MECHANISTIC INVESTIGATIONS WITH POSITIVE HALOGENS: KINETICS OF OXIDATION OF THIOSEMICARBAZIDE BY CHLORAMINE-B, BROMAMINE-B AND DICHLORAMINE-B IN ACID MEDIUM

Article abstract of DOI:10.1016/S0040-4020(01)86793-4

Kinetics of oxidation of thiosemicarbazide (TSC) by chloramine-B (CAB), and bromamine-B (BAB) in aqueous perchloric acid medium and by dichloramine-B (DCB) in 1:1 (v/v) water-methanol medium has been studied.The rate followed first order kinetics in and inverse fractional order in with all the oxidants.But it was fractional order in with CAB and independent of with BAB and DCB.Addition of benzenesulphonamide, the reduced product of the oxidants had no effect on the rate with CAB and BAB but it slightly increased the rate with DCB.Therate decreased with increase in ionis strength of the medium in all cases.Decrease of dielectric constant of the reaction medium by adding methanol had no effect on the rate with CAB and BAB but increased the rate with DCB.The mechanisms proposed and the derived rate laws are in conformity eith the observed results.The coefficients of the rate limiting steps have been calculated.Kinetics observed with HOCl and HOBr support the proposed mechanisms.