PYRUVIC ACID or PYRORACEMIC ACID, an ex tremely reactive organic acid employed in the synthesis of de rivatives of aryl-cinchonic acids including phenylcinchonic acid (Acidum Phenylcinchonicum, U.S. Pharmacopoeia), which is also known as Phenoquin or Atophan, used in neuralgia, sciatica or for the elimination of uric acid in gout and rheumatic affections.
Pyruvic acid, is best prepared by heating to gether an intimate mixture of 6 parts of fused potassium hydrogen sulphate and 4 parts of tartaric acid at 210-220° C. The distillate is fractionated under reduced pressure when a 50-55% yield of the acid is obtained (0. Kamm, Organic Syntheses, J. Wiley and Sons, 1925, vol. v., p. 63). Pyruvic acid was first obtained by Berzelius in 1855 by the dry distillation of tartaric or racemic acid. Methods of academic interest are : the acid hydrolysis of acetyl cyanide, or of ethyl oxaloacetate, (2) boiling ace'-dichloropropionic acid with moist silver oxide. As prepared by any of the foregoing methods pyruvic
acid is a liquid boiling at mm. and at 165° C/76o mm. with partial decomposition; it may be solidified and then melts at 13.6° C. With phenylhydrazine it yields a well defined crystalline phenylhydrazone and it combines additively with prussic acid and with alkali bisulphites. It forms mercaptols with the mercaptans and is reduced successively to lactic and propionic acids. Its most characteristic reaction with aldehydes and aromatic amines (Doebner's reaction) leads to the production of aryl-cinchonic acids. With benzaldehyde and aniline it furnishes phenylcinchonic acid and with other aldehydes and 0-naphthylamine it yields 0-naphthylcinchonic acids of definite melting points which on heating lose carbon dioxide and give well-defined bases. The reactions serve to identify aldehydes (q.v.).