SUCCINIC ACID is an organic compound occurring in amber (3 to 4%), from which fossilised gum it is obtained by distillation. It is also found in other resins, in lignites, in fossil ised woods and in many plants belonging to the Compositae and Papaveraceae. It occurs in the animal kingdom, as in the thymus gland of calves and in the spleen of cattle.
Chemically, succinic acid or ethylenesuccinic acid, is a saturated dibasic acid which crystallises in colourless prisms or plates melting at 186° C, and boiling at 235° C. Its vapour readily loses water to form succinic anhydride (I.) which crystallises in plates melting at I20° C.
The acid itself is soluble in water and its salts with the alkali and alkaline-earth metals are also soluble in water. Barium suc cinate is precipitated from aqueous solution by alcohol ; ferric succinate is insoluble in water and is sometimes employed in the analytical separation of iron from other metals. When heated with phosphorus trisulphide, sodium succinate yields thiophen.
Succinic acid is produced during the bacterial fermentation of ammonium tartrate or calcium malate. It arises from the oxi dation of fats and fatty acids by nitric acid. It may be prepared synthetically from ethylene, C2H4, through ethylene dichloride, ethylene dicyanide or succinonitrile, C2H4(CN)2. The last compound yields the acid on hydrolysis. Maleic acid, now produced industrially by the catalytic oxidation of benzene, yields succinic acid on reduction with sodium amalgam.
Succinyl chloride (formula II.) is obtained by the interaction of phosphorus pentachloride and succinic acid. Succinic anhy dride (formula I.), also produced by heating the acid or its salts with acetic anhydride or by heating succinyl chloride with anhy drous oxalic acid, is employed as an intermediate in colour making, when it yields two brands of Rhodamine S (see DYES, SYNTHETIC) by condensation with dimethyl- or diethyl-meta-aminophenol, Succinimide (formula III.), produced by heating succinic an
hydride in ammonia, crystallises in colourless octahedra melting at 125-126° C, and readily soluble in water. This imide when distilled with zinc dust furnishes pyrrole (q.v.).
Succinonitrile, obtained as above and also by electrolysis of potassium cyanoacetate, is a colourless solid melting at C. On reduction with sodium and alcohol it is converted into the ptomaine alkaloid, putrescine (tetra methylenediamine), NH2- [CH2]4-NH2, and into pyrollidine (tetrahydropyrrole, see PYRROLE).
Methylsuccinic acid or pyrotartaric acid, formed during dry distillation of tartaric acid, by heating pyruvic acid with concentrated hydrochloric acid, or by the reduction with sodium amalgam of citraconic and mesaconic acids, is obtained in colourless prismatic crystals soluble in water and melting at 112° C. It forms an anhydride and its sodium salt heated with phosphorus trisulphide yields 13-methylthiophen. Isosuccinic acid (ethylidenesuccinic acid), an isomeride of ordinary succinic acid, is obtained on hydrolysing a-cyanopropionic acid, or by the action of methyl iodide on ethyl sodio-malonate, It crystallises in prisms melting at 12o° C, and soluble in water. Unlike ordinary succinic acid, it does not yield an anhydride on heating, but loses carbon dioxide and passes into propionic acid. Reference : T. E. Thorpe, Dictionary of Applied Chemistry, Vol.