1911 Encyclopædia Britannica/Pyruvic Acid

PYRUVIC ACID, or Pyroracemic Acid, CH₃CO⋅CO₂H, an organic acid first obtained by J. Berzelius by the dry distillation of tartaric or racemic acids (Pogg. Ann., 1835, 36, p. 1). It may be prepared by boiling α-dichlorpropionic acid with silver oxide; by the hydrolysis of acetyl cyanide with hydrochloric acid (J. Claisen and J. Shadwell, Ber., 1878. 11, pp. 620, 1563); and by warming oxalacetic ester with a 10% solution of sulphuric acid. It is usually made by distilling tartaric acid with potassium bisulphate at about 200–250° C., the crude product being afterwards fractionated. It is a liquid which boils at about 165° C. (with partial decomposition); it may be solidified, and when pure melts at 13·6° C. (L. Simon Bull. Soc. Chim., 1895 [3],13, p. 335). It is readily soluble in water, alcohol and ether. It reduces ammoniacal silver solutions. When heated with hydrochloric acid to 100° C. it yields carbon dioxide and pyrotartaric acid, C₅H₈O₄, and when warmed with dilute sulphuric acid to 150° C. it gives carbon dioxide and acetaldehyde. Sodium amalgam or zinc and hydrochloric acid reduce it to lactic acid, whilst hydriodic acid gives propionic acid. It readily condenses with aromatic hydrocarbons in the presence of sulphuric acid. It is somewhat readily oxidized; nitric acid gives carbonic and oxalic acids, and chromic acid, carbonic and acetic acids. It forms a well-crystallized hydrazone with phenylhydrazine; and α-nitroso propionic acid with hydroxylamine. It is monobasic and yields salts which only crystallize with great difficulty; when liberated from these salts by a mineral acid it forms a syrupy nonvolatile mass. In aqueous solution it gives a red colour with ferric chloride. It shows characteristic ketone reactions, yielding a bisulphite compound and combining with hydrocyanic acid to form the nitrile of α-oxyisosuccinic acid. When warmed with baryta water it gives uvitic acid.

Pyruvic nitrile, or acetyl cyanide, CH₃CO⋅CN, may be prepared by the action of silver cyanide on acetyl chloride; or of acetyl chloride on nitrosoacetone (L. Claisen and O. Manasse, Ber., 1887, 20, p. 2196). It is a liquid which boils at 93° C. and with caustic alkalis polymerizes to diacetyldicyanide.