MODIFICATIONS OF aa'y-TRIMETHYLGLUTACONIC AClD. 155 XVIL-The cis- and trans-ModiJicntions of aay- Tri- met h y lg lutaco nic Acid. By WILLIAM HENRY PERKIN, jun., and ALICE EhirLY SMITH, B.Sc., 1851 Exhibition Scholar of University College, Brngor. IN a recently published paper (Trans., 1903, , 772), i t was shown that when ethyl aay-trimethylacetonedicarboxylate, CO,Et*CMe,*CO*C HMe*CO,E t, is reduced with sodium amalgam, it is converted into a mixture of the stereoisomeric modifications of /3-hydroxy-aay-trimethylglutaric acid, C0,H.C Me,. QH* 0 H Cis, rn. p. 115". CO,H*CMeH CO,€€*CMe,*~H*OH T~uns, m. p. 155". HCMe*CO,H * Both the cis- and trcms-acids, when t,rexted successively with phos- phorus pentachloride and diethylanilhe, yield truns-aay-trimethyl- glutaconic acid, which melts at 150" : CO,H*CMe,*CH(OH)* CHMe*CO,H --f C02H*CMe,*CHC1*C HMe*CO,H -+ CO,H*CMe,*CH:CMe*CO,H.The trans-hydroxy-acid, when rapidly heated in small quantities, distils without decomposition, whereas the cis-hydroxy-acid is readily decomposed on distillation, forming an oily acid (see below) and a neutral crystalline substance, C,H,,O, (m. p. 8So), and it was suggested156 PERKIN AND SMITH: THE CIS- AND that this latter is probably the anhydride of the cis-modification of aay-trimethylglutaconic acid : C0,H'CMe;FH ;OH; flO*CMe,'gH CO,H*CMe*H.i -* O-CO---CMe * .._. We have continued the investigation, and find that this view of the constitution of the substance CsH,,,O, is correct. It is insoluble in aqueous sodium carbonate, but dissolves in warm dilute alkalis, and the solution, on acidifying and extracting with ether, yields cis-aay- trinzethy Zglutaconic a c i d , , as a colourless, crystalline CO,H*CMe,*fiH CO,H*CMe substance which melts at 125'.cis-py-dibromo-aay-trimet?~yZgZutai.ic m i d , CO,H *CMe, CHBr 'CMeBr *CO,H, which melts at 168" and is isomeric with the corresponding tvams-acid described in the previous paper (loc. cit., p. 779). It was stated above that the trans-hydroxy-acid, when heated in small quantities, distils with little decomposition, and we now find that, when considerable quantities of the acid are slowly heated, decomposition sets in, and a semi-solid distillate is obtained which consists of the above-mentioned anhydride of cis-trimethylglutaconic acid and an oily acid boiling a t about 213'.The latter is crotoclzylcli?li,et?~ylacetic acid, produced from aay-trimethyl- glutaconic acid by the elimination of carbon dioxide according to the eqna tion : When this acid is tmated with bromine, i t is readily converted into C0,H'Ci\le,'CH:CMe*C02H = CO,H*CMe;CH:CHMe + GO,. Crotonyldimethylacetic acid is also formed in considerable quantities during the preparation of the anhydride of cis-trimethylglutaconic acid by the distillation of cis-hydroxytrimethylglutaric acid (see above). It is an unsaturated acid mhicb, when digested with dilute sulphuric acid, is converted into the lantone of y-hydroxy-aay-trimethylbutyric acid, ?Me,*CR,*FHXe co- 0 ' a substance which has already been described by Anschutz arid Gillet (Arznalen, 1888, 247, 107), who obtained it from aa-dimethyllaevulic acid, CO,H*CMe,*CH;COMe, by reduction with sodium amalgam and named it a-dimethylvalerolactone.When crotonyldimethylacetic acid is treated with bromine, the colour rapidly disappears, but, even at low temperatures and in the dark, hydrogen bromide is eliminated. The product of this reaction-TRANS-MODTFICATIOKS OF ~~~-TRIMETHYLGLUTXCONIC ACID. 157 a neutral, crystalline substance melting at 83'-is evidently the Zactone of P-bromo-y-hydroxy-aay-trirrzet~~ylbzLtyric acid, produced in the following way : YMe,'CH:CHMe + Br, = ~Me,*CHBr*CHMeBr r= CO,H C0,H e,*CHBr YHMe co-- 0 ) but the ease with which the dibromo-acid loses hydrogen bromide is very unusual. cis-aay-Trintetl~ylgl2~tnc~~zic Acid, C0,H.C Me2 CH: CMe* CO,H.I n preparing this acid, pure cis-hydroxytrimethylglutaric acid was rapidly distilled in small quantities and under the ordinary pressure, when carbon dioxide and water vapour were given off and an oily distillate was obtained, which, on cooling, became semi-solid; this mass was cooled in a freezing mixture and collected at the pump on a funnel surrounded with ice and salt, the residue being then left in contact with porous porcelain until the oily impurity had been completely absorbed. By recrystallisation from light petroleum, colourless needles were obtained which melted at 88'. 0.1239 gave 0.2829 CO, and 0,0748 H,O. C,H,,O, requires C = 62.3 ; H = 6.5 per cent. The anhydride of cis-ti.imethylylutaconic acid is very readily soluble in chloroform and in ether, less so in cold benzene, and sparingly so in cold light petroleum.The solution in chloroform does not decolorise bromine, and when the benzene solution is mixed with aniline, no crystalline anilic acid separates. The anhydride is almost insoluble in cold water, but it dissolves on warming and is not a t once hydrolysed, since, if the solution is rapidly cooled and shaken, a con- siderable amount of the anhydride crystallises out unchanged. It is insoluble in cold sodium carbonate solution, but dissolves readily in warm dilute aqueous caustic potash, and on acidifying a clear solution is obtained. I n order to isolate the very readily soluble cis-acid, the liquid was saturated with ammonium sulphate, when the acid separated in needles ; the whole was then extracted three times with ether, the ethereal solution dried over calcium chloride and evaporated, and the solid residue purified by recrystallisation from a very small quantity of water.C = 65.7 ; H = 6.7. 0.1507 gave 0,3103 GO, and 0.0945 HgO. C=56*2 ; H = 7.0. C,HI20, requires C = 55.8 ; H = 7.0 per cent,158 MODlFICATIONS OF aary-TRIMETHYLGLUTACONIC ACID. cis-aay-TrimethyZgZutaco?lic acid melts at about 125" with evolution of gas and is readily soluble in water, chIoroform, benzene, alcohol, or ether ; its solution in aqueous sodium carbonate decolorises permanganate, but not instantaneously. When the acid is exposed to dry bromine vapour for about three hours and the excess of bromine removed over caustic potash in a vacuum desiccator, a solid residue is obtained which crystallises from formic acid (sp. gr.1*22), in which it is very sparingly sdluble, in hard, crystalline crusts. The analysis shows that this acid, which melts at about 1 6 8 O with decomposition, is cis-&di- bromo-aay-trimethylglutaric acid, C0,H*CMe,*CHBr*CMeBr*C02H. 0.1929 gave 0.2180 AgBr. Br= 48.1. C,H,,04Br, requires Br = 48.2 per cent. CrotonyZdi.nzetl~ylacetic Acid, C0,H*CMe2*CH:CHMe. The oily filtrate, which had been separated from the crystals of the anhydride of cis- trimethylglutaconic acid, was dissolved in ether and the ethereal solution extracted with sodium carbonate, by which means the crotonyldimethylacetic acid is dissolved, whereas t'he above anhydride, which is still present in considerable quantities, remains in the ether.After acidifying and extracting with ether, an oily acid was obtained which distilled a t 210-220", and as this still contained traces of anhydride, the treatment with sodium carbonate was repeated and the acid again distilled, when almost the whole quantity passed over a t 213" as a colourless oil having a penetrating and most disagreeable odour. 0.1291 gave 0.3088 CO, and 0*1101 H,O. C7H1202 requires C = 65.6 ; H = 9.4 per cent. When boiIed with 25 per cent. sulpburic acid for a few minutes, crotonyldimethylacetic acid is readily and almost completely converted into the lactone of y-hydroxy-aay-trimethylbutyric acid, ~Me2*CH,*~HMe co- 0 - The product was extracted with ether, the ethereal solution washed with dilute aqueous sodium carbonate, dried over calcium chloride, and evaporated, when a colourless oil remained, which smelt strongly of camphor and crystallised on cooling.The crystals, when left in contact with porous porcelain until quite dry, melted at 48-52". C = 65.5 ; H = 9.4. C= 65.2 ; .H= 9.4. 0.1760 gave 0.4232 CO, and 0,1494 H,O. This lactone has already been prepared by Anschutz and aillet C7H,,0, requires C = 65.5 ; H = 9.4 per cent.DERIVATIVES OF P-RESORCYLIC ACID. 159 (Annulen, 1888, 247, 107,) who give 52' as the: melting point. Crotonyldimethylacetic acid dissolves in chloroform, and if the solution is treated with bromine a t the ordinary temperature the colour dis- appears, heat is generated, and a considerable quantity of hydrogen bromide is produced. This formation of hydrogen bromide cannot be avoided by keeping the chloroform solution in a blackened test tube at 0' and adding the bromine slowly. On allowing the product oll brominntion t o evaporate spontaneously, a colourless residue is obtained, which crystallises from light petroleum (b. p. 50-60') in long prisms and melts at 82-83'. 0.3020 gave 0.2748 AgBr. As stated in the introduction, this substance is evidently the Zccctoxe Br = 38.8. C7H,,0,Br requires Br = 38.7 per cent. of p-bromo-y-?~yc~roxy-aay-t.r.inzetl~ylbutyric acid. THE OWESS COLLEGE, MAN CH ESTER.