Kinetic study of the ruthenium catalysed oxidation of styrene and substituted styrenes

Abstract

The kinetics of ruthenium catalysed oxidation of styrene and substituted styrenes by sodium hypochlorite solution was investigated using gas chromatography. The substituted styrenes used were p-methoxystyrene, p-methylstyrene, p-bromostyrene and m-nitrostyrene. It was found that the reaction rates increased from p-methoxystyrene to m-nitrostyrene. The rate constants showed that an electron donating group slowed the rate of reaction while an electron withdrawing group increased the rate of the reaction. The rate constants did not give a good linear relationship with the Hammett substituent constants when correlation with the Hammett equation was attempted. On the other hand, this trend was consistent with the results of analysis by the frontier molecular orbital theory, in which the activation energy of a reaction was correlated with the energy difference between the HOMO of the substituted styrenes and the LUMO of ruthenium tetroxide.