摘要:

J O U R N A L OF THE CHEMICAL SOCIETY. TRANSACTIONS. H. F:. ARMsrRosG, Ph.D., F.R.S. J . DEWAR, LL.D., F.R.S. WYNDHAM R. DUNSTAN, M.A., F.R.S. A. VERNON HAILCOURT, M. A., F.R.S. C. T. HEYCOCK, N.A., F.R.S. R. MELDOLA, F.R.S. H. FORSTER MORLEY, M.A., D.Sc. W. RAMSAY, Ph.D., F.R. S. A. SCOTT, M.A., D.Sc., F.R.S. T. E. THORPE, LL.D., F.R.S. W. A. TILDEN, D.Sc.. F.R.S. W. P. WYNNE, D.Sc., F.R.S. @Fb-itar : C. E. GROVES, F.R.S. Sub - &bitor : A. J. GREENAWAY. 1898. Vol. LXXIII. LONDON: GURNEY & JACKSON, 1, PATERNOSTER ROW. 1898.RICHARD CLAY AND EJONS, LIMITED, LONDON AXD n u m A Y .RICHARD CLAY AND EJONS, LIMITED, LONDON AXD n u m A Y .C O N T E N T S . PAPERS READ BEFORE THE CHEMICAL SOCIETY. PAC& 1.-Decomposition of Camphoric Acid by Fusion with Potash or Soda.By ARTHUR WILLIAM CROSSLEY and WILLIAM HENRY PERKIN, jun. . . . . . . . . . 1 11.-Experiments on the Synthesis of Camphoric Acid. Part I. By WILLIAM HENRY BENTLEY and WILLIAM HENRY PERKIN, jun. 45 111.-Synthesis of an Isomeride of Camphoronic Acid. By SAMUEL IV. -Properties and Relationships of Di h ydroxy tartaric Acid. V.-Stereochemistry of Unsaturated Carbon Compounds. Part I. By JOHN J. B. SCHRYVER, Ph.D. . . . . . . . . . 68 Part I. By HENRY J. HORSTMAN FENTON, M.A. . . . 71 Etherificntion of Substituted Acrylic Acids. SUDBOROUGH~~~LORENZOL. LLOYD . . . . . 81 Kekulk Memorial Lecture. By FRANCIS R. JAPP, F.R.S. . . 97 HEIM, Ph.D., and PHILIP SCHIDROWITZ, Ph.D. . . . 139 TI.-Compounds of Piperidine with Phenols. By OTTO ROSEN- Note on the Physiological Action of Guaiacolate of Piper- idine.By F. W. TUNNICLIFFE, M.D., M.R.C.P. . . . 145 VI1.-Action of Chloroform and Alkaline Hydroxides on the VII1.-New Method of Preparing Pure Iodine. By BEVAN 1X.-Action of Alkalis on Amides. By JULIUS B. COHEN, Ph.D., and CHARLES EDWARD BRITTAIN, B.Sc., The Yorkshire College . . . . . . . . . . . . 157 X.-Formation of Monomethylaniline from Dimethylaniline. By JULIUS B. COHEN, Ph.D., and HARRY T. CALVERT, B.Sc., By HENRY J. HORST- Nitrobenzoic Acids. By WALTER J. ELLIOTT, M.A. . . 145 LEAN, B.Sc., B.A., and W. H. WHATMOUGH . . . . 148 The Yorkshire College . . . . . . . . 163 XI.-Volumetric Estimation of Sodium. XI1.-Derivatives of Bromotolylhydrazine, MAN FENTON, M.A. . . . . . . . . . 167 C,H3Br(CH3)(N,H,) [l : 3 : 6.1 By J. T.HEWITT,*M.A., D.Sc., Ph.D., and F. G. POPE . XII1.-Effect of the Mono-, Di-, and Tri-chloracetyl Groups on the Rotatory Power of Methylic and Ethylic Glycerates and Tartrates. By PERCY FRANKLAND, F.R.S., and THOMAS STEWART PATTERSON, Ph.D., late Priestley Scholar in Mason College, Birmingham . . . . . . . . 18 1 . 174 A 2iv CONTENTS. XIV.-Rotation of Ethylic and Methylic Di-monochloracetyltar- By PERCY FRANKLAND, F.R.S., and ANDREW TURN- XV.-A Chemical Investigation of the Constituents of Indian and American Podophyllum (Podophyllum emodi and Podophyllum peltaturn). By WYNDHAM R. DUNSTAN, F.R.S., and THOMAS ANDERSON HENRY, Salters’ Research Fellow in the Laboratories of the Imperial Institute . . XVL-The Volatile Constituents of the Wood of Goupia tomen- tom. By WYNDHAM R.DUNSTAN, F.R.S., and THOMAS ANDERSON HENRY, Salters’ Research Fellow in the Labora- toriesof the Imperial Institute . . . . . . XVI1.-Production of some Nitro- and Amido-oxylutidines. Part I. By Prof. J. N. COLLIE, Ph.D., F.R.S., and THOMAS TICKLE, Salters’ Company’s Research Fellow in the Research Laboratory of the Pharmaceutical Society of Great Britain . XVIII. -Production of some Nitro- and Amido oxylutidines. Part 11. By Miss L. HALL (University College, London), and J. NORMAN COLLTE, Ph.D., F.R.S. (Professor of Chemistry at the Pharmaceutical Society of Great Britain, London) . . By J. NORMAN COLLIE, Ph. D., F.R.S., and COLIN C. FRYE, Pharma- ceutical Society of Great Britain, Bloomsbury Square . . XX.-Benzene Hexabrornide.By FRAXCIS EDWARD MATTHEWS, Ph.D. . . . . . . . . . . . . XX1.-Observations on the Influence of the Silent Discharge on Atmospheric Air. By WILLIAM ASHWELL SHENSTONE and WILTJAM T. EVANS . . . . . . . . . XXI1.-Preparation and Properties of Orthochlorobromobenzene. By JAMES J. DOBBTE, M.A., D.Sc., and FRED. MARSDEN, M.Sc., Ph.D. . . . . . . . . . . XXIII. -Preparation of Dry Hydrogen Cyanide and Carbon Monoxide. By JOHK WADE, B.Sc., and LAURENCE C. PANTING, M.B., B.Ch. . . . . . . . . XX1V.-Manganic Salts. By CHARLES EMMANUEL RICE, B.A. . XXV.-Chemical Properties of Concentrated Solutions of certain Salts. Part I. Double Potassium Carbonates. By WILLIAM COLEBROOK REYNOLDS, ,A.R.C.S. . . . . XXV1.-The Colouring Matters .of the Indian Dye Stuff Asbarg, Delphinium xalil.By ARTHUR GEORGE PERKIN, F.R.S.E., and JULIUS ALDRED PILGRIM . . . . . 11. d n tjhe Oxidation of Fenchene. By JOHN ADDYMAN GARDNER, M.A., and GEORGE BERTRAM COCKBURN, B.A. . . . . . . XXVII1.-Formation of Ethylic Dihydroxydinicotinate from Ethylic Cyanacetate. By Sr ICGFRIED RUREMANN, Yh.D., M.A., and K. C, BROWNING, B.A. . . . . . . trates. BULL, Ph.D. . . . . . . . . . X1X.-Note on the Action of Bromine on Benzene. XXVI1.-Researches on the Terpenes. PAGE 203 209 226 229 235 241 243 246 254 255 258 262 267 275 280CONTENTS. V XX1X.-The Action of Alkpl Iodides on Silver Malate and on Silver Lactate. By THOMAS PURDIE, F.R.S., and G. DRUCE LANDER, B.Sc. . . . . . . . . . . XXX.-The Optical Rotations of Methylic and Ethylic Tartrates. By (the late) JAMES WYLLIE RODGER and J.S. STRAFFORD BRAME . . . . . . . . . . . XXX1.-Position-Isomerism and Optical Activity : the Com- parative Rotatory Powers of Diethylic Mono-benzoyltartrate and Mono-toluyltartrate. By PERCY FRANKLAND, F.R.S., and J. MCCRAE, Ph.D., late Priestley Scholar i n Mason University College, Birmingham . . . . . . XXXI1.-Cis- and trans-Tetramethylene-( 1 : 3)-dicarboxylic Acids and the Condensation of Formaldehyde with Ethylic Malonate. By E. HAWORTH and W. H. PERKIN, JUNR. . XXXII1.-Action of Ferric Chloride on Ethereal Salts of Ketone Acids. By ROBERT SELBY MORRELL, M.A., Ph.D., and JAMES MURRAY CROFTS, B.A., B.Sc. . . . . XXX1V.-Formation of aa’-Dihydroxypyridine. By SIEGFRIED RUHEMANN, Ph.D., M.A. . . . . . . . . XXX V.-The Preparation and Properties of Formaldoxime.By WYNDHAM R. DUNSTAN, M.A., F.R.S., and ARNOLD L. BOSSI, Ph.D. . . . . . . . . . . XXXVL-Action of Ammonia and Substituted Ammonias on Acetylurethane. By GEORGE YOUNG, Ph.D., and ERNEST CLARK . . . . . . . . . . . . . . XXXVI1.-Formation of Oxytriazoles from Semicarbazides. By GEORGE YOUNG, Ph.D., and BENJAMIN MITCHELL STOCKWELL, B.Sc. . . . . . . . . . . . . XXXVII1.-Yellow Colouring Principles contained in various Tannin Matters. Part V. Pistacia lentisczcs, P, teyebin- thus, Tamaris africana, 5”. gaZZica, AiZanthus gkandulosa, Picus curica. By ARTHUR GEORGE PERKTN, F.R.S.E., and PERCIVAL JOHN WOOD . . . . . . . . XXX1X.-Isomeric Bornylainines. By MARTIN ONSLOW FORSTER, Ph.D., B.Sc. . . . . . . . . . . XL.-The Condensation of Chloral Hydrate and Orcinol.By JOHN THEODORE HEWITT, M.A., D.Sc., Ph.D., and FRANK DIXON, B.Sc. . . . . . . . . . . XLL-Sulphonation of Benzophenone and of Diphenylmethane. By ARTHUR LAPWORTH, D.Sc. . . . . . . . XLI1.-Reduction of Bromic Acid and the Law of Mass Action. By WINIFRED JUDSON, B.Sc., and JAMES WALLACE WALKER, M.A., Ph.D. . . . . . . . . . . By H. BRERETON BAKER, M.A. . . . . . . . XLII1.-The Drying of Ammonia and Hydrogen Chloride. PAGE 287 301 307 330 345 350 35 3 361 368 374 386 397 402 410 422vi CONTENTS. PAGE X LIT.-Some Derivatives of Benzophenone. By FRANCIS XLV.-The Chlorine Derivatives of Pyridine. Part I. By WILLIAM JAMES SELL, M.A., F.I.C., and FREDERICK WILLIAM DOOTSON, M.A. . . . . . . . . . . 432 XLV1.-Note on the Action of Chlorine on Pyridine.By WILLIAM JAMES SELL, M.A., F.I.C., and FREDERICK WILLIAM DOOTSON, M.A. . . . . . . . . . . 442 XLVII. -A Possible Basis of Generalisation of Intramolecular Changes in Organic Compounds. By ARTHUR LAPWORTH, D.Sc. 44 5 XLVII1.-The Carbohydrates of Barley Straw. By C. F. CROSS, XL1X.-Reactions of the Carbohydrates with Hydrogen Per- oxide. By C. F. CROSS, E, J. BEVAN, and CLAUDE SMITH . 463 L.-Properties and Relationships of Dihydroxytartaric Acid. Part 11. Salts of the Acids. By HENRY J. HORSTMAN FENTON, M.A. . . . . . . . . . . 472 LI.-AEnity Constants of Dihydroxymaleic, Dihydroxyfumaric, Dihydroxytartaric, andTartronic Acids. By S. SKINNER, M.A. 483 LI1.-Hydrolysis of Starch by Acids. By HAROLD JOHNSON . 490 LII1.-Determination of Molecular Weights.-Modification of By JAMES WALKER LIT.-Rate of Escape of Ammonia from Aqueous Solution.By LV.-Note on the Liquefaction of Hydrogen and Helium. By LV1.-Action of Formaldehyde on Amines of the Naphthalene LVI1.-Action of Hydrogen Bromide in Presence of Ether on Carbohydrates and certain Organic Acids. By HENRY J. HORSTMAN FENTON, M.A., and Miss MILDRED GOSTLING, By SAMUEL BARNETT Stereo- isomeric Derivatives of Camphor. By T. MARTIN LOWRY, B.Sc. . . . . . . . . . . . . 569 By J. NORMAN COLLIE, Ph.D., F.R.S., and W. LEAN, Redwood Research Scholar in the Research Laborahory of the LX1.-Molecular Weights of Permanganates, Perchlorates, and By J. MURRAY CROFTS, B.A., B.Sc., EDWARD MATTHEWS, Ph.D. . . . . . . . 426 E. J. BEVAN, and CLAUDE SMITH . . . . . . 459 Landsberger’s Boiling Point Method.and JOHN S. LUMSDEN . . . . . . . . 502 EDGAR PHILIP PERNAN, D.Sc. . . . . . . . 51 1 JAMES DEWAR, M.A., F.R.S. . . . . . . . 528 Series. Part I. By GILBERT T. NORGIAN, B.Sc. . . . 536 B.Sc., Lond. . . . . . . . . . . 554 SCHRYVER . . . . . . . . . . . 559 LVII1.-Researches on Camphoric Acid. L1X.-Studies of the Terpenes and Allied Compounds. LX.-Production of some Chloropyridinecarboxylic Acids. Pharmaceutical Society of Great Britain . . . . 588 Research Student of Emmanuel College . . . . 593 Periodates in Solution.CONTENTS. vii PAGE LXII. -The Ultraviolet Absorption Spectra of some Closed By W. N. HARTLEY, F.R.S., LXII1.-Enantiomorphism. By FREDERIC STANLEY KIPPING LX1V.-Solubility of Isomeric Substances. By JAMES WALKER LXV.-Constitution of Oleic Acid and its Derivatives.Part I. LXV1.-Reversible Zymohydrolysis. By ARTHUR CROFT LXVI1.-Preparation of a Standard Acid Solution by direct absorption of Hydrogen Chloride. By G. T. MOODY . 658 LXVII1.-Constituents of the Indian Dyestuff Waras, PZemingia congsstcc. By ARTHUR GEORGE PERKIN, F.K.S.E. . . . 659 LX1X.-Azobenzene Derivatives of some Natural Yellow Colouring Matters : Apigenin, Chrysin, Morin, Euxanthone, and Gentisin. By ARTHUR GEORGE PERKIN, F.R.S.E. . 665 LXX.-The Vapour Presures, Specific Volumes, and Critical Constants of Normal Heptane. By SYDNEY YOUNG, D.Sc., LXX1.-Contributions to the Chemistry of Phenol Derivatives. By RAPHAEL MELDOLA, F.R.S., and FREDERICK HENRY STREATFEILD . . . . . . . . . . 68 1 LXXI1.-Some Iodoso-compounds.By JOHN MCCRAE, Ph.D. . 691 LXXIT.1.-Notes on the Absorption Bands in the Spectrum of By W. N. HARTLEY, F.R.S., and J. J. DOBBIE, LXX1V.--On Myrticolorin, the Yellow Dye Material of LXXV.-Chemical Properties of Concentrated Solutions of Certain Salts. Part 11. Double Potassium Succinates. By WILLIAM COLEBROOK REYNOLDS, A.R.G.S. , . , , 701 Halogen Deriva- tives of Fenchone and their Reactions. By JOHN ADDYMAN GARDNER, M.A., and GEORGE BERTRAM COCKBURN, B.A. . 704 On the Oxidation of Fenchone. By JOHN ADDYMAN GARDNER, M.A., and GEORCIE BERTRAM COCKBURN, B.A. . . . . . 7 0 8 LXXVIIL-Riintgen Ray Photography applied t o Alloys. By CHARLES THOMAS HEYCOCK and FRANCIS HENRY NEVILLE . 714 LXX1X.-A dditive Compounds of Organic Bases and Etherezl Salts of Unsaturated Acids.By S. RUHEMANN, Ph.D., M.A., and K. 0. BROWNING . . . . . . . 723 Chain Carbon Compounds. and J. J. DOBBIE, M.A., D.Sc. . . . . . . 5 9 8 and WILLIAM JACKSON POPE: . . . . . . . 606 and JOHN K. WOOD . . . . . . . . . 618 By FRANK GEORGE EDMED, B.Sc., A.R.C.S. . . . . 627 HILL, B.A. . . . . . . . . . . . 634 F.R.S., University College, Bristol . . . . . 676 Benzene. M.A., D.Sc. . . . . . . . . . . 6 9 5 Eucalyptus Leaves. By HENRY G. SMITH . . . . 697 LXXV1.-Researches on the Terpenes, 111. LXXV1I.-Researches on the Terpenes, IV.... V l l l CONTENTS. LXXX.-Formation of Ethereal Salts of P-Ketonic Acids. By s. ~ H E M A N N , Ph.D., M.A., and K. C. BROWNING, B.A. . LXXX1.-Disulphonic Acids of Toluene, of Ortho- and Para- toluidine, and of Ortho- and Para-chlorotoluene.By W. PALMER WYNNE, D.Sc., F.R.S., and JAMES BRUCE, B.Sc. , LXXXI1.-The Chlorine Derivatives of Pyridine. Part 11. Interaction of Ammonia and Pentachloropyridine. Con- stitution of Glutazine. By W. T. SELL, M.A., F.I.C., and F. W. DOOTSON, M.A. LXXXIJ.1.-Mercury Acetamide. By MARTIN ONSLOW FORSTER, Ph.D., B.Sc. . LXXX1V.-Sul phocamphylic Acid and Isolauronolic Acid, with Remarks on the Constitution of Camphor and of some of its Derivatives. LXXXV.-Researches on the Terpenes. VIII. On Carvenol : its Reactions and Products. By J. E. MARSH and A. HARTRIDGE . LXXXVI. -Optically Active Alkyloxypropionic Acids. By THOMAS PURDIE, F.R.S., and G, DRUCE LANDER, B.Sc. LXXXVII .-Optical Activity of Gallotsnnic Acid. By OTTO ROSENHEIM, Ph.D., and PHILIP SCHIDROWITZ, Ph.D.LXXXVIII. -The Influences Modifying the Specific Rotatory Power of Gallotannic Acid. By OTTO ROSENHEIM, Ph.D., and PHILIP SCHIDROWITZ, Ph.D. LXXX1X.-The Resolution of Tetrahydropapaverine into its Optically Active Components. Constitution of Papaverine. By WILLIAM JACKSON POPE and STANLEY JOHN PEACHEY . XC.-The non-Resolution of Racemic Tetrahydropapaverine by Tartaric Acid. By WILLIAM JACKSON POPE and STANLEY JOHN PEACHEY . XCL-Composition of American Petroleum. By SYDNEY YOUNG, D.Sc., F.R.S. . XCI 1,-Separation of Normal and Iso-heptane from American Petroleum. By FRANCIS E. FRANCIS, B.Sc., Ph.D., and SYDNEY YOUNG, D.Sc., F.R.S. . XCII1.-Specific Gravities and Boiling Points of Mixtures of Benzene and Normal Hexane. By D. HAMILTON JACKSON, M.A., B.Sc., Ph.D., and SYDNEY YOUNQ, D.Sc., F.R.S. XC1V.-Action of Fuming Nitric Acid on the Paraffins and other Hydrocarbons. By FRANCIS E.FRANCIS, B.Sc., Ph.D., and SYDNEY YOUNQ, D.Sc., F.R.S. . XCV.-Hexamethylene from American and Galician Petroleum. By EMILY C. FORTEY, B.Sc. XCV1.-A Composite Sodium Chlorate Crystal in which the Twin Law is not followed. By W~LLIAM JACKSON POPE . By W. H. PERKIN, jun. . . PAGE 727 730 777 783 796 852 862 878 885 893 902 905 920 922 928 932 949CONTENTS. ix PAGE XCVI1.-Contributions t o the Chemistry of Thorium ; Com- parative Research on the Oxalates of the Rare Earth. By BOHUSLAV BRAUNER, Ph.D., Professor of Chemistry in the Bohemian University, late Berkeley Fellow of Owens College XCVII1.-Studies of the Terpenes and Allied Compounds.Nitrocamphor and its Derivatives. I. Stereoisomeric Chloro- and Bromo-nitrocamphors. 11. Pseudo-nitro- camphor. 111. Camphoryloxime (Camphonitrophenol). By T. MARTIN LOWRY, B.Sc. . . 986 XCIX-Formation of Ethereal Salts of Polycarboxylic Acids. By S. RUHEMANN, Ph.D., M.A., and A. V. CUNNINGTON, B.A., Scholar of Christ’s College . . 1006 C.-Yellow Colouring Principles contained in various Tannin Matters. Part VI. Rhus Cotinus and Rhus Rhodanthemcc. By A. G. PERKIN, F.R.S.E. . . 1016 C1.-Golouring Matters of the New Zealand Dyewood Puriri, C1I.-Derivatives of Hesperitin. By A. G. PERKIN, F.R.S.E. . 1031 Anniversary Meeting . . 1039 Obituaries . 1047 951 Vitex littoral&. Part I. By A. G. PERKIN, F.R.S.E. . 1019CONTENTS. ix PAGE XCVI1.-Contributions t o the Chemistry of Thorium ; Com- parative Research on the Oxalates of the Rare Earth. By BOHUSLAV BRAUNER, Ph.D., Professor of Chemistry in the Bohemian University, late Berkeley Fellow of Owens College XCVII1.-Studies of the Terpenes and Allied Compounds. Nitrocamphor and its Derivatives. I. Stereoisomeric Chloro- and Bromo-nitrocamphors. 11. Pseudo-nitro- camphor. 111. Camphoryloxime (Camphonitrophenol). By T. MARTIN LOWRY, B.Sc. . . 986 XCIX-Formation of Ethereal Salts of Polycarboxylic Acids. By S. RUHEMANN, Ph.D., M.A., and A. V. CUNNINGTON, B.A., Scholar of Christ’s College . . 1006 C.-Yellow Colouring Principles contained in various Tannin Matters. Part VI. Rhus Cotinus and Rhus Rhodanthemcc. By A. G. PERKIN, F.R.S.E. . . 1016 C1.-Golouring Matters of the New Zealand Dyewood Puriri, C1I.-Derivatives of Hesperitin. By A. G. PERKIN, F.R.S.E. . 1031 Anniversary Meeting . . 1039 Obituaries . 1047 951 Vitex littoral&. Part I. By A. G. PERKIN, F.R.S.E. . 1019

ISSN:0368-1645    

DOI:10.1039/CT89873FP001

出版商:RSC    

年代:1898

数据来源: RSC

摘要:

BENTLEY AND PERKIN: CAMPHORIC ACID. PART I. 45 11.-Experiments orL the Synthesis of Camphoric Acid. Part 1. By WILLIAM HENRY BENTLEY and WILLIAM HENRY PERKIN, JUN. DURINU the course of a series of experiments on sulphocamphylic acid, COOH*C,H,,*S03H, on which one of us has been engaged for a long time, many results have been obtained which are very difficult to understand if we assume that Bredt’s formula for camphoric acid, F]H(COOH)CH, CH,. C( CO0H)-CH, (CH3)2? I is correct. On the other hand, if this formula be slightly modified by altering the position of one of the carboxyl groups, so as to express the constitution of camphoric acid thus, CH2--CH* COOH I I (C*3)27 CH,*C(COOH)*CH, all the results obtained during the investigation on sulphocamphylic acid may be readily explained.As, moreover, it appears that this formula is capable of account- ing for all the other known reactions of camphoric acid, it seems highly probable that it may actually represent the constitution of camphoric acid. I n order, if possible, to decide this important point, experiments were made with the object of synthesising an acid of this constitution, the method adopted being to prepare, in the first place, an isobutyl- methylhydroxyglutaric acid of the formula CH,--CH* COOH (CH~)~&H* i CH,. C(C?H)(COOH) CH,. and then to endeavour to remove the elements of water at the points **. It seemed probable that this might be effected from the consideration that the elimination of water in this may would give rise to a 5 carbon ring-the ring which is supposed to be capable of the most ready formation, and also on account of the probabilitr that camphoric acid, which is such an exceedingly stable substance, would be very likely to be produced if the conditions necessary for its formation presented themselves.We have been successful in preparing isobutylmethylhydroxyglutaric46 BENTLEY AND PERKIN: EXPERIMENTS ON THE acid, but the elimination of water from this acid in the direction shown above has, so far, not been realised; i t is to be hoped, however, that further experiments which are in progress may yet lead to the desired result. The starting point in this investigation was isobutylacetic acid, CH(CH,)2*CH2* CH; COOH, which we prepared in considerable quantity in the usual way from ethylic isobutylmalonate by hydrolysis and subsequedt distillation of the isobutylmalonic acid.When the product formed on treating this acid with phosphorus pentabromide and bromine was poured into alcohol, a very good yield of ethylic a-bromisobutylacetate, CH(CH,),* CH,*CHBr *COOC,H,, was obtained as a colourless oil boiling at 100-103° (17mm.). I f now the sodium compound of ethylic acetoacetate be digested in alcoholic solution with this brominated ethereal salt, reaction takes place readily with elimination of sodium bromide, ethylic acetyliso- butylsuccinate, a colourless oil boiling a t 160' (25 mm.) being produced, according t o the equation, CH(CH,),* CH,* CHBr*COOC,H5 + CH,. CO*CHNa* COOC2H, = CH(CHJ,* CH,* yH* COOC2H5 + NaBr. CH,* COO CH* COOC,H, The hydrolysis of this ethereal salt by means of hydrochloric acid was next investigated, and after many experiments it was found that the course of the hydrolysis did not always go in the same direction, the nature of the products depending principally on the strength of the acid employed.I f the hydrolysis is effected by boiling with dilute hydrochloric acid, the principal products of the reaction are isobutylsuccinic acid and acetic acid. CH(CH,),*CH,*QH*COOC2H5 CH,*CO*CH-COOC2H5 + 3H20 = On the other hand, boiling with concentrated hydrochloric acid decom- poses the ethereal salt in a different manner, isobutyllevulinic acid being produced. CH(CH3)2*cH2*yH*C00c2H5 + 2H,O = CH,*CO*CH*COOC,H, CH(CH3)2*CH2*~H*C00H + CO, + 2C2H,.0H CH,*CO*CH, Isobutyllevulinic acid, which is a viscid, odourless oil boiling at about 190° (30 mm.), shows all the properties of a ketonic acid, since, in ad-SYNTHESIS OF CAMPHORIC ACID.PART I. 47 dition to dissolving in alkalis, it yields a well-defined semicwbaxone, XH,-CO*NH*N:C(CH,)*CH2*CH(C0OH)*CH2*CH(CH3),, melting at 192'. Its constitution is proved by the fact that when oxidised by bromine in the presence of potash, it gives an almost quantitative yield of isobutylsuccinic acid, CH(CH,),-CH,*QH*COOH gives CH(CR,),*CH,*FH*COOH CH,*CO*CH, COO€I*CH, The next step was to investigate the action of hydrocyanic acid on isobutyllevulinic acid, and it was ultimately found that, if the con- ditions given in this paper are observed, addition readily takes place with formation of isobutylhydroxycyanovaleric acid.CH,*C(OH)(CN)*CH,*CH( C,H,)*COOH. This hydroxycyanide is a crystalline substance which melts at 95-96°, and on distillation is decomposed with loss of water and formation of the corresponding lactone which melts a t 53O, CH,. y(CN)*CH,*yH*C,H,, 0 co a behaviour which was to be expected, since the hydroxycyanide is at the same time a y-hydroxy-acid. The hydrolysis of the hydroxycyanide was carried out by saturating its alcoholic solution with hydrogen chloride, and in this way an ethereal salt was obtained which was doubtless the ethereal salt of is0 butylmet h ylhydroxyg Zutaric acid, CH,*C(OH)(COOC,H5)*CH2*CH(C4H9)*COOC2H5, but if this ethereal salt be distilled under reduced pressure (17 mm.), an oil passes over at 168' which, on analysis, proved to be the ethylic salt of the lactone of isobutylmethylhydroxyglutaric acid, CH,*y( COOC,H,)*CH,* YH*C,H,, 0 co alcohol having been eliminated during the distillation.ethylic salt, is0 butylmethylhydroxyglutaric acid, CH,*C( OH)( COOH) CH,*CH( C,HS)*COOH, is readily obtained by hydrolysing it with alcoholic potash and pre- cipitating the cold solution with hydrochloric acid ; it is a beautifully crystalline substance which melts at 134" with elimination of water From the CH,* $Y(COOH)-CH,*~H*C,H,. 0 co and formation of the lactone, The latter, which is best prepared by treating the hydroxydibasic acid with acetyl chloride, is crystalline, and melts a t about 80'. When dissolved in potash, it is converted into the potassium salt of the48 BENTLEY AND PERKIN : EXPERIMENTS ON THE hydroxy-acid, and this, on acidifying in the cold, yields the free acid, showing that this y-hydroxy-acid is not so readily converted into its lactone as is the case with most y-hydroxy-acids.The following experiments were instituted in order, if possible, to obtain either camphoric acid or an isomeride by the elimination of water from isobutylmethylhydroxyglutaric acid in the manner indicated at the commencement of this paper, but so far we have been unable to obtain the desired result. I. The diethylic salt of the acid, prepared from the silver salt by the action of ethylic iodide, was distilled under the ordinary pressure, whed the whole passed over at 290' as a colourless oil; this, on analysis, was found to consist of the ethylic salt of the lactone of the hydroxy-acid, alcohol having been eliminated during the operation.11. The diethylic salt was left in contact with excess of phosphorus pentoxide for eight days, and the product, after extraction with ether, was fractionated under the ordinary pressures ; in this case, also, the distillate was found to consist of the ethylic salt of the lactone acid. 111. In order, if possible, to prevent the formation of the lactone, the hydroxy-dibasic acid was fused with potash at about 300', at which temperature camphoric acid, if formed, would remain unattacked. It was, however, found that, during this experiment, the hydroxy-acid had en completely decomposed, isobutylsuccinic acid being produced. IV. The carefully dried silver salt of the hydroxy-dibasic acid was submitted t o distillation under reduced pressure.An oily distillate was obtained which, on refractionation, gave a large quantity of a fraction 220-222' (30 mm.) ; this, which solidified on standing, was found to be the lactone of the hydroxy-acid. Several other substances of interest which were obtained during the course of this investigation are described in this paper. Isobzctylacetic Acid, CH(CH,),*CH,-CH,*COOH. This acid has already been prepared synthetically by the hydrolysis of isoamylic cyanide with alkalis ( Frankland, Kolbe, AnnuZen, 65, 303), and also by the hydrolysis of ethylic isobutylacetoacetate with baryta (Rohn, Annulen, 1878,190, 316); the isobutylacetic acid which was employed in this research was prepared from isobutylmalonic acid, a method which does not appear to have been described, and which we found to yield the acid in a very pure state.Ethylic isobutylmalonate was prepared in the usual way by treating ethylic sodiomalonate with isobutylic bromide (compare Guthzeit, Anncden, 1881, 209, 236), and after careful fractionation * the pure * During the fractionation, a small quantity of an oil of high boiling point, ethylic di-isobutyl nialonate (see p, Sl), is always obtained.SYNTHESIS OF CAMPHORIC ACID. PART I. 49 ethereal salt mas hydrolysed by boiling with excess of alcoholic potash for four hours. After being mixed with water and freed from alcohol by evaporation, the residue was dissolved in a little water, acidified, and extracted six times with pure ether ; the ethereal solution was then dried over calcium chloride, evaporated, and the residual crude isobutyl- malonic acid decomposed by distillation.In this way, about 70 per cent. of the theoretical yield of pure isobutylacetic acid was readily obtained as a colourless, disagreeably-smelling oil boiling constantly at 200-2 0 I O. 0.1840 gave 0.41 91 CO, and 0.1738 H20. C = 62.12 ; H = 10.48. C,H,,*COOH requires C = 62.07 ; H = 10.35 per cent. Ethylic Bromisobutylacetute, C H(CH,),. CH,* C HBr*COOC,H,.--In order to prepare this, isobutylacetic acid (85 grams) mas mixed with phosphorus pentabromide (127 grams), and after some time dry bromine (140 grams) was added in small quantities at a time, and the mixture heated at 50' for about 2 hours, until the evolution of hydrogen bromide had nearly ceased ; the temperature was then raised to 100' in order to drive off the last traces of bromine.When cold, the pro- duct was poured into alcohol and the whole allowed to stand over- night. A large quantity of water was then added, the heavy oil which was precipitated was extracted with ether, and the ethereal solution, after being washed with sodium carbonate solution and with water, was dried; the ether mas then distilled off, and the oily residue fractionated under reduced pressure. Pure ethylic bromi,so- butylacetate is thus readily obtained as a heavy, colourless, pleasant- smelling oil which boils at 100-103° (17 mm.) and has properties similar to other ethereal salts of a-bromo-fatty acids. The yield is about 90 per cent. of the theoretical. 0.1522 gave 0.1280 AgBr. Br = 35.78.C,H,*CHBr*COOC,H, requires Br = 35.87 per cent. Ethylic Acetylisobwty2szcccinccte, CH( CH,),*CH2*~H*COOC2H5. CH,*CO*CH* COOC,H5 This is produced by the interaction of ethylic a-bromisobutylacetate with ethylic sodacetoacetate, as explained in the introduction of this paper. Sodium (11.5 grams) was dissolved in alcohol (130 grams), the solution mixed with ethylic acetoacetate (65 grams), ethylic brom- isobutyl acetate (11.2 grams) added, and the mixture heated for 12-15 hours in a reflux apparatus on the water bath. The product, when cold, was mixed with water and extracted with ether, &c., the residue being fractionated under reduced pressure (25 mm.). The ethylic acetylisobutylsuccinate commences to distil at 140', almost the whole VOL.LXXIII. E50 BENTLEY AND PEREIN: EXPERIMENTS ON THE passing over between 140" and 180'; a small quantity of oil boiling a t 200-230" was, however, obtained in each case, but this was not examined. The fraction boiling at 140-180' varies from 65-70 per cent. of the theoretical ; a small portion of this, which was specially collected, distilled at about 160' (25 mm.) and gave the following numbers on analysis. 0.1188 gave 0.2660 CO, and 000935 H,O. C = 61.06 ; H=8.74. Ethylic acetylisobutylsuccinate requires C = 61.76 ; H = 8*82 per cent. Other analyses gave a similar result, and it was subsequently ascer- tained that the somewhat low numbers found were due to the substance containing traces of bromine (see p. 65). Hydrolysis o f Eth ylic Acetylisobzctylsuccinate.Formation o f Tsobut yl- succinic Acid, CH(CH3)2* CH2* yH*cooH and of a-lsobuty&vu- CH 2* COOH' CH(CH,),* CH2* YH* COOH CH; COO CH, linic Acid, a. The hydrolysis of ethylic acetylisobutglsuccinate with dilute hydrochloric acid yields isobutybuccinic acid. The fraction of the ethereal salt boiling a t about 1Ei0-155° (20 mm.) and weighing 48 grams was digested for about 15 hours in a reflux apparatus with 220 grams of dilute hydrochloric acid (1 acid : 2 of water), but even after boiling for this length of time, comparatively little of the ethereal salt had been hydrolysed. The liquid was ac- cordingly extracted several times with ether, and the ethereal solution repeatedly shaken with small quantities of sodium carbonate ; the aqueous solution, after being separated from the ether, was acidified and again extracted with ether.This second ethereal solution, after being dried and evaporated, left a yellowish oil which soon solidified. The crude crystalline mass, after being left in contact with porous porcelain, was purified by crystallisation from water, when it separated in colourless prisms which melted a t logo, and gave off water at about 150". 0.1172 gave 0.2368 CO, and 0.0854 H20. C,H,,O, requires C = 55-17 ; H = 8.04 per cent. It seemed likely that this acid was isobutylsuccinic acid, identical with the acid which Demargay (Ann. Chim. Ph., [v], 20, 492) ob- tained by the reduction of isobutylfumaric acid, and for which he gives the melting point 103-104". As, however, it was important t o be quite sure of the identity of our acid, we prepared isobutylsuccinic acid C = 55.10 ; H = 8.09.SYNTHESIS OF CAMPHORIC ACID. PART I.51 by a method which left no doubt as to its constitution, namely, the action of ethylic monochloraceta,te on ethylic isobutylsodiomalonate ; the acid prepared in this way melted at log", and has all the properties of that obtained by the hydrolysis of ethylic acetylisobutylsuccinate. (?), was pre- CH( CH,),. CH,* QH* COOH The alailic acid, CH,* CO *NH* C,H, pared from both specimens by the- following method. The acid (1 gram) was heated with a few grams of acetyl chloride for hall an hour, the liquid placed over solid potash in a vacuum desiccator until the excess of acetyl chloride had been removed, and the oily residue dissolved in a little benzene and mixed with aniline (1 gram) ; the crystals which soon separated on standing were collected, dried on a porous plate, and purified by crystallisation from benzene mixed with a little alcohol ; the isobutylsuccinanilic acid was thus obtained in glistening plates melting at 138-139'.0,1792 gave 9.1 C.C. nitrogen at 17"and 745 mm. C,,H,,NO, requires N = 5-62 per cent. The same anilic acid was obtained from both preparations of iso- butylsuccinic acid ; subsequently it was also discovered that iso- butylsuccinic acid is formed when ethylic acetylisobutylsuccinate is hydrolysed by heating it with a mixture of sulphuric acid, acetic acid, and a little water. b. The hydrolysis of ethylic acetylisobutylsuccinate with strong hydrochloric acid results mainly in the formation of isobwtyZZevuZinic acid.After numerous experiments had been tried in order to ascertain the most favourable conditions for the formation of iso- butyllevulinic acid, the following method was adopted. Ethylic acetyl- isobutylsuccinate was digested in a reflux apparatus with about four times its volume of concentrated hydrochloric acid for 10 hours, but a portion only of the ethereal salt was hydrolysed. The product was shaken several times with ether, and the isobutyllevulinic acid separated from the unchanged ethereal salt, by extracting the ethereal solution with strong sodium carbonate solution, the ethylic salt recovered from the ethereal solution by evaporation being again sub- mitted to hydrolysis as before; these operations were repeated until the concentrated hydrochloric acid had no further action on the oily layer (see p.65). The combined sodium carbonate extracts were then acidified and extracted repeatedly with ether, &c., and the oil thus obtained was purified by distillation under reduced pressure ; almost the whole distilled between 160" and 180" (20 mm.), and consisted for the most part of the ketonic acid, as the following analysis shows. C = 61.51 ; H = 8.4'7. Isobutyllevulinic acid, C,H,,O,, requires C = 625'9 ; H = 9-30 per cent. N=5*82. 0.101 gave 0.2278 CO, and 0.0770 H,O. E 252 BENTLEY AND PERKIN: EXPERIMENTS ON THE From this crude product, pure isobutyllevulinic acid may be readily obtained by converting it into the semicarbazone, purifying this, and subsequently decomposing the pure semicarbazone by means of hydro- chloric acid. Semicarbtcxone of Isobutyllevulinic Acid, CH(CH,),*CH,* QH* COOH NH,* C0.NH.N: C(CH,)*CH, -This is readily prepared by adding the crude ketonic acid (30 grams), dissolved in a little alcohol, to a strong solution of semicarbazide hydrochloride (20 grams) and sodium acetate (32 grams), stirring the mixture vigorously, and heating to boiling for a few minutes ; on cool- ing, a crystalline mass separates, which is collected, dried on a porous plate, and recrystallised from 70 per cent.alcohol ; it is thus obtained in glistening plates melting at 192' with decomposition. 0.1594 gave 25.4 C.C. nitrogen a t 16' and 762 mm. C,,H,,N,O, requires N = 18.34 per cent. The semicarbazone of isobu tyllevulinic acid is almost insoluble in water, benzene, and light petroleum, but dissolves readily in alcohol and in acetic acid.It is readily decomposed by hydrochloric acid into semicarbazide hydrochloride and isobutyllevulinic acid. The pure semicarbazone (20 grams) was heated on the water bath with hydrochloric acid (30 C.C. of sp. gr. 1.1) and water (30 c.c.) until 'he crystals had been entirely decomposed and changed to an oil ; woduct was then extracted with ether in the usual may, and the oily resl, fractionated under reduced pressure. The whole distilled at about 190' (30 mm.) as a colourless oil, consisting of pure isobutyl- levulinic acid. N = 18.63. 0.1150 gave 0.2646 CO, and 0.0964 H,O. C = 62.75 ; H = 9.31. C,H160, requires C: = 62.79 ; H = 9.30 per cent, Oxidation of Pure Isobutyllevulifiic Acid by means of Potassium Hypobro- mite.Pormation of Isobutylsuccinic Acid. It has already been pointed out (p. 50) that isobutylsuccinic acid is formed i n considerable quantity during the hydrolysis, by means of dilute hydrochloric acid, of that portion of the product of the action of ethylic bromoisobutylacetate on ethylic sodacetoacetate which boils at 150-155" (20 mm.), and the formation of this acid proves that this oily product contains ethy lie acetoiso bu tylsuccina te, It seemed, however, quite likely that this oil might contain a second isomeric constituent formed by the elimination of hydrogen bro- mide from ethylic bromisobutylacetate, and the subsequent condensa- tion of the ethylic P-isopropylacrylate CH(CH,),* CH: CH* COOC,H,,SYNTHESIS OF CAMPHORIC ACID.PART I. 53 thus formed, with the ethylic acetoacetate, a series of reactions which have been repeatedly noticed in cases analogous to the above. Since, then, it was possible that the substance we call isobutyllevuli- nic acid might have been derived from this second constituent, it became necessary, before using this acid for synthetical work, to be quite sure as to its constitution, and this was proved by oxidising the acid to isobutylsuccinic acid by means of potassium hypobromite. Some of the ketonic acid which had been regenerated from the pure carbazone was dissolved in a considerable excess of strong potash solution and bromine added until, on standing for an hour, the solution liberated iodine from a solution of potassium iodide. The first drop of bromine produced a turbidity in the alkaline solution and then an oil separated which ultimately solidified; this, which consisted of carbon tetrabromide, was removed by filtration, the solution acidified with hydrochloric and sulphurous acids, and the oily acid extracted with ether, After dis- tilling off the ether, an almost colourless oil was left, which showed no signs of solidifying ; when, however, it had been dissolved in dilute sodium carbonate, the solution boiled with animal charcoal, filtered, and the filtrate acidified and allowed to stand for some days in a cold place, the acid was deposited in a semi-solid state, and in contact with porous porcelain became quite hard.After being purified by recrystallisation from water, pure isobutylsuccinic acid was obtained in colourless plates melting a t 109".0.1364 gave 0.2748 CO, and 0.099 H,O. C,H,,O, requires C = 55.17 ; H = 8.04 per cent. The identity of this acid was further demonstrated by converting it into isobutylsuccinanilic acid and isobutylsuccinanil, which were found to be identical with the substances obtained from synthetical isobutyl- succinic acid (see p. 51). c'= 54.95 ; H = 8.06. Action of Hyd.r*ogen Cyanide on a-IsobutyElevuZinic Acid. Pormation of a-lsobutyl- yy-hydroxycyanovaleric Acid, CH,* C(OH)(CN) CH,. CH(C,H,) COOH. I n the first experiments on the action of hydrogen cyanide on isobutgl- levulinic acid, the pure ketonic acid prepared from the semicarbazone was employed, and it was then found that this reaction gave rise to a solid hydroxycyanide and an oil containing much nitrogen ; the latter was at first thought to be a stereoisomeric modification of the solid cyanide.Subsequently, when it was found that it was unnecessary to employ such carefully purified ketonic acid, the usual method of procedure was as follows.54 BENTLEY AND PERKIN: EXPERIMENTS ON THE Isobutyllevulinic acid (b. p. 185-195' at 30 mm.), in quantities of 30 grams, was mixed with water (45 grams), and pure potassium cyanide (18 grams) added in small quantities at a time, the whole being cooled in a freezing mixture during the operation. The mixture, which soon became almost solid, was allowed to stand for about an hour, and concentrated hydrochloric acid (12 grams) then added, care being taken that the temperature did not rise much above 0'.After 3 hours, more hydrochloric acid (30 grams) was added, and the whole kept at Oo for about 20 hours. At the end of this time, i t was seen that the oil which separated on adding the second quantity of hydrochloric acid had almost completely solidified ; this semi-solid mass, after being washed and left in contact with porous porcelain until quite free from oily impurity, was recrystallised from dilute methylic alcohol, from which it separated in the form of beautiful, colourless needles melting at 95-96'. For analysis, the substance was dried over sulphuric acid in a vacuum, as it decomposes even below its melting point when heated in a water bath. 0.1220 gave 0,2484 CO, and 0.0980 H,O. 0,2356 ,, 13.2 C.C.nitrogen at 14" and 764 mm. N=6.63. C,,H,,NO, + H,O requires C = 55.30; H = 8-75 ; N = 6.45 per cent. Isobutylhydroxycyanovaleric acid appears, therefore, to crystallise from dilute methylic alcohol with 1H20. It is readily soluble in acetic acid, alcohol and hot water, but only sparingly in benzene, chloroform or light petroleum ; if warmed for some time with hot water, it decom- poses, yielding hydrocyanic acid and an oil which is possibly regenerated isobutyllevulinic acid. C = 55.54 ; H = 8.92. Lactone of Isobutylhydroxycyanovaleric Acid, CH, (CN) CH,* F]H*C,H,. 0-- co When pure isobutylhydroxycyanovaleric acid is distilled under re- duced pressure (40 mm.), water is first eliminated, and then the temperature rises rapidly to 175", nearly the whole of the residue distilling between 178' and 180" (40 mm.) as a colourless oil; this, however, is not the pure lactone, as is shown by the following analysis.Found, N = 5.75 per cent. ; CloH,,N02 requires N = 7.73 per cent. This oil, which appeared to contain some isobutyllevulinic acid, on long standing at O", deposited colourless plates which, after being spread on porous porcelain until quite dry and then washed with light petroleum, meltad at 40-50'. The analysis now gave the correct numbers. 0.1550 gave 10.1 C.C. nitrogen a t 22' and 760 mm.. N = 7-45. C,,H,,NO, requires N = 7.73 per cent.SYNTHESIS OF CAMPHORIC ACID. PART I, 55 This substance, which is evidently the lactone of isobutylhydroxy- cyanovaleric acid, melts at 53". It crystallises in beautiful, glistening plates, and is readily soluble in alcohol and ether, but almost insoluble in water.It is insoluble in cold soda solution, and when warmed the crystals melt and swim about in the hot alkaline solution as an oil. a-lso6utyZ-alalmethyZ?~y~~~ox?/glutccric Acid. CH(CH,),*CH,-~H*COOH FH2 CH,*C(OH)*COOH This acid is formed by the hydrolysis of isobutylh ydroxycyanovaleric acid by means of hydrochloric acid, the method which was adopted for the hydrolysis and isolation of the acid being as follows. Absolute alcohol (60 grams) was saturated with dry hydrogen chloride, and t o the cold liquid the solid cyano-acid (30 grams) was added, and the mixture then allowed to stand a t the ordinary temperature for two days. At the end of this time, a considerable quantity of ammonium chloride had separated, and the process appeared to be complete; in order, however, t o make sure that the whole of the cyano-acid had been hydrolysed, the product was heated on the water bath for 4 hours before being worked up.The whole was then cooled, diluted with water, and the oily ethereal salt which separated extracted with ether; this was washed, dried, and evaporated, and the oily residue purified by fractionation under reduced pressure. In this way, a colourless oil was obtained, which distilled almost constantly at 168O (17 mm.). 0.1152 gave 0.2666 CO, and 0.0930 H,O. 0.1080 ,, C = 63.1 1 ; H = 8.97. 0.2502 CO, ,, 0.0874 H,O. C = 63-15 ; H = 8.99 per cent. C12H2004 requires C = 63.1 6 ; H = 8-77. C14H2,0, requires C = 61 -31 ; H = 9.48 per cent.This substance is therefore not the ethereal salt of isobutylmethyl- hydroxyglutaric acid itself (C14H2605), but of the lactone of this acid (C12H2,,04), that is, CH(CH,),*CH ,* YH-FO p 2 0 C H , * ~ C O O C , H ~ It is a colourless oil of faint odour, and distils without decomposition at about 290" under the ordinary pressures (see p. 57). In order to prepare the dibasic acid from this ethereal salt, the pure substance (25 grams) was added to a solution of potash (20 grams) in pure ethylic alcohol, and the solution beated in a reflux apparatus on the water56 BENTLEY AND PERKIN: EXPERIMENTS ON THE bath. I n a short time, a solid potassium salt began to separate, which increased rapidly in quantity until the whole, after about an hour and a half, bad become quite thick ; the mass was then cooled, the solid crystalline precipitate collected with the aid of the pump, washed with alcohol, and dried a t 100'. This substance, which proved to be the potassium salt of an organic acid, was dissolved in water, and the solution, after filtering, was cooled with ice and carefully acidified with hydrochloric acid, when a beauti- fully crystalline acid was precipitated ; this was collected, washed, dried, and analysed, with the following result.0.1 164 gave 0,2348 GO, and 0.0876 H,O. C1,Hl,O5 requires C = 55.04 ; H = 8.26 per cent. The silver salt of the acid precipitated from a neutral solution of the ammonium salt is a white, amorphous, very insoluble substance. On analysis, it gave the following result. C = 55-01 ; H = 8.36. 0.1008 gave 0.0508 Ag.Ag= 50.39. These analyses prove that the acid obtained in this way is isobutyl- methylhydroxygluturic acid. When heated in a capillary tube, it softens at 128' and melts at 134' with evolution of gas, due, no doubt, to the elimination of water and formation of the lactone (p. 58). It is sparingly soluble in cold, but dissolves in warm water ; if the solution, however, be boiled, an oil separates, a change which is obviously due to lactone formation. The dibasic acid is sparingly soluble in cold benzene and light petroleum, but dissolves readily in alcohol and acetic acid. It may be obtained in a beautifully crystalline condition by dissolving it in much warm ether, distilling OE the ether until crystals begin to separate, and then allowing the solution to stand, when the greater part of the acid separates in beautiful, glistening, silky plates.Ethylic Isob~tylmetiLylhydroxy~lutarate, OH*C,H,5(COOC2H5)2.-In order to prepare this, experiments were first tried on the action of hydrogen chloride on the alcoholic solution of the acid, but as the ethereal salt which was formed proved on investigation to be the ethylic salt of the lactonic acid, we were forced to make the ethylic salt of the dibasic acid from the silver salt by the action of ethylic iodide. The dry silver salt of the dibasic acid (10 grams) was heated in a reflux apparatus with ethylic iodide (10 grams) and pure dry ether for 2 hours on the water bath; the silver iodide was then filtered off, washed with ether, the ethereal solution evaporated, and the residual almost colourless oil left in a vacuum desiccator over sulphuric C,,H,,Ag,O, requires Ag = 50.00 per cent.SYNTHESIS OF CAMPHOBIC ACID.PART I. 57 acid for about a week. that it was the ethereal salt of the dibasic acid. The analysis of the oil gave numbers showing 0.148 gave 0,3297 GO, and 0,126 H,O. When this oil is distilled under the ordinary pressure, alcohol is eliminated and a colourless, oily ethereal salt' distils remarkably con- stantly a t 290' with scarcely any decomposition; this, on analysis, proved to be the ethylic salt of the lactonic acid. C = 60.72 ; H = 9.46. OH* C,H,,(COOC,H,), requires C = 61.31 ; H = 9.48 per cent. 0.1362 gave 0.3136 CO, and 0.1116 H,O. C=62*79; H=9*10. 0 COOC,H,- C,H,,<bO requires C = 63.1 6 ; H = 8.77 per cent. This, after being hydrolysed by boiling with excess of potash or methylic alcohol, was diluted with water, evaporated to dryness, and the residue, dissolved in a little water, was cooled, and acidified, when the colourless crystalline hydroxydibasic acid was precipitated.0.1280 gave 0.2572 CO, and 0.0960 H,O. C,,H,,05 requires C = 55.04 ; H = 8.26 per cent. I n a preliminary experiment, in which less alkali mas used, some of the ethereal salt on hydrolysis yielded a solid melting a t 7S0, which evidently consisted of the lactonic acid produced by direct hydrolysis. Action of Phosphorus Pentoxide on Ethylic Isobutylmethylhydroxy- glutcurate.-As stated in the introduction, this experiment was insti- tuted with the object of eliminating water from the ethereal salt, and of thus forming a closed chain, but the reaction evidently proceeds differently, alcohol being eliminated and the ethereal salt of the lactonic acid formed. The diethylic salt (5 grams) was mixed with a large excess of phosphorus pentoxide and allowed to stand in a desiccator over phosphorus pent,oxide for 8 days ; the gelatinous mass thus formed was then mixed with water, the oil which separated extracted with ether, the ethereal solution washed with sodium carbonate, dried over calcium chloride, and evaporated.The oily residue, after standing for 7 days over sulphuric acid in a vacuum desiccator, was analysed. C = 54.80 ; H = 8-33, 0.1434 gave 0,3356 CO, and 0.1196 H,O. On distillation under the ordinary pressure, nearly the whole passed over a t 290-2992", and on analysis and further examination it proved to be the ethylic salt of the lactonic acid.C = 63.82 ; H= 9.26. 0.1290 gave 0.2976 CO, and 0.1060 H,O. C = 62.91 ; H = 9.13. COOC,H,* C,H1,<? requires C = 63.16 ; H = 8-77 per cent, co58 BENTLEY AND PERKIN: EXPERIMENTS ON THE From this ethereal salt, by hydrolysis, both the lactonic acid and the 0.1024 gave 0,2064 CO, and 0.0767 H,O. There can therefore be no doubt that the oily ethereal salt was simply the ethereal salt of the lactonic acid. Fusion of IsobutyZmethyZhydroxyglzcta~*ic Acid with Potash.-This ex- periment was made in the hope that elimination of water might take place at the temperature of fusion with formation of a closed ring, which would probably be very stable, since camphoric acid itself is hardly attacked by fused potash at 300".About 5 grams of the pure acid was fused with potash at 220-230" for half an hour ; the melt was then dissolved in water, and the clear solution acidified and extracted with ether. On evaporating the ether, an oil was left which, on standing for some days at O", gradually became nearly solid ; it was then placed on porous porcelain and subsequently crystallised from water. The crystalline acid, melting at 10S-109°7 thus obtained, proved to be isobutylsuccinic acid. dibasic acid were obtained, and the latter was analysed. C=54.97; H=8*33. CloH,,O, requires C = 55.04 ; H = 8.26 per cent. 0.1219 gave 0.24'72 CO, and 0.0892 H,O. This experiment was repeated several times under different con- C = 55-25 ; H = 8-12, C,Hl,O, requires C = 55.17 ; H = 8.04 per cent.ditions, but isobutylsuccinic acid mas formed in all cases. Lccctone of Is0 but ylrnethylhpdroxyg Zutccric Acid, CH(CHJ,* CH,* VH-70 ?HA0 CH,* C-COOH. This lactone may be obtained from the hydroxydibasic acid in several ways, but we found that treating the acid with acetyl chloride yielded the best results. The pure hydroxydibasic acid boiled for a few minutes with a little pure acetyl chloride and then allowed to evaporate in a vacuum desiccator over solid potash, deposited prismatic crystals on standing overnight. These were collected, drained on a porms plate until quite dry, and then analysed without further purification. 0.1200 gave 0.2636 CO, and 0.0882 H,O. C,,H,,O, requires C = 60.00 ; H = S.00 per cent.The luctone of iso6utylmet?~yZ?~ydroxyglutGdq'ic ucid melts at about 80°7 dissolves readily in alcohol and acetic acid, but is nearly insoluble in cold benzene, light petroleum, and water. When left in contact with water a t about 60°, it gradually dissolves, probably with forma- C=59.91 ; H=8.16.SYNTHESIS OF CAMPHORIC ACID. PART I. 59 tion of the hydroxy-dibasic acid ; in alkalis, it dissolves readily, and if the solutions are precipitated at once by hydrochloric acid, the lactone separates unchanged. I f , however, the lactooe is heated with excess of alkali for some time, and the solution then cooled with ice and cautiously acidified, the precipitate consists of the hydroxy-dibasic acid. Investigcction of the Liquid Formed during the Action of Hydrogen Cyanide o n Isobut~llevulinic Acid.It has already been stated that isobutyllevulinic acid reacts with hydrogen cyanide:with formation of isobutylhydroxycyanovaleric acid, but the yield of the latter is not more than 50-60 per cent. of the theoretical, owing to the fact that some oily substance is always obtained at the same time; this is absorbed by the porous plates during the process of purification of the solid nitrile, and as it seemed possible that the examination of this oil might yield interesting results, these plates were broken up and extracted with ether in a Soxhlet apparatus. On distilling off the ether from the extract, a thick, dark brown oil containing nitrogen was left, and with this the following experiments were made. Rehaviour of the Oil on DistiZ2cction.-About one-third of the oil was distilled under reduced pressure (30 mm.), when, after a little water had come over, the temperature rose rapidly to 140°, most of the oil distilling a t 175-1 85". Ethsr@ccction of the Crude Oil.-The crude, dark brown oil was dissolved in alcohol, the alcoholic solution saturated with hydrogen chloride, and the mixture left in the cold for two days, during which time a considerable quantity of ammonium chloride separated.The liquid was then heated in a reflux apparatus for one hour, diluted with water, and the oil which separated extracted with ether; the ethereal solution, after being washed with water and with sodium carbonate solution,-dried over calcium chloride, and the ether distilled off, left an oil which was distilled under reduced pressure (35 mm.) ; almost the whole passed over between 140" and ZOO', by far the larger portion a t 150-160". The latter fraction gave the following results on analysis.0.1170 gave 0.2810 CO, and 0.0992 H,O. C = 65.50 ; H = 9.41. 0.1285 ,, 0.3102 CO, ,, 0.1132 H,O. C = 65.84 ; H = 9.SO. Ethylic isobutyllevulinate, C,,H,,O,, requires C = 66.0; H = 10.0 p. cent. AS this oil on hydrolysis gave a liquid acid which, with semi- carbazide hydrochloride yielded a semicarbazone melting approximately a t 1854 there can be no doubt that it is ethylic isobutyllevulinate, and this experiment shows that the original brown oil either contained60 BENTTiEY AND PEKKIN: EXPERIMENTS ON THE isobutyllevulinic acid, or that the latter had been produced by the action of hydrochloric acid on the hydroxycyanide contained in the oil.A remarkable result was obtained in an experiment in which some of the fraction 150-160° (25 mm.) was boiled with water for four days in a reflux apparatus, as a t the end of this time almost the whole had been converted into a solid crystalline substance. This after being washed with water and allowed to remain in contact with porous porcelain until quite free from oil, was purified by recrystallisa- tion from 70 per cent. acetic acid, from which it separated in beautiful, rhombic crystals melting at 175-1 80'. 0.1230 gave 0.2980 CO, and 0*1050 H,O. C = 66-07 ; H = 9.48. 0.1210 ,, 0.2942 CO, ,, 0.1030 H,O. C=66*31 ; H= 9.45. C,,H,,O, requires C = 66.28 ; H = 9.20 per cent.This acid is readily soluble in alcohol and acetic acid; but almost insoluble in water and light petroleum. It dissolves readily in dilute solutions of alkalis or alkali carbonates. The silver salt, ClsH,,AgO,, was prepared from a slightly alkaline solution of the ammonium salt ; it is a whit.e, amorphous precipitate, which was analysed after washing and drying. 0.1230 gave 0,2236 CO,, 0-0770 H,O, and 0.0302 Ag. C- 49.57 ; H == 6.95 ; Ag = 24-55 C,,H,,AgO, requires C = 49.88 ; H = 6.69 ; Ag = 24.94 per cent. It is evident, therefore, that the substance C,,H,,O, is a monobasic acid, and it seems likely t h a t it is formed by the elimination of water from two molecules of isobutyllevulinic acid, thus, 2C,H1,O, = C,8H3005 + H,O. We have obtained no clue to the constitution of the acid, nor has any attempt been made to prepare the acid from pure isobutyllevulinic acid by boiling with water.The higher fraction of the ethereal salt prepared as described above by the etherification of the crude brown oil, and which boiled a t 170-190° (25 mm.), was hydrolysed by potash in the usual way. The acid which was thus obtained remained liquid for a long time, but after being in an exhausted desiccator for some weeks it had become semi-solid. The crude mass, spread on porous porcelain, was left until the crystals had become quite white; they were then dissolved in benzene, and the solvent allowed to evaporate slowly. The crystalline mass thus obtained, after drying on porous porcelain, gave the following results on analysis.SYNTHESIS OF CAMPHORIC ACID.PART I. 61 0.1168 gave 0.2564 CO, and 0.0852 H,O. C = 59-87 ; H = 8.10. C,,H,,O, requires C = 60.00 ; H = 8.00 per cent. As this substance melts a t 75-80', it is evidently the lactone of isobutylmethylhydroxyglutaric acid (p. 58). The crude brown oil so often referred t o above may then very probably be simply a solution of some isobutylhydroxycyanovaleric acid in a considerable quantity of unchanged isobutyllevulinic acid, and, so far, there is no evidence of two stereoismeric hydroxgcyanides being produced by the action of hydrogen cyanide on isobutyllevulinic acid. EthyZic L)i-isobutyZ?nuZorute, [CH( CHI,),. CH,],C(COOC,H5),. During the preparation of ethylic isobutylmalonate, varying quanti- ties of an ethereal salt boiling a t about 240-260' were always obtained, and this, on examination, proved to be ethylic di-isohtylmalonate.As this substance, or rather the di-isobutyl acetic acid prepared from it, was required for some synthetical work which is in progress, we have investigated the matter carefully, and give here a description of our ex- periments, instead of publishing them in a separate paper. The ethylic di-isobutylmalonate employed for this purpose was partly that obtained as a bye-product in the preparatim of ethylic isobutylmalonate, but the bulk of it was specially prepared in the following way. Sodium (4.6 grams) was dissolved in absolute alcohol (55 grams) and mixed with ethylic isobutylmalonate (45 grams), isobutyl bromide (30 grams) was then added, and the whole heated in a reflux apparatus on the water bath for several hours, The alcohol was distilled off, water was added, and the product extracted three times with ether ; the ethereal solution, after being washed with water, was dried over calcium chloride, the ether distilled off, and the residue purified by fractionation at the ordinary pressure.In this way, ethylic di-isobutylmalonate (43 grams) was obtained as a thick, colourless oil boiling at 245-255'. 0.0994 gave 0.2404 CO, and 0*0912 H,O. Analysis. C = 65.96 ; H = 10.19. (C,H,),C(COOC2H5), requires C = 66.17 ; H = 10-29 per cent. Bi-isobutyZmuZonic Acid, [CH( CH,),. CH,],C(COOH),. This acid is readily obtained by hydrolysing its ethylic salt with potash, Caustic potash (26 grams), dissolved in 90 per cent. alcohol, was mixed with ethylic di-isobutylmalonate (40 grams), and the whole heated on the water bath for 3 hours; the product was then diluted with water, evaporated until quite free from alcohol, acidified,62 BENTLEY AND PERKIN: EXPERIMENTS ON THE and extracted with pure ether. The ethereal solution, after being dried over calcium chloride and evaporated, gave an oily residue which solidified only very slowly, even when placed in a vacuum desiccator over sulphuric acid.After 14 days, the solid acid was pressed on porous plates in order to remove oily matter, and then purified by re- crystallisation from light petroleum (b. p. SO-go'), when it was obtained in thick prisms melting a t 145-150O with evolution of gas. 0.1 054 gave 0.2352 CO, and 0.0884 H,O. (C,H,),C(COOH), requires C = 61.11 ; H = 9.26 per cent.Di-isobutylmalonic acid is almost insoluble in water and benzene, but dissolves readily in alcohol and in hot light petroleum (b. p. 80-90') ; it is only sparingly soluble in cold light petroleum. C = 60.86 ; H = 9-32. Di-isobutylacetic Acid, [CH(CH,),* CH,],CH* COOH, und its Derivatives. In order to prepare this acid, crude di-isobutylmalonic acid was heated until carbon dioxide was no longer evolved, and it was then distilled. From the distillate, by fractional distillation, pure di-isobutyl- acetic acid was readily obtained as a viscid, colourless oil, of feeble odour, and boiling a t 225-230' (730 mm.). 0.2004 gave 0.2560 CO, and 0.1050 H,O. Di-isobutylucetyl chloride, CH(C,H9),* COCL-This was obtained by the action of phosphorus trichloride on di-isobutylacetic acid. The acid (9 grams) and the phosphorus trichloride (4 grams) were heated together for 10 minutes in an oil bath, the liquid was then decanted from the phosphorous acid, and distilled under reduced pressure.Di- isobutylacetyl chloride is a colourless, pungent-smelling liquid which boils a t 95" (20 mm.) ; it was not analysed, but at once converted into the iindermentioned derivatives. Di-isobutylacetanili~e, CM(C,H,),* CO *NH* C,H, .-This was prepared by dissolving the acid chloride (3 grams) in pure, dry ether, and adding aniline ( 5 grams) also dissolved in ether. After some time, water mas added, l&e ethereal solution separated and washed with dilute hydro- chloric acid until free from aniline, then with water, dried over calcium chloride, and the ether distilled off.The oil which was left slowly solidified, and after being spread on a porous plate t o remove oily im- purities, was crystallised from light petroleum (b. p. 100-1 20'). The pure substance was thus obtained in needles melting at 11 1". Analysis, CH(C,H,),* CO*NH*C,H, requires 5.66 per cent. C=69*54; H = 11.61. CloE2002 requires C = 69.77 ; H = 11.62 per cent. 0.1738 gave 9 C.C. nitrogen at 17" and 750 mm. Di-isobutylacetanilide dissolves in benzene, alcohol and hot light N = 5-92.SYNTHESIS OF CAMPHORIC ACID. PART I. 63 petroleum (b. p. 100-120°), but is only sparingly soluble in cold light petroleum. Di-isobutylucetopccratoluidide, CH(C,H9),*CO*NH* CGH,* CH,, was pre- pared from the acid chloride and paratoluidine in precisely the same manner as the anilide; i t crystallises from light petroleum (b.p. 100-120") in prismatic needles, melts at 140-141", and is sparingly soluble in cold light petroleum, but readily in alcohol, chloroform, and benzene. 0.2661 gave 12.6 C.C. nitrogen at 1'7" and 746 mm. N=5*36. CH(C,H,),* CO*NH* C,H,* CH, requires N = 5.36 per cent. Di-~sobuty~c~cetam~de, CH(C4H&* CO *NH,, was prepared by adding the acid chloride (3 grams) to concentrated aqueous ammonia (10 c.c.), allowing the mixture to stand for some time, and then extracting with ether; the ethereal solution, dried over potassium carbonate and evapo- rated, left an oil which slowly solidified. This was purified by crystal- lising it, first from petroleum boiling at 40-60°, and afterwards from petroleum of high boiling point (100-120") mixed with a little alcohol, when it was obtained in minute needles melting a t 120-121".0.1472 gave 10.8 C.C. N a t 17" and 750 mm. CH(C,H9)2* CO *NH, requires N = 8.18 per cent. Di-isobutylacetamide is very soluble in alcohol, but almost insoluble in water, and, when pure, almost insoluble in petroleum of high boiling point . N = 8.40. P2-eparation of Isobutylsuccinic Acid, CH(CH,),* CH,. CH(COOH)-CH,* COOH. As this acid was needed for the purpose of comparison with the acid of the formula C,H,,O,, which had been obtained by the hydrolysis of ethylic acetylisobutylsuccinate as explained on p. 50, we prepared a considerable quantity of isobutylsuccinic acid by a process which has not been described before.Sodium (2 grams) was dissolved in absolute alcohol (24 grams), mixed with ethylic isobutylmalonate (25 grams), ethylic monochloracetate (14 grams) was added, and the mixture allowed to stand for some hours; it was then heated on the water bath for 4 hours, water was added, and the oil which separated extracted with ether. The ethereal solution, after being well washed with water, dried over calcium chloride and evaporated, left an oil which was puri- fied by fractionation under reduced pressure. I n this way a moderately good yield of a substance was obtained which distilled at 170-180" (25 mm.), and, on analysis, gave the following results. 0.1146 gave 0.2484 CO, and 0.0886 H,O. C = 59.11 ; H-8.58. C,,H,606 requires C = 59.60 ; H = 8.60 per cent.64 BENTLEY AND PERKIN : EXPERIMENTS ON THE Ethylic isobutyletTLanetricarboxylnte, CH(C.H,),*CH,*C(COOC,H,),*CH,*COOC2H5, is a colourless oil which, when distilled under ordinary pressures, ap- pears to undergo but very little decomposition ; on hydrolysis, it yields a solid, tribasic acid, which, when heated at lSOo, loses carbon dioxide with formation of isobutylsuccinic acid.The oily ethylic salt was hydrolysed with alcoholic potash in the usual way, the product evaporated until free from alcohol, acidified and repeatedly extracted with ether ; after drying over calcium chloride and evaporating, the residual tribasic acid immediately solidified. This was not analysed, but at once converted into isobutyl- succinic acid by heating a t 1S0-2OO0 until carbon dioxide ceased t o be evolved; the crude product was then dissolved in hot water, filtered, and saturated with hydrogen chloride; on standing, a mass of crystals separated, which, after two recrystallisations from water, melted at 109O, and consisted of pure isobutylsuccinic acid.0.1354 gave 0.2764 CO, and 0.1002 H,O. C,H,,O, requires C = 55.17 ; H = S.04 per cent. Isobutylsuccin,anilic acid, C,H,- CH( COOH)* CH,. CO .NH* C,H, (1). -In order to prepare this substance, the acid (2 grams) was digested with acetyl chloride for a few minutes, the excess of the latter removed by exposure over potash in a vacuum desiccator, and the residual liquid anhydride dissolved in a little benzene and mixed with aniline (1.5 grams). The solid matter which soon separated, after being drained on a porous plate and recrystallised from dilute alcohol, yielded the anilic acid in beautiful leaflets melting at 138.5".C = 5567 ; H = S.22. 0.1818 gave 8.8 C.C. nitrogen at 15" and 558 mm. N = 5-66. C,,H,,NO, requires N = 5.62 per cent. Isobutylsuccinanil, c,Hg* (?H--co>N* C,H,.-This was prepared by CH, CO heating the anilic acid a t 200" for 5 minutes, and treating the gummy mass obtained with dilute ammonia, when it solidified immediately. This was ground up with dilute ammonia, collected, washed, and recrystallised from dilute alcohol. 0.1352 gave 7.1 C.C. nitrogen at 16' and 752 mm. C,,HI7NO, requires N = 6.06 per cent. lsobutylsuccinunil melts at log", and is readily soluble in alcohol and hot light petroleum, but only sparingly in cold light petroleum ; it is almost insoluble in water and in dilute sodium carbonate solution.N = 6.05.SYNTHESlS O F CAMPHORIC ACID. PART I. 65 CH(CH,),* CH,*y(OH)* COOH and a-H?ld?.oxydi-isobutylacetic acid, CH(CH3),*CH, a-~sobutyZ-P-iso~l.oz~ylacrylic m i d , CH(CH,),*CH,*#* COOH. CH(CH,),*CH I n spite of the fact that the boiling point of ethylic acetylisobutyl- succinate (p. 50) is so constant, the numbers obtained on analysis were always nearly 1 per cent. low; this was subsequently found to be due to the fact that it contains traces of bromine. When this ethylic acetylisobutylsuccinate is hydrolysed with hydrochloric acid, there is always a small quantity of oil which remains unattacked, even aft,er the treatment with hydrochloric acid has been repeated several times ; in order to ascertain the nature of this oil, the small quantities from several operations were united and fractionated, when nearly the whole passed over at 138-140" (27 mm.), and on examination was found to contain bromine.The analysis of different samples gave the following results. 0.1365 gave 0.2649 CO, and 0.1060 H,O. C=52*93; H=8.63. 0.1705 ,, 0.3540 CO, ,, 0,1460 ,, 0.2880 GO, ,, 0.1214 ,, 0.2394 CO, ,, 0.2844 ), 0.1748 AgBr. 0,2387 ,, 0.1502 AgBr. These numbers agree with C = 53.2 ; H = 8.5 ; Br = 27.3 0.1320 H,O. 0.1 166 H,O. 0.0936 H,O. C = 53.43 ; H = 8.6. C = 53.80 ; H= 8.87. C = 53-78 ; H = 8.56. Br = 26.15. Br = 26.77. the formula C,,H,,BrO,, which requires per cent. A careful examination of this oil appears to us to prove that the true formula of the brominated ethylic salt is C,,H,,BrO,, and that it is, in fact, ethylic a-6romodi-isobutyZacetate, C(C,H,),Br*COOC2H5. This formula requires C = 51.61 ; H = 8.24 ; Rr.= 28.67 per cent., and the discrepancy between these and the numbers actually found mas at first thought to be due to the possibility of some of the bromine having been replaced by chlorine during the prolonged boiling with hydro- chloric acid. That this is not the case to any appreciable extent is shown by the fact that the 0.1502 gram of silver haloid obtained in one of the above analyses, after being reduced to silver, dissolved in nitric acid, and precipitated with hydrobromic acid, yielded 0.1478 gram of AgBr. Most probably the impurity in the brominated ethylic salt consists of traces of ethylic acetoisobutylsuccinate, which had escaped the hydrolysing action of the hydrochloric acid.The presence of this brominated substance in the crude ethylic aceto- isobutylsuccinate is explained by the fact t h a t when the sodium compound of ethylic malonate is treated with isobutylic bromide, the VOL. LXXIII. F66 BESTLEY AND P E R K I N : EXPERIMENTS ON THE principal product is ethylic isobutylm donate, but there is always formed at thesame time some ethylic di-isobutylmalonste, C(C,H,),-(COOC,H,),. This ethereal salt, on hydrolysis and subsequent elimination of carbon dioxide, yields di-isobutylacetic acid, CH( C,H9),*COOH, traces of which were evidently present in the isobutylacetic acid used in these experi- ments. I n the subsequent bromination, this would be converted into a-bromodi-isobutylacetic acid, CBr(C,H9),*COOH, the ethylic salt of which is apparently not readily acted on by the sodium compound of ethylic acetoacetate, since it is found unchanged in the product of the reaction.Hydrolysis of Etlqlic Di-isobutylbronzacetate.-When the brominated ethylic salt (12 grams) was digested in alcoholic solution with potash (15 grams) in a reflux apparatus, potassium bromide soon began to be deposited in crystals on the side of the flask. After boiling for 8 hours, the product mas diluted with water, traces of a neutral oil removed by extraction with ether, and the aqueous solution evaporated with water until quite free from alcohol. The alkaline solution was then acidified, and the oily acid which separated was removed by treatment with ether.The ethereal solution, after drying over calcium chloride and evaporating, left a thick syrup which, on standing for some days over sulphuric acid in a vacuum-desiccator, gradually deposited hair- like crystals ; these were collected with the aid of the pump, drained on a porous plate, and then recrystallised from light petroleum. 0,1243 gave 0.2890 CO, and 0,1206 H,O. OH*C(C,H,),*COOH requires C = 63.88 ; H = 10.64 per cent. This beautifully crystalline substance. melts a t 123-124' and evi- dently consists of a-hydroxydi-l'sobutylacetic acid ; it is readily soluble in hot light petroleum (b. p. 60-80°), sparingly so in the cold, and crystal- lises from this solvent in slender needles which, when dry, resemble cotton wool.This acid is isomeric with a - ~ s o p ~ o p y ~ - ~ - ~ s o b u t y ~ ~ ~ y d ~ ~ n c r ~ l acid (m. p. 1 Z O O ) , CH(CH,),* CH,*CH(OH)*CH(COOH)*CH,>,, which Wohlbruck (Berichte, 1887, 20, 2337) and Hantzsch (Annalen, 1888, 249, 65) obtained by the action of sodium on ethylic isovalerate. The oily filtrate from the crude crystals of the a-hydroxydi-isobutyl- acetic acid was fractionated under reduced pressure (35 mm.) when nearly the whole distilled constantly a t 153'. The very thick, colour- less syrup thus obtained gave the following results on analysis. C=63*43 ; H= 10.77 0.1793 gave 0.4569 CO, and 0,1725 H,O. C=69*50; H= 10.69. C,,H,,O, requires C = 70.06 ; H = 10.60. This substance is evidently iso~opylisobu,tylacr~lic acid, and the fraction analysed may contain traces of hydroxydi-isobutylacetic acid,SYISTHESIS OF CAlIPIIORIC ACID. PART I. 67 which would account for the results of the a'oove analysis being some- what too low. Isobutylisopropylacrylic acid distils without decomposition under tlhe ordinary pressure a t 240-241O. I t is almost insoluble in water, but dissolves readily in dilute sodium carbonate solution, and this solu- tion of the sodium salt' rapidly decolorises permanganate, although, perhaps, not so readily as is usual with unsaturated acids. Bromine is slomly decolorised by a solution of the acid in chloroform. Salts of IsobutyZiso~l.o~~yZac,.?/Zic Acid. - The ammonium salt of this acid dissociates on evaporating its solution on a water bath, ammonia being evolved, and the oily acid separating out. The silver salt, C,,Hl7AgO,, was obtained as a white, caseous precipitate on adding silver nitrate to a solution of the acid in a slight excess of ammonia; after washing well and drying first on a porous plate and then a t 100" it was analysed. 0.2658 gave, on ignition, 0.1040 Ag. Ag = 39-12 0.2555 ,, ,, ,, 0.0998 Ag. Ag=39*06. CloH17Ag0, requires Ag = 38.99 per cent. The neutral solution of the ammonium salt shows the following Barium chloride, no precipitate. Calcium chloride.--If calcium chloride is added t o a hot dilute solu- tion of the ammonium salt, a beautifully crystalline characteristic cal- cium salt rapidly separates; this dissolves in much hot water, but does not appear to crystallise out again on cooling. Copper sulphate gives a very insoluble bluish-green, caseous precipitate. Lead acetate, a white caseous precipitate. Isopropylisobutylacrylic acid is probably identical with the ccmy- decyleizic cccid which Borodin (Julwesbericld, 1870, 680 ; Bericlbte, 1872, 5, 481) obtained by the oxidation of di-isovaleraldehyde, C,,H,,O, a substance which is produced when isovaleraldehyde is digested with potassium carbonate. I f we assume, as is probable, that in the formation of di-isovaleral- dehyde two molecules of isovaleraldehyde condense in the following way, behaviour with reagents. + H,O, - CH(CH,),* E*CHO CH(CH,),.C~H~~*CHO - CH(CH,),* CH,* UKjO I.__...> C'H(CH,),*CH,*CH then an aldehyde of this formula should, on oxidation, yield iso- propylisobuty lncry lic acid and, this appears to be the case, since amy- decylenic acid is described by Borodin as an oil boiling at 2 4 1 9 O with- out decomposition. E 2

ISSN:0368-1645    

DOI:10.1039/CT8987300045

出版商:RSC    

年代:1898

数据来源: RSC

摘要:

68 SCHRYVER: SYNTHESIS OF AN ISOMEllIDE O F 111.-Synthesis of an I s o m e d e of Cccniphoi*onic Acid. By SAMUEL BARNETT SCHRYVER, Ph.D. SOME years ago, Wreden (Ann., 1877, 187, 156) showed that when camphoronic acid was heated with concentrated hydriodic acid, it yielded a tetrahpdroisoxylene. Again, oxycamphoric acid, when dis- tilled, gives a hydrocarbon isomeric with this and having similar properties, although it is not identical with it, as Aschan, who called it laurene (Ann., 1896, 290, ISS), subsequently proved. These facts, together with others since observed by myself, and which I hope soon to communicate to the Society, led me to the con- clusion that camphoric acid was a derivative of met,adimethylhexa- methylene ; and on this assumption the formula for this acid most in agreement with its reaction seemed to be This constitution would explain the following facts.a. That when brominated by the action of phosphorus and bromine only a monobromo-derivative is obtainable, for more than one bromine atom has not, as yet, been introduced into the molecule by these means. I n accordance with the researches of Hell, Aumers, and others, the bromine always enters in the a-position relatively to the carboxyl group, and in the above formula only one replaceable hydrogen atom exists in such a position. b. When a hydroxyl group is substituted for the bromine atom, a lactonic acid is produced, hence the bromine atom must be in the ?-position relatively to the second carboxyl group. Moreover, Reyker ( I k m g . Dissert. Leipig, 1891) has shown that this lactonic acid (camphanic acid), on oxidation, yields camphoronic acid, On these assumptions, a formula for camphoronic acid would be derived as follows :CAMPHORONIC ACID.69 c CH3\\ H /\ COOH*C/ H,C CH, \ 'c c' /\ H,C CH, OH 1 1 CH, CH, I I CH, \/ b O O H COOH/ \/ \COOH COOH*HC C' C C H2 Camplioronic acid. H? Camphanic acid. H, Camphoric acid. The latter substance was synthesised in the following way. Ethylic methacrylate was heated with ethylic sodiomethylmalonate according t o the method of Auwers, Kobner, and v. Meyenburg (Bey.., 1891, 24, 2887), and the sodio-additive product, without being iso- lated, was treated directly with ethylic sodacetate and then hydrolysed. CH,:C(CH,)-COOC,H, + CH,*CNa(COOC,H,), = CH,. C( COOC,H,),* CH,-CNa(CH,).COOC,H, + CH,I- COOC,H, = CH,* C( COOC,H,), CH,.CNa( CH,) *COOC,H,. CH3* C( COOC,H,),*CH,* C( CH,)( COOC,H,) CH,*COOC,H, + NaI. CH3* C(COOG',H,),* CH,. C(CH,)(COOC,H,) CH,* COOC,H, + 4H,O = 4C,H,*OH + CO, + COOH* CH(CH3)*CH,* C(CH,)(COOH)*CH,*COOH. Ethylic &.letl~c~cs*&te. Ethylic methacrylate is most conveniently prepared by a modifica- tion of Frankland and Duppa's method (Ann., 1865, 136, 12), namely, by the action of phosphorus trichloride on ethylic hydroxyisobutyrate. Prepuration of Ethylic Hydroxyisobutymte.-Hydroxyisobutyric acid dissolved in twice i t s weight of absolute alcohol containing 3 per cent. of hydrogen chloride is left for a couple of days over fused sodium sulphate, and then heated for 2 hours on a water bath. After fractiona- tion, a portion boiling between 145" and 155" was obtained and used for subsequent operations. The yield is about 50 per cent.of the theoretical. Ps*epas.cction of Ethplic Metimmylate.--To the ethylic hydroxyisobuty- rate prepared as above, about twice the theoretical quantity of phospho- rus trichloride is added drop by drap ; the mixture is then heated gently for a few minutes on a sand bath, using a reflux condenser, until it begins t o get turbid owing t o the separation of phosphorus; i t is then distilled, &c., one fractionation being suEcient t o separate the ethylic methacrylate from the phosphorus compounds. In order t o remove the last traces of the latter, the distillate is shaken with a dilute'ro SYNTHESIS OF AN ISOMERIDE OF CAMPHORONIC ACJD.solution of potassium carbonate. It is advisable to avoid frequent fractionntioii owing to the ease with which the methacrylate poly- mer i ses. Synthesis of tlre Isomeride of Camphoronic acid. For this purpose, the ethylic methacrylate is treated with ethylic sodiomethylmalonate, according to the method employed by Auwers and others (loc. cit.) in the preparation of dimethylglutaric acid. Instead of decomposing the sodium additive product, however, ethylic iodacetate is added directly t o the alcoholic solution ; the mixture becomes hot, and the reaction is completed by heating it in a corked soda water bottle a t 100" until i t is nearly neutral. The alcohol is then distilled off, and the oily residue washed with water. As the molecular weight of the ethylic salt thus obtained is so high that it cannot be advantageously submitted to fractional distillation, it is hydrolysed directly with twice its volume of hydrochloric acid (1 water : 1 acid), as recommended by Auwers in similar cases.The product, after being filtered and distilled with steam, to separate t4e propionic and other volatile acids formed, is extracted several times with ether. It is advisable t o put a little animal charcoal into the flask during the steam distillation, so as to decolorise the liquid. The ethereal extract contains much methylsuccinic acid formed by the action of the ethylic iodacetate on unchanged ethylic methylmalonate ; there is, however, another acid present, which can be separated from the rest owing to the fact that, likc canaphoronic m i d , it forms a lead salt insoluble in acetic acid.Accordingly, the residue left on evaporating the ethereal extract is dissolved in water, and lead acetate is added without pyeviously neutwdising tJte solution ; the precipitate of lead salt, after being washed with water, alcohol, and ether, is dried, suspended in ether, and decomposed by dry hydrogen sulphide. On evaporating the filtrate from the lead sulphide, a n almost colourless syrup is left, which does not crystallise even after standing for several months in a desiccator. Attempts were made to prepare a crystalline anhydride from i t on the assumption that the syrup was a mixture of geometrical isomerides and therefore not easily crystallisable. For this purpose, it mas treated with acetyl chloride, when a minute quantity of crystals separated; water was then added to the acetyl chloride solution, the acetic acid removed by evaporation, and a silver salt prepared by precipitation.This, after being Tvashed and dried, was suspended in ether and decomposed by hydrogen sulphide, but on evaporating the ether a syrup was again obtained. This was dissolved in strong nitric acid, when a slight oxidation took place, and the solution was imme- diately diluted with an equal bulk of water. After some time, crystalsFENTON : DIHYDROXYTAKTARIC ACID. PART I. 11 of the hydroxy-acid began to separate in hard, indistinct crusts, and these, after being separated from the mother liquor, and dried over sulphuric acid and caustic soda in a vacuum, SO as to free them from the last traces of water and nitric acid, were recrystallised once or twice from ether which had been distilled over sodium. The substance was thus obtained in snow white, microscopic crystals melting sharply at 137". 0,1448 gave 0,2452 CO, and 0.794 H,O. C = 46.18 ; H = 6.09. C,H,,Op requires C = 46.15 ; H = 5.98 per cent. I t may be remarked t h a t csmphoronic acid, when treated with nitrohydrochloric acid, is also oxidised t o oxycamphoronic acid. It had been my intention to prepare this acid in larger quantities and investigate its salts, but the synthesis takes a long time to carry out and is costly, As, moreover, Drs. W. H. Perkin, jun., and J. T. Thorpe published their synthesis of the true camphoronic acid at the time my work had reached the stage described, the main object with which i t had been undertaken was accomplished, and I have therefore been compelled to relinquish any further investigations in this direct ion. ._

ISSN:0368-1645    

DOI:10.1039/CT8987300068

出版商:RSC    

年代:1898

数据来源: RSC

摘要:

FENTON : DIHYDROXYTAKTARIC ACID. PART I. 11 I: V. -Pq-operties and Relationships of Dihydroxy- tartaric Acid. Pwrt I. By HENRY J. HORSTMAN FENTON, M.A. THIS acid mas first observed by Griiber, who obtained it, in solu- tion, by the action of nitrous acid on protocatechuic acid (Ber., 1879, 12, 514). It was afterwards prepared from pyrocatechol by Barth (Sitx. Acad. Feim, 82, ii, 1024); from guaiacol by Werzig, and from '' nitrotartaric acid " by Kekuld (Annalen, 1883, 221, 230) in a similar manner ; these authors isolated it in the form of the spar- ingly soluble sodium salt, and from this the free acid was subse- quently obtained by Miller (Ber., 1889, 22, 2015). The salt was de- composed by hydrogen chloride under ether, excess of hydrogen chloride being avoided and moisture carefully excluded ; but since its isolation by Miller, the free acid appears to have been scarcely examined.I n a former communication (Trans., 1895, 6 7 , 48), it mas shown that a solution of dihydroxytartaric acid may very easily be obtained by the oxidation of the new acid C,H,G, (dihydroxymaleic acid) with bromine in presence of water. The change takes place nearly quanti- tatively according to the equation C,H,O, + 2H,O + Br2 = C,H,O, + 2HBr.72 FENTON : PROPERTIES AND RELATIONSHIPS OF The solution was precipitated with sodium carbonate, and the free acid prepared from the sodium salt by Miller's method. The yield of free acid obtained by this method appears to be small, probably owing to its very sparing solubility in anhydrous ether. It was mentioned, however, that the free acid might be directly obtained from the solution after oxidation with bromine, without first preparing the sodium salt ; this was effected by concentrating the solution in a vacuum desiccator over solid potash, but the purity of the pro- duct was uncertain.Further experiments have now shown that., by modifying, the details previously given, this process affords a very simple and productive method for the preparation of the acid in a state of purity. Having regard to the very interesting constitution of this acid and to the close relation which has been shown to exist between it and dihydroxymaleic acid, it was considered desirable to take advantage of this new method of preparation and to make a study of the proper- ties of the acid.Prepurution of the Acid. Crystallised dihydroxymaleic acid, C4H406,2H20,* is well triturated with from 4 to 5 times its weight of glacial acetic acid; and rather more than the calculated quantity of bromine, dissolved in a little glacial acetic acid, is added to the mixture in small portions a t a time. The first portions are almost instantly bleached, but the action after- wards becomes more sluggish and apparently ceases-a few drops of water are then added, whereupon the colour of the bromine is again im- mediately discharged. The addition of bromine is continued until the colour is quite permanent on standing, even when a drop or two of water is added. It has been previously shown (Zoc. cit.) that this final stage is reached when the bromine has been added in about the calculated proportion (1 mol.acid to 1 mol. bromine) ; fumes of hydrogen bro- mide are freely evolved during the operation. The dihydroxymaleic acid is nearly insoluble i n cold glacial acetic acid, but when the oxidation is finished complete solution takes place. The solution is allowed to stand for an hour or two, and then vigorously stirred, when the dihydroxytartaric acid quickly, sometimes suddenly, sepa- rates as a heavy, white, crystalline powder. The product is now collected and drained with the aid of the pump, washed once or twice with small quantities of anhydrous ether, and kept in a vacuum desiccator over solid potash and sulphuric acid to remove the last traces of hydrobromic acid, acetic acid, bromine and ether. The yield of purified product thus obtained is '70 per cent.or more of the theoretical. Thus, using 18.4 grams of dihydroxy- * For the preparation of this acid, see Trans,, 1894, 65, 901.DIHYDROXYTARTARIC ACID. PART I. 73 maleic acid, 80 C.C. of acetic acid, and 5.5 C.C. of bromine, the yield of pure product was 13.3 grams. Again, with 28 grams of dihydroxymaleic acid, 120 C.C. of acetic acid, and 9 C.C. of bromine, the yield was 21 grams. The remainder may of course be recovered as sodium salt by neutralising with sodium carbonate. The product thus obtained, when heated in a capillary tube, melts sharply, and decomposes, at 114-1 15". The acid previously prepared by Miller's method melted and decomposed a t 98". I. 0.1492 gave 0.1421 CO, and 0.0443 H,O. C = 25.97 ; H= 3.29.Theory = 18.2 grams. Theory = 27.7 grams. 11. 0.1736 ,, 0.1667 CO, ,, 0.0516 H,O. C=26*1S; H=3*30. C4H,08 requires C = 26.37 ; H = 3.30 per cent. Action of Heat. Preparation of Turtronic Acid. Dry Acid.-It might perhaps be expected from the constitution of dihydroxytartaric acid that it would tend to lose water on heating, giving the diketonic acid, (?'o'cooH especially as Anschutz has CO*COOH' shown (AnnaZen, 1891, 261, 130) that the ethylic salt has a composi- tion corresponding t o this acid; it is found, however, that the free acid when heated a t 90" in a current of dry hydrcgen for about one hour, undergoes no loss in weight. Heated in a vacuum on a water bath a t 90-loo", it loses weight slowly and somewhat irregularly, and gradually turns dark brown without melting ; the loss of weight after 5 hours heating was about 42 per cent., that is, considerably more than is represented by the loss of all the hydrogen as water.The residue, moreover, when dissolved in water and tested with sodium carbonate, no longer gives the reaction of dihydroxytartaric acid. Aqueous SoZzction.-Gruber showed that the sodium salt, when heated with water, is resolved into sodium tartronate and carbon dioxide. An aqueous solution of the free acid is found to undergo a similar change ; when this is gently heated, carbon dioxide is freely evolved, and the solution, after concentration, yields crystals of pure tartronic acid, as will be seen from the following results. A few grams of dihydroxytartaric acid were dissolved i n water, the solution heated on a water bath until carbon dioxide ceased to be evolved, and then concentrated to a small bulk and allowed to stand in a desiccator; in a few days, long, transparent prisms separated, which, after being drained on filter paper, air dried, and then heated a t 100" until the weight was constant, were snalysed.G=29*76 ; H=3.29. I. 0.1603 gave 0.1750 CO, and 0.0476 H,O. Tartronic acid, C,H40, requires c! = 30.00 ; H = 3.33 per cent.74 FENTON : PROPERTIES AND RELATIONSHIPS OF 11. 0.6067 substance, on titration, required 12.4 C.C. of a solution of caustic soda contaiuing 0.0187 Na per C.C. Theory for a dibasic acid, C,H,O, = 12.0 C.C. The crystals melted a t 158-159O ; the melting point of tartronic acid has been very variously given by different authors, but Griiber (Zoc.c i t . ) , and Rlassol (Conzpt. rend., 1892, 114, 422), both obtained anhydrous crystals melting a t 155'. [The crystals appear t o separate from the solution in the anhydrous state, and not with &H,O as sometimes stated, since they undergo scarcely any change in appearance when heated a t 100'. The u i ~ clTiecl crystals gave, on analysis, C = 29.14 ; H = 3.27. C,H,O,,iH,O would require C = 27.9 ; H = 3.8. The water is, therefore, probably only '' mechanical. "1 This reaction, then, affords an extremely easy and productive method for the preparation of pure tartronic acid; the yield is almost theoretical, and the product is pure without recrystallisation. Thus 0,9696 gram of dihydroxytartaric acid was dissolved in water, the solution heated as described above, taking care t o avoid loss by spirting, and then allowed to evaporate in a vacuum desiccator; the crptalline residue dried a t 100" until the weight mas constant, melted at 157-1558", and its weight was 0.6237 gram, theory requiring 0.6392 gram.Titnxtion by Alkalis. Judging from the observation, above referred to, that sodium dihydr- oxytartrate, when heated, decomposes into sodium tartronate and carbon dioxide, Griiber considered that the acid was " carboxytar- tronic " acid, c o o H > ~ ( ~ ~ ) - ~ ~ ~ ~ , COOH and consequently that the sodium compound was an acid salt'. Attempts to prepare the normal salt were, however, unsuccessful. Griiber found that the sodium salt was not acted on by a dilute solution of caustic soda, and Barth showed that dry ammonia was also without action on it ; a strong solution of caustic soda dissolves it, but apparently decomposes it, since the sparingly soluble salt cannot be again obtained from the solution after acidification. Bnrth, however, prepared and analysed the barium salt and found its composition to be Ba3(C4H07)2, 3H,O, corresponding with the normal salt of a tribasic acid C4H407.Since this acid had been obtained from benzenoid compounds and was regarded as tribasic, with one carbon atom directly associated t o three others, arguments were advanced from its supposed constitution which were a t variance with Kekulb's well known benzene symbol. Kekule then made an exhaustive study of the sodium salt obtained from various sources, H e showed also t h a t it could be prepared fromDIHYDROXYTXRTARIC ACID PART I.7 5 ( ( nitrotartaric ” acid, and that by reduction with zinc and acid, modifi- cations of tartaric acid were produced. His results indicated that the acid is in reality dibasic, having the formula C,H,O, (dihydroxytartaric acid, or tetrahydroxysuccinic acid), and that the sodium compound is a. nornzal salt ; he suggests that the ba.rium salt obtained by Earth, if it is a homogeneous substsnce, may be a basic salt, or that replace- ment may have taken place in the liydroxj-1 groups. The acid being now available in quantity, and in a pure state, i t was considered that the results of titration by various alkalis might he of interest, as affording further evidence with regard to the basicity of the acid.Experiments were accordingly made, using sodium, potassium, and barium hydroxides, as well as ammonia and sodium carbonate, with the following results. I. 0,3778 gram of acid dissolved in 5 C.C. of water required 6.9 C.C. of a solution of caustic soda, prepared from metallic sodium, containing 0.01877 Na per C.C. ; phenolphthalein was used as indicator, and the most minute precautions were taken in order t’o ensure the exclusion of carbon dioxide, not only during the preparation of the solution, but also from the water employed, and during the operation of titration. One mol. of acid required, therefore, 2.7 mols. NaOH for neutralisa- tion. IT. 0,6035 gram of acid in 5 C.C. of water required 8.7 C.C. of normal KOH solution. (Phenolphthalein as indicator.) One mol. of acid neutralised 2.6 mols.of KOH. 111. 0,6035 gram of acid in 5 C.C. of water required 6.4 C.C. of normal sodium carbonate. (Methyl-orange as indicator.) One mol. of acid neutralised 0.96 mol. of Na,CO,. IV. 0.2910 gram of acid required 15.5 C.C. of barium hydroxide solution containing 0.0225 gram of Ba(OH), per C.C. (Phenolphthalein as indicator.) V. 0.4218 gram of acid in about 10 C.C. of water required 11.3 C.C. of a solution of pure ammonia containing 7.5555 gram NH, per litre. (Litmus as indicator.) One mol. of acid neutralised 2.16 mols. of NH,. The colour indications with phenolphthalein, although sharp a t first, quickly faded, and another drop o r so of alkali was required t o restore the colour; in the case of litmus, the blue colour quickly changed t o wine-red in a similar way.The numbers given represent the amount of alkali required to give a colour change which was permanent for a few minutes; the differences between the initial and final colour- change, however, were small, amounting only t o about 0.2 to 0.3 C.C. Those results would appear t o indicate that dihydroxytartaric acid behavei normally as a dibasic acid towards sodium carbonate and One mol. of acid neutralised 1.27 mols. of Ba(OH),.76 FENTON : PROPERTIES AND RELATIONSHIPS OF ammonia, but that with the hydroxides of sodium, potassium, and barium, its behaviour is intermediate between t h a t of a clibasic and a tribasic acid. A t first it seemed probable that the high results obtained when " strong " bases are employed might be explained by supposing that one or more of the alcoholic hydroxyl groups in the acid exerted " acid " functions and that the compounds formed are more or less hydrolysed; or that the acid might in reality be tribasic carboxy- tartronic acid as was formerly believed, the replacement of the third atom of hydrogen giving rise to an unstable salt as in the case of orthophosphoric acid.Dilution of the solution, however, has but little effect, as seen by the following experiments. VI. 0.3158 gram of acid dissolved in 50 C.C. of water required 5.45 C.C. of NaOH solution containing 0.0189 gram Na per C.C. One mol. of acid neutralised 2.6 mols. of NaOH. VII. 0,3391 gram of acid dissolved in 150 C.C. of water required 5.8 C.C. of the same NaOH solution. One mol. of acid neutralised 2.5 mols.of NaOH. The high results might, on the other hand, be due t o the partial decomposition, at the ordinary temperature, of the acid into dibasic tartronic acid and carbon dioxide; such a decomposition would not influence the result when methyl-orange was used as indicator, but would give a high result with phenolphthalein. Various experiments were therefore made in order t o throw light upon this question. VII1.-A standard solution of the acid was prepared and a portion titrated immediately with soda; the remainder of the solution was allowed to stand for about 2 hours and a n equal portion again titrated with the same soda. 1X.-Air, carefully purified from carbon dioxide by passing it through strong caustic soda solution and then through baryta-water, was allowed to bubble through a freshly prepared solution of 0.3208 gram of acid in about 10 C.C.of water contained in a small flask, The issuing gas was carefully tested for carbon dioxide by passing it through a series of bulbs containing baryta water; no trace of turbidity could be detected for the first 10 or 12 minutes, after which, however, a faint cloudiness was perceptible in the first bulb. From the results of these last two experiments it appears to be very improbable that the high results on titration can be due to the decomposition of the acid itself. But it may be that the snlt produced is less stable than the acid, and breaks up in the manner indicated, X.-0*3223 gram of acid was dissolved in about 10 C.C. of water and the experiment conducted exactly as in IX, but with the alteration that, as soon as the acid had dissolved, standard caustic soda was run in The two results were practically identical.DIHYDROXYTARTARIC ACID.PART I. 7'7 from a burette i n quantity insufficient for neutralisation (about 0.054 gram Na). Carbon dioxide was, in this case, given off almost im- mediately ; after 3 minutes there was a dense turbidity in the first baryta bulb and after 5 minutes all three bulbs were turbid. The soda solution had been prepared from metallic sodium with great precautions to exclude carbon dioxide, and the apparatus from which it was supplied was constructed so as to avoid the possibility of contamination. Still it was considered advisable to make a blank test with the whole apparatus, and this was done, dilute sulphuric acid being partially neutralised with the same soda solution and the experiment conducted exactly as before.No trace of carbon dioxide could be detected after passing the air for 10 minutes. It is tolerably certain therefore that the high results on titration are due to the splitting up of the salts produced into tartronate and carbon dioxide; if this is so, one would expect that lower, if not normal, results should be obtained on cooling the solutions, the titrations mentioned all having been performed a t the ordinary temperature of the laboratory. XI.-0*4498 gram of acid in about 10 C.C. of water was cooled by ice and standard caustic soda containing 0.02183 gram of Na per C.C. was slowly run in, phenolphthalein being used as indicator.5.4 C.C. were required for neutralisation. One moL of acid neutralised 2.07 mols. of NaOH. XII.-0,3201 gram of acid in about 10 C.C. of water was cooled, as above, and titrated with pure ammonia solution containing 7.5555 grams of NH, per litre; 7.9 C.C. were required. Litmus was used as indicator and the final blue colour was permanent for 5 minutes or more. One mol. of acid neutralised 1.99 mols. of NH,. XIII.-0*3076 gram of acid in about 10 C.C. of water, cooled as before, required 14.7 C.C. of baryta water containing 0,02244 gram of Ba(OH), per C.C. (phenolphthalein as indicator). One mol. of acid neutralised 1.14 mols. of Ba(OH),. This indeed, is found to be the case. Reduction of Dih?/cli.oxytcLrtcLric Acid to the Acid C,H,06. It has already been pointed out (Trans., 1895, G7, 48) that the new acid, C,H,O, (dihydroxymaleic acid and its isomeride), may be regarded as intermediate between tartaric and dihydroxytartaric acids ; that is, the anhydrous acid contains 2 atoms of hydrogen less than tartaric acid, and the hydrated acid contrains two atoms of hydrogen moye than dihydroxy tartaric acid 11.C,H,0G,2H,0. n r . c,H,o,. Or, if it be assumed, as is not improbable (TOG. cit., 67 7777, that a78 FENTON : PROPERTIES AND RELATIONSHIPS O F solution of the acid C,H,06 contains trihy droxysuccinic acid, the relation is perhaps better illustrated thus, I. C,H,(OH),(COOH),. 11. C213(OH),(COOH),. 111. C,(OH),(COOH),. The conversion of I into I1 is brought about by the oxidation of tartaric acid in presence of ferrous iron, of I1 into I by hydrogen iodide, and I1 is easily oxidised to I11 by bromine and water.The missing .transformation was that of I11 into 11, that is, the re- duction of dihydroxytartaric acid to the acid C,H,06. This trans- formation has now been effected in several ways, and can be very easily recognised owing to the striking difference in properties between the two acids ; for example, dihydroxyta,rtaric acid is very easily soluble in cold water, deliquesces slowly on exposure to the air, and its aqueous solution gives no colour reaction with ferric chloride. On the other hand, both the a and forms of the acid C,H406 are very sparingly soluble in cold water, and the hydrated crystals, C,H,06,2H,0, are quite permanent in the air ; moreover, their aqueous solutions give a transient, emerald-green coloration with ferric chloride in presence of mineral acids, and a beautiful blue-violet with ferric chloride followed by caustic alkali in excess.Action of Zinc and Dilute Acid-KekulB (Zoc. cit., 239) showed t h a t sodium dihydroxytartrate, when treated with excess of zinc and hydro- chloric acid, gave rise to racemic and inactive tartaric acids (together with a small quantity of n substance assumed to be tartronic acid), This change is usually explained by supposing the dihydroxytartaric CO*COOH acid to behave as a diketonic acid, I CO C 0 0 H' It is now found that, by using a limited quantity of zinc, the acid C,H,O, may be isolated as an intermediate stage. To dihydroxy- tarta.ric acid (1 mol.) dissolved in water, and mixed with granulated zinc (1 atom), dilute sulphuric acid was gradually added, the mixture being kept cold by ice; when all the zinc had dissolved, a portion of the liquid, on being tested with ferric chloride, was found to give strongly marked colour reactions characteristic of the acid C4H406.The remainder of the liquid was carefully mixed with about one-tenth of its volume of strong sulphuric acid, twice extracted with ether, and the ethereal solution evaporated ; the white residue thus obtained was very sparingly soluble in cold water, but dissolved readily in warm water, and the aqueous solution showed all the reactions of the acid C,H,O,. On cooling this solution, crystals separated which, when ex- amined under the microscope, mere found t o consist entirely of the @modification of the acid." it Commercial sodiiini dihydroxytartrate gave an exactly similar result.DIITYDROXYTARTARIC ACID.PART I. 79 The constitution of this P-modification has not yet been ascertained, but it was shown (loc. cit., 69,561) that, not improbably, it is dihydroxy- fumaric acid. I f so, its productmion in the manner just described would seem t o be somewhat analogous t o the formation of pinacones, the group -Y=O -E-OH OH-C- becoming o=c- But this /3-acid may, instead, have the alternative formula suggested, namely, yH(OH) *COOH CO*COOH ' in which case the change would be readily understood. Hydrogen sulphicle or stunnous chloride, when used in limited quan- tity, effects a similar reduction. Action of Hydyoyen BronuzicEe.-Attempts were made by various methods to bring about the dehydration of dihydroxytartaric acid, and, with this object in view, the action of hydrogen bromide was studied. It has been previously shown that, in the case of dihydroxymaleic acid, the action of hydrogen bromide in glacial acetic acid solution brings about, as a final effect, the loss of 1 mol.H,O with production of the substance C,H,O, (which appears to be the lactonic acid corresponding with the p-form of the acid). Dihydroxytartaric acid, however, when submitted to this treatment, gave an altogether unexpected result. About 25 grams of the acid were mixed with 250 C.C. of glacial acetic acid, and the mixture satu- rated with dry hydrogen bromide a t about 15", when the acid dissolved completely after standing and shaking.The solution, after about 2 days, was heated in a pressure-bottle a t 60-7'0' for 2 hours, and the product, which was bright orange-red, was then distilled down to a small bulk under reduced pressure. It was observed that practically all the colour passed over with the first half, or so, of the distillate, leaving a colourless residue in the distilling flask. This residile, which set to a crystalline mass on cooling, was found to consist of two sub- stances, one of which was very easily soluble in ether, glacial acetic acid, or cold water, whilst the other was very sparingly soluble in these solvents; the appearance of the product was exactly like that which had been obtained in the case of dihydroxymaleic acid, and on testing it with ferric chloride and aikali, both the easily and the sparingly soluble portions were found to give the reactions of that acid.The sparingly soluble substance was then dissolved in the smallest possible quantity of hot water and cooled as quickly as possible, to avoid loss by decomposition, which began on heating, when crystals began to separate almost immediately ; these, on examination under the microscope, were seen t o consist of the characteristic diamond-80 FENTON : PROPERTIES AND RELATIONSHIPS OF shaped plates of dihydroxymaleic acid. A few crystals of the P-acid could also be distinguished, but this, of course, might be expected since the a-form is slowly transformed into the p-form by hydrogen bromide. The crystals mere collected, washed with a small quantity of cold water, air dried on filter paper for 24 hours, and analysed.0.1538 gave 0.1459 CO, and 0.0577 H,O. C,H,O,,BH,O requires C = 26.0s ; H = 4.02 per cent. That part of the residue which dissolved easily in ether, &c., cor- responded exactly with the product obtained when dihydroxymaleic acid was acted on by hydrogen bromide in acetic acid solution; the ethereal solution, on evaporation, gave radiating, feathery crystals which were extremely deliquescent. I t dissolved in alkalis giving a bright lemon-yellow solution, and on adding ferric chloride, the cha- racteristic blue-violet coloration wasmproduced. The aqueous solution, on standing for some hours, gave short prisms of the P-acid. It follows, therefore, from these results, that when dihydyox~turturic acid is acted on by excess of hydrogen bromide in presence of acetic acid, and the mixture afterwards distilled, a crystalline product is left which is identical with that obtained when dihydyoxyrnaZeic acid is treated in the same manner.The liquid distillate, however, is quite different. I n the case of dihydroxymaleic acid, it is practically colour- less and consists only of acetic and hydrobromic acids; but with dihydroxytartaric acid the first portions of the distillate are bright orange-red. When this distillate is diluted with water and shaken with ether or with carbon bisulphide, the orange-red substance may be extracted, and is found, by all the usual tests, to be bromine. Dihydroxytartaric acid therefore acts as an oxidising agent towards hydrogen bromide, liberating bromine, and becoming itself reduced to the acid C4H40A.This is the converse of the change by which dihydroxytartaric acid was prepared in the manner described above. C = 25-87 ; H = 4.16. The reaction C4H,06 + 2H,O + Br2 C4H,0, + 2HBr is therefore a reversibIe one, the direction depending on the masses of the reacting substances, and probably to some extent on the tempera- ture, The forward * change is brought about at the ordinary tem- perature, when bromine is added in excess, some water introduced, and the operation conducted in an open dish so as to allow of the free escape of hydrogen bromide. The reverse change takes place when a large excess of hydrogen bromide is used, and the mixture is heated in a closed vessel and afterwards distilled; it can take place, t o some * The terms “ forward ” and (‘ reverse ” are used, for shortness ‘ in the sense indicated by the arrows.STEREOCHEMISTRY OF UNSATURATED CARBON COMPOUNDS. 81 extent at any rate, at the ordinary temperature, for if dihydroxy- tartaric acid is mixed with excess of a saturated solution of hydrogen bromide in glacial acetic acid, allowed t.0 stand a few hours, and then kept in a vacuum desiccator over solid potash and sulphuric acid, the residue gives strongly marked reactions of dihydroxymaleic acid as well as of those of dihydroxytartaric acid. If the orange-yellow solu- tion, referred to above, be treated with water, it is instantly bleached, whereas the orange-yellow distillate obtained from it is not affected by water. It is possible that, both in the forward and reverse changes, the unstable compound, C,(OH)2Br2(COOH),' (dibromotartaric acid), is first produced as an intermediate stage, and that this, by the action of water, gives dihydroxytartaric acid, or by loss of bromine gives dihydroxymaleic acid. The reversibility of this action explains the fact, above mentioned, that, on adding bromine to the crystallised acid, the action appears to cease considerably before the calculated quantity of bromine has been introduced, but again proceeds rapidly on the addition of a small quantity of water.

ISSN:0368-1645    

DOI:10.1039/CT8987300071

出版商:RSC    

年代:1898

数据来源: RSC

摘要:

STEREOCHEMISTRY OF UNSATURATED CARBON COMPOUNDS. 81 V. -StereocImwis~~ y o f Uimturat ed Carbo 12 Compounds. Part I. EtheriJicntion of Substituted Acrylic Acids. By JOHN J. HUDBOROUGH and LORENZO L. LLOYD. IN a. series of communications presented to the German Chemical Society (Bey., 1894,27,510, 1580, and 3146), Victor Meyer and one of us were enabled t o show that, as regards the ease with which they are etherified, diortho-substituted benzoic acids differ completely from COOH their isomerides. Acids of the type x/\x , where X = C1, Br, NO,, COOH, &c., are entirely unacted on when their methyl alcoholic solu- tions are saturated with dry hydrogen chloride, either in the cold or a t the boiling point of the alcohol. Acids in which X = CH,, OH, F, &c., that is in which the weights of the substituting groups are small, yield minute quantities of their methylic salts when their boiling solutions are treated with hydrogen chloride for some time (V.Meyer, Rer., 1895, 28, 1259). V. Bleyer has since shown that the method of etheri- fication suggested b j 2, Fischer and Speier (Bey., 1895, 28, 3252), in I I VOL. LXXIII. u82 SUDROROUGH AND LLOYD : STEREOCHEMISTRY OF which the acid is boiled with a 3 per cent. solution of hydrogen chloride, yields similar results, and is preferable to the method first adopted, as many acids, which are but sparingly soluble or practically insoluble in cold methylic alcohol, dissolve readily on warming. It was stated by Victor Meyer and one of us that this abnormal behaviour of diortho- substituted benzoic acids is to be attributed to stereochemical causes, and Wegscheider (Monatsh., 1895, 16, 75) has since suggested that, if etherification be preceded by the formation of an additive compound of the acid and alcohol, the groups or atoms in the ortho-positions may be in such proximity to the csrboxylic group as to hinder or completely prevent the formation of the additive compound. This view is sup- ported by the fact that the radicle weight or volume plays an important part in the retardation or prevention of etherification (Meyer, Bey., 1895, 28, 1259).Recent investigations by Kellas (Zed. phys. Chenz., 1897, 24, 221) prove that the retardation is not merely due to the weight of the group in the ortho-position, as among ortho-substituted benzoic acids the nitro-group (NO, = 46) has a greater retarding influence than either bromine or iodine (Br = SO, I = 127).Menschutkin has also been able to draw generalisntions regarding the etherification of saturated acids of the aliphatic series from his researches on primary, secondary, and tertiary fatty acids * (Annalen, 1879,195,334, and 1879, 197, 193). Formic acid ...... 61.7 p. cent. Isobutyric acid ............ 29.0 p. cent. Acetic acid ...... 44.4 ,, Methylacetic acid ......... 21.5 ,, Propionic acid.. . 41.2 ,, Trimethylacetic acid ...... 8.3 ,, Butyric acid ... 33.3 ,, Dimethylethylacetic acid 3.5 ,, R \ From these results, it is evident that an acid with the grouping R,TC*COOH is much more difficult to convert into its ethereal salt than acids of the types RCH,* COOH and RR,CH* COOH, where R, R,, and R,, represent alkyl groups.The broader generalisation, that %I' acids of the type XI x \ -C COOH, where X not only represents alkyl XI/ groups but also C1, Br, NO,, &c., are difficult to etherify, does not, how- ever, hold good, since trichloracetic acid is more readily etherified than acetic acid itself. A reason for this anomalous behaviour of tri- halogenised acetic acid has been put forward by Feilmann and one of us (Proc., 1897, 241). * These numbers represent the initial velocity or the amount of acid (in percentage of the quantity originally present) converted into ethereal salt when nloIecular quantities of the acid and isobutylic alcohol are heated at 155" for 1 hour.UNSATURATED CARBON COMPOUNDS.PART I. 83 Although generalisations of the above nature have been made with reference to substituted benzoic acids, and also t o the fatty acids, no systematic study of unsaturated acids appears to have been made ; we therefore determined to prepare a number of the latter and to study the amounts of ethereal salt formed under different conditions, in order to find whether any general rules could be drawn from the results. A further incentive to this study was the suggestion made by one of us (Chem. News, 1895, 72, lS7) with reference t o the constitution of cam- phoric acid. I n that note, attention was drawn to the fact that Bredt's constitutional formula accounts for the characteristic behaviour of cam- phoric acid on etheritication with ethylic alcohol and hydrogen chloride, if the assumption be made that an acid with the grouping At the time this suggestion was put forward, no facts were known which justified the assumption, and it was partly with the object of determining whether further investiga- tions might supply satisfactory evidence on this point that the present research was started.Acids of the type mentioned are by no means oommon, whereas many acids are known of somewhat similar constitu- -7H2 7x0 COOH is difficult to etherify. -cx2 CXY CZ* COOH' tion, namely, unsaturated acids of the type I I We selected the latter class of acids as being the most suitable, and also because it seemed interesting to determine whether there was any great difference in the amounts of ethereal salt formed by the stereo- isomeric acids X* *H X- ;cI! *€I COOH* C *Y and Y*C*COOH' During the course of this investigation, a communication by Anschutz (Ber., 1897, 30, 2652) appeared whic' - ears on the same subject, with the exception that he investigated - -"w dicarboxylic acids, whereas we have restricted ourselves t o the study of monobasic acids.I n the summary a t the end of this paper, we discuss Anschiitz's results and compare them with our own. The following is a list of the acids we have investigated. Cinnamic acid, allocinnamic acid, atropic acid, ortho-, meta-, and para- a-Brornocinnamic acid and a-bromallocinnamic acid. The two isomeric P-bromocinnamic acids. The two isomeric up-dibromocinnamic acids. Dichloro- and di-iodo-cinnamic acids. nitrocinnsmic acids.84 SUDBOROUGH AND LLOYD : STEREOCHEMISTRY OX a-Cyanocinnamic acid, orthonitro-a-cyano- and metanitro-a-cyano- a-Phenylcinnamic acid and a-phenylallocinnamic acid.a-Phenylorthonitrocinnamic acid, a-phenylorthonitro-allocinnamic acid and the corresponding meta- and para-compounds. Triphenylacrylic acid. aj3-Di-iodoacrylic acid. The results obtained are given in tabular form a t pp. 91-92. I n some of our earlier experiments, we attempted to etherify the acids by saturating their methyl alcoholic solutions with hydrogen chloride in the cold and allowing the mixture t o stand for some time, but we found that this method was not adapted t o our purpose, as certain acids, especially nitrated acids, were almost insoluble in cold methylic alcohol and, therefore, yielded little 01- no ethereal salt by this treatment.I n all the later experiments, namely, those described in this paper, we used the Fischer-Speier met hod. A considerable amount of a 3 per cent. solution of hydrogen chloride in pure methylic alcohol (3 grams HCl in 100 grams of solution) mas prepared, and half a gram of the acid was boiled with 10 C.C. of this solution for an hour on the water bath, in a small flask fitted with a reflux condenser. For this purpose, the condenser described by Feilrnann and one of us (J. Xoc. Chem. Ind., 1897, IS, 979) is admirably adapted, as it does away with the possibility of moisture permeating the cork and thus vitiating the result. At the end of the specified time, water was added and the whole extracted twice with ether, any unaltered acid was removed by the aid of dilute sodium carbonate, and the ethereal solution, after drying with calcium chloride, was slowly distilled from a tared flask.The amount of ethereal salt formed was weighed after the flask had been standing over sulphuric acid for several hours. In all cases where the ethereal salts were solid, the residue was crystallised from methylic alcohol and the melting point taken. Oily ethereal salts were hydrolgsed, and the melting points of the acids thus obtained were determined. The melting points of recovered acids, in cases where etherification did not take place, or took place to but a slight extent, were also taken. cinnamic acid. Cinnanzic Acid, Allocinnamic Acid, and Atropic Acid. Ph.9.H H*c*Ph H*E-H H*C*COOH H*C*COOH Ph- C* COOH Cinnamic acid.Allocinnamic acid. Atropic acid. These three isomeric phlenylacrylic acids were first investigated. The The results, cinnamic acid obtained from Kahlbaum melted a t 133'. Nos. 1-8, obtained are given in the Table (p. 91).UNSATURATED CARBON COMPOUNDS. PART I. 85 The ethereal salt, after recrystallisation from methy lie alcohol, melted at 34" (Anschutz and Kinnicutt, Ber., 1879, 11, 1220, give 33.4'), and the regenerated acid obtained by hydrolysis melted at 133' (Kraut, Annalen, 1865, 133, 193, gives 133'). Allocinnamic Acid.-Prof. C. Liebermann, of Charlottenberg, was kind enough to provide us with about 2 grams of this acid, and we desire to express our thanks to him for his kindness. The acid melted at 68' (Liebermann, 68'). The results, Nos.9-14, are given in the Table, p. 91. The oily ethereal salt, after hydrolysis with warm potash, yielded an acid melting at 66-67'. It is thus evident that Fischer's method of etherification yields the salt of allocinnamic acid and not of cinnamic acid. Atropic Acid.-This acid, which we obtained from Schucharat, melted a t 106". The oily product, after hydrolysis with potash, gave an acid melting at 105'. The results, No. 15-22, are given in the Table. Ortho-, Afeta-, and Para-nitrocinnanaic Acids from Kahlbaum. Orthonitrocinrmnic Acid-See Table, Nos. 23 and 24. The ethereal salt, after crystallisation from methylic alcohol, melted a t 73' (Beilstein and Kuhlberg, Annalen, 1872, 163,126, give 72-73'), Metanitrocinnanaic Acid.-See Table, Nos. 25 and 26. This ethereal salt does not appear to have been described before.It crystallises from methylic alcohol in pale yellow prisms melting a t 123-124O. It is only sparingly soluble in methylic OF ethylic alcohol, and in ether or carbon bisulphide, but dissolves readily in chloroform or benzene. 0.500 gave 28.8 C.C. of moist nitrogen at 17" and 757 mm. N = 6.65. Theory requires 6.76 per cent. Paranitrocinnamic Acid.-See Table, Nos. 27 and 28. As the ethereal salt is almost insolublein ether, the amount formed could not be determined by the usual method. The process we adopted was as follows: water was added a t the end of the hour, the pre- cipitate collected, treated with dilute sodium carbonate solution in order to remove any unaltered acid, and then washed, dried a t loo', and weighed. After recrystallisation from alcohol, in which it is only slightly soluble, it melted a t 160' (Kopp, Jahyesbeyicht, 1861,410, gives 161").86 SUDBOROUGH AND LLOYD : STEREOCHEMISTRY OF a- am? p-Bromocinrzarnic Acids, Ph:R*H H*g*Ph Ph*fl*Br Br 9 -Ph Br*C*COOH Br-CGOOH H*C*COOH H*C*COOH a-Bromocinnamic a-Bromallo- B-Bromocinnamic B-Bromallo- acid.cinnamic acid. acid. cinnamic acid. The two a-acids were obtained by the method described by Scock- meyer (Diss., 1883), namely, by the action of alcoholic potash on cinnamic acid di bromide, and were separated by fractionally precipi- tating the solutions of their potassium salts with hydrochloric acid. The a-bromocinnamic acid, purified by crys tallisation of its sparingly soluble ammonium salt, melted a t 131O.Br = 35-21, C,H,*CH:CBr*COOH requires Br = 35.24 per cent. 0.200 gave 0.1656 AgBr. The results obtained with a-bromocinnamic acids, Nos. 29 and 30, The a-bromallocinnamic acid, after purification by recrystallisation 0.200 gave 0.1662 AgBr. Br = 35.36. Theory requires 35.24 per cent. The results obtained with a-bromnllocinnamic acid, Nos. 31-34, are given in the Table, As we thought the somewhat high numbers in 31-32 might be due to the presence of a small quantity of the isomeric acid melting at 131°, we took the acid recovered from the above experiments, and determined the amount of ethereal salt formed from this ; the results, Nos. 33 and 34, agree with those given above, The oily ethereal salts, when hydrolysed with cold aqueous potash, yielded an acid melting at 119O. From the fact that it crystallised from water in plates, that it dissolved with the greatest readiness in ammonia, and also from its melting point, the acid thus obtained was undoubtedly the a-allo-acid.From this, it is apparent that a-bromallocinnamic acid is converted into its true ethereal salt, and not into the isomeric a-bromocinnnmate, when etherified by Fischer’s method ; whereas, when its alcholic solution is saturated with hydrogen chloride, molecular rearrangement occurs, and the salt of a-bromocinnamic acid is obtained. The isomeric P-brom-acids were obtained by the method described by Michael and Brown (Ber., 1886, 19, 1379, and 1887, 20, 552), and we are able t o confirm their work in every respect; the two acids were separated by crystallieation, first from alcohol and then from chloroform, as these chemists recommend.are given in the Table (p. 91). from water, was obtained in glistening plates melting a t 1 2 0 O .UNSATURATED CARBON COMPOUNDS. PART I. 87 The P-bromocinnamic acid melting a t 134-135" crystalliscs from its chloroform solution on spontaneous evaporation in well-developed cubical crystals, 0.200 gave 0,1645 AgBr. Br = 35 0. Theory requires 35.24 per cent. The results obtained with this acid, Nos. 35-42, are given in the Table, p. 91. The oily ethereal salt, on hydrolysis, gave an acid which melted at 133-134", after recrystallisation from carbon bisulphide. P-Bronu;cZZocinnamic acid (see Erlenmeyer, Ansaalen, 1895, 287, l), melting a t 159O, is readily obtained pure after one recrystallieation from a small quantity of alcohol.0*2044gave0*1701 AgBr. Br = 35.42. Theoryrequires35.24 per cent, The results, Nos. 43-48, are given in the Table. The methylic salt crystallises from alcohol in thick, colourless prisms melting a t 58". It is moderately soluble in ethylic alcohol or benzene, and dissolves with great readiness in ether, chloroform or carbon bisulphide. 0.2423 gave 0.1887 AgBr. Br = 33.06. 0.2582 ,, 0.2019 AgBr. Br=33*28. Theory requires 33.19 per cent. The ease with which the two P-brom-acids can be obtained pure by following Michael and Brown's directions renders inexplicable such statements as those of Liebermann and Scholz (Ber., 1892, 25, 552) and of Erlenmeyer (ibid., 1886, 19, 1936) that the acid melting at 133-134' does not exist.Dichloro-, Dibromo-, alzd Di-iodo-cinnamic Acids, Ph*E'C1.-This acid Ph*g*Cl or C1 C* COOH COOH-C-Cl Dichlorocinnumic Acid, was prepared by saturating a chloroform solution of phenylpropiolic acid with chlorine. After recrystallisation from light petroleum, il melted a t 120' (Nissen, Ber., 1892, 25, 2665, gives 120-121"). The results, Nos. 49 and 50, are given in the Table. The ethereal salt was obtained in the form of an oil. Bib~*omocinnarnic Acids.-Two isomeric dibrom-acids were obtained by adding bromine to phenylpropiolic acid in chloroform solution (Roser and Haselhoff, Annalew, 188S, 24'7, 139) ; they were separated by dissolving them in a small quantity of chloroform, and adding lightS8 SUDBOltOUGH AND LLOYD : STEREOCHEMISTRY OF petroleum until a permanent turbidity was produced. The acid melting a t 139" crystallised first, and was purified by recrystallisation from boiling light petroleum (b.p. 60-80'). The isomeric acid melting a t 100' ma8 obtained pure only after repeated solution in chlorofcrm and precipitation by light petroleum. The results with the acid melting at 139" (Nos. 51 and 52), and with the acid melting a t 100' (Nos. 53 and 54), are given in the Table. The acid recovered from the former melted at 139". Di-iodocinnamic Acid, CIPh:CI* COOH, obtained by the method given by Liebermann and Sachse (Ber. 1891, 24, 4113), after several recrvtallisations from chloroform, melted at 167'. (1,. and S. give 171"). The results, Nos. 55 and 5 6 , are given in the Table (p. 92).The recovered acid melted at 170". a-Cyanocinnamic Acids. a-Cyanocinnamic acid, Ph0;CI.H or obtained NC*C*COOH CNCCOOH' by Carrick's method (J. pr. Chem., 1892, 45, 401), after recrys- tallisation from alcohol, melted at 180' (Carrick, 180'). See Table, Nos. 57 and 58. The methylic salt thus obtained crystallised from its alcoholic solution i n small, colourless prisms melting a t 89'. It is readily soluble in chloroform or ether, and moderately in alcohol, benzene, and carbon bisulphide. 0.5 gave 31.8 C.C. moist nitrogen at 13' and 752 mm. CHPh:C(CN)*COOMe requires 7.48 per cent. a-Cyctlzo-orthonitroc~nnccm~c Acid-The ethylic salt of this acid was obtained by the action of sodium ethoxide on a mixture of ethylic cyan- acetate and orthonitrobenzaldehyde (Riedel, J.pr. Chem., 1896, 54, 541), and was hydrolysed by the requisite quantity of normal sodium hydroxide a t about 60". The acid thus obtained melted at 223' (Riedel, 223'). The results obtained are given in Nos. 59 and 60 of the Table. The recovered acid melted at 220". The methylic salt crystallised from alcohol in small, discoloured needles melting a t 142'. a-Cyanometanitrocinnamic acid was obtained in a similar manner. We find that the ethylic salt melts a t 134', and that the melting point is not altered by repeated crystallisation from alcohol. (Riedel gives 0.4 gave 39.4 C.C. moist nitrogen a t 16" and 761 mm. N = 7.43. 1 2 7-1 2s'). N = l l 5 . N02*C,H,*CH:C(CN)*COOEt requires N = 11.38 per cent.TJNSATURATED CAREON COMPOUNDS. PART I , 89 The resulh, Nos.61 and 62, obtained with this acid are given i n the Table. The recovered acid melted a t 17O-17lo(Riedel, 172'). The methylic salt, after recrystallisation from alcohol, was obtained in fine, silky needles melting at 135-1 36", and readily soluble in the usual solvents. 0.3 gave 30.8 C.C. moist nitrogen a t 16' and 762 mm. N = 12.0. NO,*C,H,*CH:C'(CN).COOMe requires N = 12-07 per cent. a-Phen&innamic Acids, Ph*Q*H H*y*Ph Ph*C*COOH Ph*C-COOH a Phenylcinnamic acid. a-Phenylallocinnnniic acid. These acids were prepared and separated by Bskunin's method (Gaxx., The a-phenylcinnamic acid, melting a t 173", gave the results Nos. 63 The ethereal salt, after recrystallisation from alcohol, melted a t 77" The a-phenylallocinnamic acid, after crystallisation from water, was 1897, 27, ii, 48).and 64 of the Table. (Bakunin, 77"). obtained in colourless prisms melting a t 136'. The yield of allo-acid was extremely small. 0.5 gram, after 1 hour with 3 per cent. solution, gave 0.2137 gram ethereal salt. The methylic salt thus obtained was semi-solid, whereas Bakunin, who obtained the same compound by the action of methylic iodide on the silver salt of the acid, describes it as an oil. The solid we obtained apparently contained a considerable amount of the solid ethereal salt of the isomeric a-phenylcinnamic acid, as tho acid recovered from this first etherification yielded an oil when treated a second time with the 3 per cent. hydrogen chloride solution. The results are given in Nos. 65 and 66 of the Table. a-Phenylorthonitrocinnamic Acids.-A mixture of the two isomeric acids was obtained by the action of acetic anhydride and sodium phenylacetate on orthonitrobenzaldehyde (Bakunin, Gaxx., 1895,25, i, The recovered acid melted a t 137-138'.NO,*C!,H,*fi*H Ph*C*COOH' was 137). The a-phenylorthonitrocinnamic acid, readily obtained pure by Bakunin's method. It melted a t 195-196', and on etherification gave the results Nos. 67 and 68 of the TabIe. The ethereal salt, after recrystallisation from alcohol, melted a t 7 5 O (Bakunin, 75-76'),90 SUDBOROUGH AND LLOYD : STEREOCHEMISTRY OF A mixture of the above acid with the isomeric allo-acid was obtained by Bakunin's method; it melted a t 155", whereas the pure allo-acid melts at 146-147'. We adopted the following method for its purifica- tion.The mixture of acids was boiled for 1 hour with a 5 per cent. solution of hydrogen chloride in methylic alcohol, 20 C.C. of this solution being used for each gram of the mixed acids; after etherification, the solution was poured into water, extracted with ether, and the ethereal solution washed with sodium carbonate solution ; on the addition of hydrochloric acid to this alkaline solution, the a-phenylorthonitroallo- NO,*C,H,*Y*II cinnamic acid, , was thrown down, and after recrystal- COOH*C*Ph lisation from dilute acetic acid melted a t 146'. Whether the results, Nos, 69 and 70 in the Table, are somewhat too high owing to the presence of a small quantity of the isomeric acid, we cannot at present say with any degree of certainty, as the yield of allo- acid is extremely poor and we had but a gram or so at our disposal.a-Phenylrnetnnitrocinnanaic Acids.-The two acids were obtained by Balrunin's method (Zoc. cit.). The a-phenylmetanitrocinnamic acid melted a t 181' and gave the results Nos. 71 and 72 in the Table (p. 92). The ethereal salt, after recrystallisation from alcohol, melted a t '72'. a-PhenyZnaetnnitroaZlocinnarnic acid melted a t 196". The results, Nos. 73 and 74, obtained with this acid are given in the Table. a-P~~enylIoarc~nitrocin?zccr~zic acid melting a t 2 14' gave the results Nos. 75 and 76 of the Table. The ethereal salt crystallised from alcohol in yellow needles melting a t 141-142' (Bakunin, 141-142'). a-Phenyi'paranitronllocinnanzic acid melted a t 144' (Ba,kunin, 142'). For results, see Nos.77 and 78 of Table. The recovered acid meltedat 144'. Triphenylacrylic acid, CPh,:CPh*COOH, was prepared from the acid amide (Heyl and Meyer, Bey., 1896,29,2786) by a method very similar to that adopted by Heyl and Meyer, except that we used the amide, in a fine state of division, suspended in dilute sulphuric acid, and kept the mixture well stirred by an automatic stirrer while the nitrite solution was being run in ; the acid thus obtained melted a t 213'. The results of etherification, Nos. 79 and 80, are given in the Table. The unaltered acid melted a t 213-214". Heyl and Aleyer (Zoc. cit.) have already shown that this acid is only slowly etherified when hydrogen chloride is passed for several hours through its solution in boiling methyl alcohol. ap-Di-iodacqZic acid, CHI :CI*COOH.-This acid was prepared by the addition of iodine to propiolic acid, as described by Bruck (Ber., 1891, 24, 4120) ; after recrystallisation from chloroform, it melted a t about 7 6 O , but after recrystallisation from water at 104' (Bruck, 104').1 2 3 4 5 6 7 a 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 29 30 31 32 33 34 35 36 37 38 39 40 4 1 42 43 44 45 46 47 48 28 10 UNSATURATED CARBON COMPOUNDS.Table of Results. o * A l < A PART I. 0.5 0.5 0 -5 0.5 0.5 0.5 0.5 0 *5 0 -5 91 Name of acid. Cinnaniic. Do. Do. Do. Do. Do. Do. Do. Allocinnamic. Do. Do. Do. Do. Do. Atropic. Do. Do. Do. Do. Do. D O . Do. Orthonitrocinnnmic. Do. Metanitrocinnamic. Do. Paranitrocinnamic. DO. a-Bromocinnamic. Do. a-Bromallocinnamic. Do. Do.Do. 8-Bromocinnamic, m. p. 134-135". Do. DO. Do. Do. Do. Do. Do. 3-Bromallocinnamic, m. p. 159". Do. Do. Do. Do. Do. ;ram. 0.5 0 -5 0.5 0 *5 0.5 0.5 0.5 0.5 0.5 0 *5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0-5 0-5 0 -5 0-5 per cent. 3 3 3 3 1 1 1 1 3 3 3 3 1 1 3 3 3 3 1 1 1 1 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 1 1 1 1 3 3 1 1 1 1 I 10 ' 1 0 ' 10 , 10 j :; I ;: 10 1 0 10 10 1 0 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 1 0 10 1 10 - z .* i. .iiiiis. 60 63 10 10 60 60 30 30 60 60 10 10 60 3 0 60 60 10 10 60 60 30 30 60 60 60 60 60 60 60 ti0 60 60 60 60 60 60 60 60 10 1 60 10 70 10 10 10 10 10 10 60 30 30 6C 60 60 60 30 gr. 0.5425 0.5417 0.4958 0'4982 0.5433 0'5459 0.4996 0.5033 0'5282 0'5304 0'4269 0'4261 0'4820 0.4692 0.5102 0.5112 0.3420 0.3421 0.4442 0'4408 0,2989 0.3023 0.3176 03195 0.5227 0,5203 0.5223 0.5218 0'4091 0'4038 0.1312 0'1302 0.1332 0.1312 0.5291 0.5308 0.5256 0'5281 0.4666 0'4698 0'4222 0'4231 0.5241 Os5260 0'4648 0.4630 0.4165 , "" , " L A V A I A" I , I 1 I 2 2 2.zi 0% 4 x 3 g g 5 sz W ' c d 99.12 99.64 90.60 91-02 99-28 99.74 91.25 91 '96 96.52 96 -92 18.00 77.86 88.06 85 '73 98.22 93 '40 62.50 62.52 81.16 80.54 54.62 55.23 59.22 59.58 97'48 97.02 97.40 97.30 77.06 76-06 24-72 24.52 25-09 24'72 99.68 100*00 99.02 99.48 87.90 88.50 79.54 79.70 98.74 99.08 87.56 87-22 78.46 78-2692 XTJDBOROUGH AND LLOYD : STEREOCHEMISTRY OF TabZe OJ Results-(continued).49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 - Name of acid. Dichlorocinnaiiiic.Do. Dibromocinnamic, in. p. 139". Do. Iibromocinnamic, m. p. 100" Do. Di-iodocinnamic. Do. a- Cyanocinnamic. Do. a-Cyano-orthonitro- cinnamic. Do. x-Cyanometanitrocinnan~ic. Do. a-Phenylcinnaniic. Do. a-Phenylnlloeinnamic. Do. a-Phenylorthonitro- cinnamic. Do. a-Phenylorthonitroallo- cinnamic. a-Phenvlorthonitroallo- cinnamic. .-Phenylmetanitrocinnamic Do. a- Phenylmetanitroallo- ciunainic. Do. a-Phen ylparani troci 11 nmnic Do. a-Phen ylparanitroaI10- cinnamic. Do. Triphen ylacry lic. Do. aj3-Di-iodacry lic. Do. gram. 0'5 0.5 0 -5 0.5 0.5 0 '5 0.5 0.5 0.5 0-5 0.5 0.5 0.5 0.5 0.5 0.5 0-5 0.5 0.5 0 -5 0.5 0.5 0 *5 0 -5 0.5 0.5 0 ' 5 0'5 0.5 0 -5 0 '5 0.5 0.5 0.5 - per cent. 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 C.C.10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 - mins. 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 - gr . 0.1645 0'1615 0'0414 0.0428 0.0700 0,0687 0'0109 0.0102 0.3466 0'3472 0.2677 0,2702 0.3203 0.3176 0-3981 0.4013 0.0631 0.0596 0.3974 0,3982 0.0813 0.0795 0.3829 0.3849 0'0744 0.0710 0,3746 0.3804 0-0684 0.0657 0'0112 0'0124 0.0387 0.0352 - 30 -90 30'34 7 -92 8-19 13.38 13'13 2.10 1-96 64'14 64'24 50'32 50.78 60'20 59.70 74-94 75.54 11'88 11'22 75.55 75.70 15'45 15'11 72.79 73'17 14.14 13'53 71-21 72.32 12'99 12.48 2'14 2 3 7 7'42 6-75 The results obtained with this acid, Nos. 81 and 82, are given in the Table. The recovered acid melted at 103-104".UNSATURATED CARBON COMPOUNDS.PART I. 93 Discussion of Results. From the results of the experiments described in the pi*eceding pages, we consider ourselves justified in drawing the following con- clusions. 1. Unsaturated acids which, in addition to an a-substituting group, also contain a radicle in the cis-position relatively to the carboxylic group, that is, acids of the type H*G*X Y C* COOH are difficult to etherify when boiled for an hour with a 3 per cent. solution of hydrogen chloride in methylic alcohol. The same property is also characteristic of acids in which the third hydrogen atom of acrylic acid is replaced by a substituting group z* E'X Y* C-COOH' 2. Di-substituted acrylic acids in which one group is in the a-position and the other in the t~ans-position relatively to the carboxylic group, are readily etherified under the conditions given above.Y*I;;'*H X* C*COOH This remarkable difference in behaviour supplies us with a simple method of determining the configurations of stereoisomeric acids, CHX:CY*COOH, where X and Y may be alike or dissimilar. We require merely to boil half a gram of each acid with 10 C.C. of a 3 per cent. solution of hydrogen chloride in methylic acid, and determine which acid yields the larger percentage of ethereal salt. This acid will be the one with the substituting group in the trans-position, and the acid which yields little or no ethereal salt wiil have the substituting group in the cis-position. We also think it probable that this difference on etherification may be made use of in the separation of such stereoisomeric acids, in very much the same manner as Martz (Ber., 1894, 27, 3147) and Jannasch and Weiler (ibid., 3447) have been able to separate diortho-substituted benzoic acids from their isomerides.The separaT tion in the acrylic series will not be so complete as in the benzoic, as, according to our results, the difference on etherification is not so marked as in the benzoic series. We have found that the method can be used with advantage in the separation of a-phenylallocinnamic acid from a-phenylcinnamic acid, and it can undoubtedly be used with equal94 SUDBOROUGH AND LLOYD : STEREOCHEMISTRY OF advantage in the separation of the corresponding nitro-acids. The method adopted by Bakunin (Zoc. cit.) for the purification of these acids is lengthy and tedious, and can probably be considerably curtailed by the process of etherification.We may point out that our results confirm in a remarkable manner the constitutions of the a-phenylcinnamic acids arrived a t by Bakunin from entirely different considerations. 3. Substituted acrylic acids in which the substituting groups are only in the P-position are readily etherified under the conditions given above. As examples of this generalisation, we have the two P-bromo- cinnamic acids, both of which yield over 90 per cent. of ethereal salt. We are a t present engaged in preparing PP-di-iodacrylic acid, and hope shortly to be able to state that this obeys the same lam. 4. The results we have obtained with mono-substituted acrylic acids are somewhat too meagre for us to draw general conclusions with any degree of certainty ; those, however, which we have so far obtained by using more dilute solutions of hydrogen chloride, namely, a 1 per cent., in methylic alcohol, seem to indicate that a n a-substituted acrylic acid is more difficult to etherify than the isomeric P-compound.I n support of this, we have the fact that atropic acid (a-phenylacrylic acid) is more difficult to etherify than either of the P-phenylacrylic acids (cinnamic and allocinnamic acid), This conclusion is further supported by Anschutz’s results (Ber., lS97’,30,2652). Anschiitz finds that mesaconic acid, Me*f?cooH, when boiled for a short time COOH-C-H with a 0.5 per cent. solution of hydrogen chloride, yields the mono- Me* R*COOH methylic salt, C0OMe.C-H The differences between cinnamic and allocinnamic acids point to the conclusion that a P-substituted acrylic acid, in which the sub- stituting radicle is in the cis-position relatively to the carboxylic group, is more difficult to et,herify than the isomeric trans-compound.We give these generalisations with the greatest reserve, as further investigations with other acids, for example, crotonic acids, are necessary to prove whether they are correct. 5. The radicle weights or volumes of the substituting groups in the a- and cis-positions appear to be an importaat factor in determining the actual amount of ethereal salt formed in each case. A survey of the results obtained with dichloro-, dibromo-, and di-iodo-cinnamic acids brings out this generalisation with great clearness. The dichlor- acid yields more ethereal salt than either of the two dibrom-acids, and these again yield more than the di-iodo-acid.This conclusion is entirely in accordance with V. Meyer’s work on diortho-substituted benzoic acids, and with that of Kellas (2. physik. CThern, 1897, 24,UNSATURATED CARBOK COMPOUNDS. PART I. 95 221) on mono-substituted benzoic acids, and also with our own on substituted benzamides (Trans., 1895, 233). 6. The presence of a nitro-group in the ortho-position in cert'ain cinnamic acids, for example, in orthonitrocinnamic acid itself, and also in a-cyano-orthonitrocinnamic acid, appears t o have a retarding influence on the formation of the ethereal salt. This is in complete harmony with a suggestion made by Victor Meyer and one of u s several years ago, but which received no support from actual experi- ment conducted a t that time (Bey., 1895, 28, 1267).It is a well known fact that ortho-substituted cinnamic and hydrocinnamic acids readily undergo condensation, yielding ring compounds. For example, CH /\/\CH \/\//C*oH /\GH:CH* COOH gives I I I N CH', The fact that the isomeric meta- and para-compounds undergo no similar condensations is supposed t o be due to the fact that, in these acids, the substituting groups are not sufficiently near to the car- boxylic group t o allow of the elimination of H,O, HBr, &c The results we have obtained may be due to the fact that the nitro-group is in closer proximity to the carboxylic group in the ortho-acids than in the meta- and para-acids, and this may account for the retardation.If so, we should expect to meet the same phenomenon in all ortho- substituted cinnamic acids, and also in diortho-substituted cinnamic acids. This is a point which we consider deserves a little more atten- tion, and we purpose studying a number of these acids. 7. The results we have obtained by the etherification of allocinnamic acid and a-bromallocinnamic acid indicate that Fischer's method of etherification yields the ethereal acids of the allo-acids, and not those of the more stable isomeric acids. This is an extremely interesting point, since other authorities state that these allo-acids, when their alcoholic solutions are saturated with hydrogen chloride and allowed to stand, yield the ethereal salts of the more stable acids.8. In the introduction to this paper, we stated that one of the reasons for undertaking the investigation was t o account for the characteristic behavionr of camphoric acid on etherification by the aid of the stereochemistry of the acid molecule. As the result of our96 STEREOCHEMISTRY OF UNSATURATED CARBON COMPOUNDS. investigation, we are able t o state that in unsmturated acids a carb- oxylic group which bas substituting groups in the a- and cis-positions with respect to itself is difficult to etherify. It is true that in Bredt’s formula for camphoric acid, and also in the newer formula suggested by W. H. Perkin, jun. (Proc., 1897, ZlS), one of the carboxglic groups is thus situated, i t has substituting groups in the a- and also in the cis-position. The other carboxylic group in camphoric acid is not so situated; it has a substituting group in the cis-position, but none in the a-position. We consider, then, that our results render the behaviour of camphoric acid on etherification explicable if we adopt either Bredt’s or Perkin’s formula. The same remarks, however, do not apply to Tiemann’s formula (Bey., 1895, 28, 1079) : Me2- 7H2 (?Me, YH* COOH UHMe- CH* COOH CH,* YH-COOH CH,* CMe*COOH CMe(CO0H)-CH, The great difference is that camphoric acid is a ring compound, whereas our researches have been limited to aliphatic unsaturated acids. 9. The results we have obtained are in complete harmony with the configurations of unsaturated acids according to the van’t Hoff - Wislicenus theory, and we consider that they establish with certainty the conclusion previously arrived at, namely, that in what are usually termed cis-substituted monocarboxylic acids the substituting group is in closer proximity to the carboxylic group than when it is in the trams-posi t ion. I n conclusion, we may state that, having obtained such interesting results with monocarboxylic acids, we a t once turned our attention to dibasic acids. From a private communication from Professor Anschiitz, we learn that he has already taken up the study of a number of such acids in the direction indicated in the Berichte, and we have therefore not investigated any of these acids ourselves. The question whether generalisations similar to those we have obtained for unsaturated acids may not also hold, to some extent, for saturated acids immediately presented itself to us, and the fact that such acids as dibromosuccinic acid, dibromhydrocinnamic acid and it,s nitro-derivatives, are difficult to etherify indicates that interesting results may probably be obtained in this direction, FH*COOH 1 $JH2 Perkin. Tiemann , P 1 ?Me2 Bredt. UNIVERSITY COLLEGE, NOTTINGIIAM.

ISSN:0368-1645    

DOI:10.1039/CT8987300081

出版商:RSC    

年代:1898

数据来源: RSC

摘要:

KEKULE MEMORIAL LECTURE * (DELIVERED ON DECEMBER 15th, 1897.) By FRANCIS R. JAPP, F.R.S. THE great chemist whose life and work I shall endeavaur to pass in brief review before you this evening, was not one of the popular heroes of science. Whatever may have been his qualifications for playing such a part-and surely, great natural eloquence, unfailing lucidity, and a humour that enlivened the discussion of even the driest sub- jects, are to be thus regarded-he apparently disdained to put them to so ignoble a use as the achievement of mere popular fame. H e brought an intellect of incomparable power and subtlety to bear on problems so abstruse, so remote from the everyday thoughts and inte- rests of mankind, that the vast majority even of educated persons have never heard either of the problems, or of the man who did so much t o solve them, The greater, then, is the need that we, who realise both the direct scientific value of Kekuld’s work and the furthering influence which, in spite of its apparent remoteness, it has exercised indirectly on the welfare of mankind, should place on record our sense of his high deserts.Friedrich August Kekul6-he made use of only the second of his Christian names-was born at Darmstadt on September 7th, 1829.j- His father was a Hessian Oberkriegsrath. Even as a boy, Kekule displayed remarkable powers ; at the Gymnasium of his native town he distinguished himself in mathematics and in drawing ; whilst outside the school curriculum his instincts as an observer found congenial scope in the study of the flora and butterflies of the district.After passing the leaving examination at the Gymnasium in 1847, he determined, in accordance with his father’s wish, to become an architect, and for this purpose entered as studiosus architectum a t the University of Giessen. Kekulh, in later life, by no means regarded the time thus spent as masted ; he always laid stress on the turn which the study of archi- tecture had given to his thoughts; on the necessity which he ever afterwards felt of having before him, if possible, an actual picture of any problem he was dealing with. H e was doubtless right. After * Chemical Society’s Memorial Lectures, No. VII. t For the facts of Kekuld’s life I am indebted partly to two obitnary notices : one by Wallach (Nntu?.wisserLschaft~~~hc h’undschau, 1896, 13, 437) and the other by Konigs (Hiinchener Medicinische Wocheszschrift, 1896, 39, 920) ; and partly to ICekulQ’s well known address delivered before the German Chemical Society in 1890 on the occasion of the KekuZdfeier.VOL. LXXIII. H98 JAPP : KEKULI~ MEMORIAL LECTURE, all, he remained an architect to the last : only it was the architecture of molecules, instead of that of buildings, with which it was his lot t o concern himself. I n any case, chemists may feel thankful that KekulB’s architectural studies led him t o the University, instead of into an architect’s office. Liebig was then at Giessen; KekulC. attended his lectures on chemistry ; and such was the fascination both of the lecturer and of the subject, that the young student resolved to abandon architecture and devote himself entirely t o chemistry.His relatives insisted that he should take sufficient time to consider his decision ; and he therefore returned to his native town, where he spent a semester studying a t the Poly- technic School. At the end of that time he returned to Giessen and entered the University Laboratory as a pupil of Liebig and Will. His first research, carried out under Will’s guidance, was an investi- gation of amylsulphuric acid and its salts, published in 1850. About this time, Liebig offered Kekuld an assistantship, which, however, he declined, as he was enabled, through the generosity of a stepbrother, a merchant in London, to study for a year in Paris. Here he remained from 1851 to 1852, attended Dumas’ lectures, and made the acquaintance of Wurtz, Cahours, Regnault and others.Of most influence on the forma- tion of KekulB’s views, however, was the friendship which he formed with Gerhardt, the originator of the type theory, whose great TmitS de Chimie O~ganipue, then just ready for the press, he was allowed t o read in manuscript. On returning to Germany, he graduated as Doctor of Philosophy at Giesseu in 1852. H e then obtained his first appoint- ment, that of private assistant to Baron von Planta, at whose beauti- fully situated chiiteau, Reichenau, near Coire, in Switzerland, he spent a 3 ear and a half. H e published, jointly with von Planta, two papers on the action of ethylic iodide on nicotine and coniine, and some elaborate analyses of Swiss mineral waters; the latter work can hardly have been very congenial to Kekul6, who, as he afterwards said, was employing the leisure and freedom from distractions which his post afforded, in elaborating the ideas which he had found in Gerhardt’s unpublished manuscript.I n January, 1854, he exchanged his assistantship with von Planta for a similar post with Stenhouse in London. Here he became intimate with Williamson and Odling, both of whom, but especially the former, exercised great influence on the development of his ideas. H e says : ‘‘ If in Paris I had an opportunity of acquainting myself with Gerhardt’s unpublished views, I had now the good fortune to enter into active friendly intercourse with Williamson and to familiarise myself with the modes of thought of this philosophical intellect.‘‘ Originally a pupil of Liebig, I had become a pupil of Dumas, Gerhardt, and Williamson : I no longer belonged to any school.”JAPP : KEKULE MEMORIAL LECTURE. 99 The training which Kekule received during these Wunderjahre was undoubtedly the best he could possibly have had for the task he was destined t o perform. Suppose that, instead of going to Paris, he had been shortsighted enough to accept the assistantship which Liebig offered him. I n that case he might have shared the fate of many promising students who have been promoted to be the assistants of their teachers; he might have gone on producing research work cut to a single pattern; he might have become a ?‘&vatdocent i n the institution in which he was trained; and so on to the end of the chapter.Not that a man of Kekule’s originality and strength of intellect could ever have been satisfied to play the part of a more scientific hodman ; but had he been hampered by a one-sided training, it might have been much longer before he discovered where his strength as a reformer lay : in fact he might not have discovered it at all until the brief period-the too brief period-during which the great creative geniuses of science really create, was in his case past. A Kekule trained solely in Liebig’s laboratory would never have adopted the masterful attitude of the actual Kekule towards tho doctrines of the school of Berzelius; and although he might have excited the ire of some of his opponents less, organic chemistry would have moved more slowly.Kekule always emphasised the necessity for getting rid of pre- conceptions due to early training. “ Free yourselves from the spirit of the school,” he said ; ‘‘ you will then be capable of doing some- thing of your own. Remember that it was Mephisto who gave the Scholar the advice : Am besten ist’s auch hier, wenn Ihr nur Einen hort Und auf des Meisters Worte schwort.” A few months after his arrival i n London Kekule published his well-known “Note on a new Series of Organic Acids containing Sulphur” (Annulen, 1854, 90, 309 ; PTOC. Boy. Xoc., 1856, ’7, 37- received April 5, 1854). This paper is noteworthy as the first published work of Kekule’s which exhibits his distinctive modes of thought. Various passages contained in it clearly show that, although only briefly indicated, a t least the germ of his later system, the linking of atoms in terms of their valency, was present to his mind.I will illustrate this more fully later on when I come to deal with Kekule’s theoretical views. Meanwhile, in the present merely historical con- nection, the interesting passage from his speech delivered before the German Chemical Society (Bey., 1890, 23, 1306) on the occasion of celebrations held in his honour, in which he describes the origin of the idea of the linking of atoms, may be quoted. The local colour should commend it to a London audience. H 2100 JAPP : KEKULE MEMORIAL LECTURE!. “ During my stay in London I resided for a considerable time in Clapham Road in the neighbourhoocl of the Common. I frequently, however, spent niy evenings with niy friend Hugo Muller at Islington, at the opposite end of the giant town.We talked of many things, but oftenest of our beloved chemistry. One fine summer evening I was returning by the last omnibus, ‘ outside,’ as usual, through the deserted streets of the metropolis, which are at other times so full of life. I fell into a reverie (Triiumeyei), and lo, the atoms mere gambolling before my eyes ! Whenever, hitherto, these diminutive beings had appeared to me, they had always been in motion ; but up t o that time I had never been able to discern the nature of their motion. Now, however, I saw how, frequently, two smaller atonis united to form a pair ; how a larger one embraced two smaller ones ; how still larger ones kept hold of three or even four of the smaller ; whilst the whole kept whirling in a giddy dance.I saw how the larger ones formed a chain, dragging the smaller ones after them, but only at the ends of the chain. I saw what our Past Master, Kopp, my highly honoured teacher and friend, has depicted with such charm in his ‘ Moleknlar- welt ’ ; but I saw it long before him. The cry of the conductor : ‘ Clapham Road,’ awakened me from my dreaming ; but I spent a part of the night in putting on paper at least sketches of these dream forms, This was the origin of the Structuvtheoyie.” Then he relates a similar experience of how the idea of the benzene theory occurred to him. This refers to a later period, when Kekule mas professor in Ghent, but may be quoted here in connection with the previous passage. He describes how he was a t work one evening : “ I was sitting, writing at my .text-book ; but the work did not progress ; my thoughts were elsewhere. I turned my chair to the fire and dozed.Again the atoms were gambolling before niy eyes. This time the smaller groups kept modestly in the background. My mental eye, rendered more acute by repeated visions of the kind, could now distinguish larger structures, of manifold conformation : long rows, sometimes more closely fitted together ; all twining and twisting in snake-like motion. What was that ? One of the snakes had seized hold of‘ its own tail, and the form whirled mockingly before my eyes. As if by a flash of lightning I awoke ; and this time also I spent the rest of the night in working out the consequences of the hypothesis.‘‘ Let us learn to dream, gentlemen,” adds Kekult5, “ then perhaps we shall find the truth . . . , but let us beware of publishing our dreams before they have been put to the proof by the waking understanding.’’ After his return from England, Kekule went to Heidelberg, where on February 29th, 1856, he obtained the venia legend; in Chemistry at the University. The young Privatdocent fitted up a modest laboratory consisting of a room with a kitchen adjoining it. Among the few students whom he could accommodate was Adolf Baeyer, who there carried out his well-known work on the organo-arsenic compounds. Kekulk himself prepared the experiments and most of the specimens f o r his lectures on organic chemistry. Generally the last item of his But look !JAPP : KEKULE MEMORIAL LECTURE.101 hard day’s work was the sweeping out of the class room against next morning’s lecture. The various investigations which Kekuli: published about this time, excellent as they were from an experimental point of view, were still more remarkable for the theoretical conceptions which they embodied ; indeed, in the latter respect, as every chemist knows, they inaugurated a new era in organic chemistry. The two papers on the constitution of mercuric fulminate (1857 and 1858); that on the so-called con- jugated compounds and the theory of polyatomic radicles (1857), which contains a complete system of multiple types and mixed types based on this theory; those on the conversion of acetic acid into glycolic acid and on chlordide (1858) and finally, the celebrated paper “ On the Constitution and Metamorphoses of Chemical Compounds and on the Chemical Nature of Carbon ” (Annden, 1858, 106, 293), which con- tained a full statement of Kekulh’s views on the linking of atoms-the foundation on which our modern system of constitutional formulae rests-attracted the attention of chemists throughout the world, with the result that, in 1858, Kekulk, on Stas’s recommendation, was called as ordinary professor of chemistry to the University of Ghent.It might have seemed t h a t the inspiring influence of a great chemist and teacher had thus been lost to KekulB’s fatherland. But this was not the case. Thanks to the fact that in Germanya student need not have studied a t the university a t which he graduates, German students are attracted to teachers rather than to institutions; in fact, in their peregrinations from one university to another, they resemble the wandering scholars of former days.Many young Germans thus made the pilgrimage to Ghent t o study under Kekuli:: among their number Baeyer, Glaser, Hubner, Korner, Ladenburg, Linnemann and Wichelhaus.* Later on, these disciples, as teachers in the German universities, were instrumental in disseminating Kekulh’s doctrines. The nine years which Kekulk spent in Ghent were years of great productivity. I n the theoretical papers which he had up to that time published, he had laid down the lines of his future work-nay, of the future work of the organic chemists of his generation. That work would consist in experimentally verifying the innumerable predictions, and in considering the further logical consequences, of his theory.Of the investigations belonging to this period may be mentioned : those on organic acids, their basicity and hydricity (atomicity) ; on the re- lations between succinic, malic, and tartaric acids ; on the isomeric unsaturated dibasic acids-fumaric and maleic acids on the one hand, and mesaconic, citraconic and itaconic acids on the other-a marvellous piece of experimental work, in which, however, Kekuli: was less for- * Among English chemists, Dewar and G. Carey Foster studied under Kekul6 in Ghent.102 JAPP : K E K U L ~ MEMORIAL LECTURE. tunate than usual in the interpretation of his results, although, con- sidering the complexity of the problem, this was not to be wondered a t ; the conversion of hydroxy-acids into bromo-acids ; the electrolysis of dibasic acids; the synthesis of acids of the benzene series by the repla cement of bromine in bromobenzenes by carboxyl ; the elucidation of the constitution of azo- and diazo-compounds, and the transformation of diazo- into azo-compounds. The theoretical work is of course for the most part involved in the practical and cannot be discussed apart from it.One piece of theoretical work must, however, be specially mentioned. It is Kekuld’s benzene theory-the crowning achievement of the doctrine of the linking of atoms. OF this, more will be said later on. A new system of chemistry is not a proposition in Euclid, to be proved in a few words ; its proofs are cumulative, and its truth or error -or t o speak more accurately, its expediency or inexpediency-can be tested only by applying it to the whole body of the science.This is why so many of the great originators in our science have bent their minds t o the task of writing a text-book. The text-books of Lavoisier, Berzelius, Gerhardt, Kolbe and Kekulk are cases in point. The publication of Kekulb’s Lehr6uch dsr organischen Chemie falls for the most part within the Ghent period. The first instalment appeared in 1859. The effect produced by the book was enormous. The facts of organic chemistry appeared to group themselves spon- taneously under the new system. Whatever might be its ultimate fate, here was a method of exposition immeasurably superior t o any that had preceded i t ; and as a result, every text-book of organic chemistry that has since appeared has shown more or less distinctly the influence of this remarkable work.Even Kolbe’s accusation that the method owed its success t o the fact t h a t it saved chemists the trouble of thinking, may be regarded as indirect praise. Kekulb’s Lehbuch was never finished. The first instalment of the third volume appeared in 1867-the year in which Kekulk left Ghent-after which further publication ceased for thirteen years. On one occasion, Kekuld received from his students an amusing reminder that they desired to see the continuation of the work. It was at a Commers held at Bonn in the early seventies. For the benefit of those who may be unfamiliar with German academic customs, I may explain that the Commers is a students’ festivity in which the beer of the country plays an important part.Professors are frequently present by invitation, and just as, at the ancient saturnalia, the position of master and servant was reversed, so, a t these mild modern satumaclia, there is a certain relaxation of the attitude of strict respect which the German student otherwise maintains towards his professor. Thus cz professor may hear his work, or some literary orJAPP : KEKULB MEMORIAL LECTURE. 103 other controversy in which he is engaged, playfully discussed in a set of occasional verses, or made the theme of a humorous dramatic interlude enacted by the students. On the occasion referred to, Kekuli!, on taking his seat, Eound on the table in front of him what purported to be a complete, bound COPY of the only partially existent third volume of his Lehrbuch.On closer examination it proved to be a box, in book form, containing writing materials. KekulB enjoyed the joke, but declined to take the hint, a t least for the time being. Later on, in 1880, with the collaboration of Anschutz and Schultz, he returned to the work; but with the conclusion of the third volume this second attempt also collapsed. I n 186’7 Kekule was appointed to the Professorship of Chemistry in the University of Bonn. Here he found himself a t the head of a palatial laboratory, built shortly before from Hofmann’s designs. During the first part of the time which he spent a t Bonn his scientific activity continued, and he published various important researches, chiefly in collaboration with pupils.Among the numerous chemists who studied under Kekuli! at Bonn may be mentioned: Anschutz, Bedson, Bernthsen, Carnelley, Claisen, Dittmar, Franchimont, van’t Hoff , Klinger, Konigs, G. Schultz, Thorpe, Wallach, and Zincke. The research work belonging to this period deals with the following subjects, amongst others : phenylmercaptan and phenylic sulphide (investigated jointly with Szuch) ;, ethylbenzoic acid (with Thorpe) ; the formation of hydroxyazobenzene by the action of diazobenzene chloride on sodium phenoxide (with Hidegh) ; an aromatic glycolic acid -hydroxymethylbenzoic acid- (with Dittmar) ; the condensation pro- ducts and polymeric modifications of aldehyde (with Zincke) ; the action of phosphorus pentachloride 011 sulphonic acids (with Gibertini and BarLaglia) ; on triphenylmethane (with Franchimont) ; the formation of cymene and cyuiyl hydrosulphide by the action of phosphorus pentasulphide on camphor (with Pott and Flesch), and of cymene by the action of iodine on oil of turpentine (with Bruylants) ; the constitution of the ally1 compounds and of crotonic acid (with Rinne); and the well-lrnown speculations on the con- stitution of isatin and isatic acid, which led, later on, to the synthesis: of these compounds by Claisen and Shadwell.About the year 18i6, however, Kekulk’s physical powers began t o show signs of failure, and for the rest of his life he practically never again enjoyed a continuance of good health. H e aged prematurely and rapidly.Increasing deafness exercised a depressing effect upon him, and led him to shun the society even of his more intimate friends. Under these circumstances it is not surprising that the time which he devoted t o his laboratory was greatly curtailed. There was still, however, a.n104 JAPY : ICEHULE MEMORIAL LECTURE. occasional but unfailing incentive t o research ; namely, the publication, by other chemists, of results which clashed with his theoretical views. In such cases, Kekulk’s suspicions of the accuracy of the observations were a t once aroused; the work was carefully repeated and shown t o be vitiated by some blunder; in fact, the effect of the corrected work was generally to est>ablish KekulG’s views more securely than ever. Cases in point are the re-investigation of Tanatar’s “ bioxyfumaric acid ” and “ trioxymaleic acid,” which proved t o be rstcemic acid and mesotartaric acid respectively, published jointly with Anschutz in 1880-81 ; of Gruber and Barth’s “carboxytartronic ” (dihydroxytartaric) acid in 1883 ; and of Carius’ “ trichlorphenomalic ’’ (trichlor-/3-acetylacrylic) acid, jointly with Streeker? in 1884.The whole of this work, both experimental and theoretical, is masterly, finished in all its details, worthy of KekulB at his best. How the supposed (‘ carboxytartronic ” acid, up to that time regarded as a pillar of Ladenburg’s prism formula for benzene, was shown to be dihydroxy- tartaric acid and to furnish fresh evidence in favour of Kekulk’s hexagon ; how “ trichlorphenomalic ” acid, first discovered by Carius and furnished by him with a wrong formula and various self-contra- dictory reactions, then apparently abolished by Krafft, was finally re- habilitated, explained, and summoned as a fresh witness on behalf of the hexagon : these narratives are, to those capable of following them, of absolutely dramatic interest.Of this dramatic interest none was more conscious than Kekule himself; he calls the story of “ trichlor- phenomalic ” acid a ‘‘ Comedy of Errors.” Kekule’s premature physical decay was, therefore, entirely unaccom- panied by any corresponding failure of his mental powers. These remained fresh t o the last. Even up to a few months before his death, he would, when his strength permitted, discuss with his assistants problems connected with the recent progress of chemical science.There is no doubt that Kekulk had presumed too much on a natu- rally strong constitution and had undermined i t by excessive study in early life. I will quote the passage and also that immediately following it, which contains much excellent advice to young students : I n the speech already referred to, he admits as much. ‘( I have faithfully followed the counsel which my old master, Liebig, gave me when I was a young beginner. ‘ If you want to be a chemist,’ Liebig said t o me when I was working in his laboratory, ‘ you will have to ruin your health ; no one who does not ruin his health with study will ever do anything in chemistry nowadays.’ That was forty years ago. Is it still true 1 I faith- fully followed the advice.During many years I managed to do with four and even three hours’ sleep. A single night spent over my books did not count ; it was only when two or three came in succession that I thought I had doneJAPP : K E K U L ~ MEMORIAL LECTURE. 105 anything meritorious. At that time I had acquired such a fund of know- ledge as to make my friends think that I was more trustworthy than the Jahres berich t. “ Those good days are long past. Of the various mental powers, imagination is the first t o go ; memory follows-fortunately, slowly ; the longest to reniain is the critical faculty, but this may still do good service, provided that it rests on the broad foundation of solid knowledge acquired by thorough indnstry. May I draw a moral? I would recommend my young fellow-chemists to be diligent during youth.“ One cannot explore new countries in express trains, nor will the study of even the best text-books qualify a man to beconie a discoverer. Whoever is cpntent to follow well-laid promenades until he reaches some pleasant eminence freqnented by tourists, may, by striking into the thickets, gather some forgotten flower ; or, if cryptopms, mosses, and lichens satisfy him, may even bring home a well-filled vasculurn ; but anything essentially new he will not find. Whoever wishes to train himself as an investigator must study the travellers’ original works ; and that, too, so thoroughly that he is able to read between the lines-to divine the author’s unexpressed thought. He inust follow the paths of the Pathfinders ; he must note every footprint, every bent twig, every fallen leaf. Then, standing at the extreme point reached by his predecessors, it will be easy for him to perceive where the foot of a further pioneer may find solid ground.” These words were spoken on the occasion of what, I believe, was Kekulk’s last appearance before a public audience.The German Chemical Society had resolved to celebrate the twenty-fifth anniversary of the publication of Kekulk’s benzene theory. To this end they held, in his honour, on March l l t h , 1890, a festival of a magnificence perhaps unparalleled in the history of science. Chemical Societies in all parts of the world-our own, as the oldest, heading the list- united in sending delegates with addresses of congratulation. A portrait of Kekuli: had been painted by H.von Angeli at the instance of the German coal tar colour manufacturers, who had adopted this means of testifying t o their sense of the influence which Kekule’s theoretical views had exercised in furthering their branch of chemical industry; this portrait, which is now in the National Gallery in Berlin, was unveiled on that occasion. The President of the Society, A. W. von Hofmann, delivered one of these felicitous addresses of which I fear that the secret, so far as chemists are concerned, has died with him : in it he sketched the history of benzene from the time of its discovery as ‘‘ bicarburetted hydrogen ” by Paraday up t o the point when Kekule appeared, to ‘‘ pluck the heart out of i t s mystery.” Then .. - _ _ ., - - P .. A D _-_-_ - -.!JL- -106 JAPP : KEKULI? MEMORIAL LECTURE.cavil, the culminating point of the day’s proceedings, striking as these had been, It was the personal utterance of a man whose utterances had hitherto been confined mainly to the exposition of the impersonal facts and theories of his science. It was modestly autobiographical ; it traced the growth and training of the speaker’s powers; it afforded a glimpse into his intellectual workshop. Needless t o say that it produced a profound impression. I have already given copious extracts from this speech; I only wish that time permitted me to quote the whole. It should be read by every one who desires to understand KekulB’s character and influence. On the day preceding these celebrations, Kekulh communicated verbally * to the German Chemical Society, a t the ordinary meeting of March loth, 1890, the results of the last scientific investigation on which he was ever engaged. It was an experimental proof of the absence of a para-bond in pyridine, and was doubtless intended to have an indirect bearing on his benzene formula. A chill which Kekulk received in April, 1896, on n journey t o Cassel, told on his already weakened system.The state of his health began to occasion the gravest fears. At the same time symptoms of heart disease manifested themselves. However, his health again improved ; but just when the immediate danger appeared to have passed over, he succumbed t o failure of the heart’s action on July 13th, 1896. H e was a member of most of the European academies and other learned societies.He was elected a Foreign Member of our own Society in 1862, and of the Royal Society in 1875. He received the Copley Medal in 1885, and the Prnssian Ord9.e pour Ze Mirite in 1895. The present German Emperor, who, during his period of study a t Bonn, was a pupil of Kekuld, revived an old title of nobility which Kekule’s family had formerly borne; and during his later years the great chemist signed himself Kekule T von Stradonitz. Poaterity, however, will probably prefer to know him by the name under which the work of his life was published. Great as were Kekul6’s powers a s a thinker and an investigator, it is no exaggeration t o say that he was equally distinguished as a teacher, whether in the lecture room or in the laboratory. His speech was of extraordinary ease and precision.His lectures, which were delivered, so far as my recollection goes, without notes, might have been published in the form in which they were spoken. His Kekulk’s merits never lacked recognition. * The memoir does not appew t o have ever been written ; a t all events it was not published in the Bcrichtc. A statement of the interesting results obtained, privately coinmnnicateci by Kekul6 himself, is, however, to he found in Anschutz’s edition of Richter’s Oryanischc Chcmie, 2, 1896, pp. 518-520, t. The acute accent on the final e is dropped.JAPP : K E K U L ~ MEMORIAL LECTURE. 107 ideas were always ready a t his call; thus when, in directing the work of research students, the chances of an investigation brought him upon some subject which he could not possibly have been pre- viously considering, his exposition was as sure and as logical as in his set lectures, and save that he naturally made much freer use of colloquialisms, might, like the lectures, have been written down as i t stood.The effect of his discourse was heightened by a natural play of humour, of a somewhat dry and caustic type, for the exercise of which the opinions of scientific opponents and the blunders of students equally afforded scope. H e was invariably fresh and stimulating ; one detected no trace of that listnessness which is so frequently the bane of speakers who are compelled to lecture year after year on the same theme to what is practically the same audience of average students. He had, moreover, the advantage of a striking. personal appearance ; and his face, ordinarily of a grave and reflective cast, lighted up when he spoke.His laboratory teaching, in which, during his later years a t all events, he devoted himself almost exclusively to directing the work of research students, mas remarkable for the way in which he endeavoured to awaken independent thought in the student ; thus he did not dictate a particular course t o be carried out blindly by the student, and resent any suggestion as an impertinence-a method of teaching not unknown in some laboratories where the output of re- search work is possibly in excess of its educational value; on the contrary, he was never better pleased than when a student was full of suggestions, which he would spend much time in patiently listening to and criticising.The one thing which he never pardoned in a student was want of interest in his work; such a student was, for the future, quietly ignored. If one compares Kekulk’s published experimental work with that of many other eminent chemists among his fellow-countrymen-with that, for example, of Liebig, or Wohler, or Hofmann-one is struck by its much smaller volume. His ill-health affords only a partial ex. planation. Although no one acquainted with Kekulb’s extraordinary powers of work would dream of taxing him with indolence, yet the whole of his career unmistakably showed that with him work was a means and not an end. He began by formulating certain important theoretical conceptions, and he then, for a time, exerted himself to verify them experimentally.But when he saw that his ideas had taken root, and that hundreds of willing disciples were engaged in this task of verification ; when he realised that only by such general co- operation could the work be brought to a successful issue ; he contented himself, for the most part, with looking on and criticising. As he said, the critical faculty was, of the various mental powers, that which survived longest. His criticism, as we have seen, frequently took the108 JAPP : K E K U L ~ MEMORIAL LECTURE. useful form of the correction of inaccurate observations. Again, with a view to disseminat<ing his doctrines, he began to write his text-book. B u t long ere the text-book was finished, it had done its work; the doctrines were aImost univerally received ; and the text-book remained a noble fragment.After all, KekulB’s supreme merit lies in his contributions to theo- retical chemistry. There is, here as elsewhere, a necessary division of labour, and it is irrational to complain that the intellectual gifts of a Kekul6 do not include those of a Hofmann-that a Lavoisier is not also a Scheele. It now remains to consider, somewhat more fully than has been possible in the course of the foregoing brief sketch of KekulB’s life, the main features of his theoretical work. But here a two-fold difficulty arises. Kekulk’s greatest achievements in theoretical chemistry are : the doctrine of the linking of atoms in terms of their valency, and, growing out of this, the theory of the structure of organic molecules, both in open-chain and in closed-chain compounds. Even the youngest branch of these theories-that dealing with the structure of closed-chain or cyclic compounds-has been before the world more than thirty years.Moreover, they are not recondite theories, hidden away in the depths of the science ; on the contrary, they are organic chemistry itself, and our students learn them on their first introduction to the subject. I n addressing an audience, therefore, of expert chemists, what new thing can be said on these well-worn themes? The only admissible course is to take up the question of origins. Here the second difficulty presents itself. Great theoretical conceptions are not created out of nothing. Not only is, in most cases, the substratum of experimental or observational fact on which they rest previously on record ; but later historical re- search generally discloses the presence, scattered throughout the lite- rature of the subject, of anticipatory germs of the theories themselves.This commonplace in the history of science finds expression in the saying that (‘ the theory was in the air.” Hence arise the innumerable claims to priority, with some of which I fear I must deal on the present occasion. As a preliminary to the discussion of the theoretical conceptions which we owe to Kekulb, it will be necessary to consider briefly the state of organic chemistry a t the time when he came upon the scene. The dualistic electro-chemical theory elaborated by Berzelius, which for many years had dominated the entire field of chemistry, had, so far as organic chemistry was concerned, fallen before the attacks ofJAPP : KEKULk MERIOIIIAT, LECTURE.f 00 ’Ilumas, Laurent, and the other supporters of the doctrine of substitu- tion. I n 1842, 3Ielsens showed that trichloracetic acid could be re converted into acetic acid ; and Berzelius, compelled a t length to admit that the two compounds belonged to the same class, made a noteworthy concession to the doctrine of substitution. Unable to accept without qualification the view that elements so widely separated in the electro-chemical scale as hydrogen and chlorine could mutually replace one another in compounds without materially changing the properties of the latter, he devised the doctrine of conjugated com- pounds, and limited the operation of this process of substitution t o the conjuncts.Thus acetic acid and trichloracetic acid were conjugated oxnlic acids in which the respective conjuncts were C,H, and C,CZ, ; Acetic acid .............................. Trichloracetic acid ..................... C‘,H, + C,O, +NO C,CZ, + C,O, + I10 According to Berzelius, the replacement of hydrogen by chlorine, as long as it was confined t o the conjunct, did not materially change the properties of the compound. This limitation of the action of substitution to the conjuncts, and indeed the ent<ire theory of conjugated compounds, has generally been looked upon as an unconscious subterfuge, adopted by Berzelius to cover his retreat. I think, however, that, regarded even from the standpoint of our modern electro-chemical theories, the limitation appears a perfectly legitimate one. The error in Berzelius’ original system was an error of excess : it had arisen from applying conceptions drawn from the behaviour of electrolytes, or ionisable compounds, to non-electrolytes, or non-ionisable compounds.I n making the limita- tion just referred to, Berzelius merely withdrew the previous undue extension of his system, whilst retaining the portions which still held good. It is precisely when a halogen atom replaces hydrogen of the conjunct--that is, of the hydrocarbon radicle of a compound- that it is not ionisable; and i t is only when the substituents are non-ionisable that the Dumas-Laurent statement of the law of sub- stitution is valid. I mention this, because it appears to me that, in this matter, Berzelius hardly received justice from his opponents. Kekuld, for example, ridiculing Berzelius’ change of front, says (Lehrbuch, 1, 74-75): “That which had been absurd as long as it was regarded without any hypothesis, became ‘ surprisingly clear and simple’ when seen through the medium of the hypothesis of the conjuncts .. . . I n his joy over the conjuncts, he [Berzelius] had forgotten that his object mas to combat the theory of substitution.” The chief point, however, is that Berzelius and his school were thus compelled to abandon their doctrine of the unchangeable nature of compound radicles.110 JAPP : K E K U L ~ MEMORIAL LECTURE. Kolbe, the great continuator of Beizelius’ system, adopted and extended this doctrine of the conjuncts. At the same time he introduced the conception of more complex radicles (nnlihere Radicale) which were built up from simpler radicles (entferntere Radicale). Thus, according to Kolbe, acetic acid contains a conjugated radicle, C2H3^C2 (called by Kolbe “acetyl”) consisting of carbon conjugated with methyl ; this unites with oxygen to form C2H3^C203, acetoxyl ; and the latter in turn combines with water t o form acetic acid, C,I€3^C,0,H0.This view of the constitution of acetic acid is, as will be seen, not far removed from that now held ; it clearly indicates that one half of the carbon in the molecule is present as methyl, whilst the other half serves to satisfy the affinity of oxygen. Kolbe’s extraordinary power of expressing chemical reactions in terms of chemical constitution was unfortunately coupled with an almost complete inability to realise the force of arguments drawn from physical laws.One result was that until 1870 he continued t o use Gmelin’s equivalents instead of our present atomic weights. There can be little doubt that this both hampered his efficiency as an in- vestigator and prevented his theoretical views from being received a t their full value. Kolbe, however, afterwards contended that his mistaken adherence to the old equivalents had facilitated his discovery of the constitution of acids, aldehydes, and ketones, and his prognosis of secondary and tertiary alcohols. Thanks mainly to the conceptions of chemical structure which we owe to Kekulk, we can, looking back on the disputes which raged roiind the radicle theory, perceive where truth lay, and where error ; nay, we can often see that, of two competing rational formulz, both were right, each affording a partial glimpse of a truth which after- wards found its fuller expression in the structural formula of the compound.But KekulB’s predecessors were not in this position, and it is not surprising that the manifold hypotheses, and the contra- dictions, real or apparent, of the radicle theory led many t o regard the problem of the constitution of chemical conipounds, at least in the sense in which the supporters of this theory understood it, as insoluble. Gerhardt was one of those who held this view, and in his earlier exposition of his “unitary system” (1848) he employed empirical formuh only.His chief efforts were at that time directed to representing the various chemical compounds by comparable quantities-their mole- cular weights-and for this purpose he selected as his unit the molecular weight of water, the formula of which he wrote H,O. He employed our present atomic weights for carbon, oxygen, sulphur and their analogues ; but somewhat misleadingly called these atomic weights ‘‘ equivalents.”JAPP : K E K U L ~ MEMORIAL LECTURE. 111 The difficulty of dealing with organic compounds by means of empirical formulae alone, led Gerhardt to extend his original system, and to introduce into the formuls certain atomic groups which he termed “ residues.” When two compounds interact, eliminating jointly the elements of water or of some simple inorganic compound, the two residues of the original compounds combine.Thus, in the formation of nitrobenzene from benzene and nitric acid, water is eliminated, and the “ benzene residue,” C,H,, unites with the “ nitric acid residue,” NO,. The so-called residues were thus in many cases identical with the old radicles (leaving out of account the fact that Gerhardt used the new atomic weights), and the system was an attempt to secure the benefits of the radicle theory whilst avoiding its more or less hypothetical basis. The way was thus paved for the union of the radicle theory with Dumas’ type theory, the outcome of which union was Gerhardt’s type theory. As regards the latter theory, the idea of the ammonia type was furnished by the researches of Wurtz and Hofmann (1849-50) on the substituted ammonias, in which 1, or 2, or 3 hydrogen atoms of the original ammonia molecule were replaced by alcohol radicles.Williamson (1850) showed that alcohol and ether might in like manner be derived from 1 mol. of water by the replacement of either 1 or 2 hydrogen atoms by such radicles; and in the following year (1851) he adopted a similar view in the case of the acids ; thus, he regarded acetic acid as 1 mol. of water in which a hydrogen atom is replaced by acetyl, C,H,O. Shortly afterwards (1852), Gerhardt, applying to the monobasic acids a method analogous t o that by which Williamson had effected the synthesis of ether, obtained acetic anhydride and its analogues, which were thus shown to stand in the same relation to the monobasic acids as the ethers to the alcohols.When once i t had been recognised that organic compounds might be derived by substitution (double decomposition) from simple in- organic compounds like water and ammonia, and might therefore be formulated on the-type or pattern of these, the process of finding other simple inorganic compounds which should serve a similar purpose and so complete the type theory, was a tolerably obvious one. Gerhardt selected, as his four types, hydrogen (free hydrogen was, according to the Laurent-Gerhardt view, a compound, HJ, hydrochloric acid, water, and ammonia. The typical formulae were not intended to indicate the constitution of the compounds as the term was understood by the adherents of the radicle theory. I f two compounds belonged to the same type it meant merely that they had in common certain functions and cortain modes of formation and decomposition.The idea of valency, both of elements and of compound radicles, had already been propounded. In his well-known paper “On the112 JAPP : KEKULh MEMORIAT, LECTURE. Constitution of Salts ” (LS51 *), Williamson points out that certain compound radicles, such as C,H,O and NO,, can replace 1 atom of hydrogen in 1 mol, of water, giving rise t o monobasic acids; whilst others, like CO, C,O,, and SO,, can replace 2 atoms of hydrogen in 2 mols. of water, yielding dibasic acids. That the linking function of these dyad groups was clearly present to his mind is shown by the following passage (this Journal, 1852, 4, 353) in which, speaking of Wurtz’s decomposition of ethylic isocyanate by potassium hydroxide, he says : “ One atom of carbonic oxide is here equivalent t o 2 atoms of hydrogen, and by replacing them, holds together the 2 atoms of hydrate in which they were contained, thus necessarily forming a bibasic compound, (g!)02, carbonate of potash.” This important passage contains the earliest statement of the fact that a double type (here the double water type) is possible only when the compound con- tains a dyad radicle.Later on, in 1854, Williamson (Proc. Roy. XOC., 7, 11) showed that, by the action of phosphorus pentachloride on sulphuric acid, sulphuryl chlorhydrate and sulphuryl dichloride could successively be obtained, thus proving sulphuric acid to have the formula SO,(OH), which he had previously assigned to it, but which had been called in question by Gerhardt.I n the same year he pre- pared, jointly with his pupil Kay (Zoc. cit., p. 135), the tribasic formic ether (ethylic orthoformate), CH(OC,H,), by the action of chloroform on sodium ethoxide, and pointed out that it was ‘‘a body in which the hydrogen of three atoms of alcohol is replaced by the tribasic radical of chloroform.” About the same time, Odling (this Journal, 1855, 7, 1) extended Williamson’s views on the constitution of salts and assumed the presence of a triad rildicle PO”’ in the acids of phos- phorus : thus orthophosphoric acid WFLS formulated on the triple water PO’” type as 3H’ } 0,. And just as Williamson had shown that the dyad group SO, could unite two water residues to form sulphuric acid-a double water type-so Odling employed this same group t o unite together a water residue and a sulphuretted hydrogen residue t o form thiosulphuric acid-a mixed type ; he formulated sodium thiosulphate $$:, } 0’ + S’.H e thus laid down the conditions under which a mixed type might exist : namely, when the molecule contains a polyad radicle capable of holding together the various residues.? In the same * First published in the Chemical Gazette for 1851 ; afterwards reprinted in full in the Joum. C‘he7n. Soc., 1852, 4, 350. t Ladciiburg (E~LtwickZz~nysyeschichte dcr Chemie, 2nd ed., 11. 232) credits Gerhardt and Chiozza with having, in 1854, derived succinainic acid from the mixed type NH,+H,O in which the two residues were united by the dyad radicle succinyl.In that case these chemists would have anticipated Odling in showing how mixed typesJAPP : KEKULk MEMORIAL LECTURE. 113 year, Berthelot showed that glycerol formed ethereal salts containing 1, 2 and 3 radicles of a monobasic acid, a result which Wiirtz correctly interpreted as proving that glycerol was a trihydric alcohol formulating it on the triple water type. From this Wurtz was led to foresee the existence of a class of dihydric alcohoIs, the first member of C3H51” } o,, H3 which,glycol, ‘2%; } 0,, he prepared in the following year (1856). Chemists were thusbeginning to familiarise themselves with the idea of polyvalent compound radicles of different hydrogen-replacing power. I n the memoir just quoted, Odling employs his well-known valency marks to indicate the valency not only of compound radicles, but also of elements.The conception of a valency of the elementary atoms was introduced into chemistry by E. Frankland in 1852. As Frank- land’s claims in this respect have been called in question by a t least one member of the Kekule school and were never openly acknowledged by Kekul6 himself, I will quote the original passage more fully than would otherwise have been necessary. It occurs a t the end of a paper “ On a New Series of Organic Bodies containing Metals ” (Phil. Trans., 1852, 417). Frankland, who up to that time had been a follower of Kolbe, now criticises unfavourably Kolbe’s doctrine of conjugated compounds. After referring to Kolbe’s view that cacodyl is “ arsenic conjugated with two atoms of methyl, (C,H,),As ” (Frankland uses Gmelin’s equivalents in this paper), and pointing out that the various organo-metallic compounds obviously belong to the same class as cacodyl, he proceeds (Zoc.cit., p. 439) : “It is generally admitted t h a t when a body becomes conjugated, its essential chemical character is not altered by the presence of the conjunct : thus for instance, the series of acids CnHn04, formed by the conjunction of the should be formulated. What they really say, however, is : “ Succinamic acid repre- sents the hydrate of an ammonium in which 2 atoms of hydrogen are replaced by their equivalent of succinyl : ”%}O (Cornpt. rend., 1854, 38, 458)’ which is a very different matter. Ammonium hydrate is here formulated on the water type, and succinyl replaces two atoms of hydrogen in ammonium : it does not link two residues together.Bearing in mind that, in Part 4, vol. 4 of the Traitd, Gerhardt formulates the ammonium compounds with pentad nitrogen, it would seem that Ladenburg has read into Gerhardt and Chiozza’s formula: a meaning that was not present to the minds of the authors. Gerhardt had not grasped Williamson’s principle that polyvalent radicles are necessary t o link together the residues in multiple types, and in Part 4, vol. 4 of the Trnzt4 he frequently writes formulz that are quite at variance with i t : thus CaHao}02 for glycerol ; N, for hydrobenznmide. H, VOI,. 1,XXIJ.I. z114 JAPP : KEKULk MEMORIAL LECTURE radicals C,H(,,+I, with oxdic acid, have the same neutralising power as the original oxalic acid ; and, therefore, if we assume the organo-metallic bodies above mentioned to be metals conjugated with various hydrocarbons, we might reasonably expect, that the chemical relations of the metal to oxygen, chlorine, sulphar, &c., would remain unchanged ; a glance at the formuke of these compounds will, however, suffice to show us that this is far from being the case : it is true that cacodyl forms protoxide of cacodyl and cacodylic acid, corresponding to a somewhat hypothetical protoxide of arsenic, which, if it exist, does not possess any well-defined basic character, and the other to arsenious acid ; but no known compound corresponding to arsenic acid can be formed, and yet it cannot be urged that cacodylic acid is decomposed by the powerful reagents requisite to procure further oxidation, for concentrated nitric acid may be distilled from cacodylic acid without decomposition or oxidation in the slightest degree; the same anomaly presents itself even more strikingly in the case of stanethylium, which, if we are to regard it as a conjugate radical, ought to combine with oxygen in two proportions at least, to form compounds corresponding to protoxide and peroxide of t i n ; now stanethyliuni rapidly oxidises when exposed to the air, arid is converted into pure protoxide ; but this compound exhibits none of that powerful tendency to combine with an additional equivalent of oxygen, which is so characteristic of protoxide of tin ; nay, it may even be boiled with dilute nitric acid without evincing any signs of oxidation : I have been quite unable to form any higher oxide than that described ; it is only when the group is entirely broken up and the ethyl separated, that the tin can be induced to unite with another equivalent of oxygen.Stibethyl also refuses to unite with more or less than two equivalents of oxygen, sulphur, iodine, &c., and thus forms compounds which are not represented amongst the combinations of the simple metal antimony. " When the formula of inorganic chemical compounds are considered, even a superficial observer is struck with the general symmetry of their con- struction ; the compounds of nitrogen, phosphorus, antimony, and arsenic especially exhibit the tendency of these elements to form compounds con- taining 3 or 5 equivalents of other elements, and it is in these proportions that their affinities are best satisfied ; thus in the ternal group we have NO,, NH,, NI,, NS,, PO,, PH,, PCI,, SbO,, XbB,, SbCI,, AsO,, ASH,, ilsCI,, &c.; and in the five-atom group NO,, NH,O, NH,I, PO,, PH41, &c. With- out offering any hypothesis regarding the cause of this symmetrical grouping of atoms, it is sufficiently evident, from the examples just given, that such a tendency or law prevails, and that, no matter what the chai-actw of the uniting atonas may be, the conzbining power of the attyacting element, if Imay be allowed the term, is always satisjed by the same number of theseatonzs. It was probably a glimpse of the operation of this law among the more complex organic groups, which led Laurent and Dumas to the enunciation of the theory of types ; and had not those distinguished chemists extended their views beyond the point to which they were well supported by then existing facts-had they not assumed that the properties of an organic compound are dependent upon the position, and not upon the nature of its single atoms, that theory would undoubtedly have contributed to the development of the science to a still greater extent than it has already done ; such an assumption could only haveJAPP : KEKULli MEMORIAL LECTURE. 115 been made at a time when the data upon wliich i t was foundecl were few and imperfect, and, as the study of the phenomena of substitution progressed, it gradually became untenable, and the fundamental principles of the electro- chemical theory again assumed their sway.The forniation and examination of the organo-metallic bodies promise to assist i n effecting a fusion of the two theories which haveaso long divided the opinions of chemists, and which have too hastily been considered irreconcilable ; for, whilst it is evident that certain types of series of compounds exist, it is equally clear that the nature of the body derived from the original type is essentially dependent upon the electro-chemical character of its single atoms, and not merely upon the relative position of those atoms. , . . ‘‘ Taking this view of the so-called conjugate organic radicals, and regarding the oxygen, sulphur, or chlorine compounds of each metal as the true molecular type of the organo-metallic bodies derived from it by the substitu- tion of an organic group for oxygen, sulphui-, &c., the anomalies aboi-e mentioned entirely disappear, and we have the following inorganic types and organo-metallic derivatives :- Inorganic types.As {g} ........................ As ........................ As Z n 0 ........................ Zn z n { tx} ........................ z r i 83 0 ........................ SB GI- ........................ s!, ........................ S b Sn 0 ........................ Sn sn { g} ........................ SI1 H g { f } ........................ Hg Organo-metallic derivatives. Cacodyl. Oxide of Cacodyl. Cacodylic acid. Zincmethylium. Oxide of Zincmethylimn. Stibethine. Binoxide of Stibethine. Oxide of Stibethyliuni. Stamthylinm. Oxide of Stanethylium.Iodide of Hyclrargyro- 1 2 methylium.”116 JAPP : ICEKULI~ MEMORIAL LECTURE. The foregoing extract from Frankland’s paper contains a complete statement, in terms of Gmelin’s equivalents, of the valency of the various elementary substances employed as “ grouping elements ” (to make use of a term introduced later by Frankland) in the formulae given. I n the case of the perissads-hitrogen, phosphorus, arsenic, and antimony-the valencies are 3 and 5, being thus identical with those now assigned to these elements. Arsenic appears in cacodyl as a dyad -a pseudo-dyad, as Frankland would have called it later. I n the case of the artiads, zinc and tin, the atomic weight is twice the equivalent ; hence the valency given by Frankland must be doubled. Mercury has been taken with the atomic weight 300, and its valency is correctly given.Another important point is, that Frankland rejects the conception of conjugated compounds and writes typical formulze explicitly based on the valency of the elements. One result of Frankland’s employing Gmelin’s equivalents was that his statement of the law of valency did not impress the adherents of the type theory so much as it might otherwise have done, Kekul6, who in the introduction to his Lehrbuch fully acknowledges his obliga- tions to “Williamson and Odling, Hofmann and Wurtz,” does not mention Frankland ; and a similar omission occurs in Wurtz’s Atomic Theory. Kekule, as already mentioned, never expressed himself, a t all events in his published writings, on the subject of Frankland’s claims ; lout, if we have not Kekulb’s “ official ” opinion on the subject, we have an opinion, put forward in a paper published by Baeyer in 1858, when the latter was a student in KekulB’s laboratory, which must, I think, be regarded as “ semi-official.” Baeyer gives a list of compounds formed by the union of monads alone (methyl and chlorine) with the elements of the nitrogen group, in which the latter exhibit either triadic or pentadic character-belonging, as Baeyer expresses it, either to the ammonia type, or to the ammonium chloride type-and adds (Annalen, 1858,105, 274) :- ‘‘I would here remind the reader of the series of compounds which Frankland gave i n his investigations on zinc-ethyl, in which he drew a parallel between the compounds of the metals with oxygen and those with the alcohol radicles, whilst the latter are analogous to hydrogen and not to oxygen. The view which is thus gained is purely superficial ; it vanishes immediately when the proper atomic weight of oxygen is adopted, and the forniulz which contain an odd number of atoms of that element are doubled.” With regard to the foregoing passage, I think we may lay it down as a safe general principle, to be adopted in dealing with this interest- ing period of chemical history, that a discovery, made by an adherent of the radicle theory and correctly formulated by him in terms of theJAPP : K E K U L ~ MEMORIAL LECTURE.117 old equivalents, does not become the property of the first adherent of the type theory who happens to translate it into the new atomic weights.Baeyer’s criticism has been replied t o by Frankland in the intrcj- duction t o the series of papers on organ o-metallic compounds reprinted in his Experimentccl Researches (p. 153). As some chemists may not have seen the passage, I will quote it :- ‘‘ Exception has been taken, I think somewhat unfairly [here Baeyer’s criticism is given as a footnote], t o the analogies upon which, in the following papers, I have founded the doctrine of atomicity. It has been stated, for instance, that there is no real analogy between antimonic anhydride and anti- monic triethoxide, if the dyadic atom of oxygen be used in the formula of the first-that the real analogy is between antimonic chloride and antimonic triethoxide, &c. But even i n the light of our most recent conceptions of the constitution of chemical compounds, the analogies which I pointed out are strictly correct ; for i n antimonic anhydride each atom of antimony has five bonds satisfied by oxygen, whilst i n the organo-metallic analogue, antimonic triethoxide, the oxygen of three of these bonds has been replaced by ethyl : E t a Et Antimonic anhydride.Antinionic triethoxide. “At the time when the second paper of this chapter was written, I employed, in common with nearly all chemists, what is known as the small atom of oxygen (0=8). With this atoiiiic weight oxygen was monadic ; and as it formed the only pentadic inorganic compound of arsenic, it lent itself, on the whole, better to the expression of my analogies than either chlorine, bromine, or iodine ; but (and it is on this ground that I complain of the unfairness of my critic) I distinctly stated * that I regarded ‘ the oxygen, sulphur, or chlo~ine compounds of each metal as the true molecular types of the organo-metallic bodies derived from them by the substitution of an organic group for oxygen, sulphur, &c.,’ and I actually used, in the table of analogous compounds, HgI, as the type of HgMeI.” If Kekul6 did not express himself regarding Frankland’s claims, he went further than this, for he claimed to have been himself the first propounder of the doctrine of the valency or, as he termed it, the atomicity, of the elements.In a note “ On the Atomicity of the Ele- ments ’) (Compt. rend., 1864, 58, 510), published in reply to views put forward by Naquet and others, he says : ‘‘ I consider that it is all the more my duty to intervene in this discussion, seeing that, if I am not mistaken, it was I who 6rst introduced into chemistry the conception of the atomicity of the elements.” (It should be mentioned that the first occasion on which Kekul6 refers t o valency is in his paper on thiacetic acid, published in 1854, two years later than Frankland’s * See the extract from Frankland’s paper already given.OXSb-0- O=Sb-Et I118 JAPP : KEKULE MEMORIAL LECTURE. paper.) H e then proceeds t o combat the doctrine of varying valency : the equivalent of an element may vary ; but its valency is as invari- able as its atomic weight. Neither is valency to be regarded as identical with maximum capacity for saturation : thus, in reply t o Naquet, who regarded iodine as triadic and the elements of the sulphur group, including oxygen, as tetradic, he points out that if iodine is triad in ICY3, tellurium must be dodecadic in Te1,-a supFosed wductio cbd absurdum which KekulB’s opponents might justly regard as a travesty of their views.H e then defines the conditions which, he considers, alone render the determination of the valency of an element possible : the element in question must be combined solely with monads, and the resulting compound must be volatile without decom- position. Two or more atomic molecules may unite to form a moleculcw compound ; such a compound may be distinguished by the fact that, when volatilised, it dissociates; it is not available for the purpose of determining the valency of the elements which it contains.Thus ICl, Pel,, and NH,, are atomic compounds, and their formulz show iodine to be monadic, and phosphorus and nitrogen to be triadic. Iodine trichloride, phos- phorus pentachloride, and ammonium chloride are represented a s molecular compoiinds, ICl,CI, ; PCl,,Cl,; NH,,HCl. (At that time the existence of phosphorus pentafluoride, a compound of pentadic phos- phorus gaseous at ordinary temperatures, and the fact that dry ammonium chloride may be vaporised without dissociation, were, of course, unknown.) Again, referring to his doctrine of fixed valency, he speaks (Zoc. cit., p. 512) of the reasoning which has made me remain faithful to my original manner of viewing the subject, and which, I venture to hope, will end by carrying the day against the modifications which have been proposed since.” Surely, Frankland’s doctrine of varying valency was earlier in the field I Of all the doctrines which we owe to Kekul6 that of fixed valency is probably the one which has met with least acceptance, even among chemists of his own school.At the present day it is, so far as I am aware, without supporters. Whilst we must thus admit t h a t it was with Frankland and not with Kekule that the idea of the valency of elementary substances originated, we are in a position, I think, to explain how it was that Kekulk came to ignore Frankland’s work and to claim the theory for himself. To Kekulk, varying valency and, moreover, varying valency referred to equivalents instead of to atoms, was not valency a t all, as he understood it.We must bear in mind the attitude of the two opposed schools in questions of chemical theory : how each seemed to labour under an absolute inability to place itself in the mental posi- tion of the other. I have no doubt that Kekul6 paid very little atten- Such a compound he regards as atomic. Yet KekulB held it to the last.JAPP : KEKULE MEMORIAL LECTURE. 119 tion t o Frankland’s theoretical views ; t h a t he evolved the doctrine of valency in part independently and in part from the indications which he found in the writings of Williamson, Odling, and Wurtz; and t h a t afterwards, perceiving t h a t Frankland had put forward similar ideas, he came t o the conclusion that they had not been deduced by a legitimate process and were not correctly stated.These considerations, which may have appeared important at the time, need not weigh with us at the present day. The battle between the radicle theory and the type theory is long past. The victory was not entirely with either, for t h e theory of chemical structure, based on the doctrine of valency, absorbed and assimilated both. Frankland correctly perceived that the views which he was advocating promised “ to assist in effecting a fusion of the two theories which have so long divided the opinions of chemists, and which have too hastily beencon- sidered irreconcilable.” But the theory of chemical structure which effected this fusion is imperishably associated with the name of Kekulb, and, therefore, if he did not originate the doctrine of valency, no other chemist used it to so good purpose.Frankland, speaking of valency, says (Experimental Researches, p. 154) : ‘‘ I do not forget how much, i n its present developments, this law owes t o the labours of other chemists, especially t o those of Kekul6 and Cannizzaro. Indeed, until the latter had placed the atomic weights of the metallic elements on their present consistent basis, the satisfactory development of the doctrine was impossible.” In his later years, Kekul; looked back upon those troublous times with a more tolerant eye. I again quote from his Berlin address : “ No science has developed so steadily as chemistry, although during one period of its development which fell partly within my own experience, the ve.ry opposite seemed for a time t o be the case. Fifty years ago, the stream of chemical progress had divided into two branches. The one flowed, chiefly on French soil through luxuriant flower-decked plains ; and those who followed it, with Laurent and Dumas at their head, could reap, during the whole voyage, almost without effort, an abundant harvest.The other followed the course indicated by an old and approved guide-post set up by the great Swedish chemist, Berzelius ; it led for the most part through broken boulders, arid only later on did it again reach fertile country. At length, as the two branches had again approached much nearer to one another, they were separated by a thick growth of misunderstandings, so that those who were sailing along on the one side neither saw those on the other, nor understood their speech.Suddenly a loud shout of triumph resounded from the host of the adherents of the type theory. The others had arrived--Frankland at their head. Both sides saw that they had been striving towards the same goal, although by different routes. They exchanged experiences ; each side profited by the con- quests of the other; and with united forces they sailed onward on the re- united stream. One or two held themselves apart and sulked ; they thought120 JAPP : K E K U L ~ MEMORIAL LECTURE. that they alone had held the true conrse--the right fair-way-but they followed the stream. Our present opinions do not, as has frequently been asserted, stand on the ruins of earlier theories. None of the earlier theories has been recognised by later generations as entirely false ; all, when stripped of certain ill-propor- tioned, meaningless excrescences, could be ntilised in the later structure, and form with it one harmonious whole.“ Here and there a seed may have lain in the ground without germinating ; but everything that grew came from seed that had been previously sown. My views also have grown out of those of my predecessors and are based 011 them. There is no such thing as absolute novelty in the matter.” I have allowed the protagonists to speak for themselves, and so great is their agreement, a t least in their later utterances, that it seems almost superfluous t o call in the aid of a n umpire. For the sake of completeness, however, I venture to do so. Lsdenburg, although a pupil of Kekulh and thoroughly imbued with his master’s teaching, has displayed, in his well-known historical treatise, a most praiseworthy spirit of impartiality in dealing with the various questions at issue between the adherents of the radicle and the type theories.Referring to Frankland’s enunciation of the doctrine of valency already quoted, he says (Entwickl~ngsgesc~~~c?~€e der Ciiemie, 2nd ed., p. 251):- ‘( With this memoir of Frankland’s the first step was taken towards a re- conciliation of the hitherto opposed schools- the means was furnished for a mutual understanding. This means was destined to lead to a fusion of the different opinions, and out of the fusion the theory of valency developed. It WRS a gain for the adherents of the type theory to have secured Frankland’s adhesion to their principles ; for he brought with him ideas foreign to their modes of thought and capable of being turned t o excellent account.I will not assert that the former school could not have taken the final great step- the differentiation of the atoms in terms of their valency-independently ; but, having regard to the course which the development actually followed, the influence of Kolbe, and especially of Frankland, on the representatives of the Gerhardt-Williamson school (Wurtz, Kekuli, and Odling) can hardly be mis- taken. The efforts of both schools were necessary to impart to formuh the significance which they afterwards acquired.” I have treated this question of the authorship of the doctrine of valency at considerable length ; but the subject seemed to mo by its importance t o justify this, especially in the present connection, seeing that the whole of Keknlh’s work is based on this doctrine.We must now pass on to consider the use which Kekulh made of the ideas which he found scattered throughout the writings of his predecessors ; how he added t o them ; and how he welded the wholeJAPP : KEKULE MEMORIAL LECTURE. 121 into the coherent system which forms our present theory of the structure of organic compounds. KekulB’s first published work of theoretical importance was, as has already been mentioned, his (‘ Note on a New Series of Organic Acids containing Sulphur ” (Annalen, 1854, 90, 309). H e treats various organic compounds of the water type, such as acetic acid and acetic anhydride, with the sulphides of phosphorus, and in this way replaces the typical oxygen by sulphur.He compares the action with that of the chlorides of phosphorus and significantly remarks : “ One sees, indeed, that the decomposition is essentially the same ; only, when the chlorides of phosphorus are employed, the product breaks up into chloride of othyl [acetylic chloride] and hydrochloric acid, or into two atoms of chloride of othyl, as the case may be; whereas, on employing the sulphur cornpounds of phosphorus, both groups remain united, because the quantity of sulphur epuicalent to 2 atoms qf chlorine i s not divisible.” Elsewhere, in the same paper, he refers this difference to “the dibasic nature of sulphur.” H e then proceeds to defend Gerhardt’s new atomic weights, and declares the formuh written with these t o be a better expression of the facts than the prevailing formulse.H e says: “It is not merely a difference in the mode of writing, it is an actual fact, that 1 atom of water contains 2 atoms of hydrogen and only 1 atom of oxygen ; and that the quantity of chlorine equivalent to one atom of oxygen is divisible by 2, whereas sulphur, like oxygen itself is dibasic, EO that 1 atom is equivalent t o 2 atoms of chlorine.” We thus see that the theory of the linking of atoms and groups by means of polyad radicles was already present to Kekulk’s mind. Moreover, as was always the case with him, the thought is expressed with such precision and emphasis, as t o render i t impossible for even the least attentive reader to overlook his meaning.” After this apparently iinconditional acceptance of Gerhardt’s atomic weights, it may surprise us to find Kekul6 returning in his next published work to the use of Gmelin’s equivalents.The same con- cession to the prevailing usage was, however, made by other members of the Gerhardt-Williamson school whenever they were merely stating experimental results, or explaining theories for the understanding of which the new atomic weights were not required. Later on, in adopting the new atomic weights, the adherents of this school used, as is well known, crossed symbols for the aytiads, thus: 8 = 12, 8 = 16, as proposed by Williamson, partly in order to indicate * Kolbe’s well-known hostile criticisms on KekulB’s literary style deal almost exclusively with verbal points ; they seldom touch the meaning, which ind.ed Kolbe’s own preconceptions prevented him from grasping.This, it need hardly bc said, is written in no spirit of detraction of Kolbe’s ow11 work and influence.122 JAPP : K E K U L ~ MEMORIAL LECTURE. t h a t the atom was in these cases equal to twice the equivalent, and partly to avoid confusion with the uncrossed symbols which were em- ployed by the opposed school to denote the old equivalents. Kekule continued to use these crossed symbols until 1867. How liable t o misinterpretation these concessions t o the prejudices of opponents mere, and how little gratitude they evoked, may be seen from the accusations which Kolbe (J. pi.. Chem., 1881, [ii], 24, 398) brings against Kekuli!: firstly, of having until 1857 held the view that the old equivalents were identical with the true atomic weights, whereas we have seen that as early as 1854 Kekuli! had perfectly clear views to the contrary, although be for some time continued t o use the equivalent formule for purposes of exposition ; and secondly, of after- wards, ‘( until 1867, attributing the atomic weight 16, not, strictly speaking, to the single oxygen atom, but to the double oxygen atom 0.” Kolbe goes on to state that he himself adopted the new atomic weights in 1870, and draws the comforting conclusion t h a t Kekul6 anticipated him in this course by only three years ! The first of these papers in which Kekule reverts to the use of the old equivalents is entitled (‘ On the Constitution of Fulminic Acid ” (Annalen, 1857, 101, ZOO), and was followed a year later by a second paper on the same subject.The experimental work was difficult and dangerous, The conclusion at which Kekuli! arrived, namely, t h a t fulminic acid is nitroacetonitrile is no longer held by chemists; but the work is of great interest. Perhaps the most important point in the paper is a tabular arrangement of compounds of the marsh gas type : the earliest enunciation of the tetravalency of carbon. After ascribing $0 mercnric fulminate the formula C,(NO,)(C,N)Hg,, Kekul6 adds (loc. cit., p. 204) : <( This formula shows at the first glance that mercuric fulminate exhibits in its composition the closest analogy with a large number of known compounds, to which, for example, chloroform, C, H Cl Cl Cl, belongs.We might regard it as nitrated chloroform in which the chlorine is replaced partly by cyanogen and partly by mercury. ‘( The following compounds may be referred t o the same type : H H Cl Cl Cl Br €1 Cl H HY Marsh gas. Methylic chloride, &c. Chloroform, &c. Chloropicrin. Marignac’s oil. Rromopicrin. Acetonitrile. Trichloracetonitrile. Mercuric fulniinate. Hypothetical fulininic acid,JAPP : KEKULB MEMORIAL LECTURE. 123 “ . , . In assigning these compounds to the sanie type, I do not use the word in the sense which it bears in Gerhardt’s unitary theory, but in that in which it was first employed by Dumas on the occasion of his fruitful investigations on the subject of types. I wish essentially to indicate the relations in which the said compounds stand to one another ; that the one, under the influcnce of appropriate agents, can be prodncetl from, or tr:msforriied into, the other.” I have quoted this passage somewhat fully because Kolbe (J.pr. Chem., 1881, [ii], 23, 374, footnote) bas denied that Kekuld here refers mercuric fulminate to the marsh gas type and, indeed, that the pissage affords any justification for ascribing to Kekule the enuncia- tion of the marsh gas type and of the tetravslency of carbon. H e bases this denial on Kekule’s statement that he uses the word “ type ” in Dumas’ sense (“mechanical type”) and not in Gerhardt’s sense (“ chemical type ”). Why this statement should deprive Kekuld of all right to the theory which he so clearly expresses in Ibis formulze, Kolbe does not explain, unless, indeed, the explanation is to be found in a reference which he makes a little further on (Zoc.cit., p. 375) to KekulQ’s paper ‘‘ On the So-called Conjugated Compounds,” and in which, speaking of Kekule’s direct statement t,hat carbon can be shown t o be “ tetrabasic or tetratomic,” he says : “ He nevertheless feels so uncertain of his ground, that he still hesitates to add the type ‘ marsh gas ’ to Gerhardt’s three types.” The meaning of Kekuld’s remark about types, which Kolbe has, i t seems to me, entirely mistaken, i s perfectly clear if we view it by the light of the various statements on the subject of types to be found in Kekulk’s writings. Kekulb’s types (compare Annulen, 1857, 104, 132 ; Lehrbuch, 1, 116-1 17), even when outwardly identical with Gerhardt’s 6‘ chemical types,” were in reality ‘‘ mechanical types ” : that is, they were based solely on the valency of the constituent elements.Thus, whereas Gerhardt classed the hydrogen type, HH, and the hydro- chloric acid type, HC1, as distinct cl~erniccd types, Kekul6, looking upon them as naechunicul types, regarded the latter as merely a special case of the former. Applying this to the matter under consideration, i t is evident, that, if Kekuli: had employed Gerhardt’s types, he could not have tabulated the foregoing compounds in the may he did, as they would not have belonged to the same type, Thus, if he had followed Gerhardt, marsh gas would have belonged to the hydrogen type, methylic chloride to the hydrochloric acid type, and so on; and the parallelism which Kekuli: wished t,o indicate would have been com- pletely hidden.It was, therefore, necessary for him not merely to tabulate the compounds on the marsh gas type, but, seeing that he had used the word “ type,” to obviate any possible misunderstanding by stating that he did not mean Gerhardt’s types.* * Kolbe also argues (Zoc. c i t . ) that, in the passage just quoted, KekulQ refers marsh gas to the chloroform type, not chloroform to the marsh gas type. To124 JAPP : KEKUTJE MEMORIAL LECTURE. The foregoing demonstration of the tetravalency of the double equiva- lent of carbon, C, (which, as we have seen, meant for Kekulk the atom C = 12), is obviously incomplete, as i t holds good only for the limited class of compounds derivable from methane by the replacement of the hydrogen atoms by the same number of monad radicles.It contains no suggestion of the law of mutual linking of carbon atoms and can a t most be regarded as the germ of KekulB’s later theory. I n the same year, Kekul@ published a n important theoretical paper : ‘‘ On the So-called Conjugated Compounds and the Theory of Polyatomic Radicles ” (Annulen, 1857, 104, 129). As the question is entirely one of valency and there are no experimental results to state, he uses Gerhardt’s atomic weights, although in three experimental papers published the following year he again reverts, for the last time, how- ever, to the old equivalents. I n the introduction t o the paper he states that the views which he advocates have, in great part at least, no claim to originality : they are an extension of ideas incidentally put forward by Williamson and forming what might be termed his ‘‘ theory of polyatomic radicles ” ; ideas which had already been extended by Odling in his paper (( On the Constitution of Acids and Salts,” and which had been adopted, although not in a strict, form, by Gerhardt in the fourth volume of his Trait& Kekulk divides the ele- ments into monobasic or monatomic, dibasic or diatomic, and tribasic or triatomic, and points out that the three principal types-hydrogen, water and ammonia-follow from this.classification.I n a footnote he adds (Zoc. cit., p. 133) : ‘‘ Carbon is, as may easily be shown, and as I shall explain in detail on a later occasion, tetrabasic or tetratomic : that is, 1 atom of carbon 8= 12 is equivalent t o 4 atoms of H.” He shows that, as regards the so-called conjugated compounds, there is no need t o refer these to a separate class : their constitution may be ex- pressed in terms of the valency of the radicles, simple and compound, which they contain.We have already seen, however, that this view of the nature of conjugated compounds had been clearly stated by disprove this i t is only necessary to point out that in the table of compounds which L‘may be referred to the same type,” the formula of chloroform is given under that of marsh gas. Kolbc apparently understands the words “referred to the same typo ” to mean “ referred t o the same type as chloroform,” whrreas the sense is : “ niay all be referred to one and the same type,” namely the type that heads the list.This is clearly shoivn both by the contcxt and by the way in which the words “ same type ” are again used after the table of compounds. Kolbe put himself completely out of court in any discussion involving a know- 13dgc of Kckuld’s writings, by the statement that he did not consider them worthy of serious attention. In his historical study : ;Ifcine licthei7ipng an der Entwicke- king der theorelischcn Chciiiie (J. p r . Chcm., 1881, [ii], 23, 377) he says : “ I n this eoniiection I have had occasion for the first time to read attentively KekulB’s Lchrbisch, cspccially the historical and theoretical chapters. Until then, I had only glanced hastily through it, as I perceived that I could learn nothing useful from it.”JAPP : KFXIJL~! MEMORIAL LECTURE.125 Frankland in 1852. KekulB, starting, as he premises, with the theory of multiple types and mixed types containing polyvalent radicles, as ex- pounded by Williamson and Odling, develops it into a complete system, laying special stress on the fact that these classesof types are possibleonly when such polyvalent radicles are present. taining the divalent radicle SO2, he gives : Thus, of compounds con- Type. Salph~iric acid. H H Sulphurous acid. H IIr. { H Hydrogen ethylic sulphate. Beiizenesulphonic acid. “ Compound radicle ” is understood in Gerhardt’s sense of ‘‘ a residue left unattacked in any particular reaction,” and the “ basicity ” (valency) of these radicles is deduced from the number of atoms, greatly differing from the radicles themselves in chemical character, with which they combine.This introduction of the radicles into the types, which must at the time have appeared to place the type theory on a firm basis, was destined to render that theory unnecessary. Another point worthy of note is the way in which Kekule uses the action of the chlorides of phosphorus t o distinguish between the water type and the hydrogen type. Ueveloping an idea to be found in his memoir on thiacetic acid, he points out,,that, in the case of the water type, two atoms of chlorine replace one atom of typical oxygen, causing the compound to break up type is not acted upon into two atomic groups, whereas the hydrogen and remains intact. Thus yields ~- C , H , , E SO,”,Cl, _____- H, C1126 JAPP : KEKULI~ MEMORIAT, LECTURE. C6H5 yields SO,”,Cl H, C1 I n the foregoing paper, Kekulh accepts the radicles (residues) i n the form in which he received them from his predecesors and empirically deduces their valency from a study of their compounds.I n his great theoretical paper, published the following year (Annulen, 1858, 106, l a g ) , ‘‘ On the Constitution and Metamorphoses of Chemical Com- pounds, and on the Chemical Nature of Carbon ”-a paper which is the foundation of our present theories of organic chemistry-he goes t o the root of the matter. H e says:- “ I regard it as necessary and, in the present state of chemical knowledge, as, i n many cases, :possible, to explain the properties of cheniical compounds by going back to the elements themselves which compose these compounds.I no longer regard it as the chief problem of the time, to prove the presence of atomic groups which, on the strength of certain properties, niay be regarded as radicles ; and in this way to refer compounds to a few types, which can hardly have any significance beyond that of mere pattern formulae. On the contrary I hold that we must extend our investigation to the constitution of the radicles themselves ; that we must ascertain the relation of the radicles to one another and, from the nature of the elements, deduce both the nature of the radicles and that of their compounds.” H e then points out how the conception of the valency of the different elements mag be utilised for this purpose. I n this connection he further develops his ideas on the tetravalency of carbon, and gives the list of compounds : CH,, CCl,, CH,Cl, CHCI,, COCl,, GO,, CS,, CNH, pointing out that “ t h e sum of the chemical units combined with one atom of carbon is 4.This leads to the view that carbon is tetrutomic (or tetrabasic).” At this point he introduces (Zoc. cit., p. 153, footnote) a passing reference to the advantage of referring com- pounds t o the marsh gas type : ‘& If carbon isintroduced as a tetrutomic rudicle among the types, several already known compounds may be formulated in a relatively simple manner.” He next proceeds to discuss the question of the linking of carbon atoms with one another : ‘( In the case of substances which contain severd atoms of carbon, one must assume that some at least of the atoms are held in the conipound in the same way [as in the cases already quoted] by the affinity of the carbon, and that the carbon atoms themselves are attached together, whereby a portion of the affinity of the one carbon atom is of course held in combination by an equal portion of the affinity of the other.“ The simplest and therefore most probable case of this union of two carbon atoms is that in which one unit of affinity of the one carbon atom is combinedJAPP : I< EKULB MEMORIAL LECTURE. 127 with one unit of affinity of the other. Of the 2 x 4 units of affinity of the two cttrbon atoms, two are used up in holding the two atoms together ; there tliere- fore remain six which may be held in coiiibination by atonis of other eleiiients. I n other words the group C2 is hexatomic.. . . . . “ If more than two carbon atoms unite in the same way, the basicity of the carbon group will be increased by two units for each fresh carbon atom. Thus the number of hydrogen atoms (chemical units) which rnay Le combined with n carbon atoms is expressed by n(4 - 2)+2 = 2?1+2. ‘ r . . . . Up to this point we have assuiued that all the atonis attaching themselves to carbon are held by the affinity of the carbon. I t is eqiially conceivable, however, that in the case of polyntoxnic elements (0, N &c.) only a part of the affinity of these-for example, only one of the two units of’ affinity of the oxygen, or only one of the three units of the nitrogen-is attached to carbon ; so that one of the two units of affinity of the oxygen, and two of the three units of affinity of the nitrogen, remain over and may be united with other elements.These other elements are therefore only in indirect union with the carbon, a fact which is indicated by the typical mode of writing the formulae : ‘‘ I n like manner the carbon groups are held together by the oxygen or the nitrogen.” * H e points out t h a t a great many organic compounds may be formu- lated on the basis of the “ simplest ” attachment of carbon t o carbon, but that, i n others which contain more carbon in proportion the “ next simplest ” attachment may be assumed, involving a closer union of the carbon atoms. H e does not, however, go into details regarding the principles t o be adopted in formulating such unsaturated compounds. It is t o be noted t h a t at t h a t time Kekulb still held Gerhardt’s view that rational formuh were merely a n expression of chemical reactions.The idea t h a t it was possible to express the relative positions of the atoms within the molecule was of later growth. KekulB had by his interpretation of the types in terms of the law of valency, and by his dissection of the compound radicles in accordance with t h e same law, superseded both t h e type theory and the radicle * As a further example of how little Kolbe thought it necessary to master the details of theories he set himself to criticise, the following passage may be quoted, in which, after making merry over the expression “ carbon skeleton,” used by Kekul6 in the foregoing paper, he says (J. pr. Chem., 1881, [ii], 24, 407) : “ If 1 am not mistaken, i t is assumed that all organic compounds which contain more than one atom of carbon possess snch carbon skeletons. Where, then are we to place the cacodyl Compounds, trimethylamine, trimethylsulphine iodide and other organic substances ? ”128 JAPP : KEKULB MEMORIAL LECTURE, theory, except so far as they might be useful for purposes of exposi- tion.Nevertheless, partly as a concession to the prevailing usage of his school, and partly, doubtless, from force of habit, he continued for a long time to write typical formulx. This led to R somewhat mechanical mode of formulation, occasionally attended with misleading results. Thus, in the paper just quoted (pp. 145-146), we find benzene for- mulated on the hydrogen type and benzoic mid on the wat,er type, which leads him to state that, in the sulphonation of benzene, it is the typical hydrogen, but, in that of benzoic acid, hydrogen of the radicle, which is replaced, and to assign these reactions to two distinct categories.Again the hydroxy-Rcids are formulated on the double water type ; thus lactic acid is C3Hgi ) 0, ; a mode of representing these substances which obliterates the distinction be- tween the acidic and the alcoholic hydrogen atoms, and was responsible for the errors into which Wurtz fell in the earlier part of his well- known controversy with Kolbe. Kekulk himself is perfectly clear about the difference between these two typical hydrogen atoms and explains its cause with all possible precision (LeTLrbuch, 1, 731) ; nevertheless he quotes the formula C3H4(H0g } 0 for lactic acid (first put forward in the old equivalents by Kolbe) only to reject i t with the remark (Zoc.cit., p. 736) : ‘‘ Such formulae offer no advantages over the typical formuls ; on the contrary they conceal a great number of analogies and, in other cases, cause analogies to be suspected where none exist.,’ I venture to think t h a t I have just shown t h a t the typical formulae are not quite free from these defects. As regards the particular case of the formula of lactic acid, there is no doubt that the reluctance which Kekulk and his school a t t h a t time displayed to make use of the hydroxyl group in formulating compounds was an effect of Laurent’s supposed burlesque proof of the existence of the radicle eurTqxene, that is, hydroxyl (see Laurent’s Chemical Method, Odling’s translation, p.293). I say “ supposed burlesque,’’ because, at the present day, there is probably no chemist who has occasion to refer to ‘‘ the hydroxyl-group ”-which, in chemical compounds, is a n abstrac- tion and, in certain electrolytic dissociations, an entity-but would willingly subscribe, in all seriousness, the words which Laurent wrote in jest.* * When, however, Kekul6 (Lchrbuch, 1, 736, footnote) quotes Laurent’s ezcrhyzcne as a proof that Kolbe’s view of the constitution of the acids of the lactic series a3 hydroxy-derivatives of the acids of the acetic series, is not original, one can only surmise that he was infectod by Laurent’s spirit of elaborate pleasantry.JAPP : KEKULE MEMORIAL LECTURE.129 This adherence to the outward form of the typical formulz was, however, a minor defect, especially as KekulC? showed in his LeJwbuch how, by means of his graphic formulz!, the relations of the different atoms t o one another within the molecule might be clearly exhibited. The graphic symbols were, however, as Kekulb himself pointed out, too cumbrous for ordinary use; they shared the fate of Dalton's atomic symbols and had to yield to the superior simplicity of those of Berzelius, which, with a few additions in the shape of bonds and valency marks, were found to satisfy all requirements. Even the circles with which Crum Brown, in his system of graphic formulz!, a t first surrounded the symbols, were soon discarded. KekulB's models of atoms, on the other hand, to which reference will be made later, had a brilliant future before them.It must be mentioned that, shortly after the publication of Kekulb's paper on the constitution of chemical compounds, analogous views were put forward independently by Couper (Ann. ClZm. PJqs., 1858, [ iii], 53, 469 ; PJd. Mug., 1858, [ i ~ ] , 16, 104). The two investigators followed different paths, and their results were in some respects different. Kekule accepted the type theory and furnished it with a philosophical basis by explaining the existence of the pattern formuh, or types-simple, multiple, and mixed-by mea.ns of the valency of the constituent elements; Couper, on the other hand, rejected the type theory alto- gether, and, starting with the idea of the valency of the elements, proceeded to construct constitutional formulz for various compounds.Couper held peculiar views on the subject of the atomic weights : thus, whilst carbon was C = 12, oxygen was only 0 = 8. Carbon was tetrsdic ; and the small oxygen atoms were dyadic, but were supposed always to occur linked together in pairs, so that the resulting group, 0 a - 0 0, as Couper wrote it, was also dyadic, and was therefore, to all intents and purposes, identical with the dyadic 0 = 16. The following formuls will illustrate his system : Meth ylic alcohol. Formic acid. VOL. LXXIII. 0 * * * O H C C -** H, Ethylic alcohol. p { ;;**OH C ***H, Acetic acid. C .*.II, H, ***C Etliylic ether. Propylic a1 coliol. K130 JAPP : KEKULE MEMORIAL LECTURE. Couper’s formulae are thus, in spite of the peculiarity in the mode of writing oxygen, nearer to our present formulze than those used by Kekuld at that period, and from the manner in which he discusses them it is evident that he intends them to be constitutional formulze and not mere “ f o r m u l ~ of double decomposition” such as were emplojed by Gerhardt’s school.The constitution assigned to the foregoing compounds is, however, identical with that previously pro- posed by Kolbe, with a difference, however, in the mode of writing the formuh. Kolbe (J. jur. Chenz., 1581, [ii], 23, 366) and Frankland (PYOC. Roy. Soc., 1865, 14, 108) claim to have anticipated Kekule’s enunciation of the tetravalency of carbon in a paper which they Q published in 1857 (Annalefi, 1857, 101, 262 seq.).This claim, however, cannot be sustaiued, unless we ignore the list of compounds formulated on the marsh gas type, which Kekuld drew up in his paper on mercuric fulminate published a short time previously. Kolbe, indeed, gave what he considered to be reasons for ignoring this list; but I believe I have shown (p. 123) that these supposed reasons are based on a misunderstanding of Kekulk’s meaning. Kol be and Frankland’s paper appeared so soon after KekulB’s that there can be no doubt of their having arrived a t their conclusions quite independently of Kekulk, the more so as these conclusions are drawn entirely from their own work. Moreover, as the whole paper deals with the ap- plication of the law of valency, discovered by Frankland, t o the interpretation of the constitution of organic compounds, i t is clear that the authors had the tetravalency of carbon, or rather the tetravalency of the double equivalent, C,, in their minds, although they did not mention it in so many words.Frankland had alreadyshown (v. supra) how cacodylic acid might be derived from arsenic acid, or, strictly speaking, how the hypothetical cacodylic anhydride might be derived from arsenic anhydride, by replacing two equivalents of oxygen by two of methyl. Kolbe and Frankland iiow apply this view to the hydrated acids : thus from 3HO,AsO, 2110,s20, 2HO,C20, Arsenic acid, Sulphuric acid. Carbonic acid. they deduce H07(C2f13)2As0, 110 ) ( c, f f 3 ) s2 0 j HO, (C2~3~C20, Dimethylarsenic 1Iethylsulphnric Methylcarbonic (cacodylic) acid. (i~iethylsnlplionic) acid.(acetic) acid. * Through inadvertence this paper appeared under Kolbe’s name only (compare Frankland’s Experimcntal Researches, p. 148). Except in the opening sentences, in which Iiolbe is referring to previous work of his own, the pronoun “ we ” is used throughout as denoting the joiu t authors.JAPP : KEKULE MEMORIAL LECTURE. 131 They point out that, for each atom (equivalent) of oxygen which is replaced by methyl, one equivalent of water HO is simultaneously removed, so that for each introduction of a methyl group the basicity of the acid is reduced by 1. By replacing a further atom (equivalent) of oxygen in acetic acid by hydrogen or by methyl and again simul- taneously removing HO, they obtain and A1 de h y de Ace tone which are no longer acids a t all.Further on, in the same paper, they point out that carbonic acid may be formulated 2H0,(C,0,)02, and that it is the two ‘‘ extra-radical ” oxygen atoms which are replaced by methyl, each carrying with it an equivalent of water. If we translate this into modern atomic weights, each “extra- radical ” equivalent of oxygen, plus an equivalent of water, represents a hydroxyl group : 0 + HO(0 = 8) = OH(0 = 16) ; so that the above formula for carbonic acid is identical with CO(OH),. It is thus hydroxyl of the hypothetical carbonic acid, and not, as the authors suppose, oxygen of carbonic anhydride, which is replaced by methyl or hydrogen in the foregoing mode of deducing acetic acid, aldehyde, and acetone from carbonic acid. The tetravalency of the double equivalent of carbon, C,, is certainly implied in Kolbe and Frankland s paper ; but, as already mentioned, it is nowhere expressly stated, and one may be permitted to doubt whether many chemists could a t t h a t period have disentangled the doctrine from the very complicated hypothesis in which the me of the old equivalents had compelled the authors to involve it.Those who profited most by the work were those who could translate it into Gerhardt’s atomic weights, and probably Kekul6 and his school were more indebted to it than they were a t that time conscious of. It is clear, however, that the paper contains no hint of the linking of carbon atoms, as this conception could not be developed in terms of Gmelin’s equivalents. Indeed, so far as Kolbe was concerned, even after he had accepted the new atomic weights, he continued, to the end of his life, to cast ridicule on this conception (compare J.pr. Chem., 1881, [ii], 24, 414). That Kolbe and Frankland’s work on the tetravalency of carbon did not, therefore, exercise a direct and immediate influence in any degree comparable with that produced by Kekulk’s great paper on the same subject, is to be ascribed to the fact that their conclusions were stated in terms of an inconsistent scheme of atomic weights. We must not forget, however, that the same principle, namely, that of the K 2132 JAPP : KEKULk MEMORIAL LECTURE. derivation of org’anic acids, aldehydes and ketones from carbonic acid, led Kolbe, later on, to the prognosis of secondary and tertiary alcohols, of which triumph of theoretical foresight the germ is con- tained in the concluding paragraph of Kolbe and Franklaad’s paper (compare Annulen, 1857, 101, 265).The concep- tion which he introduced in these, as to the distribution of the four affinities of the carbon atom, has led to most important results. He begins by referring (2eitschr.f. Chem., 1867, N.F., 3,217) to the im- perfections of his original system of graphic formuh and of the models based upon them, and further points out that models con- structed on the basis of Crum Brown’s graphic formulE and consisting of spheres with rods radiating from them in one plane, do not really express more than the graphic formulce themselves, inasmuch as the representation which they afford of a space formula is only apparent, the atoms being all in the same plane; and that, unless the rods are bent or arbitrarily displaced, certain combinations, e.g.triple bonds between carbon atoms, cannot be represented by them at all. He then proceeds to describe a model of the carbon atom which he has devised and which avoids these difficulties : “The four units of affinity 0; the carbon atom, instead of being placed in one plane, radiate from the sphere representing the atom in the direction of hexahedral axes, so that they end in the faces of a tetrahedron. . . . A model of this description permits of the union of 1, 2 and 3 units of affinity, and, it seems to me, does all thnt a model can do.” Even while making this apparently sweeping statement, Kekulh can hardly have realised the part that this model was destined to play in the development of theoretical chemistry; how in van’t Hoff’s hands it was to be the means of tracing the subtle asymmetry which Pasteur had deduced from the optical behaviour and the crystalline form of certain organic compounds, back to the asymmetric structure of the molecule itself; of explaining the mysterious isomerism of fumaric and maleic acid, which had baffled Kekulh’s own acumen ; and of laying down the space conditions of existence or non-existence of the closed-bhain compounds of which Kekuli: himself had introduced the conception into chemistry in his benzene theory.I have already referred to Kekulb’s benzene theory as the crowning achievement of the doctrine of the linking of atoms. To give a com- plet,e account of this theory and of the criticisms to which it has been subjected, mould far exceed the scope of the present lecture; whilst to treat it briefly may seem superfluous, as the theory, in its main outlines, is familiar to every one with even the most elementary know- ledge of organic chemistry.I have already referred t o Kekalb’s models of atoms.JAPP : KEKULI~ MENORIAL LECTURE. 133 This theory was first published in 1865 in the Bulletin de la Xoc. ~himique (1, 9s). I quote, however, from the fuller account published a year later in Liebig’s Annalen (1866, 137, 129). I n this paper, ‘‘ On the Constitution of the Aromatic Compounds,” Kekuld begins by stating that none of the chemists who have dealt with the subject of benzene and its derivatives, have attempted t o deduce the constitution of these compounds from the tetravalency of carbon and that some have gone so far as t o state that this cannot be done.H e then enumerates various distinguishing characteristics of the benzene compounds: amongst others, that there is no benzene compound containing fewer than six carbon atoms. After pointing out that six carbon atoms might be linked together by alternate si isle and double bonds, he says : ‘‘ If one assumes that six carbon atoms are attached to one another according to this law of symmetry, one obtains a group which, regarded as an open chain, contains eight unsaturated units of affinity. By making the further assump- tion that the two carbon atoms at the ends of the chain are linked together by one unit of affinity each, a dosed chain (a syrnnietrical ring) is obtained, which still contains six unsaturated units of affinity.* “From this closed chain all the substances ueually designated as ‘aromatic compounds ’ are derived.. . . ‘‘ In all aromatic substances a common nucleus niay be assumed : it is the closed chain C,A, (in which A denotes an unsaturated affinity). “The six affinities of this nucleus may be satisfied by six monatomic elements. They may also, wholly or at least in part, be satisfied by one affinity of polyatomic elements, the latter necessarily bringing with them other atoms into the compound, thus producing one or more side chains, which in their turn may be lengthened by the addition of other atoms. ‘‘ The satisfying of two affinities of the nucleus by one atom of a diatomic element, or of three affinities by one atom of a triatomic element, is, according to the theory, impossible. Compounds of the molecular formulz, C,H,O, C,H,S, C,H,N, are, therefore, unthinkable.” Here we meet for the first time (if we except Kekule’s preliminary note on the same subject) with the now familiar expressions ‘‘ closed chain,” “ nucleus,’’ and ‘‘ side chain,” without which it would, a t the present day, be impossible t o discuss the problem of the constitution of the benzene compounds. The last paragraph quoted is worthy of note : it contains a very positive statement on a point which does not appear t o follow with absolute necessity from the formuls which Kekuld uses.It involves conceptions regarding the actual distribution of the atoms in space; and the conclusion at which Kekulk arrives suggests that he was already using the space-models of atoms which he described two years later.* I n the original paper these atomic groups are represented by means of KelrulB’s graphic formulae.134 JAPP : K E K U L ~ MEMORIAL LECTURE. He points out that the foregoing constitution of the benzene nucleus involves the equivalence of the six unsatisfied affinities and proceeds to deduce the number of possible substitution derivatives of benzene, containing 1, 2, 3, &c., identical substituents, the isomerism depending on the relative positions of the substituents towards one another. Amongst other things he points out that whereas there are only three substitution derivatives possible of the general formula c6H3x3, there are six of the formula C,H,X2Y. I n stating this conclusion he makes use of a hexagon lettered as follows d and says : ‘‘ For dibromnitrobenzene, for example, there would be the following forms : ‘‘ (1) For a b c : C,H3BrBr(N0,) C,H,Br( N0,)Br (2) For a b d : CGH,(N0,)HBr2 C,H,BrH(NO,)Br C,H,BrHBr( NO,) (3) For u c e : C6HBrHBr(N02).” It was this series of compounds that Korner used later (Gaxxetta, 1874,4,305) inhis well-known method for the orientation of the bromine atoms in the dibromobenzenes. ‘‘ The homology may depend either upon an increase in the number of the side chains, or on the lengthening of side chains the number of which remains the same.” Thus there ought to be three dimethylbenzenes (only one was at that time known) and, isomeric with these, the synthetical ethylbenzene of Fittig and Tollens.The lam of oxidation of the homologues of benzene is laid down : namely, that each hydrocarbon side chain, no matter how many carbon atoms it may contain, is oxidised away, with the exception of the carbon atom attached to the nucleus, which remains in the shape of a carboxyl-group. The resulting acids thus contain as many carboxyl- groups as there were hydrocarbon side chains in the original compound. By more moderate oxidation intermediate products are obtained : thus, xylene and cymene both yield toluic acid. Moreover, the possibility is foreseen, in the case of side chains containing more than one carbon atom, of oxidising only a portion of the chain, and thus obtaining an acid in which the carboxyl is not directly attached to the nucleus.The question of substitution in the nucleus and substitution in the The homologues of benzene are discussed.JAPP : KEKULh MEMORIAL LECTURE. 135 side chain is also gone into, and the difference in the character of the At the end of the theoretical portion of the memoir, Kekul6 says, referring t o different possible formulce for benzene : ‘( A problem of this kind might at first sight appear quite insoluble ; but I nevertheless believe that experiment will furnish a solution. I t is only necessary t o prepare, by methods as varied as can be devised, as great a number of substitution products of benzene as possible ; to compare them very carefully with regard to isomerism ; to count the observed modifications ; aiid especially, to endeavour to trace the cause of their difference to their mode of formation.When all this is done we shall be in a position t o solve the problem.” Could the course of subsequent investigation in this field have been more accurately laid down in advance? Kekulh’s memoir on the benzene theory is the most brilliant piece of scientific prediction t o be found in the whole range of organic chemistry. What Kekuld wrote in 1865 has since been verified in every essential particular. Not only have the various substitution derivatives been discovered, in the number and with the properties required by the theory, but various observations which appeared to contradict this theory have been proved erroneous. Moreover, the theory has shown itself capable of boundless development.There seems t o be no limit to the fruitfulness of Kekule’s conception of closed chains or cycloids. The extensions of the idea, of which exten- sions Erlenmeyer’s naphthalene formula and Dewar’s formuh for pyridine and quinoline were amongst the earliest instances, have gone on increasing in a rapid geometrical ratio, until, at the present day, the literature dealing with cycloids, although of so recent growth, is more than twice as voluminous as that of the paraffinoids. To quote the words of the address which our Society presented to Kekuli! on the occasion of the Benxolfeeier : ‘‘ This theory found the chemistry of even the immediate derivatives of benzene an almost untilled field ; i t has transformed i t into a fertile province, to which hare been annexed regions the very existence of which was unknown.” But even in the undeveloped state of the subject prior to Kekule’s theory, the facts were apparently so intricate and so unconnected that few chemists could claim to have mastered them.The theory appeared ; the previously unmarshalled facts fell into their proper places ; and not only this, but it was possible t o say whether, in any given section of the subject, the facts were complete or only frag- mentary. The increased ease in dealing with this branch of chemistry, the fascination of the numerous scientific problems which KekulB’s theory suggested, and lastly the economic importance of many of the benzene compounds and of other allied cycloids, attracted to this Geld restilting sl6riratiTes is pointed oat.136 JAPP : KEKULlf: MEMORIAT, LECTURE.a crowd of workers, whose numbers, if they have not of late years actually increased, at least show no signs of diminishing. The debt which both chemical science and chemical industry owe to Kekuld’s benzene theory is incalculable. As regards the former, three-fourths of modern organic chemistry is, directly or indirectly, the product of this theory; and as to the latter, the industries of the coal-tar colours 2nd the artificial therapeutic agents, in their present form and exten- sion, would be inconceivable without the inspiration and guidance which they have received and still receive from Kekule’s fertile idea. Various points in Kekule’s theory which were at first either funda- mental assumptions, or deductions from these fundamental assump- tions, have since been experimentally proved : thns the equivalence of the six hydrogen atoms in benzene by Ladenburg, and the fact that there is, relatively to every hydrogen atom, a symmetrically situated ortho-pair and a symmetrically situated meta-pair, by Hubner and Petermann, Wroblewsky, and others.The orientation of the substituents in the derivatives of benzene, merely indicated by KekulB, has been successfully carried out by von Baeyer, Graebe, Ladenburg, Griess, and, above all, Korner. The con- cordant results obtained by the most diverse methods have placed this part of the subject on a sure foundation. The non-identity of the two ortho-positions 1 : 2 and 1 : 6 in Kekulk’s formulz containing alternate double and single bonds, which is in contradiction to the proved identity of the two ortho-products and which would necessitate the existence of four isomeric disubstitution derivatives instead of three, has called forth much criticism.Kekulk sought to meet the difficulty by means of his well-known oscillation formula, in which the double and single bonds continually exchange places. This is virtually a return t o the simple hexagon, given as an alternative formula by Kekuli: in his original paper : the distribution of the unsaturated affinities is ignored. 01 the various formula which have been proposed in place of KekulB’s, I will mention Ladenburg’s prism formula, CIaus’s diagonal formula, and Armstrong and von Baeyer’s centrical formula.All of these agree with Kekule’s formula in connecting together six CH-groups by single bonds so as to form a closed chain; the disposal of the re- maining six affinities is the point wherein they differ. Ladenburg’s formula is seldom discussed at the present day. It represents the ortho-carbon atoms as not directly connected, thus ignoring the analogy between the ortho-position in benzene compounds and the a-position in paraffinoid compounds, and rendering the formulation of compounds like naphthalene and phenanthrene impossible, a t least in accordance with the prevailing views. Moreover, the substitution of any two dissimilar groups for hydrogen would render carbon atoms ofJAPP : REKULE MEMORIAL LECTTJRE. 137 the nucleus asymmetric, so that every compound of the general formula C,H,XY ought to exist in two enantiomorphous forms, whereas all efforts to isolate such forms have hitherto proved fruitless, benzene derivatives being optically inactive unless there is an asymmetric: carbon atom in a side chain, Claus’s diagonal formula was formerly objected to on the ground that the ortho- and para-positions were identical and that it therefore required the existence of only two di- substitution products. This difficulty has been got over by introduc- ing spatial considerations and assuming that the greater distance between the para-carbon atoms, as compared with the ortho-, con- stitutes a difference.It is necessary, however, further to assume that the carbon and hydrogen atoms lie in one plane, obherwise asymmetric substitution derivatives would exist ; and this assumption, taken in conjunction with that of para-bonds, would appear t o demand the placing of the four affinities of carbon in one plane; in other words, i t would involve the abandonment of van’t Hoff’s tetrahedron. The centrical formula is difficult to criticise ; the mode of disposing of the central bonds is entirely without analogy and does not appear to be accessible t o the test of experiment. I n its application and predic- tions, the centrical formula is identical with Kekulh’s simple hexagon. The question of the disposal of these unsaturated affinities is, indeed, a very difficult one. Thus von Baeyer, who formerly opposed Claus’s formula, has now, with certain limitations, adopted it (Annalen, 1892, 269, 177). According to him, it is impossible to devise a benzene formula which shall be applicable t o all derivatives of benzene. H e regards (Zoc. cit. p. 188) phthalic acid as derived from a benzene of Claus’s formula and phloroglucinol from one of Kekulb’s formula with alternate double and single bonds : OH HOII IOH Phthalic acid. Phloroglucinol. /’\ \/ Possibly the solution of this difficulty will be found when we possess a space formula capable of representing these various modes of distri- buting the unsaturated affinities as different desmotropic oscillation - phases of a ring of 6 CH-groups (compare Collie, Trans., 1897, 71, 1013). Of such a formula KekulB‘s oscillation formula is a partial anticipation. Meanwhile chemists will doubtless continue to emploj. Kekule’s simple hexagon, without alternate double and single bonds, as a statical representation of the symmetry of the benzene molecule. Various other important theoretical questions discussed by Kekule might be mentioned here; but time does not permit.1 :38 JAPP : K E K U L ~ MEMORIAL LECTURE. If, in conclusion, we ask ourselves what is the characteristic note of Kekulk’s theoretical creation, the chemistry of structure, I think we may reply that it is the treatment of the problem of isomerism-the problem which first necessitated the use of constitutional formulae- as one of geometrical symmetry. Kekulb’s formulae, stripped of the fetters of the type theory with which he a t first encumbered them, were, from one point of view, merely more or less symmetrical geo- metrical figures. I n order to predict the number of substitution com- pounds, it was only necessary to consider the degree of dissymmetry of the parent compound : the less the symmetry, the greater the num- ber of isomeric substitution compounds. The extraordinary fertility of this conception is shown by the development which it has under- gone a t the hands of van’t Hoff, J. Wislicenus, von Baeyer, and others. Kekul6’s structural formulae cleared away at one stroke the entire brood of pseudo-constitutional formulae. If organic chemists no longer waste their time in wrangling over the question whether, for example, methylamine is methane in which one atom of hydrogen is replaced by the amido-group, or ammonia i n which one atom of hydrogen is re- placed by methyl, the merit is Kekuld’s. The accuracy of Kekulk’s predictions has done more to inspire a belief in the utility of legitimate hypotheses in chemistry, and has therefore done more for the deductive side of the science, than that of almost any other investigator. His work stands pre-eminent as an example of the power of ideas. A formula, consisting of a few chemical symbols jotted down on paper and joined together by lines, has, as we have just seen, supplied work and inspiration for scientific organic chemists during an entire generation, and affords guidance to the most complex industry the world has yet seen. Although much research remains t o be done on the lines laid down by Kekul6, yet other problems are clamouring for solution, and other methods of investigation have been called into existence to solve them. The younger generation of chemists are, fortunately, labouring dili- gently in the field of physico-chemical research, which the organic chemists, occupied with questions of chemical structure, had perhaps unduly neglected. One problem, however, which, in many points at least, still awaits the physical chemist, is the correlation of his results with those of the structural chemist. When this is fully accomplished, there will be a debt of gratitude on both sides; but no one will be entitled t o more gratitude than August Kekul6.

ISSN:0368-1645    

DOI:10.1039/CT8987300097

出版商:RSC    

年代:1898

数据来源: RSC

摘要:

COMPOUNDS OF PIPERIDf NE WITH PHENOLS. 139 By OTTO ROSENHEIM, Ph.D.: and PHILIP SCHIDROWITZ, Ph.D. INTRODUCTORY. THE action of pipcridine on dihydric and trihydric phenols and their derivatives in the presence of dehydrating agents was studied with the object of obtaining compounds of the general formula as such substances, on account of their relation to the phenylene- diamines and the polyamines, would be of interest. Our experiments in this direction have not as yet led to the desired result, but, instead, a series of additive products wag obtained, and as these have not hitherto been described * we propose to give some account of them in this paper. As a rule, they can be obtained well crystallised and practically pure by mixing solutions in ether or light petroleum of the base and the phenol, Their behaviour towards strong acids and alkalis, by which they are a t once resolved into their components, is evidence of the labile, ad- ditive character of the salts.With the exception of the yellow nitro- derivatives, they are all colourless, and, as a rule, easily soluble in water and most organic solvents. After a time, and in some cases almost instantaneously, the aqueous solutions undergo characteristic colour changes (compare Oechsner de Coninck, Zoc. cit.), possibly due t o the formation of more complicated substances, in which the piperidine radicle is directly united to the benzene ring. This change was studied more minutely in the case of the quinol derivative, the colouring matter formed being well crystallised and easily isolated. The analysis of these substances and their behaviour towards acids lead us to the conclusion that they are of the nature of salts in which piperidine is the basic, and the phenol the acid constituent.? Phenol aud a- and ,&naphthol do not yield crystallisable compounds.$ * Oechsner de Coninck (Co?npt. rend., 1897, 124, 563), in a paper entitled “Action du tannin et d’autres dCriv@s aroinatiqnes sur quelqoes alkaloids et ur6es compos4es,” describes various colour reactions obtained by the action of piperidiiie on phenols in dilute aqueous solutions, but apparently did not observe the formation of the primary acid i tive prodnc ts..t. Substances of a similar nature mere obtained by the action of phenols on aniline (A. Hebebrandt, Ber., 1882, 15, 1973 ; P.Mylius, Ber., 1886, 19, 1002), and piperazine (Schmidt u. Wichmann, BcT., 1891, 24, 3237). :: T. Abel (Bcr., 1895, 28, 3106) only obtained a very small quantity of v-phenyl- piperidine, when operating with phenol and piperidiiie in sealed tubes a t high temperatures, but found that a- and &naphthol reacted easily. C”H,e - n)( CsNlo:N),,,140 ROSENHEIM AND SCHIDROWITZ : COMPOTJNDS O F There is apparently no direct connection between the number of piperidine molecules uniting with the phenol and the number of hydroxy- or other radicles of an acid nature contained in the l a t t e r ; but the position of the ncgative group appears to be of importance : (1.) In regard to the f o r m a t i o n of t?te compounds.-The meta-position appears to be the most unfnvourable.Resorcinol,* phloroglucinol, and metanitrophenol do not yield crystallisable compounds, whereas pyro- catechol, quinol, 1 : 2 : 4-a-dinitronaphthol, ortho- and para-nitrophenol, guaiacol, picric acid, &c., do so with ease. (2.) In regard to moleculccr combining proportions.-The influence of position is apparently of a more complex nature, and the most notice- able feature is rather the lack of influence of the number of negative groups, more especially of the hydroxyl-group, in the acid constituent. Thus 1 mol. of piperidine combines with 1 mol. of quinol (2 hydroxyls), 1 mol. of pyrogtlllol (3 hydroxyls), 1 mol. of vanillin, and 1 mol. of ortho- or pars-nitrophenol; but with 2 mols. of pyrocatechol and 2 mols. of pyrocatechol monomethyl ether.It may be added here that, in all cases, variation in the proportions of the substances employed has no effect on the composition of t,he final product. EX P E R I M E N T A L. I n the majority of cases, the method of o’atnining these substances Any clis tinct The yield is in almost was broadly as described under piperidine-pyrocatechol. variation will be noted in the proper place. every instance quantitative. Piperidine-Pyocat echol, C,H, ,N, (C,H,O,), . Cold concentrated ethereal solutions of pyrocatechol (2 mols.) and piperidine (1 mol.), when mixed, began t o boil owing t o the violence of the action, aad the salt separated almost immediately in glistening scales, which were at once collected, mashed with a little ether, and rapidly dried in a vacuum. The white crystals thus obtained, as also the ethereal solution (if not anhydrous), quickly assume a red- dish tint, and finally become brown on exposure t o the air.If aqueous solutions of piperidine and pyrocatechol are mixed, using the former in excess, the liquid remains clear, but rapidly becomes wine red and finally dark brown. If excess of pyrocatechol is employed, however, the salt described above is precipitated as an oil, which solidifies on rabbing it with a glass rod. * F. Mylius ( B e y . , 1886, 19, 1002) failed to obtain an additive product from aniline and resorcinol, but succeeded in the case of pyrocatechol.PIPERIDINE WITH PHENOLS. 141 The substance melts a t 80--81", and is very soluble in water and most organic solvents, with the exception of light petroleum.Found, C = 67.10 ; H = '7.52 ; N" = 4.87 per cent. C17H,,04N requires C = 66.S5 ; H = 7.59 ; IS = 4.60 per cent. Pipedin+Guaia;coZ, C,H,,N, [ C,H4( OC €I,) (0 H)I2, is best obtained by dissolving the guaiacol (2 mols.) in benzene and the piperdine (1 mol.) in light petroleum, and after thoroughly washing the white, crystalline mass with light petroleum, recrystallising from acetone or a mixture of benzene and light petroleum. It forms splendid colourless prisms, melting a t 79-80', and fairly soluble in water, very easily in benzene, slcoliol, ether, acetone, and ethylic acetate, but almost insoluble in light petroleum. The pure substance gradually assumes the odour of guniacol on exposure to the air. Found, C = 69-02 ; H = S.21 ; N = 4.32 and 4.41 per cent.C,,H,7N0, requires C = 68.42 ; H = 8.16 ; N = 4.21 per cent. The substance, when evaporated several times on the water bath with concentrated hydrochloric acid, is totslly decomposed, the whole of the guaiacol being volatilised and piperidine remaining as hydro- chloride. I n a quantitative experiment, this was dried and weighed. Found, 36-6 per cent.; calculated for weight of piperidine hydro- chloride, 36 *5 per cent. Under similar conditions, pyrocatechol monethyl ether gives no crystallised salt. We are indebted to Dr. F. W. Tunnicliffe for the physiological and therapeutical examination of this product, and a short note on this subject, which he has sent us, will be found a t the end of this paper. Pipwidine-Quinol, C,HIIN,C,H,O,. This was obtained from the ethereal solution (1 mol.of each) of the components in a pure state as colourless nodules made up of small needles; on heating, i t turns brown, and finally melts a t 102-104°. The white crystals gradually become reddish, and finally deep purple on exposure to the air, even when kept in a stoppered bottle, Lachowitz's dipiperilhenzoquinone being no doubt formed (Monatsl~. , 1888, 9, 506). This transformation proceeds with great rapidity in an alcoholic solution of the salt, which, after 24 hours, becomes deep purple and deposits dark blue crystals. These were easily We found that Gunning's modification of Kjeldahl's method (Zcitschr. f, anal. Chenz., 1889, 28, 189), which has always given us admirable resnlts in the analysis of food stuffs, &c., invariably yielded several per cent.too little in the case of the substances described in the present paper. * Nitrogen WRS throughout estimated by Dumas' method.142 ROSENHEIM AND SCIEIDROWITZ : COMPOUNDS OF identified by their melting point, 178", and their insolubility in water and organic solvents, with the product obtained by Lachowitz men- tioned above. This change, however, does not take place if the salt is kept in a sealed tube, even when exposed for several months to strong s iinl ig h t . The transformation of the white additive product into the blue substance which, according to Lachowitz, contains the piperidine radicle directly united to the benzene ring, appears to be due to the action of oxygen, 2[CGH,(OH),,C,H,,N] + 3 0 = C,H,02,(C5H,oN), + C6H,(OH)2 + 3H,O.The fact that Lachowitz worked with an alcoholic solution in which piperidine-quinol is easily soluble, is no doubt the reason why he failed t o observe the formation of the intermediate product. Found, C = 67.52 and 67.96 ; H = 8.6 6 and 8.69 ; :N = 7.27 per cent. C,,H,pNO, requires C = 67.61 ; H = 8.77 ; N = 7-19 per cent. When resorcinol or phloroglucinol were treated with piperidine under similar conditions, a thick, resinous mass was obtained, from which no crystalline product could be isolated. This is obtained in white needles, which evolve gas a t l l O o , become discoloured at 140", and melt a t 171" ; it is easily soluble in water and alcohol, but almost insoluble in benzene, chloroform, acetone, and ethylic acetate. The aqueous and alcoholic solutions of the salt rapidly change colour, passing through yellow to a dirty brown.Found, N = 6.60 and 6.57 per cent. C,,HlpNO, requires N = 6.63 per cent. Piperidine- Vanillin, C,H,,N,OH* CGH,(OC'H,) COH. This separates from the ethereal solution as a n oil which is converted into a crystalline mass on rubbing it with a glass rod. When recrystal- lisedfrom ethylic acetate,it is obtained in well-defined, colourless crystals melting at 70"; it is soluble in water, alcohol, and benzene, but almost insoluble in ether and light petroleum. When kept, it is gradually transformed into a dark-red, resinous mass smelling strongly ot vanillin; the alcoholic and aqueous solutions of the salt show the same change of colour. Found, N=5*63 per cent. C,,H,,NO, requires N = 5.90 per cent.PIPERIDINE WITH PHENOLS.143 Salts of the ATitropheno2s.* Piperidine- Parcmitropheno I, C,H,,N,C, H4( NO,).OH. This is formed from its components in molecular proportion dissolved in ether. When recrystallised from acetone, it fcrms large, lemon- yellow rhombohedrons about 1 em. in length ; it melts a t 110", and is easily soluble in water, alcohol, or chloroform, less readily in ether, and almost insoluble in light petroleum. It is a t once decomposed by alkalis and by acids even in dilute solution, the disappearance of the yellow colour on adding acids to an aqueous solution indicating the point of saturation. Taking advantage of this, it was found that 0.1206 gram required 5.25 C.C. N/10 hydrochloric acid. A nitrogen determination gave N = 12.87 per cent., whilst C,,H,,N,O, requires N = 12.54 per cent.Calculated 5.30 C.C. Piperidine-Orthonitro2~~enoZ1 C,H,,N,C,H,(NO,)*OH. In adding a solution of orthonitrophenol (1 mol.) in benzene to piperi- dine (1 mol.) diluted with light petroleum, the colour of the solution changes t o a brilliant orange and an oil of the same colour is deposited ; the latter rapidly solidifies to a crystalline mass on adding a small crystal of the salt (accidentally obtained by evaporating a few drops of the solution on the water-bath). After recrystallisation from a mixture of benzene and light petroleum, i t was obtained in stellaOe clusters of slender orange prisms, melting a t 83-84'; it is easily soluble in water, alcohol, ether, and most organic solvents. The aqueous solution is decomposed on boiling, yellow vapours of orthonitrophenol being given off. Found, N = 12.66 per cent.C,,H,,N,O, requires N = 12.50 per cent. 0.1884 gram (standardised as described under paranitrophenol, piperidine) required 8.3 C.C. X/lO hydrochloric acid. Calculated 8.4 C.C. Pipevidine-Yicrate, C,H,,N, C,H,( NO,) ,*OH. This substance has been mentioned in literature, but not described, and as it may be of use for the identification of piperidine, we think it of interest to give a short description of its properties, On * T. Abel (Ber., 1895, 28, 3106) examined the action of piperidine on mono- nitrophenols a t higher temperatures, with the object of obtaining nitrophenol- piperidines, but does not seem t o have observed the formation of in termediate prod~cts.144 ROSENHEIM AND SCHIDROWITZ : COMPOUNDS OF adding piperidine (1 mol.) diluted with a little ether to trinitro- phenol (1 mol.) dissolved in equal parts of alcohol and ether, the mixture became warm; on cooling, the picrate crystallised out in brilliant yellow needles, which, after recrystallisation from water or alcohol, melted at 145" (but were partially decomposed at 112").It is sparingly soluble in cold, easily in hot water, and melts under boiling water to a yellow oil ; it is easily soluble in acetone or ethilic acetate, but nearly insoluble in benzene and light petroleum. Found, N = 18.07 per cent. CllH1,N,O7 requires N = 17.88 per cent. Neither a- nor &naphthol forms salts with piperidine, a fact which is somewhat surprising, when we take into account the ease with which piperidine reacts with naphthols at higher temperatures to form naphthylpiperidines (T.Abel, Ber., 1895,28, 3106). On the other hand, I : 2 : 4-dinitronaphthol forms an additive product with the greatest ease. Piperidine-Dinitronapl~thol, [ 1 : 2 : 41 C,HllN,Cl,H,(NO,),*OH. This is obtained by mixing solutions of piperidine and dinitronaphthol (in light petroleum and benzene respectively) in molecular proportion ; after recrystallising from alcohol, it is obtained in orange needles melting a t 205". It is easily soluble in water and hot alcohol, but only very sparingly in ether and benzene. Fouud, N = 13.44 per cent. C,,H17N,0, requires N = 13.1 6 per cent. Tannin, when treated with piperidine in ethereal solution, yields a substance which becomes resinous and undergoes further changes so rapidly that we refrained from analysing it (see Oechsner de Coninck, Zoc. cit.). Gallic ucid, like other acids, yields a salt ; it melts a t 206-207" and decomposes at 210". We propose to examine the action of other secondary bases on phenols under similar conditions, and may add that, from our preliminary experiments, tertiary bases do not seem to yield additive compounds. As a curious fact, however, we may mention that, although pyridine does not react with phenols, quinoline, in ethereal solution, forms a well crystallised product (m. p. 94-95') with quinol.

ISSN:0368-1645    

DOI:10.1039/CT8987300139

出版商:RSC    

年代:1898

数据来源: RSC

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ACTION OF HYDROXIDES ON THE NITROBENZOIC ACIDS. 145 VIL-Action of Chloroform and Alkali Hydroxides on the Nitrobenxoic Acids. By WALTER J. ELLIOTT, M.A. IN a former communication (Trans., 1896, 69, 1513), it was shown t h a t potassium hydroxide in aqueous solution and chloroform, by their conjoint action on metarnidobenzoic acid, produced a substance allied t o the aldehydes, The action of these agents on other substituted benzoic acids is now being investigated, this communication dealing with their action on the nitro-acids. As in the previous research the amido-group had not been attacked, it was thought that the nitro-group would also remain unchanged but this has not proved to be the case. When the attempt was made to bring about a change under the conditions obtaining in the case of the VOL.LXXIII LI46 ELLIOTT: ACTION OF CHLOROFORM AND amido-acid, no action occurred ; however, on varying the proportions and the time, products were eventually obtained from the meta- and para-acids which proved t o be products of reduction, azoxy-acids, in fact. No compound was formed from the ortho-acid, although some slight action apparently takes place. The yield in every case is small. Prepumtion of Metccxoxpbenxoic Acid. After many trials, the following method mas found to give the best yield. Both potassium hydroxide and sodium hydroxide were used, but no difference in their action could be detected. To 10 grams of metanitrobenzoic acid dissolved in a solution of 40 grams of sodium hydroxide in 250 C.C. of water, 30 grams of chloroform were added, and the vihole heated by a small flame for 6 hours in a flask fitted with a reflux condenser.The solution, after being filtered, diluted, and acidified with dilute sulphuric acid, was boiled, and again filtered ; the filtrate contains the greater part of the un- altered nitro-acid, which can be easily recovered by crystallisation ; t.he crystals had the melting point of the nitro-acid (141°), and, on analysis, gave numbers corresponding with 8.37 per cent. of nitrogen. The precipitate, after being well washed with boiling water to remove the rest of the nitro-acid, was boiled with alcohol, which removed the last traces, filtered, and washed with hot alcohol. As the residue was only slightly soluble in alcohol and insoluble in water, i t was purified by dissolving it in dilute ammonia and precipitating with dilnte sulphuric acid; after washing with hot water and hot alcohol and drying at loo", a product was obtained which gave concordant results on analysis.The purified product is a yellowish powder slightly soluble in alcohol, from which it separates as a crystalline powder, slightly soluble in ether, insoluble in water. It does not melt below 300°, but becomes darker in colour above 250'. The following numbers were obtained on analysis. I. 0,1703 gave 0.0556 H,O and 0,3658 CO,. C = 58.58 ; H = 3.62. 11. 0.1892 ,, 0.0603 H20 ,, 0.4082 CO,. C=58'83; H=3*54. 111. 0.1806 ,, IV. 0,1651 ,, 15.6 C.C. moist nitrogen a t 17Oand 760.6 mm. N = 9.96. 14.2 C.C. moist nitrogen ah 16Oand 762.6 mm. N = 9.94. This acid was prepared by Griess (Annalen, 1864, 131, 92) by the action of alcoholic potash on metanitrobenzoic aotion.A specimen prepared by Griess's method was found to have properties similar to those of the acid described above. The silver salt was obtained as a flocculent, faintly-pllow pre- C,,H,,N,O, requires C = 58.74. H = 3.49 ; N = 9.79 per cent. It is therefore metazorrybenzoic acid.ALKALI HYDROXIDES ON THE NITROBENZOIC ACIDS. 147 cipitate on adding silver nitrate solution to a neutral solution of the ammonium salt ; it is slightly soluble in boiling water, and separates as a flocculent precipitate which is very stable in air, and is not affected by light a t the ordinary temperature, The silver salt, dried at loo', was analysed. I. 0.1460 gave 0.0626 Ag.Ag = 42.87. II. 0.2754 ,, 0.1182 Ag. Ag=42*91. C,,H,N,O,Ag, requires Ag = 43.2 per cent. The barium salt, obtained as a yellow, crystalline precipitate on adding barium chloride solution to a neutral solution of the ammonium salt, is almost insoluble in water, and was purified by repeated washing with boiling water ; the crystals are in the form of minute plates. The salt was dried at 120' and analysed. I. 0.4385 gave 0.2419 BaSO,. Ba= 32.43. 11. 0,5367 ,, 0.2953 BaSO,. Ba= 32.35. C,,H,N,O,Ba requires Ba = 32.54 per cent. Preparation of Pavaxoxybenxoic Acid. This acid was obtained and purified by the methods used in the case of the meta-acid. It is a bright yellow, amorphous powder, insoluble in all solvents; it does not melt, but becomes darker in colour when heated to a high temperature. The purified acid, dried at lQO', gave the following numbers on analysis.0.1933 gave 0,0636 H,O and 0,4148 CO,. 0.2504 ,, 22 C.C. moist nitrogen at 17' and 759 mm. N = 10.06. The silver and barium salts were obtained by the methods used for the preparation of similar salts of the meta-acid. The silver salt is a bright yellow, amorphous substance, insoluble in water, and very stable in air. 0.2315 gave 0.1002 Ag. The barium salt is precipitated in minute, dark yellow plates in- It was dried at 120' and analysed. 0,2928 gave 0.1617 BaSO,. Ba = 32.47. Aftermany trials with varyingquantities of theinteractingsubstances, nothing but t h e original nitro-acid was obtained from orthonitro- benzoic acid. Some slight action takes place, since there is consider- able change of colour on prolonged heating, but all attempts to isolate a definite product have failed; from this it would seem that the nitro- c! = 58.52 ; H = 3.65. It was dried a t looo and analysed. Ag = 43.28. 0.4172 ,, 0.1792 Ag. Ag=42*95. soluble in water. L 2148 IJEAN AND WHATMOUGH: NEW METHOD OF group in the ortho-position is less easily reduced than when it is in the meta- or para-position. In the cases where the azoxy-acid is produced, there is brisk effer- vescence on acidifying the solution after boiling with chloroform, carbon dioxide being evolved in considerable quantity ; this fact seems to show that the reduction of the nitro-group is accompanied by oxida- tion of the alkali formate to carbonate. The investigation of the conjoint action of chloroform and alkali hydroxides on other substituted benzoic acids, such as the chlorinated acids and the ortho-amido-acid, is now being attempted, and I hope to communicate the results to the Society in a short time. THE GRAMMAR SCHOOL, BRISTOL.

ISSN:0368-1645    

DOI:10.1039/CT898730145b

出版商:RSC    

年代:1898

数据来源: RSC

摘要:

148 IJEAN AND WHATMOUGH: NEW METHOD OF VIIL-New Method of P w p a ~ i ~ ~ Pu~e Iodine. By BEVAN LEAN, D.Sc., B.A., and W. H. WHATMOUGH. Intmduction. IN his Nouvelles Recherches .sur les Lois des Proportions Chinaiques (p. 136), Stas says :- ‘‘ Pour effectuer une synthese complhte d’iodure d’argent, j’ai dQ nhcesssire- ment ine procurer d’abord de l’iocle pur. Tous les moyens indiqds pour arriver A ce r6sultat ne m’ont point parn presenter des garanties auffisantes. Aucnn de ces nloyens, en effet, n’exclut la possibilitd de la presence clu chlore ni cle brome. Aprks avoir mfirement examine toutes les conditions dam lesquelles on peut probablement parvenir B obtenir cle l’iode ; j e n’ai pu en ddconvrir que deux : l’une consiste dans la prbcipitation, par l’eau, de l’iode clissons dans une solution d’iodure de potassium ; l’autre &side dam la d6ccm- position de la diiodamine par la chaleur.En effet, le chlore et le brome, con- tenus dans l’iode employ&, doivent rester unis soit au potassium, soit l’am- moniuni. . . . . DQlayb clans de l’esu, l’iode a 6th introdnit ensuite dans une grande cornue tubulee, et distill6 B la vapeur cl’eau pure. Cet iode npr& avoir btk 6goutt6, a Bt6 expose sous une cloche contenant de l’azotate de cliaux desshche. Ce sel de chaux a 4th la seuIe matiere que j’ai pu dkouvrir pour s6cher l’iode sans lui communiquer des impuretds. ‘‘ L’iode, dess6che aussi bien que possible, a dt6 m6lB de cinq pour cent de son poids de protoxyde de baryum pur finement pulverisd et soumis B la distillation seche.11 a Bt6 r e p dans une cornue tubulee qui servait de r6cip- ient et qui contenait aussi du piotoxyde de baryum pur finement pulverise ; il a dt6 rectifi6 une deuxiQme fois, en condensant sa vapeur dans m e cornue vide. . . . . En distillant l’iode sur du protoxyde de baryum, j’avais un double but : j e vonlais le priver de l’eau qu’il retient avec m e grande opiniiitretd ainsi que l’acide iodhydrique. . . . L’azotate de chaux a Qtd renouvel6 tant qu’il s’est humect6.PREPARING PURE IODINE. 149 L'iode, produit itinsi, differe notablement, par soii aspect, cie celui cln commerce. Apres nvoir 6t6 fondn dans nn tube de verre, il est absolunient noir h 1'6tat liquide et solide : h la tempdrature ordinsire, il n'6met aucunc vapeur visible dam l'air. . . . . 011 admet gh6rdement qne le point cie fusion cle l'iocle est lO'i", et que soii point ci'6bullition est conipris eiitre 175' et 180".L'iode cle Is diiodaiiiine est encore solide a 1133 ; mais il est liqnide B 115", et ne bout pas encore B 200"." The chief difficulties which Stas had to overcome in the preparation of iodine mere its separation from bromine and chlorine, and subse- quently the removal of moisture and hydriodic acid. It would be of great interest t o learn in detail how Stas assured himself that his ' iodine' was free from other halogens, and that calcium nitrate was the only desiccating agent which did not introduce impurities t o the iodine. No further information on these points can, however, be gleaned from his published researches ; several of his laboratory note-books kept in the Solvay Institute at Brussels, and courteously lent to us by the Director, Dr.Paul HBger, have also been carefully examined with the same object, but without success. A few months ago, we observed incidentally that no iodine was set free when cuprous iodide was heated, even till fused, in a current of carbonic anhydride, although, as is well known, iodine is readily evolved when cuprous iodide is heated in air to a moderate temperature. A few pre- liminary experiments showed that the action was probably represented by the equation Cu2T, + o2 = 2Cn0 + I,. Now i t hase commonly been supposed that an iodide c.an be detected in the presence of other haloids by precipitation as cuprous iodide, and if so, i t should be possible to prepare cuprous iodide free from bromide or chloride, and then from it liberate pure iodine in the way indicated above.With the object of preparing iodine, free in particular from chlorine, bromine, hydriodic acid or water, the whole question was submitted to careful examination, Prepamtion of Cuprous Iodide. Action of Copper SuZplmte 8c&mzted with Sulphurous Acid on Hccloid Su1t.s.-It is well-known that cuprous iodide is immediately precipitated when a solution of copper sulphate saturated with sulphurous acid is added to a solution of an iodide (Duflos, Annalen, 39, 253). Thus :- ZCUSO, + 2KI + SO, + 2H20 = Cu,12 + K2S0, + 2H2 SO,. Cuprous iodide was prepared by this method :-TWO gram-molecules of copper sulphate were dissolved in 3 litres of water, the solution150 LEAN AND WHATMOUGH: NEW METHOD OF saturated with sulphur dioxide, and 2 gram-molecules of potassium iodide dissolved in 150 C.C.of water were added. The pale yellow precipitate which was immediately formed was allowed t o settle, the supernatant liquid poured off, and the residue washed with sulphurous acid solution by decantation until the whole of the sulphate had been removed; it was then boiled with water to render it granular, collected on linen, the product spread upon a porous tile, and finally exposed over sulphuric acid in a vacuum. Cuprous iodide retains moisture somewhat obstinately ; after exposure for three weeks over sulphuric acid, a sample still contained 0.18 per cent. of moisture, but this was removed after further exposure. The dried iodide was reserved for future experiments. One of the recognised methods of preparing cupozcs chloride is very similar to the above.A solution of copper sulphate and potassium chloride is saturated with sulphur dioxide, when a crystal- line, white precipitate of cuprous chloride is gradually deposited ; excess of sulphurous acid, however, retards the precipitation of the chloride. If the clear solution is decanted from the precipitate and boiled, a further quantity is deposited. The cuprous chloride can be purified by washing it first with a solution of sulphurous acid and afterwards with glacial acetic acid, the product being then pressed between paper and dried in a warm place (Wohler, AnnaZen, 1864, 130, 373; Rosenfeld, Bell., 1879, 954). Cuprous chloride cannot be washed by much water without under- going decomposition, for as soon as the excess of acid is removed, the following interesting action begins in the presence of air, and, as was shown by Vogel, is rendered evident by the orange or red colour which the precipitate suddenly assumes : 2Cu2CI, + 0 = Cu20 + 2CuC1,.Cuprous chloride can thus be almost completely decomposed by repeated treatment with water in the presence of air. Freshly precipitated cuprous chloride is redissolved by sulphurous acid. I n view of the knowledge that both cuprous chloride and cuprous iodide can be prepared by the action of sulphur dioxide on a mixture of copper sulphate with potassium chloride or iodide in presence of water, it might be expected that cuprous bromide could also be prepared by a similar method.This we have found to be the case, although we have not met with any mention of this method of preparation compare Dammer’s Handbuclr. der Bnorg. Chenaie, 1894 edition). About 20 grams of copper sulphate and 8 grams of sodium bromide were dissolved i n 300 C.C. of water, and sulphur dioxide passed in ; after a time, small, white crystals were deposited, These were filtered rapidly from the mother liquor, washed with sulphurous acid, spread upon a porous tile, and then exposed over potassium hydroxide in a vacuum.PREPARING PURE IODINE. 151 If the mother liquor was heated so as to expel sulphur dioxide, more crystals were deposited. The crystals, which were pale greenish-yellow, subsequently became pale bluish-grey. The copper in the cuprous bromide was determined rolumetrically.0.662 corresponded with 0.5830 iodine. Cu = 44.29. 0.6740 gave 0.8808 AgBr. Br = 56-00. Cu2Br, requires Cu = 44.21 ; Br = 55-79 per cent. Cuprous bromide, like the chloride, is decomposed by water in the presence of air, but the action does not take place so readily. It also can be dissolved by sulphurous acid. Both cuprous chloride and bromide may, therefore, be precipitated by the action of sulphur dioxide on solutions containing copper sulphate and a chloride or bromide; and if the solution is but moderately concentrated (twice decinormal in the case of the bromide) the precipitation cannot be prevented, contrary t o the statement of Fresenius, by the presence of excess of sulphurous acid. I t seemed, therefore, desirable to determine the dilution necessary t o prevent t?he precipitation of the chloride o r bromide.To ascertain this, 100 grams of copper sulphate were dissolved in 1 litre of water, and the solution saturated with sulphur dioxide. Twice normal solutions of potassium chloride, bromide, and iodide were made, and 10 C.C. of each added severally to 25 C.C. of the solution of cuprous sulphate in small stoppered flasks, and it was observed in each case whether a precipitate occurred or not. The haloid solutions were then diluted ten-fold, and again 10 C.C. of these were added severally to 25 C.C. of the same solutions of cuprous sulphate. Similar experiments were made when the haloid solutions were diluted one hundred-fold, a thousand-fold, &c. On adding silver nitrate to the last solution, containing 0.000033 gram of potassium iodide, an opalescence was produced immediately.From these experiments, it is clear that, whilst cuprous iodide, bromide, and chloride may all be precipitated by the addition of a haloid salt to a solution of cuprous sulphate, there is a great difference i n their degree of solubility, cuprous iodide being much less soluble than the bromide, and, similarly, the bromide than the chloride. This explains the anomalous results sometimes obtained by students in the practice of qualitative analysis. The results are recorded in Table I, p. 152. It is a common practice to remove iodine from a mixture of haloid salts by the addition of a solution of copper sulphate mixed wit,h ferrous sulphate, as well as by the method already examined.Experi- ments similar to those described above were, therefore, made to test the152 0-0024 gram. No opalescence after 10 days LEAN AND WHATMOUGH: NEW METHOD OF 0'0033 gram. Immediate opalescence and KCI. -- 1.5 grams. Little or no ppt. after 1 houi Crystals after 10 days. 0'0033 gram. Immediate opalescence and gradual formation of a ppt. I -I 0'00033 gram. Nu opalescence. 0.15 gram. No ppt. after 10 days. ~ - _ ~ - _ . _ _ _ _ TABLE I. I KI. KBr. 2.4 grams. Ppt. within 1 minute. 3.3 grams. Immediate ppt. 0 -24 gram. Ppt. within 3 minutes. 0.33 gram. Immediate ppt. 0.024 gram. Slight ppt. within 10 days 0-033 gram. Immediate ppt. 0.000033 gram. No opalescence after 10 days efficacy of this method; 100 grams of crystallised copper sulphate and 114 grams of ferrous sulphate were dissolved in 1 litre of water, and t o 25 C.C.of this solution, placed in small stoppered flasks, were added as before, in each case, 10 C.C. of solutions of the haloid salt. The results are summarised in the following table. TABLE TI. KCI. KBr. I KI. I I 1.5 gram. No ppt. 2.4 grams. No ppt. 3.3 grams. Immediate ppt. I I 0.33 gram. Immediate ppt. 0.033 gram. Immediate ppt.PREPARING PURE IODINE. 1.53 I n each case, after standing some time, a little ferric hydroxide was precipitated. A comparison of Tables I and I1 shows that a mixture of copper sulphate and ferrous sulphate is not nearly so liable to precipitate cuprous bromide and chloride along with iodide as a solution of copper sulphate saturated with sulphurous acid (the cuprous iodide may contain a little iron hydroxide.) Table I1 shows, moreover, that by securing a proper dilution it is very probable that cuprous iodide can be precipitated by a mixture of copper sulphate and ferrous sulphate, unaccompanied by cuprbus bromide or chloride ; if, further, the cuprous iodide, precipitated under such conditions, is collected and washed repeatedly with a solution of sulphurous acid, it is probable that every trace of cuprous bromide and chloride can be removed.A New Met?Locl of Prepcwing Cuprous Iodide.--If copper foil is torn into shreds and heated in the presence of air in a porcelain basin over a Bunsen flame, and iodoform sprinkled over it in small quantities at a time, a violent action bakes place, violet clouds of iodine being evolved, while a flame plays over the contents of the basin.The copper is then found to be coasted with a black scale which is very readily peeled off, leaving a clean copper surface, and the copper may then be re-treated with iodoform until little or no metallic copper remains. The black scale, on analysis, was found to contain a little carbon and cupric oxide, but it was almost wholly cuprous iodide (about 98 per cent.). On account of the difference in the properties of chloroform, bromoform, and iodoform, it is probable that by this method also cuprous iodide can be prepared entirely free from bromide or chloride. Prepu~ntion of Iodine frona Cuprous Iodide. As already stated, one of us observed incidentally a few months ago t h a t when cuprous iodide was heated in a current of carbonic anhy- dride no violet vapours appeared, although iodine was freely liberated if air or oxygen was substituted for the carbonic anhydride.It was found, also, that if carbonic anhydride free from air and dried by sulphuric acid was passed over cuprous iodide in a boat within a glass tube, and the iodide heated even until f u s e d , no trace of iodine could be detected in the effluent gases by means of starch paper. Cuprous iodide can, therefore, in all probability be completely freed from moisture and from hydriodic acid by fusion in a current of carbonic anhydride. Experiments showed, however, that if cuprous iodide was heated in a current of air, oxygen, nitric oxide, or nitrogen peroxide to tempera- tures between 200° and 300°, iodine was very readily liberated, the iodide at the same time becoming black.It appeared that the libera-154 LEAN AND WHATMOUGH: NEW METHOD OF tion of the iodine was dependent on the oxidation of the copper: Cu2T2 + 0, =3 2CuO + I,. We khen endeavoured to ascertain (1) whether the whole of the iodine was liberated, (2) whether the action was de- pendent on the presence of moisture, and (3) whether the iodine liberated in this way from pure cuprous iodide was pure and free from iodic anhydride or any compound of copper. A long piece of hard glass tubing, AB, heated by a gas furnace at C I), the temperature of which could be regulated by a thermostat, was connected a t E with a water pump, so $hat air could be aspirated through the tube.GH was a The following apparatus was employed. FIG. 1. glass tube through which cold water circulated, providing a condensing surface for the iodine vapour, and IK was a porcelain boat containing cuprous iodide. Action of Gases at the Ovdinarp Temperature.--The action of gases which liberate iodine from cuprous iodide with great readiness a t elevated temperatures was tried a t the ordinary temperature of the laboratory, the gases being dried by sulphuric acid. I n no case, how- ever, was sufficient iodine liberated to be condensed ; its liberation in any particular case was only detected by starch paper introduced into the tube between A and C. Air passed over cuprous iodide exposed to the light caused a slight coloration of the starch paper after 3 hours, and after 2 days the paper was quite blue. When air was passed over the iodide in the dark for 1 day, no iodine could be detected.Oxygen did not liberate any iodine in the dark. Nitric oxide and nitrogen peroxide each liberated iodine at once, both in the light and in the dark, Action of Ail* on Hot Cuprous Iodide.-It was desirable to find the lowest temperature at which iodine could be liberated in sufficient quantity to be condensed and collected, so that the chance of volatilisa- tion of cuprous iodide might be minimised (cuprous iodide boils at 759-772") ; below .200', iodine was liberated only very slowly, but between 220' and 240°, a continuous stream of violet vapour was carried forward and condensed in beautiful crystals upon the con- denser.Three experiments were made t o test whether the whole of the iodine was expelled. I n I, 2,5249 grams of cuprous iodide were heated a t 230-240" for 11 hours ; in 11, 1.7101 grams mere heatedPREPARING PURE IODINE, 156 to 400' for 18 hours, and in 1111, the cuprous iodide was heated a t 380'. I n I, 0.42, and in 11, 0.15 per cent. of the iodide remained un- decomposed. I n No, 111, the effluent vapours were passed into standard aolut'ions of sodium thiosulphate, which were afterwards titrated with standard iodine solution ; it, was found that 22 per cent. of the iodine in the cuprous iodide was liberated in the first half-hour, 54 per cent. in the second half-hour, and 19 per cent, in the third half-hour, or 95 per cent. in 18 hours ; whilst after 6 hours more a small amount of iodine was still left in combination.It is clear, therefore, that it is not easy to liberate the zuhole of the iodine from a given quantity of cuprous iodide, otherwise the relation Cu,12 : 2CuO mould connect in a way capable of exact determination the atomic weights of copper, iodine, and oxygen. Further experi- ments are being made on this point. ItaJEuence oJ Moisture on the Liberation of Iodine.--When cuprous iodide was heated a t 240' in air dried by passing it slowly through strong sulphuric acid, iodine was readily evolved. Experiments mere then made t o find whether air which had been more carefully dried FIG. 2. had the same effect. Tubes of the shape shown in the figure, made from soft glass tubing, were drier1 by heating them t o 200', and passing air dried by calcium chloride through them.A plug of glass wool, which had been dried at 200' for some hours, was placed at B, and the end A sealed. By means of a thistle funnel, about 1 gram of finely divided cuprous iodide, which had previously been fused and then allowed to cool in a current of carbonic anhydride, mas intro- duced into C, and a plug of glass wool placed in D. A layer of phosphoric anhydride was next placed in E, and another plug of glass wool at F ; the open end, G , was then drawn out, but not sealed. Two similar tubes were made ; these mere exhausted by a mercury pump and then sealed. Both tubes mere heated for 10 days in a steam oven, and allowed to remain for four weeks more at the ordinary temperature. I n one of the tubes, the bulb C, containing the cuprous iodide, was heated a t 400' for one hour, but no trace of iodine vapour could be seen.Air which had been dried over phosphoric anhydride was intro- duced into the other tube, which was then again sealed. After two weeks, this second tube mas heated to 230', when violet vapours were1.5 6 NEW METHOD OF PREPARING PURE IODINE. at once freely evolved and condensed on the cool portions of the tube. The experiments mere repeated with similar results. It seemed, there- fore, that the pres&ce of water vapour was not essential to the action of air on cuprous iodide. I n order to ascertain whether water vapour alone had any action on cuprous iodide, steam was passed over hot cuprous iodide, but no iodine was liberated even when the iodide was fused.Purity of the Iodine Prepred from Cuprous Iodide.-Iodine liberated as described from cuprous iodide a t a temperature of 240' might conceivably contain a small quantity of some substance which would not be volatile at a much lower temperature, iodic anhydride, for example. Some of the iodine, 2.7529 grams, was therefore introduced into a short glass tube open a t both ends, which was placed within a long wide tube heated to 75", and a slow current of air passed through ; after heating during four hours, a slight brown residue was left on the tube, weighing 0.3 milligram. It was found, however, that this residue was due to impurities in the air, as when the air passed over the cuprous iodide and that in which the iodine volatilised, was filtered through cotton wool, the surface of the tube remained perfectly clean, and no change of weight could be detected.In order to show that the iodine did not contain any compound of copper, the violet vapours liberated from cuprous iodide a t 240' were mixed with coal gas and air and the mixed gases burnt at the mouth of a glass tube. On examining the flame spectroscopically, no evidence of the characteristic copper bands could be detected, whilst they at once became visible when a copper wire was held in the flame. The melting point (uncorrected) of the iodine, determined in the usual way, was found to be 118*5-114". It has a blacker appearance than commercial iodine, and does not so readily emit violet vapours. Cone Zusion s. From the results of these experiments, it is evident- 1. That cuprous iodide can be prepared free from cuprous bromide or chloride. 2. That cuprous iodide can be heated without decomposition and completely dried in an atmosphere of carbonic anhydride. 3. That when dry air is passed over cuprous iodide heated at 240" the iodine is liberated and can readily be condensed. 4. That the iodine obtained in this way is free from any compound of copper. Whether such iodine is as pure or not as that prepared by Stas by other methods, in which one main difficulty was the drying of theCOHEN AND BRITTAIN: ACTION OF ALKALIS ON AMIDES. 157 iodine and the removal of hydriodic acid, it appears desirable to re- determine the atomic weight of the element prepared by this entirely distinct method. It may be added that iodine is also readily liberated, in a similar way, from palladious iodide, but owing to the costliness of this sub- stance a detailed examination of the action has not been made. OWENS COLLEGE AND ACKWORTH SCHOOL, Jn~ii~nn~, 1890,

ISSN:0368-1645    

DOI:10.1039/CT8987300148

出版商:RSC    

年代:1898

数据来源: RSC

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COHEN AND BRITTAIN: ACTION OF ALKALIS ON AMIDES. 157 1X.-Action of Alkalis on 14micZe.s. By JULIUS B. COHEN, Yh.D., and CHARLES EDWARD BRITTAIN, B.Sc., The Torkshire College. COHEN and ARCHDEACON (Trans., 1896, 69, 91) have shown that many amides of aromatic bases form additive compounds with sodium alco- holates containing 1 mol. of amide in combination with 1 mol. of the alcoholate. That analogous compounds might exist containing sodium or potas- sium hydroxide in place of the alcoholate mas a natural inference, but every attempt to prepare them by t h e usual method employed in the case of the alcoholates mas unsuccessful. I n the latter case, the addition of the alcoholate to the amide suspended in ether, as a rule, yielded a clear solution, which, after a short time, deposited the crystal- line additive compound.If powdered caustic soda is added to acetani- lide dissolved in ether, the alkali remains undissolved, and on filtering and evaporating the solution, the unchanged amide is deposited. An attempt to precipitate the additive compound by adding a concentrated alcoholic solution of the alkali to the ethereal solution of the amide proved equally unsuccessful, the mixture remaining perfectly clear, and on evaporation a t the ordinary temperature depositing a flocculent pre. cipitate, which did not invite further investigation. We then adopted mother method which had been found useful in the preparation of alcoholates where the amide was only slightly soluble in ether. I n this case, the powdered sodium alcoholate was added to the powdered amide suspended in ether, and, after shaking well, the liquid was filtered ; on standing, the additive compound crystallised from the clear solution. During the process of shaking caustic soda with acet- anilide in ether, a very noticeable change was observed.Both powdered caustic soda and acetanilide alone, after being shaken up in cther, rapidly subside; but when the two are mixed together, a bulky, light, and apparently homogeneous powder is produced quite distinct in charac- ter from either constituent. On filtering, a small quantity of a crys-158 COHEN AND BRITTAIN: ACTION OF ALKALIS ON AMIDES. talline deposit appeared in the ether, which, when decomposed with water, gave a strongly alkaline reaction, but the analytical results oh- tained with different preparations did not agree, and the quantity of alkali was invariably too low.Exactly the same thing occurred in the case of paracetotol uidide. I n spite of these indefinite results, the existence of additive coin- pounds seemed sufficiently clearly indicated to justify further experi- ments. It appeared probable that a n amide more soluble in ether than either acetanilide or paracetotoluidide might be more suitable for the purpose, and this view has proved to be correct. We first selected paracetobromotoluidide, as it is comparatively soluble in ether, and, although the yield was small, we obtained very satisfac- tory results by a method similar to that just described. After repeated trials, with the object of improving the yield by the use of different solvents, we returned .to the original method, which, with slight modi- fications, has been adopted throughout.An excess (about 1 gram) of clean caustic soda is placed iu a mortar under a layer of dry ether and finely powdered; 1 gram of the amide in powder is then added and well mixed with the alkali for a few moments. The sodium hydroxide compound, like the alcoholate com- pound, first dissolves and then rapidly crystallises out. By selecting the moment at which solution occurs, and filtering before the new com- pound has time t o separate, a clear solution is obtained which immedi- ately begins t o deposit crystals. The mixture is filtered into a weighed flask, the ether is decanted a s soon as the crystals have separated, and the latter, after being washed once or twice with ether by decantation, are dried in a vacuum and weighed.The substance is then decomposed by water and the amount of alkali determined by titration with deci- normal hydrochloric or oxalic acid solution. I n all cases, well-defined crystals were obtained, and occasionally transparent needles a quarter of an inch long. These compounds exhibit considerable differences in solability in ether. Thus the sodium hydroxide compound of acetanilide, paraceto- toluidide, and a-acetonaphthalide are nearly insoluble, whereas those obtained from ortho- and para-acetobromotoluidide and potassium hydroxide only deposit the additive compound on concentrating the ethereal solution ; apparently the potassium hydroxide compounds are much more soluble than the corresponding sodium hydroxide compounds.They are all decomposed by water, or more or less rapidly in contact with moist air, and, like the corresponding alcoholates, may be dis- sociated, not only i n boiling ether, but even in some cases by washing with cold ether; this occurs notably in the case of the bromine deriva- tives of the amides, probably by reason of their greater solubility, whereas the amides themselves are not affected in this way.COHEN AND BRITTAIN: ACTION OF ALKALIS ON AMIDES. 159 The following amides appear to form additive compounds with caustic soda, but only those have been analysed which gave a satisfactory yield of the pure product. Acetanilide, acetobromanilide, acetiodanilide, paracetotoluidide, par- acetobromotoluidide, orthoacetotoluidide, orthoacetobromotoluidide, a- acetonaphthalide, a-acetobromonaphthalide, P-acetonaphthalide, p-aceto- bromonaphthalide.The potassium hydroxide compounds of ortho- and para-acetobromo- toluidides have also been investigated. It would have been a simple matter to have multiplied examples; but the results obtained convinced us that the reaction was of a general character, and that the compounds were of a perfectly definite type. Apart from a certain theoretical interest which attaches to these compounds and which is discussed further on, they form a class which, we Selieve, has no analogues among inorganic or organic substances, for they may be regarded as containing the sodium and potassium hydroxide in the loose form of combination which is exhibited by water, alcohol, or benzene of crystallisation. Another point of interest is the fact that, as the alkali readily dis- solves in ether in presence of certain of the nmides, and as the former retains its alkaline character unchanged in this solut,ion, an ethereal solution of caustic alkali is thereby obtained, which may be found ap- plicable as a reagent where aqueous or alcoholic potash or soda do not fulfil the requirements of the reaction.We have, for example, at- tempted to prepare glycol from ethylenic bromide in this manner. On boiling up an ethereal solution of paracetobromotoluidide potassium hydroxide with rather more than the calculated quantity of ethylenic bromide for several hours, potassium bromide separated, and the liquid became neutral ; the potassium bromide, after being collected and care- fully washed with ether, was extracted with a small quantity of pro- pylic alcohol in the cold, and the alcohol filtered and evaporated, when a small quantity of a viscid liquid was left.As the ethereal solution might also contain a little glycol, i t was shaken up with water ; on evaporating the water, a few crystals of acetobromotoluidide separated (m. p. 11S0), together with some globules of liquid. The latter were separated by again extracting with water and evaporating, but the liquid thus obtained was so small in quantity that it could not be further examined, although it is not improbable that the substance is glycol. By the action of chloroform on boiling ethereal solution of ortho- acetobromotoluidide sodium hydroxide, the liquid became neutrbl, and sodium chloride mixed with a crystalline compound separated.There was a faint smell of isocyanide, but no formic acid was formed. The compound which separated, along with the common salt, was a t first160 COHEN AND BRITTAIN : ACTION OF ALKALIS ON AMIDES. thought t o be acetobromotoluidide as i t had the same melting point, but it is much less soluble in ether, and insoluble in boiling water; moreover, it crystallises in feathery tufts aod not in needles. We briefly mention these facts, as some little time may elapse before it will be possible t o continue this investigation. Paracetobromanilide sodium hydroxide, C,H4Br *NH* C,H,O,NaOH. -One gram of finely powdered acetobromanilide was added to an excess of caustic soda finely ground under ether, and the whole well mixed. The ether was then filtered ihto a weighed flask, corked, and allowed t o stand 12 hours; after decanting the ether from the crystalline deposit, the latter was dried in a vacuum, weighed, and analysed.0.183 gram required 6.8 C.C. of N/lO oxalic acid. Na = 8.55 per cent. C,H,Br*NH*C,H,O,NaOH requires Na = 9.0 per cent. Pas*cLcetobromotoZuidide sodium hydroxide, CH3*C6H3*Br*NH*C,H,0,NaOH, was prepared as above described, but crystallised from the ethereal solution more readily than the corresponding anilide. The following results were obtained. I. 0.192 gram required 7-5 C.C. N/10 hydrochloric acid. Na = 8.9. 11. 0.214 ,, 7 , 8.1 9 , 9 , Na = 8.7. 111. 0.115 ,, 9 9 4.6 9 , 9 9 Na = 9.0. IV. 0.124 ,, 9 , 4.7 9 , > 9 Na = 8.7.The average on the four determinations is Na=8.8 per cent. CH3* C,H,Br*NH* C,H30,NaOH requires Na = 8.6 per cent. Pnracetobromotoluidide potassium hydroxide, CH,. C6H3Br*NH* C,H,O,KOH, is very soluble in ether, for the whole of the amide in combination with the potassium hydroxide dissolves. One gram of the acetobromo- toluidide was ground up with an excess of potash under ether, filtered, and the ether evaporated in a vacuum ; the residue weighed 1.223 grams (calculated 1-24 grams). It is a comparatively stable com- pound, and requires t o be boiled with water some time before it is completely decomposed ; the residue on titration required 38 C.C. N/10 oxalic acid; K=12*1 per cent. (calculated 13.7). A purer product was prepared by partially evaporating the ether, allowing a portion of the compound t o crystallise, and draining this on a porous plate.The following results were then obtained. I. 0.401 gram required 14 C.C. N/lO oxalic acid. K = 13.6 per cent. 11. 0.3355 ,, 9 9 11.6 9 7 9 , K=13*5 ,, CH,*C,H,Br*NH*C,H,O,KOH requires K = 13.7 per cent,COHEN AND BRITTAIN: ACTION OF ALKALIS ON AMIDES. 161 Orthoacetotoluidide sodium hydroxide, CH3*C6H4*NH*C2H,0,NaOH, which was prepared in the usual way, on titration with N/10 oxalic acid, gave Na = 12.2 per cent, in each of two experiments, CH,*C,H,*NH*C,H,O,NaOH requires N a = 12-17 per cent, CH3*C~H,Br*NH*C2H,0,NaOH, is very soluble in ether, and considerable difficulty was experienced in obtaining a pure preparation, When the ethereal solution was eva- porated, some of the free toluidide crystallised at the same time, and the percentage of sodium was generally about 1 per cent.too low. A.ttempt,s t o precipitate the compound by adding to the ethereal solu- tion indifferent solvents such as chloroform or benzene proved fruit- less. The following melhod was finally adopted ; the sodium hydroxide was powdered under about 10 C.C. of ether, transferred to a flask, and the acetobromotoluidide added in quantities of about 0.25 gram, being well shaken after each addition. The toluidide dissolved readily a t first, more slowly after 0.75 gram had been added, and very soon crystallisation of the sodium hydroxide compound was observed. At this point, the liquid was rapidly filtered, and left to crystallise.Orthoaceto bromotoluidide sodium hydroxide, 0.089 gram required 3.45 C.C. N/10 oxalic acid. N R = 8.9 per cent, CH,*C6H,Br*NH*C2H,0,NaOH requires Na = 8.6 per cent, CH,*C,H,Br *NH* C,H,O,KOH, like the para-compound, is exceedingly soluble in ether, but differs from the latter in forming a non-crystalline glassy mass on evaporating the ethereal solution ; it was therefore impossible to purify the product. Like the para-compound also, it is only slowly decomposed by water, and requires to be boiled with it for some time before complete decom- position is effected. A rough determination of the composition of the substance was effected by shaking up 0.25 gram of the amide with an excess of potash in ether, filtering, evaporating the ether, and titrating the product.It required 9.85 C.C. N/10 oxalic acid. K=12.4 per cent. (calculated 13.7 per cent.). The low resnlt is no doubt due to presence of uncombined amide. a-Acetonaphthalide sodium hydroxide, C,oH7*NH*C,H,0,NaOH, crys- tallises very rapidly, and the ethereal solution must be filtered as quickly as possible after mixing the amide with the alkali. A mean of four titrations with N/10 hydrochloric acid gave Na= 10.23. CloH7*NH*C2H,0,NaOH requires N a = 10.3 per cent. O~thoacetobromototuidide potassium hydroxide, a-Acetobronaonu~ht~~ulicle sodium hydroxide, VOL, LXXIH, M C',,H,Br * NH*C,H,O,NaOH,162 COHEN AND BRITTAIN : ACTION OF ALKALIS ON AMIDES. is fairly soluble in ether and crystallises slowly on standing. A mean of three titrations with N/10 oxalic acid gave Na=’i*5 per cent.CloHGBr*NH* C2H30,NaOH requires Nx = 7.5 per cent. P-8cetonc~pl~tl~alide sodium hythoxide, C,,,H7*NH*C,H,0,NaOH.-The mean of four titrations with NjlO oxalic acid gave N ~ L = 10.2 per cent. C,oH7-NH-C12H30,NaOH requires Na = 10.2 per cent. P-Acetob*om.onaphthalide sodium hydroxide, C,oHGBr*NH*C,H30,NaOH, dissolves easily in ether, but does not crystallise readily, and a pure product could not be obtained. On account of the ready solubility of the potash compound of paracet.obromoto1uidide in ether, it was chosen in order to study the action of various reagents on it. When iodine dissolved in ether is allowed to drop into an ethereal solution of the potash compound i t is immediately decolorised, and a crystalline mixture of potassium iodide and iodate separates.The action of iodine on the substance is there- fore the same as on aqueous potash. A small quantity of iodoform was also detected ; and this, which was also observed in the case of acetanilide sodium methoxide, is probably due in both cases to the decomposition of the ether in presence of the alkali. By the action of acetic chloride in slight excess in the cold, both potassium chloride and potassium acetate mere formed, so that both free acetic acid and free hydrochloric acid must be produced at the same time. Benzoic chloride acts similarly ; the theoretical quantity of benzoic chloride yielded a mixture of potassium chloride and benzoate, together with free hydrochloric and benzoic acids. 1. CH,.C,H,Br*NH*C,H,O,KOH + CGH,*COCl 2. CH,.C,H,Br*NH*C,H,O,KOH + CGH,*COCl Thus : = CH,-C6H3Br*NH*C,H,0 + C,H,*COOH + KCl. = CH,*C6H,Br*NH*C,H,0 + HC1+ C,H,*COOK. The theoretical bearings of these compounds on the constitution of the amides has been discussed in the paper by Cohen and Archdeacon (Zoc. cit.) ; what has been stated there applies with equal force in the present case. If we are to regard these substances as anything more than ‘ molecular ’ compounds, the following formula must be assigned R‘*y*Na for there can be no doubt as to the strict to CH,*C(OH)2’ analogy which exists between them and compounds of the amides with sodium alcoholate. This constitution of the sodium alcoholate compound has recently been disputed by Hantzsch (Annulen, 1897, 296, p. 61) who prefers theFORMATIOX OF MONOMETHYLANILINE FROM DIMETHYLANILINE. 163 R*NH following formula, 1 ONa , but this view can scarcely be CH3' '<OC,H, reconciled with the fact that, by heating the substance on the water bath, it loses a molecule of alcohol and yields sodium acetanilide (Seifert, Bey., 1885, 18, 1358), and that the latter, by the action of methylic iodide, can be readily converted into methylacetanilide and finally into methylaniline. Hantzsch's formula would necessitate a molecular change of a very complex character, which is scarcely justified by the facts.

ISSN:0368-1645    

DOI:10.1039/CT8987300157

出版商:RSC    

年代:1898

数据来源: RSC