Two acids corresponding to this empirical formula are known - namely ethylene succinic acid, H0 2 C CH 2 CH 2 CO 2 H and ethylidene succinic acid CH3 CH(C02H)2.
Ethylidene succinic acid or isosuccinic acid, CH3 CH(C02H)2, is produced by the hydrolysis of a-cyanpropionic acid and by the action of methyl iodide on sodio-malonic ester.
This is true of the fatty acid series, and the corresponding ketones and alcohols, and also of the succinic acid series.
Ethylene succinic acid occurs in amber, in various resins and lignites, in fossilized wood, in many members of the natural orders of Papaveraceae and Compositae, in unripe grapes, urine and blood.
Some fusel oil, glycerin and succinic acid appear to be formed simultaneously, but in small amount.
It may be distinguished from the isomeric ethylene succinic acid by the fact that its sodium salt does not give a precipitate with ferric chloride.
Succinic anhydride, C 2 H 4 (CO) 2 0, is obtained by heating the acid or its sodium salt with acetic anhydride; by the action of acetyl chloride on the barium salt; by distilling a mixture of succinic acid and succinyl chloride, or by heating succinyl chloride with anhydrous oxalic acid.