Surfactant catalyzed electron transfer mechanism in the oxidation of racemic tartaric acid by Ce(IV)

Abstract

Oxidation of α-hydroxy acid, racemic tartaric acid and its kinetic studies have been carried out to establish the mechanism of oxidation. The electron transfer reaction was performed in presence of surface active agents, surfactants, a clean and green catalytic material, using Ce(IV) as the oxidant. The progress of the reaction was monitored using a spectrophotometer by recording the fall in absorbance of Ce(IV) at its λ max (wave length of maximum absorbance) of 380 nm. Disappearance of Ce(IV) is observed to be first order at constant [H + ]. Plot of log(Absorbance) against time is found to be linear in the initial stages of the reaction. The results of oxidation rates show a complex dependence of rate on [H + ]. The pseudo first order rate constants ( k ) obtained with varying substrate concentration and the plot of k obs /[substrate] vs [substrate] are observed to be excellently linear with positive slope. Plots of pseudo first order rate constants in presence of surfactant (sodium dodecyl sulphate, SDS) against the [SDS] abruptly rises in the concentration range below cmc (critical micelle concentration) after which the rate exponentially falls. Based on all the findings, Berezin model has been advanced to explain the observed kinetic phenomenon in the surfactant medium.