Kinetics and mechanism of reduction of bromothallium(III) complexes by hydrogen peroxide in perchloric acid media
Abstract
The thallium(III)–H2O2 reaction was found to be catalysed by bromide ion and the maximum rate observed at a bromide to thallium(III) ratio, R, of 2 : 1; the rate decreased at higher values of R. The reactivity of various bromothallium(III) species follows the order [TIBr]2+ < [TIBr2]+ > TIBr3 > [TIBr4]-. The complicated rate law of the reaction is as in equation (I) where k1, k2, k3 and k4 are the rate constants for –d[TIIII]/dt =(kK[TI3+][H2O2]+k1K1[TIBr2+]+k2K2[TIBr2+]+k3K3[TIBr3]+k4K4[TIBr4–])[H2O2/[H+](i) the steps involving [TIBr(O2H)]+, [TIBr2(O2H)], [TIBr3(O2H)]– and [TIBr4(O2H)]2– and K1, K2, K3 and K4 the respective formation constants, and k and K are the rate and formation constants for the steps representing the bromide-ion independent path.