US EPA

1204047 

Journal Article 

KINETICS AND MECHANISM OF OXIDATION OF THIOSEMICARBAZIDE BY POTASSIUM BROMATE IN AQUEOUS SULFURIC-ACID AND WATER-ACETIC ACID-MEDIA 

Gowda, BT; Pardhasaradhi, V 

1992 

Yes 

Journal of the Indian Chemical Society
ISSN: 0019-4522 

69 

2 

75-79 

WOS:A1992JL88200004 

http://://WOS:A1992JL88200004
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The oxidation kinetics of thiosemicarbazide (TSC) with potassium bromate in aqueous sulphuric acid and water-acetic acid (1 : 1, v/v) media have been studied under varying conditions. The rates of reactions show first order kinetics in [oxidant] in both the media, but show different behaviour in [TSC] and [H+]. The rate shows fractional order kinetics in [TSC] and nearly 1.5 order in [H+] in aqueous medium, compared to first order dependence in [TSC] and fractional order in [H+] observed in water-acetic acid. Addition of KBr, the reduced product of the oxidant has no significant effect on the rate of oxidation, while increase in ionic strength of the medium decreases the rate in both the cases. Decrease in dielectric constant of the medium by increasing the acetic acid composition of the solvent increases the rate. Suitable mechanisms consistent with the observed results have been considered and the related rate laws deduced. Coefficients of the rate limiting steps have been calculated at different temperatures and the related Arrhenius expressions deduced. The validity of rate laws have also been tested by recalculating the rate constants from the deduced rate law as [TSC] and [H+] varied. A good agreement between the recalculated values and the experimental constants provides support to the proposed mechanisms.