The role of electron transfer processes in the photoinduced decarboxylation reaction of α-oxo-carboxylic acids

Abstract

Irradiation of pyruvic acid in the presence of electron acceptors gives rise to enhanced carbon dioxide production, and in the case of methylviologen, this leads to the formation of reduced methylviologen, which provides further evidence that the photodecarboxylation of pyruvic acid proceeds via an electron transfer process. The addition of pyridine to benzene solutions of pyruvic acid enhances decarboxylation. The effect of added triplet quenchers on the decarboxylation of a variety of α-oxo-carboxylic acids is reported. In some cases this led to enhanced carbon dioxide yields, e.g. this occurs on the addition of various aromatic hydrocarbons to benzene solutions of pyruvic acid. The fact that the quenchers can enhance or ‘sensitise’ carbon dioxide production from α-oxo-carboxylic acids is explained on the basis of an electron transfer mechanism.