Oxidative Properties of Quinolinium Dichromate

In acid medium, quinolinium dichromate oxidized aromatic acids to the corresponding hydroxybenzoic acids, and dicarboxylic acids to the corresponding semialdehydes. The rate of the reaction showed a first order dependence on the concentrations of substrate, oxidant and acid. For the oxidation of the aromatic acids, the rate-determining step involved the formation of a cyclic chromate ester, which underwent decomposition to give the product. In the case of dicarboxylic acids, the mechanistic pathway was via the formation of the intermediate acyclic chromate ester which underwent decomposition, in the slow step, to give the product.