Abstract: Kinetics and mechanism of Os(VIII) catalysed oxidation of crotonic acid (CA) by alkaline solution of chloramine-T have been investigated at 35°C. First order kinetics with respect to each chloramine-T and Os(VIII) was observed. The reaction exhibits linear dependence of reaction rate at low [CA] tending towards zero order at its higher concentrations. Accelerating effect of [OH ¯ ] ion on reaction rate was observed. The reaction shows positive effect of variation of ionic strength of medium while successive addition of para – toluenesulphonamide (a reduction product of chloramine-T) decreases the rate. ClO¯ and [OsO₄(OH)₂]^-2 have been postulated as the reactive species of chloramine-T and Os(VIII), respectively. The reaction was studied at four different temperatures and the overall activation parameters have been computed. The main oxidation products have been identified as acetaldehyde and glyoxylic acid. A suitable mechanism involving attack of chloramine-T species on complex formed between catalytic species of osmium tetroxide and crotonic acid in the slow and rate determining step is suggested and the following rate law consistent with observed kinetic results is presented.

 
 

Keywords: Kinetics, Reaction mechanisms, Chloramine-T, Crotonic acid, Osmium tetroxide