Mechanism studies of the catalytic oxidation of propylene

Abstract Rates of oxidation of various deuterated propylenes over bismuth molybdate show that the rate-determining step is hydrogen abstraction from the methyl group, with a kinetic isotope effect of k D k H = 0.55 at 450 °C. Percentage retentions of deuterium in the acrolein and acrylonitrile products from 1-propene-1 d over both bismuth molybdate and cuprous oxide, after reasonable corrections for propylene isomerization and deuterium exchanges, are in agreement with a model in which allylic hydrogen abstraction occurs to form an allylic intermediate followed by hydrogen abstractions from either end. The isotope effect calculated from these retentions agrees with that of the kinetic isotope effect. The results indicate that the allylic intermediate is attacked at a hydrogen atom rather than at a carbon atom. Oxidation of a deuterated butylene to butadiene over bismuth molybdate is in qualitative agreement with the above model.