Kinetics of the base-catalyzed permanganate oxidation of benzaldehyde

The kinetics of the base-catalyzed permanganate oxidation of benzaldehyde have been reexamined. The rate is proportional to the first power of the aldehyde and permanganate concentrations, and there are terms that are zero order, first order, and second order in hydroxide ion. The reaction has an isotope effect, and the effect of substituents gives rho = +1.58. The possible mechanisms for the reaction are discussed in the context of ab initio calculations at the B3P86/6-311+G and MP2/6-31G theoretical levels, and both one- and two-electron processes are possible. Benzaldehyde hydrate dianion is calculated to have a remarkably small C-H bond dissociation energy.