MICELLAR CATALYSIS ON THE REDOX REACTIONS OF DIALKYL SULFIDES WITH CHROMIUM(VI)

Chromium(VI) oxidation of diethyl sulphide (DES), diisopropylsulphide( DPS), di-n-butyl sulphide (DBS) and di-t-butyl sulphide (DTBS) in 99% acetonitrile-1% water(v/v) follows second order kinetics, first order in each reactant. A mechanism involving the rate determining nucleophi lic attack of sulphide on Cr of H2CrO4 followed by fast ligand couplin g between O- and S+ to form sulphoxide as the product has been formula ted. The anionic surfactant, sodium dodecyl sulphate, catalyses and th e cationic surfactant, cetyltrimethylammonium chloride, inhibits the r ate of oxidation which is explained by the proposal that the reaction takes place both in aqueous and micellar phases. The catalytic role. o f H+ and development of positive charge on sulphur due to the electron transfer from sulphide to Cr(VI) favour the reaction in the anionic m icelle and disfavour in the cationic micelle.