Eiard reaction, the, 434 Ethal, 05. Ethanalj 147. Ethanalic acid, 239. Ethane, 17, 48. Ethane-amide, 198. Ethane-amidine, 200. Ethane di-acid, 250. Ethane-dial, 238. Ethane-dicarboxylic acid, 233, Ethane-diol, 206. Ethane-dithio-ethane, 106. Ethane-dithiol, 208. Ethane-nitrile, 118. Ethane-oxime, 150. Ethane-oxy-ethane, 100. Ethane-phenyl-hydrazone, 140. Ethane-sulphone-ethane, 106. Ethane-sulphoxy-ethane, 106. Ethane-tetra-carboxylic acid, 268, 499. Ethane-tetra-carboxylic ester (symmetrOt 268, 490. Ethane-thiol, loSj 106. Ethane-thiolic acid, 193, 226. INDEX. 579 Ethane-thion-amide, igo. Ethane-tricarboxylic acid, 266. Ethanoic acid, 170. Ethanoic anhydride, 193. Ethanol, 88. Ethanolal, 237. Ethanol-amine, 148, 21Z, Echanolic acid, 225. Ethanoyl, 167. Ethanoyl chloride, 191. Ethene, 60. Ethene-thio-ethene, 106. Ethenol, 96. Ethenyl-amidoxime, 202. Ethenyl-diphenyl-amidine, 200. Ethenyl-triethyl ether, 214. Ether, 100. Ether-acids, 108. Ethereal oils, 548. Ethers, alcoholic, 97. Ethers, compound, 79, 107, 188. Ethers, simple, 98. Ethers of the fatty acids, 188. Ethidene chloride, 77. EthinCj 65. Ethionic acidj 212. Ethyl-acetamide, 195. Ethyl-acetamido chloride, ig8. Ethyl acetate, 189. Ethyl-aceto-acetic ether, 24s- Ethyl-acetimido chloride, 198, Ethyl alcohol, 88. Ethyl-amine, 127. Ethyl-aniline, ^7S. Ethyl-aniline-nitrosamine, 400, Ethyl-benzene, 351, 356, 363. Ethyl-benzoic acids, 446. Ethyl bromide, 74. Ethyl-camphor, 556, Ethyl-carbamic ether, 291. Ethyl-carbamine, 120. Ethyl carbinol, 92. Ethyl carbonate, 288. Ethyl -carbonic acid, 289. Ethyl-cetyl ether, loi. Ethyl chloride^ 73. Ethyl cyanamide, 285. Ethyl cyanide, 118. Ethyl-dim ethyl-benzene, 356. Ethyl disulphide, 106. Ethyl-dithiocarbamic acid compounds, 297. Ethylene, 60. Ethylene bromide, 76. Ethylene chloride, 70, 76, Ethylene cyanhydnn, 208. Ethylene cyanide, 207. Ethylene diamine, 210, Ethylene-disulphonic acid, 211. Ethylene glycol, 206. Ethylene hydramines, 209. Ethylene-imine, 209. Ethylene iodide, 76. Ethylene-lactic acid, 232. Ethylene-mono-thio-hydrate, 208. Ethylene oxide, 208.^ Ethylene-succinic acid, 253. Ethyl ether, 100. Ethyl fluoride, 74. Ethyl-glycollic acid, 226. Ethyl-hydrazine, T29. Ethyl hydride, 48. Ethyl hydrosulphide, 102 et seq. Ethyl hypochlorite, 113. Ethyl h3rpophosphite, 116. Ethylidene-acetone, 237. Ethylidene bromide, 69. Ethylidene chloride, 69, 77. Ethylidene cyanhydrin, i^, 208. Ethylidene-diphenyl diamme, 379. Ethylidene-disulphonic acid, 116. Ethylidene glycol, 142, 206. Ethylidene-lactic acid, 229. Ethylidene-succiuic acid, 254. Ethyl-indoxyl, 473. Ethyl iodide, 69, 74. Ethyl isocyanate, 279. Ethyl isocyanide, izo. Ethyl isothiocj^anate, 284. Ethyl-lactic acid, 231. Ethyl-malonic ethers, 253. Ethyl mercaptan, 106. _ Ethyl-methyi-acetic acid, 173. Ethyl-methyl-aceto-acetate, 245. Ethyl-methylene-amine, 144. Ethyl-methyl-pyridine, 526. Ethyl monochlor-acetate, 189. Ethyl nitrate, 109. Ethyl nitrite, no. Ethyl-nitrogen chloride, 127. Ethyl-nitrolic acid, 112. Ethylol-trimethyl-ammonium hydroxide, 211. Ethyl oxalate, 251. Ethyl-oxalic acid, 251. Ethyl-oxalyl chloride, 251. Ethyl oxamate, 252. Ethyl-phenol, 423. Ethyl-phosphines, 130, 132. Ethyl-pyridine, 523. Ethyl-salicylic acid, 457. Ethyl sulph-hydrate, 106. Ethyl sulphide, 106. Ethyl-sulphinic acid, 115. Ethyl-sulphonic acid, 115. Ethyl-sulphonic chloride, 115. Ethyl-sulphonic ether, ir6. Ethyl sulph'Oxide, 106. Ethyl-sulphuric acid, 114. Ethyl-sulphurous acid, 115. Ethyl thiocyanate, 283. Ethyl-toluenes, 356. Ethyl-urea, 293. Ethyl-xylenes, 365. Eucalyptene, 548. Eucalyptol, 556. Eugenol, 425, 437. Eupion, 54. Eupittone, 493. Eurhodine, 540. Eurhodol, 540. Euxanthone, 483. Fast blue, 542. Fast red, 506. Fast yellow, 403. 580 INDEX. Fats, 176. Fatty acid series, 156. Fekling's solution, 262, 311. Fenchene, 550. 553. Fenchone, 557. Fennel oils, 557. Fermentation, amyl-alcohol, 94. Fermentation, butyl-alcohol, 94. Fermentations, 89. Ferments, 322. Ferments, unorganized, 566. Fernambuco wood, 561. Ferricyanide of potassium, 276. Ferrocyanide of copper, 276. Ferrocyanide of potassium, 276. Ferulic acid, 463. Fibrin, 564. Fibrinogene, 564. Fiddle resin, 551. ^zV^r^ reaction, the, 357. Flavaniline, 301, 536. Flavean hydride, 273. Flavol, 511. Flavo-purpurin, 511, 514. Fluo-benzene, 369. Fluorane, 495. Fluoranthene, 516. Fluorene, 480, 4?4. Fluorenyl alcohol, 484. Fluorescein, 495. Fluorescin, 495. Fluoroform, 78. Formamide, 197. Formanilide, 351. Formazyl hydride, 397. Formic acid, 168. Formic aldehyde, 146. Formic ether, i8g. Formo-rhodamine, 538. Formose, 309. Formula, calculation of the, 7. Formulae, constitutional, 17 et seg. Formyl, 167. Formyl-acetic acid=oxy-acrylic acid, 240. Formyl-acetic ether, 244. Formyl-diphenylamine, 537. Formyl-trisulphonic acid, 213-214. Freezing temperature of solutions, 11. Friedel-Krafts reaction, the, 357. Fructose, .316. Fruit ethers, 189. Fruit sugar, 316. Fuchsine, 488, 490. Fuchsine S, 491. Fuchsine-sulphurous acid, 491. Fucose, 308. Fulminates, 118-119. Fulminic acid, 118, Fumaric acid, 255, 256. Furfurane, 326, 329, Furfurane alcohol, 326. Furfurane aldehyde, 329. Furfurane derivatives, 264, 308, 326, Furfurazane, 334. Furfurol, 326, 329, Fusel oilj 89. GJalactonic acid, 236. Galactose, 316. Gala-heptose, 310. Galipot resin, 559. Gallein, 495. Gallic acid, 426, 447, 461, 514. Galline, 495. Gallo-cyanine, 542. Gallo-flavin, 483. Gallo-tannic acid, 462. Garlic, oil of, 107. Garnet brown (dye), 420. Gasoline, 52. Gelatine, 565. ** Gelatine sugar'', 228. Geranium, oil of, 558. Globuline, 564. Gluco-heptite, 219. Gluco-heptonic acid, 237. Gluco-heptose, 310. Gluconic acid, 236, 310. Gluco-nonite, 219. Gluco-octite, 219. Glucosamines, 312. Glucose-carboxylic acid, 237. Glucoses, 309, 314. Glucosides, 469, 559. Glucosone, 312. Glue, 565. Glutamic acid, 259, 563. Glutamine, 259. Glutaric acid, 254, 522. Glutazine, 525. Glutin, 563. Glyceramic acid ; see Serine^ 235. Glyceric acid, 234. Glyceric aldehyde, 237. Glycerides, 162, 176, 233. Glycerine, 214. Glycerine nitrates, 216. Glycerose, 307, 309. Glyceryl-phosphoric acid, 2x5, 566. Glyceryl-sulphuric acid, 215. Glyceryl-tri-chloride, 78, 215-216. Glycide alcohol, 216. Glycide compounds, 216. Glycocholic acid, 227, 566. Glycocoll, 226, 227, 563, 566. Glycocoll-amide, 226. Glycocoll, salts of, 228 Glycocyamidine, 299. Glycocyamine, 299. Glycogen, 322. Glycol bromhydrins, 207, Glycol chlorhydrins, 203, 207. Glycol, ethers of, 207. Glycolide, 227. Glycol iodhydrin, 207. Glycol mercaptan, etc., 208 Glycollamide, 225, 226. GlycoUic acetates, 203, 207 GlycoUic acid, 221, 225. Glycollic aldehyde, 237. GlycoUic anhydride, 227. Glycollic chloride, 225. GlycoUic cyanhydrins, 223. INDEX 581 GlycoUic di-nitrate, 207. Glycollic ether, 225. Glycols, 202. Glycol-sulphuric acid, 207. Glycoluric acid, 294. Glycolyl-urea, 294. Glycuronic acid, 240. Glyoxal, 238, 334. Glyoxalic acid, 239. Glyoxalic di-ureide, 304. Glyoxaline, 317. Granulose, 321. Grape sugar, 314. Grape sugar group, the, 309. Griess reaction, the, 397. G-salt, 506. Guaiacol, 414, 424. Guanamines, 299. Guanidine, 290, 298. Guanidines, alkyl-derivatives of, 299. Guanidines, phenylated, 392. Guanine, 306. Galenic acid, 236. Guloses, 310, 315-316. Gum henzoin, 468. Gum lac, 559. Gums, 322. Gun cotton, 321. Gutta-percha, 555. H. Haematin, 565. Hxmatoxyliu, 561. Hsmin, 565. Haemoglobin^ S6^~S6S- Halogen derivatives of the aromatic series, 366. Halogen derivatives of the fatty series, 67. Halogens, determination of, 7. Harmalin, 561. Harmin, 561. Hatcheit's brown, 276. Heat of combustion, 37. Heat of formation, 37. Helianthin, 394, 405. Helicin, 560. Hemellithene, 364. Hemi-albumoses, 563. Hemi-mellitic acid, 468. Hemipinic acid, 467. Hemiterpene, t^. Henei-cosane, 42. Hentria-contane, 42, Hepta-cosane, 42. Hepta-decane, 42. Hepta-methylene, 323- Heptanes, 52. Heptanone, 157. Heptine, 62. Heptoses, 310, 313, 316. Heptyl alcohols, 95. Heptylene, 55. Heptylic aldehyde, 149. Hesperidene, 553. Hesperidin, 560. Hexabromo-benzene, 70, 369. Hexachloro-benzene, 70, 366, 369. Hexachloro- ethane, 69, 78. Hexachloro-triketo-hexamethylene, 426. Hexa-contane, 53. Hexa-decane, 42. Hexa-decoic acid, 177. Hexa-decyl alcohol, 95. Hexa-decylene, 55. Hexa-decylidene, 62. Hexa-diine, 67. Hexagon formula, 344. Hexahydro-benzene, 344, 353, 362. Hexahydro-benzoic acid, 449. Hexahydro-cumene, 364. Hexahydro-dipyridyl, 529. Hexahydro-isophthalic acid, 354, 467. Hexahydro-phenol^ 416. Hexahydro-phthalic acid, 344, 465-466. Hexahydro-pyrazine, 530. Hexahydro-pyridine, 518, 522, 527. Hexahydro-terephthalic acid, 344, 466. Hexahydro-tetroxy-benzoic acid, 462. Hexamethyl-benzene, 353, 356, 365. Hexa-methylene=Cyclo-hexane, 344, 362 Hexamethyl-para-rosaniline, 45. Hexa-naphthene-carboxylic acid, 449. Hexane-pentolic acids, 235. Hexanes, 52. Hexane-tetrolic acids, 235. Hexanitro-diphenylamine, 389. Hex-ethyl-benzene, 356. Hexine, 62. Hexonic acids, 235. Hexoses, 309 et seq. Hexoxy-anthraquinones, 511, 514. Hexoxy-benzene, 354, 427. Hexoxy-diphenyl, 479. Hexyl alcohols, 95. Hexyleue, 55. Hexylene glycols, 206. Hexylic acids, 175. Hexyl iodide, 75, 354. Hippuric acid, 227, 450. Hoffmant^s drops, loi. Homatroijine, 547, Homoconic acid, 233. Homologous series, 27. Homology, 27. Homo-phthahc acids, 467. Homo-pyrocatechin, 425. Honey-stone, 468. Horn substance, 566. Hydantoic acid, 294. Hydantoi'n, 294. Hydracetamide, 144. Hydracrylic acid, 232. Hydramines, 209. Hydranthranol, 511. Hydratropic acid, 446, 453. Hydrazides, 407. Hydrazine, 22B, 299. Hydrazines, aromatic, 381, 406. Hydrarines, fatty, 128, 228. Hydrazo-benzene, 401. Hydrazo-compounds, T19, 401. Hydrazo-dicarboxylic amide, 279, 299. Hydrazoic acid, 228, 299, 398, 450. Hydrazones, aromatic, 404, 407. Hydrazones, carbohydrate, 312. 582 INDEX. Hydrazones, fatty, 146, 156, 397. Hydra 20-toluene, 401. Hydrindene, 508. Hydrindic acid, 459. Hydro-acridine, 518. Hydro-anthracene, 508. Hydro -an thranol, 511, 512. Hydro-benzamide, 434. Hydro-benzoinj 497. Hydrocarbons, aromatic, 356. Hydrocarbons, classification of, 30. Hydrocarbons, fatty, 42. Hydro-carbostyril, 453, 531. Hydro-chelidonic acid, 265'. Hydrocinnamic acid, 452. Hydrocinnamo-carboxyiic acid, 467, 504. Hydro-ccerulignone, 479. Hydro-coUidine-dicarboxylic acid, 521. Hydrocumaric acids, 444, 447, 458. Hydrocyanic acid, 2^3. Hydro-ferricyanic acid, 277. Hydro-ferrocyanic acid, 276. Hydrogen, estimation of, 4, Hydrogen isomerism, 287. Hydro-isophthalic acids, 467. Hydrolysis, 84, 317. Hydro-mellitic acid, 468. Hydro-muconic acid, 255. Hydronaphthalene-tetracarboxylic ether, 499. Hydro-naphthoquinones, 506. Hydro-ortho-cumaric acid, 458. Hydro-paracumaric acid, 458. Hydro-phenazine, 394, 539-540. Hydro-phthalic acids, 349, 465-467. Hydroquinone, 354, 424. Hydroquinone-carboxylic acid, 461. Hydroquinone-dicarboxylic acid, 467. Hydroquinone-tetracarboxylic acid, 468. Hydro-sorbic acid, 179. Hydrosulphides, 102 et seq. Hydro-terephthalic acids, 349, 465-466, Hydroxamic acids, 202. Hydroxyl, 18. Hydroxy lamines, 128. Hyoscine, 547. Hyoscyamine, 547. Hypnone, 436. Hypochlorous ether, 113. Hj^oxanthine, 306. I. z=inactive, 309. Imesatin, 471. Imides, 121, 250. Imido-azole, 238, 334. Imido-bases, 121. Imido-carbamic compounds, 295 et seq. Imido-carbamide, 2C)S. Tmido-carbamine-thio-methyl, 296. Imido-carbo-compounds, 295-296. Imido-carbonic acid, 290. Imido-chlorides, 187, ig8. Imido-dicarboxylic-diethyl ether, 291. Imido-ethers, 187, 200, 391, Imido-thio-compounds, 187. Imido-thio-ethers, 199. I mines, 209. Indamines, 389-390. Indazoles, 475, 567. Indene, 507-508. Indican, 469. Indicator, 405. Indigo, 435, 469. Indigo-brown, 469. Indigo-carmine, 469. Indigo-dicarboxylic acid, 470. Indigo-gelatine, 469. Indigo-purpurin, 470. Indigo-red, 469, Indigo-sulphonic acids, 469, 47a Indigo-white, 469. Indin, 470. Indirubin_, 470. Indo-anihne, 390. Indole, 474, 563. Indole-carboxylic acids, 475. Indonaphthene, 507-508. Indophenin, 331. Indophenols, 390. Indoxyl, 471, 473. Indoxyl-sulphuric acid, 473. Indoxylic acid, 473. Indoxylic ether, 473. Indulines, 541-542. Inosite, 427, International Chemical Nomenclature, 28. Inulin, 322. Inversion, 317. Invert sugar, 317. Invertin, 322. lodo-acetylene, 353. lodo-aniline, 386. lodo-benzene, 366, 369. lodo-propioHc acid, 183. lodo-propionic acids, 1S4, z86. Iodoform, 78. Iodoform reaction, the, 92. lodol, 330. lodoso-benzene, 369. Iridoline, 5^6. Iron albuminate, 564. Iron peptonate, 564. Isatic acid, 460, 471. Isatin, 452, 460, 471. Isatin chloride, 472. Isatoic acid, 472. Isatoxime, 472. Isethionic acid, 212. Iso-amyl-iso-valerate, 189. Iso-anthraflavic acid, 511. JsO'barbituric acid, 303. Iso-butane, 49. Isobutyl alcohol, 94. Isobutyl carbinol, 94. Iso-butylene, 61. Isobutyric acid, 174. Iso-cinchomeronic acid, 527. Iso-cinnamic acid, 454. Iso-citric acid, 268. Iso-crotonic acid, 180. Isocyanic ethers, 279. Isocyanides, 119. Isocyanuric ethers, 280-281. Iso-cymenes, 365. INDEX. 583 [so-cymidme, 303. !so-dialuric acid, 303. !so-dulcite, 308. !so-durene, 356. sodynamic molecular transformation, 287. so-ferulic acid; see Uesperetic acidf 560. !so-glucosamine, 312. so-hydrobenzoin, 497. 'so-melamine, 286. isomerism, 14, 49. somerism, mixed, 351. somensm, nucleus, 341 et seg. isomerism, side-chain, 251. somerism, stereo-chemical, 21. somerism in the cyanogen group, 286. somerism of position, 102, 341 ei seg. somerism of the benzene derivatives, 339, 351- somers of the diazo-compounds, 400. 'so-naphthazarine, 50&-507. !so-nicotinic acid, 526. !so-nitriles, lig, 379. !so-nitroso-acetone, 157, 530. 'so-nitroso-ketones, 156. !so-nitroso-methyl-acetone, 157. 'so-nitroso-naphthols, 506. ;so-paraffins, 51. !so-pentane, 52. 'sophthalic acid, 363, 4G5. isoprene, 66. :so-propyl, 50.^ !sopropyI-acetic acid, 174. 'sopropyl alcohol, 93. sopropyl-benzene, 364. sopropyl-benzoic acid, 453. ^sopropyl chloride, 74. sopropyl iodide, 69, 74. sopropyl-methyl-henzene, 364. 'sopropyl-pyridine, 523. so-purpuric acid, 420. so-quinoline, 506, 536. Iso-saccharic acid (monobasic), 235. so-saccharic acid (dibasic), 264. !so-saccharine, 235. so-succinic acid, 254. so-thiacetamide, 199. !so-thiocyanic acid, 284. :so-valenc acid, 174. so-valeryl chloride, 191. !soxy-azoles, 334. ^so-xylene, 363, suret, 202._ taconic acid, 255. :tamalic acid, 259. Japan camphor, 555. Juglone, 507. Juniper, oil of, 551. K. Keratin, 366. Ketine, 530. Ketines, 530. Keto-butyric acid, 240, 243. Keto-compounds, 1^3. Keto-dihydro-pyridine, 525. Ketols, 237. Ketone-alcohols, 220, 237, 314, 436. Ketone-aldehydes, 239, 354. Ketones, aromatic, 435. Ketones, fatty, 151, 353. Ketones, mixed, 152. Ketonic acids, aromatic, 458. Ketonic acids, fatty, 220, 240. Ketonic decomposition, 245. Keto-pentamethylene, 324. Ketoses, 31-1,. Kinno-tannic acid, 462. Kd'rfter's benzene formula, 348. L. /=l£evo-rotatory, 309. Lactame formation, 452. Lactames, 452. Lactamide, 231. Lactic acids, 229 et seq. Lactic acids, derivatives of, 231. Lactic ether, 231. Lactic fermentation, 230. Lactide, 231. Lactime formation, 452. Lactimes, 452. Lacto-biose, 317, 319. Lactones, 233. Lactose, 319. Lactyl chloride, 231. Lactylic acid or Lactic anhydride, 231. Lactyl-urea, 294. Laevo-conine, 528. Laevo-limonene, 553. Lsevo-tartaric acid, 261, 263. Laevulose, 316. Lakes, 513-514- Lanolin, 566. Laubenkeimer x^z-z^ioiii the, 516. Laurie acid, 175. Laurone, 157. LautKs violet, 543, Lavender, oil of, 558. Lead acetates, 172. Lead, sugar of, 172. Lead, tetra-methide, 139. Leaf green, 561. Leather, 565. Le Bel-van 't Hqff'XaMf, the, 20, 23. Lecithin, 566. Legumin, 564. Lekene, 54. Lepargylic acid, 247. Lepidine, 536. Leucaniline, 458. Leucaurin, 493. Leucein, 563. Leucic acid, 232. Leucine, 232, 563, 566. Leuco-bases, 487. Leuco-compounds, 487. Leucoline, 534- Leuco-malachite green, 488. Leuco-rosolic acid, 493. 584 INDEX, Leuco-thionine, 543 Leuconic acid, 325. Levulinic acid, 246. Lichen acids, 461. Lichenin, 322. Liebemiann reaction, the, 387, 415. " Life force", i. Light blue, 492. Light green, ^92. Lignoceric acid,. x6i. LigroTn, 45. Limonene, 550, 553. _ Limonene tetrabromide, 553. Linalool, 548, 551, 558. Linking, 59, 64. Linoleic acid, i8z. Litmus, 425, 561. Liver starch, 322. Logwood, 561. Lupetidines, 527. Lutidines, 519, 520, 526. Lutidinic acid, 527, Lysine, 563. Lysol, 423. M. ?«=meta; see M eta-compounds. Madder root, 513. Magdala red, 541, Magenta, 488, 490. Magnesium methide, 139. Malachite green, 488. Malamic acid, 258. Malamide, 258. Maleic acid, 255, 256. Maleic ether, 256. Malic acid, 257. Malonic acid, 252. Malonic aldehyde-acid, 445. Malonic ether, 252. Malonic ether synthesis, 253, 443. "Malonyl", 248. Malonyl-urea, 303. Maltobiose, 320. Malto-dextrine, 322. Maltose, 320. Malt sugar, 320. Mandelic acid, 43B, 444, 459. Mannide, 219. Mannitan, R19. Mannite, 218. Manno-heptite, 219 Manno-hepto$e, 310. Mannonic acid, 236, 310, 311. Manno-nonose, 310. Manno-octite, 219. Manno-octose, 310. MannO'Saccharic acid, 264. Mannose, 310, 311, 315. Mannose-carboxylic acid, 310. Margaric acid, 177. Marsh gas, 47. Martins' yellow, 505. Mauvei'ne, 541. Meconic acid, 529. Meconine, 545. Meconinic acid, 467. Melanij 286. Melamine, 286. Melampyrine, 219. Melebiose, 320. Melene, 55, 6i. Meletriose, 320, Melilotic acid; see o-Cztmaric acid^ 458. Melissic acid, 161, 177, Melissic alcohol, 95. Melissic palmitate, 189. Mellitene, 365. Mellitic acid, 354, 365, 468. Mellophanic acid, 465. Melting point, rules regulating, 35. Mendius' reaction, the, 123. Menthene, 555. Menthol, 557. Menthone, 557. Mercaptals, 143. Mercaptan, 102, 104, 106. Mercaptides, ic6. Mercaptol, 157. Mercurialin, 126. Mercuric cyanide, 275. Mercuric mercaptide, 106. Mercurous thiocyanate, 282 Mercury, fulminate of, n8. Mercury diphenyl, 362, 408. Mercury ethide, 138. Mercury-ethyl hydroxide, 139. Mercury methide, 138. Mercury-methyl chloride, 139, Mesaconic acid, 255. Mesidine, 393. Mesitylene, 347, 353, 363. Mesitylene hexahydride, 363. Mesitylenic acid, 452. Mesityl oxide, 157. Meso-paraffins, 51. Mesorcin, 412, 425. Meso-tartaric acid, 260, 261, 264. Mesoxalic acid, 265. Mesoxalic aldehyde, 397. Mesoxalyl-urea, 303. M eta-compounds, 341, 345. Metacyl chloride, 157. Meta-globuline, 564. Metaldehyde,^ 148. Metallic cyanides, 275 et seq. Metamerism, 14, 102, 351. Metanilic acid, 410. Metaniline yellow, 410. > Meta-saccharic acid, 235. Meta-saccharine, 235. Meta-styrene, 366. Methacrylic acid, z8o. Methanal, 146. Methane, 47. Methane-amide, 197. Methane-di- and tri-carboxylic acids, 252 266. Methane-di- and tri-sulphonic acids, 116. Methane series, 42. Methane-thiol, 105. Methane-thio-methane, 106. Methanoic acid, 168. Methanol, 87. Methanoyl, 167. INDEX. 585 Methene, 60. Methenyl-amido-thiophenol, 421. Methen^l-amidoxime, 202. Methionic acidj 211. Methoxy-anilines, 421. Methoxy-pyridine, 525. Methoxy-quinolines, 535. "Methyl'*, 30, 48. Methyl-acetanilide, 375, 391. Methyl-aceto-acetic ether, 245. Methyl-acetyl-urea, 196. Methyl-acrid ine, 537. Methylal, 147. Methyl alcohol, 87. Methyl aldehyde, 146. Methyl-alloxan, 304. Methyl-amido-croton-anilide, 333. Methyl-amido-phenol, 421. M ethyl-am ine, 126. Methyl-amyl ether, loi. Methyl-aniline, 375, 377, 387. Methyl-aniline-nitrosamine, 387. Methyl-anthracenes, 509, 511, 514. Methyl-arbutin, 560. Methyl-arsenic compounds, 133 et seq. Methyl-arsine chlorides, 133 et seq. Methyiates, 88. Methyl-benzene; see Toluene^ 362, Methyl-benzimido-azole, 383. Methyl bromide, ^% 73. Methyl-butane, 52. Methyl-butane di-acid, 254. Methyl-butanoic acid, 174. Methyl-butanol, 95. Methyl-carbamine, 120. Methyl carbonate, 289. Methyl-carbostyril, 532. Methyl chloride, 73. Methyl-chloroform, 78. Methyl-cumarin, 444. Methyl-cyanamide, 285. Methyl cyanide, x^.^. Methyl-dtphenylamine, 389. "-Methylene", 60. Methylene blue, 394, 543. Methylene bromide, 69, 75. Methylene chloride, 69, 75, 443, 521. Methylene disulphonic acid, 211. Methylene glycol, 206. Methylene iodide, 69, 75. Methylenitan, 309. Methyl ether, 18, loi. Methyl-ethyl-acetic acid^ 175. Methyl-ethyl-ace to-acetic ether, 245. Methyl-ethyl-benzenes, 356, 364. Methyl-ethyl-benzoic acids, 44S. Methyl-ethyl-carbinol, 93. Methyl-ethyl ether, 98. Methyl-ethyl ketone, 157, 353. Methyl-ethyl-sulphide, 104. Methyl-furfurane, 326, 329. Methyl-furfurol, 329. Methyl -green, 492. Methyl-glycocoll, 228. Methyl-glyoxal, 239. Methyl-hexylene ketone, 556. Methyl-hydantoin, 294. Methyl-hydrazine, 128. Methyl-hydroquinone, 560. Methyl-hydrosulphide, 102 et seq, Methyl-hydroxylamine, 128. MethyHmesatin, 472. Methyl indole, 475. Methyl-iodide, 69, 73. Methyl-iodo- propane, 75. Methyl-isatic acid, 472. M ethyl -isatin, 472. Methyl isocyanide, 119, 120. Methyl-isopropyl-benzene, 364. Methyl-iso-thiacetanalide, 200. Methyl isothiocyanate, 284. Methyl-mercaptan, 105. Methyl -morphine, 545. Methyl-morpholine, 530. Methyl -naphthalenes, 507. Methyi-naphthylamines, 504. Methyl-nitramine, 126. Methyl nitrate, 109. Methyl nitrite, no. Methyl-nonyl ketone, 157. Methyl-orange, 405. Methyl oxalate, 251. Methyl-oxamic ether, 123. Methyl-oxy-quinoline, 532. M ethyl -parabanic acid, 303. Methyl-phenazine, 540. Methyl- phosphine, 131, 132. Methyl-phosphonic acid, 131. Methyl-piperidines, 528. Methyl-propane di-acid, 254. Methyl-propanoic acid, 174. Methyl-propanols, 94. Methyl-propene, 61. Methyl-propenic acid, 180. Methyl-propyl-benzenes, 364. Methyl-pseudo-isatin, 472. Methyl-pyridines, 521, 525. Methyl-pyridone, 525. Methyl-pyrogallol, 412. Methyl-pyrrol, 33a Methyl-quinoljne, 531, 535. Methyl-succinic acid, 254. Methyl sulphide, 106. M ethyl -sulphonic acid, 115. Methyl-sulphuric acid, 114. Methyl-thio-carbamide, 296. M ethyl- thiophenes, 326, 331. M ethyl- thio-urea, 298. Methyl-toluidines, 393. Methyl-uracyl, 303. Methyl-urea, 293, Methyl-uric acid, 305. Methyl violets, 491. Methyl-xanthamide, 297. Miazine, 530, Milk sugar, 319. Millon's reagent, 562. Mineral lubricating oils, 361. Mint camphor, 557. Molasses, 319. Molecular rearrangements, 179, 341, 381. Molecular refraction, 37. Molecular volume, 32. Molecular weight, determination of, 8, la Monochloro-acetone, 157, 333. Monochloro-acetyl chloride, 192. Monochloro-aldehyde, 149, 333. Mono-compounds (see individually). 586 INDEX, Mono-ethylin, 215. Monoformin, 168, 217. Mono-ureides, 300. Mordants, 514- Morintannic acid, 462. Morphine, 544. Moipholine, 530. Moss starch, 322. Mucic acid, 264, 327. Mucilage, 322. Mucin, 566b Mucus, 566. "Multi-rotation", 315. Murexide, 304. Muscarine, 211. Muscle albumen, 564. " Musk, artificial ' , 373. Mustard oil reaction, the, 124. Mustard oils, the, 283, 379, 384. Myosin, 564. Myricyl alcohol, 81, 95. Myricyl iodide, 53. Myristic acid, 175. Myristone, 157. Myronic acid, 560. Myrosin, 560. N. Naphtha ; see Petroleum ether, 52. Naphthalene, 464, .jgg. Naphthalene, constitution of, 500. Naphthalene-dicarboxylic acids, 507. Naphthalene dichloride, 501. Naphthalene hydrides, 5or. Naphthalene-mono-sulphonic acids, 504, 567. , . . Naphthalene-sulphomc acids, 504. Naphthalene tetrachloride, 501. Naphthalene yellow, 505. Naphthalic acid, 507. Naphthazarine, 507. Naphthazines, 539, 54a Naphthenes, 54. Naphthindulines, 542. Naphthionic acid, 504. Naphtho-acridines, 537. Naphthoic acids, 507. Naphthol-acetyl ethers, 505 Naphthol blue, 390. Naphthol dyes, 505, 506. Naphthol ethyl ethers, 504. Naphthols, 390, 500, 505. Naphthol-sulphonic acids, 505. Naphthol yellows, 505. Naphtho-phenazine, 540. Naphtho-quinolines, 536. Naphtho-quinones, 506, 537. Naphtho-salol, 505. Naphtho-tolazine, 540. Naphthylamines, 503, 504. Naphthylamine-sulphonic acids, 504. Naphthylene-diamines, 504. Narceine, 545. Narcotine, 545. Negative nature of phenyl, 338, 350, 374. Neo-paraffins, 51. Nerve substance, 566. Neurine, 211. Neutralization, heat of, 36. Neutral red, 540. Nicholson's blue, 492. Nicotine, 52^, Nicotinic acid, 526. Nile blue, ^^2. Nitracetanilides, 386. Nitramines, 126, 397. Nitranilic acid, 429. Nitranilines, 375, 376^ 386, Nitric acid, constitution, in. Nitric ether, log. Nitriles, aromatic, 441, Nitrites, fatty, 117. Nitriles, fatty, constitution of, 12a Nitro-aceto-nitrile, 119. Nitro-alizarin, 514. Nitro-amido-phenols, 421, Nitro-anthracenes, 511. Nitro-benzaldehydes, 435. Nitro-benzene, 337, 372, 397. Nttro-benzene-sulphonic acids, 410. Nitro-benzoic acids^ 438, 450. Nitro-benzoyl-forraic acid, 460. Nitro-bitter-almond-oil green, 488. Nitro-bromo-benzoic acids, 340. Nitro-camphor, 556. Nitro-chloro-benzenes, 373. Nitro-cinnamic acids, 454. Nitro-cinnamic dibromide, 453. Nitro-cumene, 373, Nitro-derivatives, aromatic, 370. Nitro-derivatives, fatty, no. Nitro-diamido-triphenyl-methane, 488. Nitro-dibromo-benzenes, 346. Nitro-dibromo-ethane, 112. Nitro-dimethyl-aniline, 388. Nitro-diphenyl, 476. Nitro-ethane, no. Nitroform, 113. Nitrogen, estimation of, 5. Nitrogen, pentavalent, 26. Nitrogen bases of the alcoholic radicles, 120. Nitrogen isomerism, 25, 26. Nitro-glycerine, 216. Nitro-^anidine, 299. Nitro-isatin, 471. Nitrolic acids^ 112. Nitro-malachite green, 488. Nitro-mannite, 219. Nitro-mesitylene, 373. Nitro-methane, no. Nitro-naphthalenes, 500, 503. Nitro-naphthols, 505. Nitro-naphthylamines, 504. Nitro-oxybenzoic acids, 340. Nitro-phenols, 35r, 372, 387, 420. Nitro-phenols, salts of, 420. Nitro-phenyl-acetylene, 373. Nitro-phenyi-lacto-methyl ketone, 470. Nitro-phenyl-nitrosamine, 400. Nitro-phenyl-propiolic acid, 455, 470. Nitro-prussic acid, 277. Nitro-pseudo-cumene, 373. Nitro-quinolines, 535. Nitrosamine red, 40a INDEX. 587 Nitrosamines, 125, 381, 400. Nitrosamines of aromatic bases, 400. Nitrosates, 57, no. Nitroso-aniline, 388. Nitroso-benzene, 373, 397. Nitroso-compounds ; see also Isoniiroso- compounds. Nitroso-dimethyl-aniline, 374, 384, 388, 419. Nitroso-dipentene, 553. Nitroso-indole, 474. Nitroso-indoxyl, 473. Nitroso-limonenes, 551, 553. Nitroso-methyl -aniline, 381, 388. Nitroso-phenol, 419, 428. Nitroso-reaction, the, 387. Nitro-styrenes, 373. Nitro-tartaric acid, 263. Nitro-thiophene, 331. Nitro- toluenes, 348, 372. Nitro-toluidines, 393. Nitro-uracyl, 303. Nitro-uracyl-carboxylic acid, 303. Nitro-xylenes, 346, 371, 373. Nitrous ether, 110. NobeEs explosive oil, 216. Nomenclature, international, 28. Nomenclature of the alcohols, 86. Nomenclature of the hydrocarbons, 49 et seq. Nona-decane, 42. Nonanes, 41, 52. Nono-naphthene, 364. Nonyl alcohols, 81. Nonylenes, 55. Nonylic acid, 177. Nonyl -methyl-ketons, 157. Nuclei'ns, 565. Nucleo-albumens, 565. O. tf=ortho; see Ortho-compounds. Oak-tannic acid> 462. Octa-decane, 42. Octa-decyl alcohol, 81, 95. Octa-decylene, 55. Octa-decylidene, 62. Octanes, 41, 52. Octoses, 310, 313. Octyl alcohols, 81, 95, Octyl-benzene, 357. Octylenes, 55. Octylic acid ; see Caprylic actdj 175. CEnanthol, 149. CEnanthyl alcohol, 95. "Official names", 28. "Oil-forming gas", 60. "Oil of mirbane", 352, Oil of the Dutch chemists, 57. Oils, ethereal, 548 Oils, fatty, 176. Olefinesj 54. Oleic acid, 180. Olein, 176, 217. Olibene, 548. Olides, 233. Olive oil, 217. "O.N."=offi-ial name, 28. Opianic acid, 467-468. Opium bases, 344. Optical behaviour, 37. Optically active compounds, their prepara- tion by means of ferments, 39. Orange II., 404, 506. Orange III., 405. Orange, oil of, 548. Orange peel, oil of, 508. Orange rind, oil of, 553. Orcein, 425. Orchil, 425. Orcin, 425. Organo-metallic compounds, 137, 408. Orsellinic acid, 425, 461. Ortho-acetic ether, 214. Ortho-acids, derivatives of, 189. Ortho-carbonic ether, 218. Ortho-comjiounds, 341, 345. Ortho-formic ether, 163. Ortho-leucaniline, 488, Osazones, 238-239, 312, 407. Osmotic pressure, iz. Osones, 312. Oso-triazole, 334. Oxalate developer, 251. Oxalic acid, 168, 247, 250. Oxalic ether, 122, 251. Oxalo-acetic acid, 265. Oxalo-ethyline, 334. Oxaluric acid, 300, 302. "Oxalyl", 248. Oxalyl chloride, 251. Oxalyl-urea; see Parahanic acid, 300, 302. Oxamethane, 252. Oxamic acid, 252. Oxamide, 251. Oxanthranol, 511, 512. Oxazines, 538, 542, Oxetones, 234. Oximes, 150, 158. Oximide, 252. Oxindole,_ 472. Oxy-acetic acid, 221, 225. Oxy-acids, aromatic, 437. Oxy-acidSj fatty, 221. Oxy-acrylic acid, 241, 354. Oxy-alcohols, aromatic, 436. Oxy-aldehydes, 237, 436. Oxy-alkyl bases, 209. Oxy-anthracenes, 511. Oxy-anthraquinones, 511, 513. Oxy-azo-benzene, 405. Oxy-azo-compounds, 397, 402. Oxy-azoles, 333. Oxy-benzaldehydes, 436, 437. Oxy-benzoic acids, 339, 340, 456 ei seq. Oxy-benzyl alcohols, 436. Oxy-butyric acids, 221, 223, 232. Oxy-butyric aldehyde; see A /do/, 237. Oxy-caproic acids, 221, 232. Oxy-chloro-methyl ether, 147. Oxy-cinnamic acids, 463-464. Oxy-citric acid, 268. Oxy-cymene, 555. Oxy-diphenylamines, 389. Oxy-dipicolinic acid, 527. "Oxy-ethyl", 209. 588 INDEX. Oxy-ethylamine, 211. Oxy-ethyl-methyl-tetrahydro-pyridine, 528. Oxy-ethyl-sulphonic acid, 212. Oxy-fatty acids, 221. Oxygen, estimation of, 7. Oxy-glutaric acids, 259. Oxy-naemoglobin, 565. Oxy-hydroquinone, 412, 427, Oxy-isobutyric acid, 232. Oxy-isopropyl-benzoic acid, 365. Oxy-lepidine, 532. Oxy-malic acid, 259. Oxy-malonic acid, 257, Oxy-methyl-benzoic acid^ 459. Oxy-methylene-acetic acid 240. Oxy-methylene-acetone, 239. Oxy-methylene acids, 239. Oxy-methylene ketones, 239. Oxy-methyl-sulphonic acid, 211. Oxy-naphthoic acids, 507. Oxy-naphthoquinones, 506. Oxy-nicotinic acid, 527. Oxy-phenyl-acetic acid, 458. Oxy-phenyl-alanine, 458. Oxy-phthalic acids, 346, 46^. Oxy-pyridine-carboxylic acids, 527, Oxy-pyridines, 519, 525. Oxy-quinaldine, 532. Oxy-quinolines, 531, 535. Oxy-stearic acid, 233. Oxy-stearic acid, sulphuric ether of, 233. Qxy-succinic acid, 257. Oxy-toluic acids, 447. Oxy-uracyl, 303. Oxy-valeric acids, 221, 232. Ozokeritj, 54. ^=:para; see Para-compounds. Palmitic acid, 176, 566. Falmilic ethers, 217. Palmitin^ 176, 217. Palmitohc acid, 1S2. Palmitone^ 157. Palmito-nitrile, 118. Palmityl chloride, 191. Papaverine, 545. Para-aldehyde, 148. Para-anthracene, 510. Parabanic acid, 302. Para-compounds, 341, 345. Para-cumaric acid, 446, 463 Para-cyanogen, 273. Paraffin, 54. ParafSns, 42, 51, 54. Para-formic aldehyde, 147. Para-globuline, 564. Para-lactic acid, 231. Para-leucaniline, 489. Parame, 286_. Para-rosaniline^ 489. Para-rosolic acid, 489. Para-tartaric acid; see Racetnic acidy 263, Para-xylic acid, 452, Parchment paper, 321. Parvoline, 520. Pelargonic acid, 177. Pentacetyl-glucose, 315. Penta-chlor-aniline, 386. Penta-chloro-benzene, 3661 Penta-decane, 42. Penta-decylene, 55. Penta-decylic acid, 161. Penta-diene, 66. Penta-diinic acid, 182. Penta-erythrite, 218. Penta-keto-pentamethylene, 325. "Pental", 61. Penta-merfiyl-amido-benzene, 393. Penta-methyl-benzene, 356. Penta-methylene, 324. Penta-methylene bromide, 77. Penta-methylene derivatives, 323 ei sef. Penta-methylene-diamine, 210, 521, 563. Penta-methylene-dicarboxylic acid, 324. Penta-methylene-imine, 209, 522. Penta-methyl-phenol, 412. Penta-methyl-rosaniline, 492, Pentiimido-benzene, 394. Pentane di-acid, 254, Pentane di-acid-3-carboxylic acid, 266. Pentanes, 42, 52. Pentane-tetracarboxylic ether, 354. Pentane-tetrolic acids, 235. Pentanoic acid, 174. Pentanol, 94. Pentanone, 157. Pentanone di-acid, 265. Penta-triacontane, 42. Pen-thiophene, 331. Pentine, 62, Pentonic acids, 235. Pentoses, 307, 308^ 320. Pentoxy-antruraquinone, 514. Pentoxy-caproic acid; see Manjionic acid, 236, 310. 311- Pentoxy-pentane, 218. Peppermmt, oil of, 557. Pepsin, 322, 563, 566. Peptones, 563. Per-acid salts, 165, 251. Perbromo-acetone, 157, 355. Perchloric ether, 113. Perchloro-ethane, 69, 78. Perchloro-ether, loi. Perchloro-eth^lene, 79. " Peri "-position, 502. Perkitt reaction, the, 444. Perseite, 219. Persulphocyanic acid, 282. Peru balsam, 432, 448. Petroleum, 53, 353. Petroleum ether, 52. Phaseo-mannite, 427. Phellandrene, 550, 554. " Phenacetine ", 421. Phenacyl bromide, 436, 474. Phenanthrene, 515, 545. Phenanthrene-hydroquinone, 516. Phenanthrene-quinone, 516. Phenanthrol, 516. Phenazine, 539, 541. Phenetedines, 421. Phenetol, 417. Phenol, 339, 416, 478, Phenol blue, 390. INDEX. 589 Phenol-calcium, 416, Phenol-carbonic acid, salts of, 418. Phenol-carbonic ether, 418. Phenol-disulphonic acids, 422. Phenol, ethers of, 417. Phenolic acids, aromatic, 455. Plienol-methyl ether; see Anisol, 417. Phenol-phthalein, 495. Phenol-phthaline, 495, Phenol-potassium, 416. Phenol-sulphonic acids, 341, 417, 422. Phenols, 411, 422-427. Pheno-safranine, 541. Phenoxazine, 539, 542, Phenthiazine, 539, 543, "Phenyl", 338. Phenyl-acetaldehyde, 435. Phenyl-acetic acid, 446, 451. Phenyl -acetylene, 366, 455. Phenyl-acridine, 537. Phenyl-acrylic acid, 439. Phenyl-alanine, 453. Phenyl alcohol, 416. Phenyl-amido-acetic acid, 452. Phenyl -amido-crotonic ether, 532. Phenyl-amido-propionic acids, 453, 563. Phenyl-amine, 375, 384. Phenyl-anthracene, 511. Phenyl-anthranol, 511, 512, Phenyl- bromo-acetic acid, 483, Phenyl-butylene dibromide, 499. Phenyl-butyric acids, 448. Phenyl-carbinol, 432. Phenyl carbonate, 418. Phenyl- chloracetic acid, 452. Phenyl-cinnamic acid, 497. Phenyl cyanate, 375, 392, 397. Phenyl cyanide; see Beiizonitrile^ 451 Phenyl-dibromo-propionic acid, 454. Phenyl-dimethyl-pyrazolone, 332. Phenyl disulphide, 409, 419. Phenylene blue, 390. Phenylene brown, 405. Phenylene diamines, 375, 383, 393. Phenylene-di-ureas, 3S4. Phenylen e-ethenyl-amidine, 383-384. Phenyl ether, 417. Phenyl-ethyl alcohols, 432. Phenyl-ethylamine, 375. Phenyl -ethyl- hydrazine, 406. Phenyl-e thy 1-sul phone, 410. Phenyl-glucosazone, 315. Phenyl-glycerine, 432. Phenyl-glycocoU, 392, 470. Phenyl-glycollic acid, 459. Phenyl-glyoxal,_ 437. Phenyl-glyoxylic acid, 460. Phenyl-guanidines, 392. Phenyl-hydrazine, 406. Phenyl-hydrazine-potassium sulphite, 406. Phenyl -hydrazine-sulphonic acid, 407. Phenj^ hydrosulphide, 417, 418. Phenyl-imido-butyric acid, 392. Phenyl-induline, 542. _ Phenyl-isocrotonic acid, 454, 500, Phenyl isothiocyanate, 375, 39^. Phenyl-Iactic acid, 460. Phenyl-methyl-carbmol, 433 Phenyl-methyl ketone, 43^, Phenyl-methyl-pyrazolone, 332, Phenyl-methyl-pyrrol, 436. Phenyl-naphthalene, 507. Phenyl-naphthylamines, 504, Phenyl-nitramine, 397. Phenyl-oxanthranol, 511. Phenyl-oxyprop ionic acids, 460. Phenyl-phosphine, 408. Phenyl-phosphinic acid, 408. Phenyl-propiolic acid, 366, 446, 455. Phenyl -propionic acids, 452, Phenyl-propyl alcohol, 432. Phenyl-pyridines, 519, 526. Phenyl-quinohnes, 519, 536. Phenyl- rosinduline, 542. Phenyl salicylate, 457, Phenyl-salicylic acid, 457, 483. Phenyl-sulphamic acid, 391. Phenyl sulphide, 409, 419. Phenyl sulphone, 409. Phenyl-sulphuric acid, 417, 418. Phenyl- tetrose, 435. Phenyl-thio-urea, 375, 392. Phenyl-tolyls, 476. Phloretic acid, 560. Phloretin, 426, 5C0. Phloridzin, 560. Phloroglucin, 354, 412, 425, 560. Phloroglucin -tricarboxylic acid, 468. Phloroglucin-tricarboxylic ether, 354. Phloroglucin-trimethyl ether, 426. Phloroglucin-trioxime, 426. Phloxin, 495. Phoenicin-sulphonic acid, 469. Phorone, 157. Phosgene, 289. Phosphenyl chloride, 408. Phosphin, 538. Phosphine-oxides, 130, 131, Phosphines, 130 et seq. Phosphinic acids, 131, 132, Phosphino-benzene, 408. Phospho-henzene, 408. Phosphonic acids, 131, 132. Phosphonium bases, 131, 132. Phosphoric ethers, 116. Phosphorous ethers, n6. Phosphorus compounds of the alcohol radicles, 130 et seq. Phosphorus, estimation of, 6. Photographic developers, 251, 422, 425, 426, 506. Phthalei'ns, 494. Phthalic acids, 346, 441, 464. Phthalic acid, semi-aldehyde of, 460. Phthalic anhydride, 465. Phthalide, 460. Phthalidems, 496, 511. Phthalidines, 496, 511. Phthalimide, 465. Phthalines, 494. Phthalo-nitriles, 410. Phthalo-phenone, 465, 494. Phthalyl alcohol, 432. Phthalyl chloride, 465. Phycite, 218. Physical isomerism : dimorphism, 26. Physical properties of organic compounds, 31 et sea. 690 INDEX. Phyto-albumen, 564. Phyto-globuline, 564. Phyto-myosin, 564. Picolines, 150, 519, 525. Picolinic acid, 526- Picramide, 387. Picric acid, 417, 420. Picrotoxin, 561. Picryl chloride, 373, 420. Pimaric acid, 559. Pimelic acid, 247. Pinacoline, 157, 207. Finacone, 207. Pinene, 550, 55I. Pinene hydrochloride, 552. Pinene nitroso-chloride, 552. Pinite, 427, Pinol, 556. ■ Pinol hydrate, 556. Pipazerine, 530. Pipecolein, 327. Pipecolines, 527. Piperic acid, 461, 463. Piperideins, 527. Pipendine, 211, ^21, 522, 528. Piperidine, constitution of, 522. Piperine, 528. Piperonylic acid, 461. Piperylene, 66, 528. Pirylene, 66. Pittacall, 403. Pivalic acid, 175. Plaisters, 177. Polarization, circular, 38. Polyamines, aromatic, 393. Polymerism, 14. Poly-terpenes, 551. Ponceau 2 R, 506. Populin, 560. Position, determination of, in aromatic bi- derivatives, 345 et seq. Position-isomerism, 102, 351. Potassium carboxide, 354, 427. Potassium cyanate, 279, Potassium cyanide, 275. Potassium-diazo-benzene, 400. Potassium-diazo-ethane sulphonate, 129. Potassium ethide, 137-138. Potassium-ethyl-hydrazine sulphite, 129. Potassium ferricyanide, 276, Potassium ferri-ferrocyanide, 277. Potassium-ferri-thiocyanate, 282. Potassium ferrocyanide, 276. Potassium isocyanate, 279. Potassium methide, 137-138 Potassium methylate, 88. Potassium-phenyl-nitrosamine, 400. Potassium-pyrrol, 330, 521. Potassium thiocyanate, 282. Prehnidine, 393. Prehnitene, 356. Prehnitic acid, 468. Primary, secondary, and tertiary com- pounds, 71, S3-84, 224. Primuline, 421. Prism formula of benzene, 348. Propadiene, 66. Propane, 49. Propane di-acid, 252. Propane-diolj 206. Propane-diolic acid, 234. Propane-imine, 210. Propane-nitrile, 118. Propane-pentacarboxylic acid, 268. Propane-tricarboxylic acid, 266. Propane-triol, 214. Propane-trisulphonic acid, 116 Propanol di-acid, 257. Propanolic acids, 229 et seq. Propanol-nitrile, 208. Propanolone, 237. Propanone, 156. Propanoxime, 158. Propargylic acid, 181, 333. Propargylic alcohol, 97. Propenal, 149. Propene, 60. Propene-thio-propene, 107. Propenic acid, 179, Propenol, 96, Propine, 66. Propinic acid, 181. Propinol, 97. Propinyl alcohol, 97. Propiolic acid, 181. Propione, 137. Propionic acid, 164, 173. Propio-nitrile, 118. Propionyl-carboxylic acid, 243. Propionyl chloride, 191. Propyl-acetic acid, 174. Propyl-alcohols, 92. Propyl aldehyde-phenyl-hydrazone, 474. Propyl-benzenes, 336, 364. Propyl-benzoic acids, 446, 453. Propyl bromides, 69, 74. Propyl carbonate, 289. Propyl chlorides, 6% 74. Propylene, 35, 60. Propylene bromides, 77. Propylene chlorides, 77. Propylene glycols, 206. Propylic aldehyde, 149. Propyl iodides, 69, 74. Propyl-methyl-benzenes, 364. Propyl-phenols, 423. Propyl-piperidines, 328. Propyl-pseudo-nitrol, 113. Propyl-pyridines, 323. Protein substances; see A Ibumens, 362. Protocatechuic acid, 447, 461. Protocatechuic aldehyde, 436, 437. Prussian blue, 277. Prussic acid, 273. Pseudo-azimido-benzene, 398. Pseudo-butyl ene, 61. Pseudo-cumene, 336, 363. Pseudo-cumidine, 375, 393. Pseudo-forms, 286, 426, Pseudo-indoxyl, 473. Pseudo-IeucaniUne, 488. Pseudo-nitrols, 112-113. Ptomaines, 211, 347, 563, Ptyahn, 322, 366. Pulegone, 357. Purpuric acid, 304. Purpurin, 511, 514. Purpuro-xanthine, 511. INDEX. 091 Putrescine, 21a Pyrazine, 530. Pyrazolidine, 332. Pyrazoline, 332. Pyrazolone, 332. Pyrazols, 332, Pyrene, 516. Pyridine, 519, 520, 524. Pyridine-carboxylic acids, 519, 526. Pyridine derivatives, 517, 520. Pyridine-sulphonic acid, 519, 526. Pyridone, 525. Pyrimidine, 529, 530. Pyrocatechin, 355, 423. Pyrocatechin-carboxylic acids, 461, 467. Pyro-cinchonic acid, 253. Pyro-coraane, 529. PjTogallic acid, 426. Pyroligneous acid, 88, 171, Pyru-meconic acid, 529. Pyro-raellitic acid, 468. Pyro-mucic acid, 329. Pyrone, 522, 529. Pyronine, 538. Pyro-racemic acid, 242. Pyro-racemic aldehyde, 239, Pyro-tartaric acids, 254. Pyro-terebic acid, 180. Pyrocoll, 330. Pyrogallol, 412, 426. Pyrogallol-carboxylic acid, 462. Pyrogallol-dimethyl ether, 426. Pyroxyline, 321. Pyrro-diazole, 334. Pyrrol, 326, 330, Pyrrol-carboxylic acids, 326, 330. Pyrrol group, 326. Pyrrolimne, 330. Pyrrolxne, 330. Pyrrolylenej 66, Q. Quercitej 427. Quercitrin, 308, 560. Quick vinegar process, the, 170. Quinaldine, 519, 531, 535. Quinaldine-car boxy lie acids, 519. Suinalizarin, 5x1, 514. uinanisole, 535. Quinazine, 537. Quinazole compounds, 537. Quinhydrone, 425, 428. Quinic acid, 447, 462. Quinine, 536, 545. Quinine alkaloids, 545. Quininic acid, 536, 546. Quinitol,_425, 429. Quinizarin, §11. Quinoid linking, 490, 509. Quinoline, 385, 51^, 530, 534. Quinoline-ammonium bases, 554. Quinoline-benzo-carboxylic acids, 536. Quinoline-carboxylic acids, 519, 536. Quinuline decahydride, 535. Quinoline group, 530. Quinoline-sulpnonic acids, 519, 535. eujnoline yellow, 535, uinolinic acid, 527. Quinone, 38s, 421, 427, Quinone-aniles, 430. Quinone-carboxyfic acid, 461, Quinone chlorimide, 421, 430. Quinone dichlorimide, 430. Quinone-dioxime, 429. Quinone hydrazone, 404. Quinone-oxime; see Nitroso-phenol^ 410. Suinone phenol-imide, 390. ujnone-tetracarboxylic acid, 468. Quinone tetrahydride, 429, 467. Quinoxaline, 384, 537. R. Racemates, 263. Racemic acid, 263. " Racemic " modification, 39. Radicles, 15, 29. Radicles, mixed, 46. Raffinose, 320. Raoulfs method, 10. Rapinic acid, 233. Rational formulse, 26. Red prussiate of potash, 276. "Reduced" benzene ring, 349, Refraction, molecular, 37. Resin acids, 559. "Resinification", 558. Resins, 558. Resin soaps, 558. Resorcin, 355, 412, 424. Resorcin-phthaleio, 495, Resorcylic acids, 461. Retene,_ 516. Rhamnite, 218. Rhamno-hexite, 219. Rhamno-hexonic acid, 237, Rhamnose, 308. Rhigolene, 52. Rhodamin, 495, 538. Rhodizonic acid, 430. Ribonic acid, 235. Ribose, ^08. Ricinoleic acid, 233. "Ricinoleic sulphonic" acid, 233 " Ring-shaped " formation, 20. Rocellic acid, 247. Rochelle salt, 262. Roman oil of cumin, 54S Rosaniline, 488. RosaniHne blue, 492. Rosaniline group, 488. Rose de Bengale, 495. Rosinduline, 542. Rosolic acid, 493. R-salt, 506. Rubean hj^dride, 273, Ruberythric acid, 513, 560 Rufigallic acid, 511, Rufiopin, 51X. Rufol, 5x1. 592 INDEX. j=symmetrical, 345. Saccharates, 318, 319. Saccharic acid fmonobasic), 235. Saccharic acid (dibasic), 264, 219. Saccharimetry, 319. Saccharine, 235. "Saccharine* (from coal tar), 451. Saccharo-biose, 319. Saccharose, 319. Safranines, 541. Sage, oil of, 551. Salicin, 560. Salicylic acid, 336, 447, 456. Salicylic aldehyde, 436. Salicylic methyl ether, 87, 456. Saligenin, 436. Salol, 457. Saftdmeyer tesiCtloTi, the, 397, 442, Santonin, 561. Saponification, 108. Saponin, 560. Sarcine, 306. Sarco-lactic acid, 231. Sarcosine, 228. Saturated hydrocarbons, 42. Scarlet, Biebrich, 404. Sebacic acid, 247. Secondary alcohols, 82 ei seq. Secondary compounds, 71, 82, 224. Secondary ring, 349. Seignette salt, 262. Selenium compounds, 107. Serine, 235. Serum albumen, 564. Sesqui-terpenes, SSo-SSi- Shellac, 1:59. Side chain isomerism, 351. " Side chains", 336, Silicic ethers, 116. Silicium tetramethyl, 137. Silver cyanide, 275. Silver fulminate, 119. Sinapine, 211, 547. Sincaline, 211. Skatole, 474, 563, SkaCole-acetic acid, 4^5. Skatole-carboxylic acid, 475. Skraup synthesis, the, 531. Soaps, 177. Sodio-aceto-acetic ether, 245. Sodio-malonic ether, 253, 354, 468. Sodium acetanilide, 391. Sodium ethide, 137. Soduim ethylate, 02. Sodium mercaptide, 106. Sodium methide, 137. Sodium nitro-prusside, 277. Solanine bases, 546. Solubility, 32. Solubilitjr, decrease in, 12. Sorbic acid, 182. Sorbin, 316. Sorbinose, 316. Sorbite, 219. Sozo-iodol, 422. Sozolic acid, 422, Sparteine, 547. Specific gravity, 32. Specific gravity of gases, etc., 12. Specific rotatory power, 38. Spermaceti, 95, 176. Sprit blue, 492. Starch, 321. Starch, animal, 322. Starch gum, 322. Stearic acid, 176, 566. Stearin, 176, 217. Stearin candles, 176. Stearolic acid, 182. Stearone, 157. Stearoptenes, 548. Stereo-chemical isomerism, 21. Stilbene, 496. Stilbene dibromide, 496. Stilbene-dicarboxylic acid, 497. Storax, 36s, 433, 453. Structural formulae ; see Constitution^ et seq. Strychnine, 546. Strychnine bases, 546. Stycerine, 4^2. Styphnic acid, 424. Styracin, 433. Styrene, 363, 3S5. Styrone, 433. Suberic acid, 247. Suberone, 325. " Substantive dyes ", 478. Substitution, backward, 45. Substitution, laws governing, 35a Succinamic acid, 254. Succinic acid, 253, 327. Succinic anhydride, 254. Succinic ether, 354. Succinimide, 254, 327. Succino-diethyl ether, 354. Succino-succinic acid, 467. Succino-succinic ether, 254, 354. "Succinyl", 248. Succinyl chloride, 254. Sugars, the, 235, 264, 307. Sulphanilic acid, 410. Sulphides, 102 et seq. Sulphine bases, 105. Sulphine-hydroxides, ;[05-io7. Sulphinic acids, aromatic, 409. Sulphinic acids, fatty, 115. Sulpho-acetic acid, 186. Sulpho-benzide, 409. Sulpho-benzoic acids, 451. Sulpho-benzoic imide, 451. Sulphonal, 157. " Sulphonation ", 408. Sulphones, 105. Sulphonic acids, aromatic, 408. Sulphonic acids, fatty, 115. Sulpho-^hthalic acids, 467. Sulphoxides, 104-105. Sulphur, estimation of, 6. Sulphur, valency of, 106. Sulphuric acid, constitution of, 116. "Sulphuric ether", loo. Sulphuric ethei^, 113, 114. Sulphurous ethers, 114. Sylvane, 329. INDEX. 593 Sylvestrene, 550, 554. Sylvestrene dihydrochloride, 554, Syntonin, 564. T. Tallow, 176. Talo-mucic acid, 264, 311. Talonic acid, 236, 311. Talose, 311, 316. Tanacetone, 558. Tannic acids, 462. Tannin, 447, 462. Tanning, 462. Tar, 352. Tartar, 262. Tartar emetic, 262. Tartaric acid, 259 et seq. Tartaric acJd, ethers of, 262. Tartaric acids, inactive, 2G0, 263, 2G4, 355, See also Dextro-, La'vo-, and Para-tar- taric acids. Tartaric acids, isomerism of the, 260. Tartramides, 263. Tartrates, 262. Tartrazine, 265. Tartronic acid, 214, 257, Tartronyl urea, 303. Taurine, 212. Taurocholic acid, 566. Tautomerism, 26, 287. Tellurium compounds, 107. Teraconic acid, 255. Terebic acid, 259. Terephthalic acid, 363, 465. Terephthalic aldehyde, 435. Terpenes, 548 ei seq. Terpenylic acid, 552. Terpin, 554. Terpinene, 550, 554. Terpineol, 554. Terpin hydrate, 554. Terpinolene, 550, 554. Tertiary alcohols, 82. Tertiary compounds, 71, 82. Tertiary hydrogen atoms, 459. Tertiary ring, 349. Tetra -acetyl ene-dicarboxylic acid, 257. Tetra-amido-benzenes, 394. Tetra-amido-phenazine, 540. Tetra-bromo-di-iodo-eosin, 495. Tetra-bromo-dinitro-benzene, 371. Tetra-bromo-ethane, 508. Tetra-bromo; fluorescein, 495. Tetra-bromo-methane, 78. Tetra-bromo-quinone, 429. Tetra- chloro-ani line, 386. Tetra-chloro-benzenes, 366. Tctra-chloro-ethylene, 69. Tetra-chloro-hydroquinone, 429. Tttra-chloro-indigo, 470. Tetra-chloro-methane, 78, 442, 488. Tetra-chloro-quinone, 429. Tetra-cosane, 42. Tetra-decane, 42. Tetra-decyl alcohol, 81, 95. Tetra-decylene, 55. (606) Tetra-decylidene, 62. Tetra-ethyl-benzene, 356. Tetra-ethyl-tetrazone, 129. Tetra-hydro-benzoic acids, 449. Tetra-hydro-carveol, 557. Tetra-hydro-carvone, 557. Tetra-hydro-naphthols, 505. Tetra-hydro-naphthylamines, 503-504. Tetra-hydro-phthalic acids, 465. Tetra-hydro-picoline, 522. Tetra-hydro-pyridine, 527. Tetra-hydro-quinoline, 519, 535. Tetra-hydro-terephthalic acids, 349-350, 465- Tetra-iodo-pyrrol, 330. Tetra-methyl-amido-benzenes, 393. Tetra-methyl-ammonium compounds, 127. Tetra-methyl-arsenic compounds, j-^^etseg. Tetra-methyl-benzenes, 356, 364. Tetra-methyl-diamido-benzophenone, 388, 482-483. Tetra -me thyl-diamido-diphenylamine, 375, 39°- Tetra-methyl-diamido-triphenyl-carbinol, 488. Tetra-methyl-diamido-triphenyl-methane, Tetra-methylene bromide, 77. Tetra-methylene-diamine, 210. Tetra-methylene-dicarboxylic acid, 324. Tetra-methylene group, 324. Tetra-methylene-imine, 330. Tetra-methyl-ethylene glycol, 207. Tetra-methyl-hexoxy-diphenyl, 479. Tetra-methyl-indamine chloride, 390. Tetra-methyl-methane, 51. Tetra-methyl-phosphonium hydroxide, 13a. Tetra-methyl-quinoline, 536. Tetra-methyl-rosaniline, 492. Tetra-methyl-stibonium hydroxide, 136. Tetra-nitro-methane, 113. Tetra-nitro-naphthalene, 503. Tetra-oxy-anthraquinones, 511, 514. Tetra-oxy-benzene, 427. Tetra-oxy-benzoic acids, 462 Tetra-oxy-quinone, 430. Tetra-ph en yl-e thane, 498. Tetra-phenyl-ethylene, 498. Tetra-phenyl-thio-urea, 392, Tetrazo-diphenyl-chloride, 440. Tetrazole, 334. Tetrazones, 129. TetroHc acid, 182, 186, Tetrose, 307. Thalline, 535. Theba'ine, 545. Thei'ne, 306. Theobromic acid, 176. Theobromine, 306. Thiacetamide, 199. Thiacet-anilide, 200, 3ri. Thiacetic acid, 193. Thiacetic ether, 194. Thials, 145. Thiamides, 187, igg. Thiazines, 539, 543. 'Thiazoles, 333. Thio-acetone, 155. Thio-acids, 193. 2P 594 INDEX. Thio-alcohols, 102. Thio-aldehydes, 145. Thio-anhydrides, 193. Thio-aniline, 385. Thio-benzamide, 450. Thio-carbamic compounds, 295 et seq. Thio-carbaraide, 295, 297-298, 333. Thio-carbonic acids, 296. Thio-carbonic compounds, 295. Thio-carbonyl chloride, 296. Thio-carbonyl compounds, 295. Thio-compounds. 102. Thio-cyanates, 2S2. Thio-cyanic acid, 282. Thio-cyanic ether, 283. Thio-cyanuric acid, 284. Thio-cyanuric trimethyl ether, 284. Thio-diglycoUic chloride, 208. Thio-diphenylamine, 389, 543. Thio-diphenylamine dyes, 543. Thio-ethers, 102, 105. ' Thio-ethyl, 106. Thio-glycollic acid, 226, Thio-hydantoin, 298. Thio-hydrates, 102 et seq. Thio-ketones, 155. Thiolic acids, 193. Thiols, 103. Thio-naphthene = thiophtene, 507-508. Thionic acids, 193. Thionine, 543. Thionine dyes, 543, Thiophene, 326, 330, \,0^ Thiophene alcohol, 326. Thiophene aldehyde, 326. Thiophene-carboxylic acid, 326. Thiophene group, 526. Thiophene-sulphonic acid, 331. Thio-phenols, 417-418. / Thio-phosgene, 296. Thiophtene, 507-508, Thiotenol, 331. Thiotolene, 331. Thio-ureas, 284, 297, 333, 379. Thio-urethane, 297. Thioxene, 331. Thujone, 557. Thyme, oil of, 423, 548. Thymene, 548. Thymo-hydroquinone, 425. Thymol, 412, 423, Thymo-quinone, 430. Tiglic acid, 180. Tin, alkyl compounds of, 139. Tolane, 497. Tolidine, 479. Tolu, balsam of, 432, 449. Toluene, 337, 356, 362. Toluene, formation of, 357 Toluene hydrides, 362. Toluene-sulphonic acids, 411. Tolu-hydroquinone, 425. Toluic acids, 363, 451. Toluic aldehydes, 435. Toluic anilide, 484. Toluidines, 377, 392. Tolu-quinoline, 534. Tolu-quinone, 430. Tolu-safranine, 541 Toluylene blue, 540. Toluylene diamines, 375, 394. Toluylene red, 384, 394, 540, Toluyl-phenyl-propane, 509. Tolyl alcohols, 432. Tolyl-diphenyl-methanes, 486, 488. Tolylene glycol, 432. Tolyl-mcthyl-ketone, 365. Tolyl -phenyl, 476. Tolyl-phenylamine, 393. Tolyl-phenyl-carbinols, 480. Tolyl-phenyl-e thane, 484, Tolyl-phenyl-ketones, 480, 484, 508. Tolyl-phenyl-ketoximes, 484. Tolyl-phenyl-methanes, 483. Toxines, 211, 563. *' Trans" form, 25. Transformations, isodynamic, 287. Transformations, molecular, 22, 179, 341, 364, 381, 399, 504. acetamide, 198. acetin, 213, 217. amido-azobenzene, 405. i-amido-benzenes, 375. amido-phenazine, 540. amido-phcnol, 421. ■amido-tolyl-diphenyl-carbinol, 489. amido-tolyl-diphenyl-me thane, 489. amido-triphenyl-carbinol, 4S9. ■amido-triphenyl-methane, 4S9. -amines, aromatic, 382. -benzoyl-methane, 498. i-bromhydrin, 78. ■bromo-benzenes, 346, 353, 369, ■bromo-phenol, 415. Lcarballylic acid, 266. L-carbimido ethers, 280. L-chlorhydrin, 78, 215. ■chloro-acetal, 149. ■chloro-acetamide, 198, chloro-acetic acid, r86. chloro-acetic ether, 1S9. ■chloro-aceto-acrylic acid, 355. .-chloro-aldehyde^chloral, 149. chloro-aniline, 386. chloro-benzenes, 366, 369. chloro-cyanogen, 278. chloro-ethanal, 149. chloro-e thane, 78. chloro-ethylene, 69. Tri Tri- Tri Tri Tri Tri Tri Tri Tri Tri Tri Tri Tri Tri Tri Tri Tri Tri Tri Tn^ Tri- Tri T Tri Tj Tri Tri Tri Tri Tri I'ri Tri Tri Tri Tri T Tri 1 Tri T] Tri Tri Tri Tri Tri Tri Tri Tri Tri- chloro-methane, 77. chloro-methyl-sulphonic chloride, 115. chloro-phenomalic acid, 355. chloro-propane, 78. cosane, 42. cyanides, 275, 530. cyanogen, 278. decane, 42. decylene, 55. ethyl amine, 127. ethyl-arsine, 155. ,-ethyl-arsine oxide, 135. -ethyl-benzene, 353, 356. ethylin, 215. ^ ethyl-phosphine, 132. i-ethyl-phosphine oxide, 132, glycollamic acid, 227. -hydrocyanic acid, 275. ■iodo-benzene, 353. INDEX. 595 Tri-keto-hexamethylene, 426. Tii-keto-hexamethylene-tricarboxylic acid, 468. Tri-mellitic acid, 468. Trimesic acid, 353, 468, Trimesic ether, 354. Tri-m ethyl-ace tic acid, 175, 184. Tri-methylamine, 127, 528. Tri-methyl-arsine, 133, 135. Tri-methyl-arsine dichloride, 133. Tri-methyl-arsine oxide, 133. Tri-methyl-benzenes, 353, 356, 363. Tri-methyl-benzoic acids, 448. Tri-methyl-carbiiiol, 94. Tri-methylene, 323, 324. Tri-methylene bromide, 77. Tri-methylene-diamine, 210. 'J'ri-methylene-dicarboxyllc acid, 324. Tri-methylene glycol, 210. Tri-methylene-imine, 210. Tri- methyl -ethylene, 61. Tri-methyl-glycocoll, 228. Tri-methyl-methane, 49-50. Tri-methyl-oxyethyl-ammonium hydrox- ide, 196. Tri-methyl-phenyl-ammonium hydroxide, 582. Tri-methyl-phenyl-ammonium iodide, 377. Tri-m e thy 1-phosphine, 131, 132. Tri-m ethyl-phosphine oxide, 131, 132. Tri-methyl-pyridine-dicarboxyiicether,52i. Tri-methyl-pyridines, 519. Tri-methyl-quinolines, 519. Tri-methyl-stibine, 136. Tri-methyl-sulphine hydroxide, 106. Tri- methyl -sulphine iodide, ro6. Tri- me thy 1-viny 1-am monium-hy droxid e, 211. Tri-nitraniline, 387. Tri-nitrin, 216. Tri-nitro-benzene, 371. Tri-nitro-chloro-benzenes, 373. Tri-nitro-naphthalene, 503. Tri-nitro-phenol; see Picric acid, 420. Tri-nitro- tertiary butyl toluene, 373. Trl-nitro-triphenyl-carbinol, 486. Tri-nitro- triphenyl-mcthane, 486. Tri-oleTn, 217. "Trioses", 317. Tri-oxy-anthraquinone, 511. Tri-oxy-benzenes, 412, 426. Tri-oxy-benzoic acids, 461. Tri-oxy-benzophenone, 483. Tri-oxy-cinnamic acids, 464. Tri-oxy-glutaric acid, 264. Tri-oxy-methylene, 147. Tri-oxy-pyridine, 522, 525. Tri-oxy-triphenyl-methane, 487, 493. Tri-palmitin, 217. Tri-phenylamine, 37s, 389. Tri-phenyl- benzene, 476, 479. Tri-phenyl-carbinol, 486. Tri-phenyl-carbinol-(?-carboxyIic acid, 494. Tri-phenyl-guanidine, 392. Tri-phenyl-methane, 475, 485- Tri-phenyl-methane bromide, 486. Tri-phenyl-methane-carboxylic acid, 487, 494- Tri-phenyl-methane dyes, 486. Tri-pbenyl-rosaniline, 492. Tri-phenyl-rosaniline-sulphonic acid, 492. Tri-phenyl-thio-urea, 392. Triple bond, 64. Tri-quinoyl, 427, 430. Tris-azo-compounds, 404. Tri-stearin, 217. Tri-thio-carbonic acid, 296. Tropaoline O, 406. Tropei'nes, 547. Tropic acid, 460, 546. Tropidine, 544. IVopilidene, 67. Tropine, 67, 544, 546. Tropinic acid, 544. Trypsin, 322, 566, Turkey red, 514. Turmeric, 561. TiimbulVs blue, 277, Turpentine, 548, 551. Turpentine, oil of, 548, 551. Types, theory of, 14-15. "Typical" hydrogen, 82, 167. Tyrosine, 458, 563, U. Umbellic acid, 463. Umbelliferone, 463. Undecane, 42 Undecolic acid, 182. Undecylene, 55. Undecylenic acid, 180. Undecylic acid, 177. Unitary formulae, 14. ^^^^ Urea, i, 279, 292. Urea, acid derivatives of, 293-294 Urea, alkyl derivatives of, 293. Urea, determination of, 292. Urea, salts, etc., of, 293. Ureide-acids, 300 et seq. Ureides, 293, 300 et seq. Urethane, 291. Uric acid, 301, 305. Uric acid group, 300. Urine-indican, 473. V. z/=vicinal, 345. Valency of sulphur, 106. Valency, tlieory of, 14. Valeric acids, 174. Valero-nitrile, 118. Valerjflene, 62, 66. Vanillic acid, 461. Vanillic alcohol, 436. Vanillin, 436, 437. Van V Hoff's law, 20. Vapour density, determination of, 10. Vapour pressure, lowering of, 12. Vaseline, 54. Vegetable albumen, 562, 564. Vegetable substances of unknown constitu- tion, 558 et seq. 596 INDEX. Veratric acid, 461. Veratrine, 547, Veratrol, 424. Verdigris, 173. Vesuvine, 405. Victoria blue, 492. Victoria green, 4SS. Victoria orange, 423. Vinasse, 88. " Vinyl ", 211, Vinyl alcohol, 96, Vinylamine, 127. Vinyl bromide, 69, 79. Vinyl' chloride, 6g. Vinyl-ethyl ether, loi. Vinyl sulphide, 107. Violaniline, 385. Vitellin, 564. "Vitriol ether", locx Vulcanite, 554. Vulpic acid, 498, W. Water blue, 492. Wax varieties, 162, 176. WitliajiisoiUs blue, 277. Wine, go. Wine, spirits of, 88. Wintergreen, oil of, 87, 456. Wood gum, 323. Wood spirit, 87. Wood sugar, 308. Wood tar, 88. Wool fat, 566. X. Xanthamide, 297. Xanthates, 297. Xanthic acid, 297. Xanthine, 302, 306. Xanthone, 483. Xantho-prote'm reaction, the, 56* Xantho-rhamnin, 308. Xylane, 323. Xylene-carboxylic acids, 452, Xylene hydrides, 363. Xylenes, 346, 347, 356, 360, 362, Xyleiie-sulphonic acids, 411. Xylenols, 412. Xylic acids, 446, 452. Xylidines, 375, 393. Xylite, 218. Xylonic acid, 235. Xylo-quinone, 430. Xylorcin, 412, 425. Xylose, 308. Xylyl chlorides, 366. Xylylene bromides, 366, 499. Xylylene-diamines, 394. Yeast, 8g, 322. Yellow prussiate of potash, 276. Zinc ethide, 138. Zinc methide, 138. Zinc-methyl iodide, 138. iffilSIM