Kinetics of the Oxidation of Aliphatic Aldehydes by Chromic Acid

Abstract

The kinetics of chromic acid oxidation of propanaldehyde, butyraldehyde and isobutyraldehyde in aq. acetic acid have been studied. The product of the oxidation is the corresponding carboxylic acid. The reaction is of first order with respect to each the acid chromate ion, HCrO4 ⊖, and the aldehyde but of second order to hydrogen ion. The rate increases with proportion of acetic acid in the solution. The activation parameters for the oxidation and enolisation reactions have been evaluated. The rate of enolisation under similar condition is less than that of oxidation. A mechanism in which the first step is the rapid reversible formation of a chromate ester followed by a hydrideion transfer in the rate determining step has been suggested.