2572 BRADY AND DUNN :CCLXVII1.-The Isomerism of the Oximes.p- Dimet h?ilaminobenzuldoxime.Part VI.By OSCAR LISLE BRADY and FREDERICK PERCY DUNN.ALTHOUGH p-dimethylaminobenzaldoxime, NMe,*C,H,-CH:NOH,has been described (Knofler and Boessneck, Ber., 1887, 20, 3195)it has not' been studied from the point of view of the' Hantzsch-Werner hypothesis.As this compound cont'ains no possibly labile hydrogen atom inthe para-substituting group it would be expected t o exist in thetwo isomeric forms, aizti and s y ~ z (compare Brady and Dunn, thisvol., p. 824); indeed, as the basicity of the substituting groupseems t o influence the stability of the two isomerides, it seemedpossible that the oxime prepared from p-dimethylaminobenzalde-hyde by the usual methods would be a syiz-derivative, or, if not, thesyn-isomeride would be readily obtained from it, and would bemore stable than is usually the case with these compounds.Addi-tional interest is added by the fact that no benzaldoxime containinga basic group as a substituent has been obtained in two isomericforms; indeed, compounds of this class have been little studied.As regards the preparation of a syn-derivative of this compoundthe authors' expectations have not been fulfilled, and pdiinethylTHE ISOMERISM OF THE OXIMES. PART VI. 2873aminobenzaldoxime must be added to the considerable number ofaromatic aldoxiines that appear t o exist only in one form.The oxime, as ordinarily prepared by the action of hydroxylaminehydrochloride on the aldehyde in the presence of sodium carbonatehas undoubtedly the an ti-configuration, since i t yields an acetylderivative' and not a nitrile on treatment with acetic anhydrideand sodium carbonate solution.This acetyl derivative yields theoriginal oxime on hydrolysis with alkalis. Dry hydrogen chloride,when passed into a dry ether or chloroform solution of the oxime,precipitates a hydrochloride which regenerates the original oxiineon treatment with sodium carbonate solution. Under the aboveconditions the oximel unites with only one molecule of hydrogenchloride, and it was possible that the acid was attached t o thedimethylamino- and not to the oximino-group, a fact which wouldaccount for the failure t o obtain a syrz-oxime. Support is lent t othis contingency by the behaviour of the 0-methyl ether of pdi-methylaminobenzaldoxime, which readily yields a hydrochlorideunder similar conditions, differing in this respect from the 0-methylethers of oximes which contain no basic substituent in the benzenering.On the other hand it is noteworthy that, the hydrochlorideof the 0-methyl ether, in which the1 hydrogen chloride is un-doubtedly attached t o the dimethylamino-group, does not evolvehydrogen chloride a t its melting point, whereas the hydrochlorideobtained from pdimethylaminobenzaldoxime resembles the hydro-chlorides of other oximes and suffers decomposition a t its meltingpoint owing to loss of hydrogen chloride.An attempt was made t o overcome this difficulty by preparingthe hydrcchloride directly from the aldehyde and hydroxylaminehydrochloride in the absence of alkali (Beckmann, A nirnlen, 1909,365, 201):NMe2-C,H,*CH0 + NH2*OH,HC1=This method yielded, however, a hydrochloride melting a t thesame temperature as the hydrochloride obtained from the oxime,and this hydrochloride gave the afsti-oxime on treatment withsodium carbonate solution.It is possible that by this method thehydrochloride, NMe2*C,H,*CH:NOH,HC1, is first formed which isthen decomposed with the formation of the hydrochloride,HCl,NMe,*C,H,*CH:NOH ;this seems, however, unlikely, although the basic nature of theoximino-group is much less marked than that of the dimethyl-amino-group.Diphe nyl curb am yl-p-di rn e t h ylamino 6 e n xaldoxime has been pre-pared, and like other diphenylcarbamyl derivatives of the aromaticNMe2*C,H,-CH:NOH,HCl + H202874 BRADY AND DUNN :aldoximes has the syn-configuration, yielding on hydrolysisdiphenylamine and pdimethylaminobenzonitrile (compare Bradyand Dunn, T., 1913, 103, 1613):NMe2*C6H,*R H= NMe,*C,H,*CN + NHPh, + CO,.Nil*CO*NPh2C a d anilino-pdirnet hylamino b enzaldoxime,NMe,*C6H,*CH:NO*CO*NHPh,obtained by the action of phenylcarbimide on the oxime, is ofespecial interest as it resembles carbanilino-m-nitrobenzaldoxime inthat the compound first obtained, on boiling with alcohol, changesto an isomeric compound of higher melting point, which seems stillt o be a carbanilino-oxime. Up t o the present there has been nosatisfactory explanation suggested for the existence of the threecarbanilino-derivatives obtained from the m-nitrobenzaldoximes,two from the anti- and ocne from the syn-colmpound.The authorshave been engaged f o r some time on this question, which will formthe subject of their next communication; for the present it willbe sufficient to state that the carbanilino-derivative of pdimethyl-aminobenzaldoximel as prepared by the action of phenylcarbimideon the anti-oxime is the syn-derivative, and gives on hydrolysispdimethylaminobenzonitrile and aniline, whereas the product ofhigher melting point obtained by boiling this compound withalcohol is the anti-compound, and on hydrolysis gives aniline andp-dimethylaminobenzaldoxime as its main decomposition products :NMe,*C6H4*IC;H p&NCO NMe,*C,H,*fi Hp-Dime thylamino -benzantialdoxime benzaynaldoxime.HON - + NO*CO*NHPhCarbadino -p - dime thylamino -N Me2= C,H,*CNCarbanilino -p- dimethyladno- p-Dimethylamino -NMe,*C,H,* $ HNHPh*CO*ONbenznntialdoxime.benzonitrile.EXPERIMENTAL.The p-dimethylaminobenzaldoxime employed was prepared byKnofler and Boessneck's method (Zoc. cit.) by boiling a mixture ofthe aldehyde, hydroxylamine hydrochloride, and anhydrous sodiumcarbonate in equivalent proportions with alcohol under a refluxcondenser for three hours, and pouring the product into water. As,however, in the authors' experiments the oxime separated as THE ISOMERISM OF THE OXIMES. PART VI. 2875crystalline solid on stirring the aqueous emulsion, it was removedby filtration instead of extraction with ether.After recrystallisa-tion from alcohol the oxime melted at 144O.Acetyl-p-dimethy1aminobenzantialdoxime.-The oxime was dis-s o h d in acetic anhydride, warming very gently, and left forfifteen minutes. A bright green solution was thus obtained (itmay be noted here that this colour is very generally met with inworking with dimethylaminobenzaldoxime, and is probably due toa trace of some oxidation product). The excess of acetic anhydridewas decomposed by shaking with sodium carbonate solution, whenthe acetyl derivative was obtained as a mass of pale green cryst,als,which separate from dilute alcohol in colourless needles meltinga t 108O:0.1569 gave 18.2 C.C. N, a t 1l0 and 746 mm. N=13*7.C1,H,,O,N, requires N = 13.6 per cent.This compound was boiled for ten minutes with 2N-sodium hydr-oxide when it passed completely into solution, the solution wasacidified with dilute sulphuric acid, and made faintly alkaline withsodium carbonate; the solid separating proved to be pdimethyl-aminobenzaldoxime, and acetic acid could be detected in t'he motherliquor.The formation of this acetyl derivative and its hydrolysisestablish the1 anti-configuration of the oxime.A ction of Hydrogen Chloride on p-Dimet hylaminobenzanti-ctldoxim e.The oxime was dissolved in anhydrous ether, and dry hydrogenchloride passed into the solution; a yellow, pasty mass was firstprecipitated, which rapidly became white and crystalline. Thehydrochloride obtained inTthis way melted and decomposed a t 170° :0.3078 required 15.2 C.C.N/10-AgNO,.C,H,,ON,,HCl requires C1= 17.7 per cent.When decomposed with sodium carbonate solution the originaloxime was obtained, the crude product melting a t 140°, and afterrecrystallisation from cold acetone and water at 144O, moreover,admixture with this substance did not depress the melting point ofpdimethylaminobenzamtialdoxime.The action of dry hydrogen chloride on a solution of the oxime indry chloroform was also investigated, but a hydrochloride of thesame melting point was obtained, and this also regenerated theoriginal oxime on treatment with sodium carbonate solution. Thehydrochloride was also prepared according to Beckmann's method(loc. c i t . ) . Equivalent quantities of the aldehyde and hydroxyl-amine hydrochloride were heated in alcohol for three hours a tC1= 17.52876 BRADY AND DUNN:50-55O. A copious precipitate formed, which proved t o be thesame hydrochloride as previously obtained, melting a t 170° andgiving pdimethylamiiiobenmn tialdoxime on treatment with sodiumcarbonate solution.0 - M e t fi y l Ether of p-Diwiet hy7o miti ob eii zantin1doxime.-This dasprepared in the usual way by boiling on the water-bath for fifteenminutes an alcoholic solution of the oxime with an equimolecularamount of sodium ethoxide and a slight e'xcess of methyl iodide.Tlie green product was poured into water and extracted with ether,the ethereal solution being shaken with sodium hydroxide solutionto remove unaltered oxime, washed with water, and evaporated.Apale amber-coloured oil was thus obtained, which when cooled inice set t o a greenish-white, crystalline mass. On recrystallisationfrom dilute alcohol the ether separates in colourless plates with aslight fragrant' odour, and melting a t 6 9 O :0.1638 gave 22.2 C.C. N, a€ 1 7 O and 751 mm. N=15.8.C,oH,,ON, requires N = 15.7 per cent.Hydrocli loride of t h e 0-Me tli yl E t he^ of p-Dime t h y 7nwLiizob ell z-The 0-methyl ether was dissolved in dry ether, and dry hydrogenchloride was passed into the solution. A viscid substance wasprecipitated, which soon became crystalline. This hydrochloridemelt's at 118-1 22O, but, unlike the hydrochlorides of the oximes,does not evolve hydrogen chloride a t its melting point :Cl,,Hl,0N2,H@1 requires C1= 16.5 per cent.antinl<doxime.0.2134 required 10.0 C.C.N/10-AgNO,. C1= 16.6.Decomposition of the hydrochloride with sodium carbonate solu-tion regenerated the 0-methyl ether.Diphe n ylccar bnmyl-p-disne t h ylnmin o b en zsynaldoxime.This compound was prepared by dissolving the oxime in alcoholand adding one equivalent of sodium in alcohol and one equivalentof diphenylcarbamyl chloride. On adding the latter a voluminous,pasty inass was formed, which was well shaken, heated on thewater-bath for ten minutes, cooled, filtered, and washed withwater. This substance is almost insoluble in hot alcohol, but isreadily soluble in CEJoroform, and may be recrystallised from amixture of this solvent and light petroleum, when i t separates insmall, colourless needles, melting and decomposing at 171' :0.2930 gave 29.0 C.C.N, at 16O and 751 mm.Diphenylcarbamyl-p-dimethylaminobenzsyjraldoxime was hydro-N=11*5.C,,H,,O,N, requires N = 11.7 per centTHE ISOMERISM OF THE OXIMES. PART vr. 2877lysed by boiling with alcoholic sodium hydroxide for two hours.The sodium carbonate which separated was filtered off, and thesolution diluted considerably with water and filtered. The solidso obtained was washed repeatedly with very dilute hydrochloricacid, and the residue recrystallised from alcohol; this proved t o bediphenylamine. The washings were extracted with ether to removediphenylamine, then made alkaline, and again extracted with ether,After removal of the ether the residue was crystallised from alcohol,and found to be diniethylaminobenzonitrile.From the first filtrateabove a small quantity of dimethylaminobenzaldoxime was obtainedby extracting the alkaline solution with ether to remove diphenyl-amine, etc., acidifying, making faintly alkaline with sodium car-bonate, and again extracting with ether. This ethereal solutionyielded a small quantity of solid, which was recrystallised fromalcohol and shown to be the oxime.solution ofpdimethylaminobenzanttialdoxime in ether was treated with anequimolecular amount of phenylcarbimide. After a few momentspale brown, shining plates began to separate; the solution was leftf o r twenty-four hours and then filtered. The solid was recrystal-lised from cold acetone and water, from which solution it separatedin sulphur-yellow plates, melting and decomposing a t 117O.Afurther recrystallisation from alcohol removed most of the colour,but did not raise the melting point:C'arb anilino-p-dim e thy lamiiao b enssynaldoxim e .-A0.2021 gave 25.2 C.C. N, a t 16O and 761 mm. N=14.7.This carbanilino-derivative was hydrolysed by boiling with30 per cent. sodium hydroxide solution for five minutes. Anilinewas easily recognised in the steam, whilst oily drops remainedsuspended in the liquid. These on cooling set to a solid, whichwas crystallised from dilute alcohol, and melted a t 75O; a mixturewith p-dimethylaminobenzaldehyde (m. p. 73O) melted a t 55O, andwith p-dimethylaminobenzonitrile (m.p. 75-76O) a t 75O. Themother liquor from the hydrolysis was acidified, and then madefaintly alkaline with sodium carbonate solution, when, after sometime, a small quantity of substance crystallised out, which provedto be pdimethylaminobenzaldoxime, f orrned probably by the con-version of a little of the syn- into the anti-carbanilino-compoundduring the warming and the subsequent hydrolysis of the latter.A similar decomposition takes place if the carbanilino-derivativeis boiled 'with alcohol alone for some time. Carbanilino-pdimethyl-aminobenzsynaldoxime was boiled with alcohol under a reflux con-denser for twenty-four hours; the solution so obtained was dilutedwith about half its volwne of water and cooled. The crystallineC16H1,02N3 requires N = 14.8 per cent.VOL.cv. 9 2878 BRADY AND DUNN : ISOMERISM OF THE OXIMES. PART VI.precipitate which formed proved t o be diphenylcarbamide (m. p.232O). The mother liquor was diluted, and the milky liquid acidi-fied with dilub hydrochloric acid ; silky needles which remainedsuspended in the solution were collected, and shown t o be diphenyl-carbarnide. The filtrate was again made alkaline with sodiumhydroxide, stirred, and set aside for some hours, when a quantityof dimethylaminobenzonitrile separated out. The mother liquorwas acidified a-tid made alkaline with sodium carbonate, and thesolid separating was crystallised from alcohol, and proved t o bedimethylaminobenzaldoxime.I n each of the above cases the primary products of the reactionmay be regarded as p-dimethylaminobenzonitrile and the hypo-thetical phenylcarbamic acid ; the latter in the presence of alkalisis decomposed into carbon dioxide and aniline, and in the absenceof alkalis two molecules yield water, carbon dioxide, and diphenyl-carbamide :C,H,*NH*CO,H = C,H,*NH, + CO,.2C,H,*NH*C02H = (C,H,*NH),CO + CO, + H,O.The nuch larger ainount of oxime found as the result of pro-longed boiling with alcoliol is due t o the conversion of most of thesyn- into the 0)) ti-derivative, and the subsequent hydrolysis of t h a tcompound (see below).Cccrba?tilztzo-p-dimet hylrc m in o benzantiaZdoxirne.-The freshly pre-pared syn -carbanilino-derivative described above was covered withalcohol and boiled under a reflux condenser for one hour.On cool-ing, carbanilino-pdiniethylaminobenznntialdoxime crystallised inlarge, colourless plates, melting and decomposing a t 152O :0.2646 gave 32.4 C.C. N, a t 1 3 O and 768 mm. N=14*9.C,,H,,O,N, requires N = 14.8 per cent.This compound is also formed if the syn-carbanilino-derivativeis kept for any length of time, there being formed simultaneouslya small amount of aniline and dimethylaminobenzonitrile. Carb-anilinodimethylaminobenzan tialdoxime on boiling with 2N-sodiumhydroxide passes almost completely into solution, no nitrile beingformed; the solution on treatment in the usual way yields dimethyl-aminobenzaldoxime and aniline.I n conclusion, the authors beg to express their thanks to theResearch Fund Committee of the Chemical Society for a grantwhich has defrayed the expenses of this work.ROYAL COLLEGE OF SCIENCE,SOUTH KRNSIKGTOK.THE IMPERIAL COLLEGE O F SCIENCE AND TECHX OLOGY