Decarboxylation by S . O 4 - Radicals

Decarboxylation by the reaction of SO/sub 4//sup -/ radical with aliphatic and aromatic carboxylic acids has been examined. Most aliphatic acids undergo efficient decarboxylation by SO/sub 4//sup -/ whereas their reactions with hydroxyl radical result in little decarboxylation. Aromatic acids decarboxylate to varying degrees depending on the other substituents. For example, benzoic and the phthalic acids undergo efficient decarboxylation, while o-toluic, p-hydroxybenzoic, and p-methoxybenzoic acid show only a small degree of decarboxylation. The findings support the conclusion that SO/sub 4//sup -/ reacts by electron transfer oxidation while OH either adds or abstracts H. Decarboxylation by H/sub 2/PO/sub 4/ radicals was also examined in a few cases and found to be less efficient than that by SO/sub 4//sup -/.