Pyro racemic acid

Pyro-racemic Acid.—By oxidation lactic acid has the secondary alcohol group converted into a carbonyl group yielding a ketone acid known as pyro-racemic acid (p. 253). 

Pyro-racemic Acid CH3—CO—COOH. I uvic Acid... 

Synthesis from Acelyl Chloride.— As can be readily seen this is the simplest ketone acid that is possible and it is an alpha-V.tiont acid. Its name is derived from the fact that it is obtained from racemic acid by heat. It is a liquid boiling at 165°. Its constitution is best shown by the following syntheses. Acetyl chloride by means of silver cyanide yields acetyl cyanide which by hydrolysis gives pyro-racemic acid. 

From a-a-Di-brom Propionic Acid.—Di-brom propionic acid with both bromine atoms in the alpha position yields pyro-racemic acid by treatment with silver oxide. 

From Lactic Acid.—When lactic acid, a-hydroxy propionic acid, is oxidized pyro-racemic acid is obtained as was recently stated (p. 248). Also pyro-racemic acid may be reduced to lactic acid. 

From Acetic and Formic Acids.—A fourth method of synthesis from acetic and formic acid esters will be explained in detail in connection with the next acid. All of these syntheses prove the constitution of pyro-racemic acid as an a//>/fa-ketone acid as given. It may be considered as aceto formic acid which is in accord with the fourth method of synthesis. As an acid it forms all acid derivatives and as a ketone it undergoes the characteristic ketone reactions, e.g.y with phenyl hydrazine and hydroxyl amine. On heating to 150° with dilute sulphuric acid in a sealed tube it loses carbon dioxide and yields acet aldehyde. 

This corresponds to pyro-racemic acid in being the simplest beta-ketone acid possible. While it is known in the free state as an easily decomposed hygroscopic syrup its principal form is as the ethyl ester CH3—CO—CH2—COOC2H5, ethyl aceto acetate. In this form it is prepared and in this form it is used as a synthetic reagent. The ester is a colorless liquid boiling at 181°, with a characteristic fruity odor. 

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