Kinetics and Mechanism of Oxidation ofPhenols by Pyridinium Dichromate

Abstract

The kinetics of oxidation of phenols by pyridinium dichromate (PDC)

has been studied in 60% acetic acid-water (v/v) medium. The reaction

shows unit order dependence each with respect to oxidant and substrate.

The reaction is acid catalysed and the medium of low dielectric constant

favours the reaction. Increase in ionic strength has no effect on the reaction

rate. In the case of substituted phenols, the order with respect to substrate

varies depending upon the nature of the substituent present in the ring. In

general, the electron withdrawing substituents retard the reaction rate while

the electron releasing substituents enhance the rate of the reaction. From

the kinetic data obtained the activation parameters have been computed

and a suitable mechanism has been proposed in accordance with

muliparameter correlation analysis.