Abstract:

The kinetics of oxidation of crotonic acid by chloramine –T in the presence of alkaline solution of rhodium (III) chloride complex as homogeneous catalyst has been investigated at 308 K. A 1:2 stoichiometry has been observed. The reaction exhibits pseudo-first order kinetics with respect to both [choramine-T] and [crotonic acid]. The linear dependence of the reaction rate at lower [Rh (III)] tends towards zero order at its higher concentrations. Retarding effect of added para–toluene sulphonamide on the reaction rate has been observed. Positive effect of [OH^-] at low concentrations is observed and after reaching a maximum the rate decreases on increasing [OH^-]. Negligible effect of ionic strength variation on the reaction rate has been observed. A zero effect of added [Cl^-] on the rate suggests non-replacement of chloride ion from reactive species of rhodium (III) chloride complex in alkaline medium during the course of the reaction. The overall activation parameters have been evaluated from the Arrhenius plot. Acetaldehyde and glyoxylic acid are identified as major products of the reaction. Mechanistic steps are discussed and rate law derived was found to conform to the observed kinetics results, stoichiometry and reaction products.


KEY WORDS: Mechanism, oxidation, crotonic acid, chloramine –T, Rh (III) chloride.