An analytical and kinetic investigation of the vanadium(V)-catalysed bromate oxidation of Bordeaux. Part II. Kinetics of the vanadium(V)-catalysed bromate oxidation of Bordeaux

Abstract

The kinetics of the vanadium(V)-catalysed oxidation of Bordeaux by bromate have been investigated and a rate equation is proposed together with a possible reaction sequence. The reaction was found to exhibit an induction period and to be autocatalytic, with both the initial and subsequent reaction rates dependent on the vanadium(V) concentration. Rate equations for both the initial and subsequent reactions have been deduced, together with an equation that gives the concentration of Bordeaux during the reaction at any time under the conditions used, all of which are in agreement with the observed experimental results. Slight differences in the reaction rate were found, depending on whether the vanadium added was in the +4 or +5 oxidation state.

Evidence is described suggesting that the autocatalytic nature of this reaction is caused by an intermediate oxidation product of Bordeaux. By a comparison with the reactions of similar compounds a possible structure for this intermediate is suggested. The general application of this mechanism to related catalytic systems is discussed.