The formation of diacetyl and acetoin from α‐acetolactic acid

Of several ions tested, only Fe+3, Cu+2 and Al+3 catalysed the decarboxylation of α‐acetolactic acid at pH 4.8. At pH 2.2, only Fe+3 and Cu+2 were active. Fe+3 and Cu+2 were shown to form complexes with α‐acetolactic acid. Fe+3 and Cu+2 not only decarboxylated but also oxidized α‐acetolactic acid, with, as a result, formation of diacetyl. Decarboxylation of α‐acetolactic acid by these ions is compatible with the mechanism suggested by Martell and Calvin. α‐Acetolactic acid is subject to autoxidation. 2‐Butene‐2,3‐diol may be an intermediate product.