862 SILBERRAD AND EASTERFIELD :

LXXXVII.-Studies o u E’thyl Cctrboxyglutarate. By OSWALD SILBERRAD, Ph.D., and THOMAS HILL

EASTERFIELD, M.A., Ph.D.

Action of Halogens on EtfqI Xodiocarboxyglutarale (compare Proc., 1904, 20, 114).-It has been found by Bischoff and Hausdorfer (Annalen, 1887, 239, 110) that when the sodium derivative of ethyl ethylmalonate or ethyl benzylmalonate is treated with iodine, the pro- duct formed is not a derivative of ethanetetracarboxylic acid, but a halogen derivative of the alkyl malonate. Ethyl sodiocarboxyglutarate has been found to furnish a further interesting instance of this behaviour. When halogens are allowed to act on ethyl sodiocarboxy- glutarate, no condensation occurs, but instead of ethyl carboxydiglu- tarate, the halogen derivatives of the original ethyl carboxyglutarate are formed. The latter proved to be identical with the compounds obtained by the direct halogenation of ethyl carboxyglutarate, the reaction being thus represented :

C2H,*C0,*CH,*CH,*CNa(C02*C2H5), + I, = N a I + C,H5*C0,*CH,*CH2mCI(C02*C2H5)2g

This having been shown to take place for the three halogens, it appeared of interest to ascertain the nature of the reaction between ethyl bromocarboxyglutarate and ethyl sodiocarboxyglutarate.

Action of Ethyl Byomomrboxyglutarate on Ethyl Sodiocarboxyglutarate (compare Proc., 1904, 20, 141).-On bringing together the halogen and sodium derivatives, they react and give rise to a mixture of the original ethyl carboxyglutarate and a new unsaturated ester, C,,H,,O,. The reaction, which appears to be unlike anything hitherto observed, may be represented as follows :

C,H,*CO,* CH,*CH;CNa(CO2*C2H5), + C,H5*C0,*CH2~CH2-CH(C0,*C,H5), + NaBr +

C,H,*C02*CH,*CH2*CBr(C02*C2H5)2 =

C,H,*CO,*CH,* CH: C(CO,* C2H5),. This unsaturated ester is thus to be regarded as ethyl a-carboxy-

A@ -glutaconate. On saponification, it yields a new carboxyglutaconic acid, which readily breaks up into glutaconic acid and carbon dioxide :

C,H,(CO,.C,H,), + 3H,O = CO,H*CH,* CH:CH*CO,H + 3C,H,*OH + GO,,

from which it will be seen that the constitution of t he ester must be represented by one of the following formulae :

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STUDIES ON ETHYL CARBOXYGLUTARATE. 863

(I) C2H,*C02-CH:CH*CH(,C02*C,H,)2 or (TI) C211,*C02*CH2~CH:C(C02~C2H5)2.

Of these, the former represents ethyl isoitaconate, from which the new ester differs in containing no active hydrogen, as i t will not form a sodium derivative.

EXPERIMENTAL.

(I) Action of Halogens on Ethyl Sodiocarboxyglutarute.-Ethyl carb- oxyglutarate (26.4 grams) (Emery, Ber., 1891, 24, 282) was mixed with 3 grams of finely-divided sodium suspended in 150 C.C. of toluene, and to t b i s mixture 17.5 grams of iodine dissolved in toluene were gradually added, the whole being then warmed for 10 hours on the water- bath. The product was then freed from excess of iodine by means of sodium hydrogen sulphite, washed, dried, and the toluene distilled off on the water-bath, the pressure being finally reduced to 2 mm. The iodo-ester so obtained is a pale amber-coloured, heavy oil, which readily loses iodine.

Found I = 31.60. Ethyl a-iodocarboxyghtarate, Cl2H1,O,1, requires 32.73 per cent.

Ethyl a-bromocarbozyglutarate was prepared both as above and also, much more readily, by gradually adding a slight excess of bromine to ethyl carboxyglutarate previously warmed to 40'. I n the latter case, bromination occurred with copious evolution of hydrogen bromide, from which the ester was finally freed by being placed over caustic potash in a vacuum desiccator. After washing with sodium hydrogen sulphite in order to remove the last traces of bromine, the compound was obtained as a colourless, highly refractive oil having a sp. gr. 1.325 at 1 5 ' / 4 O and possessing an odour resembling that of the bromo- paraffins.

A specimen prepared from the sodio-ester gave 23.01 Br. 9 , ?, ,, by direct bromination ,, 23.53 and 23.55 Br,

C,,H,,O,Br requires 23.60 Br per cent.

Ethyl a-chZorocul.boxyg~utu~ut$ was obtained in a manner precisely similar to tha t employed for the bromo-ester, which it closely resembles.

A specimen prepared from the sodio-ester gave 11.72 C1. 99 ? ? ,, by direct chlorination ,, 11.80 C1.

C,,H,,O,CI requires 11 -90 per cent.

(3) Action of Ethyl B~omocccrboxygEutarate O./L Ethyl Xoclioccrrboxy- gZutarate.-Ethyl a-bromocarboxyglutarate (340 grams) was gradually added to the sodio-ester prepared by mixing 260 grams of ethyl

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864 STUDIES ON ETHYL CARBOXYGLUTARATE.

carboxyglutarate with the calculated quantity of sodium ethoxide dissolved in absolute alcohol ; t h e mixture became warm and sodium bromide was rapidly precipitated, the reaction being completed by warm- ing on the water-bath for an hour. On pouring the product into water, a heavy oil separated, which, after washing with dilute acid and drying over potassium carbonate, was distilled under 15 mm. pressure. The entire quantity passed over between 163' and 180', and was ultimately found to consist of almost equal quantities of two compounds, which were separated by systematic fractionation under diminished pressure.

a-carboxy-Aa~-gZutaconate, C,H,*CO,* CH,*CH :C (GO,* C,H,),, formed the less volatile fraction of the above mixture, and, when pure, was a colourless oil (b. p. 173-176'/15 mm.) which readily absorbed two atoms of bromine.

Found C = 55-67' ; H = 7.14. C,,H1,06 requires C = 55.8 j H = 7.0 per cent.

The fact tha t the new ester is not acted on by granulated sodium suspended in toluene is additional evidence in favour of the up-position for the unsaturated bond.

Hydrolysis of Ethyl Car6oxyglutaconate.- Et by1 csrboxygl u tacona te (10 grams) was hydrolysed by boiling with aqueous hydrochloric acid (1 : 3). The product was freed from hydrochloric acid by evaporation and precipitated in the form of its silver sa l t ; the latter mas then suspended in water and decomposed with sulphuretted hydrogen. After concentrating on the water-bath, a syrup was obtained ; this, when left in a vacuum desiccator, slowly solidified to a crystalline mass which, after recrystallisation, melted at 132' and proved to be glutaconic acid.

Ethyl

Found C = 46.06 ; H = 4.79. C,H,O, requires C = 46.6 ; H = 4.6 per cent.

Ethyl carboxygluta!mte, C2H6*C02*CH,*CH2-CH(C02*C2H5)2, formed the more volatile fraction of the product resulting from the action of ethyl bromocarboxyglutarate on ethyl sodiocarboxyglutarate ; it boiled a t 162-163' (15 mm.).

C = 65.33 ; H = 7.82. C12H2006 requires C = 55.4 ; H = 7.7 per cent.

The ester was further identified as follows: 25 grams were dissolved in boiling aqueous hydrochloric acid (1 : 3). The concentrated solution was left in a vacuum desiccator until a syrupy, semi-crystal- line mas8 was obtained, from which glutaric acid was isolated after repeated crystallisation.

UNIVERSITY LABORATORY, CAMBRIDGE.

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