Kinetics and mechanism of the oxidation of aromatic aldehydes with bromine

Abstract

The kinetics of the oxidation of benzaldehyde to benzoic acid with bromine have been investigated in buffers of pH 1–5 and in aqueous acetic acid. The substituents of ten substituted benzaldehydes have little effect on the rate of oxidation and there is a poor Hammett correlation. Benzaldehyde is oxidised 2·5 times faster than [²H₁]-benzaldehyde at 70°. There is little difference of solvent isotope effect in the oxidation of benzaldehyde and acetaldehyde measured in normal water and deuterium oxide, contrary to the findings of other authors. The evidence presented is in favour of a similar mechanism for the oxidation of both aliphatic and aromatic aldehydes.