Oxidation of tellurium(IV) by tetrabutylammonium tribromide

Abstract

The reaction between tetra butylammonium tribromide and tellurium(IV) has been studied in 50% (vlv)<i> </i>acetic acid under second order conditions. The overall order of reaction is found to be two, unity each in both the reactants. The reaction involves a direct two-electron transfer step since the test for the formation of free radicals due to single electron step was negative. The reaction is retarded by hydrogen ions due to protonation prior equilibria of the reductant, tellurium(IV). The active species of the reactants is found to be tribromide ion of the oxidant and HTeO₃ˉ of the reductant. Considerable decrease in the entropy of activation of the reaction indicates formation of an ordered transition state between the two reactants analogous to that in alcohol oxidation by tetrabutylammonium tribromide ion.