Original Articles: 2012 Vol: 4 Issue: 4
Kinetics and mechanism of oxidation of acetals by N-bromoisonicotinamide in acetonitrile medium
Kinetics of oxidation of acetals (XC6H4CH(OR)2 by N-bromoisonicotinamide (NBIN) in acetonitrile medium in the presence of sodium perchlorate has been investigated by iodometric method. The observed rate of oxidation is first order in both [NBIN] and [XC6H4CH(OR)2]. An increase in the dielectric constant of the medium increases the rate. The variation of ionic strength has no significant effect on the reaction rate and addition of isonicotinamide has retarding effect. The stoichiometry of the reaction is found to be 1:1. The corresponding ester has been identified as the product of oxidation. The reaction fails to induce polymerization of acrylonitrile under the experimental conditions employed. The Hammett reaction constant (ρ) for the reaction is found to be -0.71 at 313 K and -0.73 at 323 K. The isokinetic temperature evaluated from Exner plot is found to be β = 202 K (r = 0.9938). The Arrhenius and activation parameters for the reaction have been evaluated from Arrhenius plot by studying the reaction at different temperatures. A suitable mechanism is proposed and an appropriate rate law is deduced to account for the observed kinetic data.