Kinetics and Mechanism of Oxidation of Aromatic Aldehydes by Imidazolium Dichromate

Abstract

The kinetics of oxidation of para and meta-substituted benzaldehydes by imidazolium dichromate has been studied 70% acetic acid-water medium. The order with respect to oxidant, substrate and [H⁺] is found to be unity. The rate increases with the increase
in the percentage of acetic acid. An increase of ionic strength has
an appreciable effect on the rate. The reaction does not induce
polymerisation of acrylonitrile indicating the absence of free radical
pathway. The retardation of the rate by the addition of Mn²⁺ ions
confirms that a two electron transfer process is involved in the
reaction. Electron releasing substituents retard the reaction rate and
the electron withdrawing substituents enhance the rate of the reaction.
From the kinetic data obtained, the activation paramters have
been computed and a suitable mechanism has been proposed.