Kinetics and Mechanism of Oxidation of Phenoxyacetic Acids by Chromic Acids

Abstract

The kinetics of oxidation of phenyoxyacetic acid and several para- and meta-substituted phenoxyacetic acids by chromic acid in presence of perchloric acid have been studied in 502% (v/v) aqueous acetic acid. The oxidation is fractional order (0.74) with respect to substrate. The increase in concentration of perchloric acid increases the rate of the oxidation with an order of 0.62 (fractional). The added Mn²⁺ decrease the rate considerably suggesting a two electron transfer at the rate limiting step. In general electron releasing substitutes accelerate the rate while electron attracting groups retard the rate. A good correlation is found to exist between log K₂ and Hammett constants.