Reactivity and selectivity in the oxidation of styrene derivatives, II studies on the oxidation of p-substituted α-methylstyrenes

Article abstract of DOI:10.1002/prac.19963380147

The liquid phase oxidation of p-substituted (Br-, Cl-, t-Bu-, MeO-, CF₃-) α-methylstyrenes and of α,p-dimethoxystyrene with pure oxygen was investigated in chlorobenzene solution and in presence of cumene and of cumene hydroperoxide in the temperature range 65-125°C. The product yields were determined gaschromatographically. The differences of the activation energies of the epoxide formation and the parallel reactions amount to 19-48 kJ/mol. The epoxide selectivity increases with increasing temperature and concentration of olefine. The relative chain propagation constants k_p (C=C) were determined by competitive oxidation with cumene. The k_p(C=C) values of p-substituted α-methylstyrenes can be correlated by the Hammett equation with both σ and σ⁺ substituent constants.