2048-2050The reaction between tetra butylammonium tribromide
and tellurium(IV) has been studied in 50% (vlv) 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