racetoin

Racetoin, or racemic acetoin, is the racemic mixture of the chiral molecule acetoin, also known as 3-hydroxy-2-butanone. It consists of equal amounts of the enantiomers (R)-acetoin and (S)-acetoin.

Chemical identity: IUPAC name (RS)-3-hydroxybutan-2-one. Molecular formula C4H8O2. It is a colorless liquid with a mild buttery odor, and is soluble in water and many organic solvents.

Occurrence and biosynthesis: In microbial fermentation, several bacteria and yeasts produce acetoin and racetoin as intermediates in the 2,3-butanediol pathway. Pyruvate is converted to alpha-acetolactate, which can be decarboxylated to acetoin; acetoin can then be reduced to 2,3-butanediol. The racemate is obtained when no stereoselective control is exerted during synthesis or production.

Applications and properties: Acetoin imparts buttery notes in foods and beverages; racetoin is primarily of interest as an intermediate and for enantioselective synthesis, since the two enantiomers can have different reactivity and aroma. Chemical or enzymatic methods may be used to resolve racetoin to obtain enantiomerically pure acetoin for applications in chemistry and pharmacology.

Safety notes: Specific toxicology data for racetoin are limited. As with related small chiral ketols, it is generally handled under standard laboratory safety practices, and exposure should be minimized.