Kinetics and mechanism of oxidation of DL-methionine by Keggin-type 12-tungstocobaltate(III) in aqueous acetic acid medium

摘要

The kinetics of the reaction of DL-methionine with 12-tungstocobaltate(III) has been studied over the range of 8.4 <=10~3 [DL-methionine] <=14.0,3.0 <=pH <=5.0 and 20 <=T <=35 deg C in aqueous acetic acid medium.The electron transfer reaction showed first-order dependence each in [DL-methionine]_T and [12-tungstocobaltate(III)]_T.The main product of the reaction was found to be mcthionine sulfoxide.The activation parameters of the redox reaction were found to be DELTA H~#=106+-3 kJ mol~(-1) and DELTAS~#=75.7+-10 JK~(-1) mol~(-1) respectively.High positive value of DELTA S~# indicates the reaction to be outer sphere.