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Org. Synth. 1925, 4, 63
DOI: 10.15227/orgsyn.004.0063
PYRUVIC ACID
Submitted by J. W. Howard and W. A. Fraser.
Checked by C. S. Marvel and R. L. Shriner.
1. Procedure
An intimate mixture of 600 g. (4.4 moles) of finely powdered, freshly fused potassium acid sulfate and 400 g. (2.7 moles) of powdered tartaric acid, prepared by grinding them together in a mortar, is placed in a 3-l. round-bottomed Pyrex flask connected with a condenser which is filled with water but does not have any water flowing through it. The mixture is heated by means of an oil bath maintained at a temperature between 210 and 220° until liquid no longer distils over. Some foaming takes place (Note 1), but, if fused potassium acid sulfate is used and the temperature of the bath does not rise above 220°, it is not difficult to control. The distillate is then fractionated under reduced pressure. Pyruvic acid passes over at 75–80°/25 mm. and the yield is 117–128 g. (50–55 per cent of the theoretical amount) (Note 2).
2. Notes
1. If the mixture foams badly, it may be kept from frothing over by heating the upper part of the flask with a free flame.
2. The cake left in the reaction flask may be removed readily by inverting over a steam jet.
3. Discussion
Pyruvic acid can be prepared by the hydrolysis of α,α-dichloropropionic acid,1, 2 α,α-dibromopropionic acid,2 acetyl cyanide,3 and oxal-acetic ester;3 and by the distillation of tartaric acid or glyceric acid.4 Better results are obtained, however, by the distillation of tartaric acid in the presence of a dehydrating agent such as potassium bisulfate,5 and the procedure described was adopted after a study of a variety of dehydrating agents and various experimental conditions. The ethyl ester can be prepared by the catalytic oxidation of ethyl lactate,6 and the acid has been obtained by the oxidation of methylglyoxal bisulfite.7
This preparation is referenced from:

References and Notes
  1. v. Richter, Ber. 5, 477 (1872); Beckurts and Otto, Ber. 10, 264, 2037 (1877); Ber. 18, 228, 235 (1885).
  2. Kowski, Ann. 342, 132 (1905).
  3. Claisen and Shadwell, Ber. 11, 620, 1563 (1878); Wislicenus, Ann. 246, 327 (1888).
  4. Berzelius, Ann. Physik (2) 36, 1 (1835); Moldenhauer, Ann. 131, 338 (1864); Böttinger, Ann. 188, 314 (1877).
  5. Erlenmeyer, Ber. 14, 321 (1881); Simon, Bull. soc. chim. (3) 13, 335 (1895); de Jong, Rec. trav. chim. 19, 278 (1900); Döbner, Ann. 242, 269 (1887); Wohl and Maag, Ber. 43, 2188 (1910).
  6. Häussler, U. S. pat. 1,164,195 [C. A. 21, 746 (1927)].
  7. Neuberg and Kobel, Biochem. Z. 258, 365 (1933).

Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)

potassium acid sulfate

oxal-acetic ester

potassium bisulfate (7646-93-7)

tartaric acid (87-69-4)

ethyl ester (141-97-9)

Pyruvic acid (127-17-3)

α,α-dichloropropionic acid (75-99-0)

α,α-dibromopropionic acid

acetyl cyanide (631-57-2)

glyceric acid (600-19-1)

ethyl lactate (687-47-8)

methylglyoxal bisulfite