REACTIVITY AND SELECTIVITY IN THE OXIDATI ON OF STYRENE DERIVATIVES .2. STUDIES ON THE OXIDATION OF BETA-SUBSTITUTED ALPHA-METHYLSTYRENES

The liquid phase oxidation of p-substituted (Br-, Cl-, t-Bu-, MeO-, CF 3-) alpha-methylstyrenes and of alpha,p-dimethoxystyrene with pure oxy gen was investigated in chlorobenzene solution and in presence of cume ne and of cumene hydroperoxide in the temperature range 65-125 degrees C. The product yields were determined gaschromatographically. The dif ferences of the activation energies of the epoxide formation and the p arallel reactions amount to 19-48 kJ/mol. The epoxide selectivity incr eases with increasing temperature and concentration of olefine. The re lative chain propagation constants k(p) (C=C) Were determined by compe titive oxidation with cumene. The k(p)(C=C) values of p-substituted al pha-methylstyrenes can be correlated by the Hammett equation with both sigma and sigma(+) substituent constants.