Mechanistic Studies of Chloramiee-T oxidation of dimethyl Sulphoxide in thePresence of Nano-raege Concentrated Aquachlororhodium (III) Complex asCatalyst in Perchloric Acid: A Kinetic Approach

摘要

The kinetics of oxidation of dimethyl sulphoxide (DMSO) by Chloramine-T(CAT) in the presence of acidic solution of aquachlororhodium(III) complex in its nano-concentration range used as homogeneous catalyst have been investigated at 35 °C for the first time. Almost constant values of pseudo-first-order rate constant (k_(obs)) throughout the variations of [CAT] in the oxidation of DMSO clearly demonstrate that order of the reaction with respect to Chloramine-T is unity. The results indicate that the order with respect to [DMSO] is first and with respect to [Rh(III)] is less than unity. Decreasing effect of [H~+] and zero effect of variation of ionic strength of the medium on the rate of oxidation were observed. Addition of p-toluene sulphonamide (PTS) and variation of [Cl~- ] have not affected the rate of oxidation of DMSO. The results are in accord with a proposed mechanism in which an electrophilic attack at the sulphur site in DMSO by the positive chlorine in the complex [RhCl5-CRNCl)]~(-3) (formed between reactive species of Rh(III) chloride and chloramine-T) takes place in slow and rate determining step to form an intermediate which finally changes into product through a series of fast steps with regeneration of effective species of catalyst.