Organic Syntheses, Coll. Vol. 1, p.475 (1941); Vol. 4, p.63 (1925).
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. |