1510 BENTLEY AND PERKIN ON v-ACETOBUTYRIC ACID. XCVT1.-Note on y-Acetobuty-ic acid, CH;CO.CH;CH;CH;COOH. By W. H. BENTLEY and W. H. PERKIN, jun. DURING the course of an investigation on sulphocamphylic acid, the results of which, it is hoped, will soon be ready for publication, a ketonic acid was obtained, which had many properties in common with, and was for a long time thought to be, yacetobutyric acid. This acid has already been prepared by Wolff (Annalen, 1883, 216, 129) from ethylic rtcetylglutarate, by hydrolysis with dilute hydro- chloric acid, CH3*CO*CH(COOC2H,)*CH2*CH2*COOC2Hs 4- 2H2O = CH,*CO*CH~*CHz*CRz*COOH + CO2 + 2C2HS*OH, and by Lipp (Bey., 1885, 18, 3251), by the oxidation of acetobutylic alcohol, CR3*C 0.C Hz*C H2.C Hz* CH2*OH, with potassium dichromate and snlphuric acid.It is a colourless oil, which boils at 274-275" with siight decom- position ; it solidifies in a freezing mixture with difficulty, the crys- talline substance melting at 13O, whilst with water i t yields st crystalline hydrate, CH3.C(OH)2*CH2*CH&'H2*COOH, which melts at 35-36O. As these properties of acetobutyric acid proved to be altogether insufficient for the purposes of comparison with thc acid obtained from sulphocamphylic acid, we have prepared considerable qwmtities of the former and carefully examined two new derivatives,BENTLEY AND PERKIN ON ~~-ACETOBUTYRIC ACID. 1511 namely, the oxime, CH& (NOH)*CH2~CB2*CR2*COOH (m. p. 104- CH,*CH2*CH2*COOH 105O), and the semicarbazone, CH3*'C<N,NH,C0.NH2 (ma P. 173-174'), which are well characterised, and will serve in future for the identification of the acid.A t the same time, we have introduced some improvements into the preparation of this acid, and hope that the followicg short account will be of value to subsequent investigators. Pyeparation of y- Acetobuty ric acid, CH,*CO*CH,*CH2*CH2-COOH. The method which we employed in the preparation of this acid was similar to that recommended by Wolff and mentioned above, namely, by the hydrolysis of ethylic acetoglutarate. Sodium (3.4 grams) is dissolved in alcohol (45 grams), and to the well-cooled solution, first ethylic acetoacetate (19 grams) and then ethylic P-iodopropionate (33 grams) are added. The reaction takes place readily, the mix- ture getting quite hot; after standing for half an hour, the whole is heated on a water bath for two hours, water is then added, and the oily product extracted with ether.The ethereal solution after being well washed with water containing a little sulphurous acid to remove traces of iodine, is dried over calcium chloride, evaporated, and the oily residue, which weighs about 26 grams, is purified by distillation under reduced pressure (50 mm.). The crude substance commences to boil at 130°, but, after a few drops have passed orer, the tempera- ture rises rapidly to 190°, and nearly the whole passes over between this and 200°, a small quantity only of a residue of high boiling point remaining in the retort. Pure ethylic acetylglutarate is a colourless oil, which boils at 195-197' (50 mm.); on analysis, it gave the €0110 wing result. 0.1180 gave 0.2478 COz and 0.0845 HzO.C = 57.27 ; H = 7-94, CllH1806 requires C = 57.39 ; H = 7.83 per cent. It is best to distil this ethereal salt under reduced pressure, as it is then readily obtained pure, whereas, if distilled at the ordinary pres- anre, as recommended by Wislicenus and Limpach, it decomposes somewhat, owing to the high temperature at which it boils (271-272'). In order to obtain acetobutyric acid, the fraction of the ethereal salt distilling at 190--200° (50 mm.) is boiled in a reflax apparatus with 5 vols. of dilute hydrochloric acid (1 vol. of concentrated acid to 2 vols. of water). The oily layer rapidly disappears with evolution of carbon dioxide, and hydrolysis is complete after five hours, allhough Wolff recommends boiling for 8-10 hours. I n order to isolate the product, Wolff fractionated the hydrochloric acid liquid direct, but thir always causes considerable decomposition of the acetobntyric acid,1512 BENTLEY AND PERRIN ON v-ACETOBUTPRIC ACID.and we found that a much better result was obtained by proceeding as follows. The acid liquid, while still warm, is saturated with ammonium sulphate, and the acetobutyric acid, nearly the whole of which separates on the surface as an oily liquid, is extracted six times with ether. The ethereal solution is dried over calcium chloride, evaporated, and the residual, almost colourless oil is fractionated under reduced pressure, when almost the whole distils at 195--200° (65 mm.), the yield being about 85 per cent. of the theoretical.0,1322 gave 0.2676 C02 and 0.0926 H,O. C6HloOs requires C = 55.38 ; H = 7.69 per cent. The acetobutyric acid prepared in this may was a perfectly colour- less, moderately thick oil, which when mixed with a little water rapidly solidified to colourleas crystals of the hydrate C = 55.20 ; H = 7.79. CH3.C (OH)2*CHz*CH2*CH2*COOH. Oxidation with Nitric acid.-A few grams of the pure acid were gently heated with nitric acid (sp. gr. 1.2) in a reflux apparatus, when oxidation SOOLL commenced, red fumes being copiously evolved. After boiling for about two hours, the product was diluted with water, evaporated to dr-yness on the water bath, and the crystal- line residue, after being left in contttct with porous porcelain until colourless, was recrystallised from concentrated hydrochloric acid.The colourlesfi crystals which separated melted at 180-183", and were found to consist of pure szcccinic acid, the oxidation having taken place at the epCH2 group marked *, CH,* C0.C kz*CH2*CH2*C OOH. It was at first thought probable that the reaction might take place in snch a way that glutaric acid mould be produced ; probably this acid is formed when bromine in presence of potash is used as the oxidising agent, as in this case quantities of tetrabromomethane, CBr4, are deposited in a crystalline condition. Oxirne of Acetobu.tyric acid, C H3*C (NOH). CH2*CH,*CHz*C0 OH. This was prepared by dissolving hydroxylamine hydrochloride (5 grams) in a small quantity of water, adding acetobutgric acid (6 grams) and then, after cooling, mixing the clear solution with a concentrated solution of potash (7 grams).After 20 hours, the liquid was acidified, saturated with ammonium sulphate, and extracted at least 25 times with ether. The ethereal solution was dried over calcium chloride, evaporated, and the solid residue purified by recry stallisation from benzene. 0,1563 gave 13 C.C. moist nitrogen at 18" and 760 mm. N = 9.60. CsH,,N03 requires N = 9.65 per cent.ACTION OF CHLOROFORM, ETC., ON BlEThMIDOBENZOIC ACID. 151 3 The oxime of acetobutyric acid crystallises from benzene in colour- less prisms, and melts at 104-105°. It, is readily soluble in alcohol, water, and hot benzene, but only sparingly in ether, light petroleum, or cold benzene. Acetobut yric acid semicm?mzone, CH3*( cH2* H2' co H. N-NH-C O*NH2 In order to prepare this substance, semicarbazide hydrochloride was dissolved in a very little warm water, the solution mixed with an equal quantity of hot concentrated sodium acetate solution, the acetobutyric acid added, and the clear liquid heated to boiling for a few seconds ; on cooling, the semicarbazone rapidly separated in crystals, which, after standing over night, were collected, washed, and purified by recry stallisation from a little hot water. 0.1016 gave 20 c.c moist nitrogen at 19' and 758 mm. C7H,3N30, requires N = 22.46 per cent. N = 22.56. Acetobutyric acid semicarbazone, when heated in a capillary tube, softens at 168O, and melts and d.ecomposes at 173-174'. It is readily soluble in hot water, and crystallises from the solution on cooling in colourless, glistening needles.