Oxidation of Vanadium(III) by Hydrogen Peroxide and the Oxomonoperoxo Vanadium(V) Ion in Acidic Aqueous Solutions: A Kinetics and Simulation Study

The reaction between vanadium(III) and hydrogen peroxide in aqueous acidic solutions was investigated. The rate law shows first-order dependences on both vanadium(III) and hydrogen peroxide concentrations, with a rate constant, defined in terms of -d[H2O2]/dt, of 2.06 (plus-minus) 0.03 L mol^-1 s^-1 at 25 °C; the rate is independent of hydrogen ion concentration. The varying reaction stoichiometry, the appreciable evolution of dioxygen, the oxidation of 2-PrOH to acetone, and the inhibition of acetone formation by the hydroxyl radical scavengers, dimethyl sulfoxide and sodium benzoate, point to a Fenton mechanism as the predominant pathway in the reaction. Methyltrioxorhenium(VII) does not appear to catalyze this reaction. A second-order rate constant for the oxidation of V3+ by OV(O2)+ was determined to be 11.3 (plus-minus) 0.3 L mol^-1 s^-1 at 25 °C. An overall reaction scheme consisting of over 20 reactions, in agreement with the experimental results and literature reports, was established by kinetic simulation studies.