The Autoxidation of α-Methylstyrene in the Presence of Metal Salt

The azobisisobutyronitrile-initiated autoxidation of α-methylstyrene in the presence of metal salt was studied from the viewpoints of rate and products. The over-all activation energy was found to be 19.7 kcal./mol. In most cases, metal salts had a retarding effect on the rate of oxidation. With manganese and copper salts, an increase in the concentration of the metal decreased the rate of oxidation monotonously. However, cobalt naphthenate had an accelerating effect within a limited range of concentration, although it also had an inhibiting effect at higher concentrations. The products were acetophenone, formaldehyde, α-methylstyrene oxide and α-methylstyrene polyperoxide. Metal salt had little effect on the products of oxidation, with the exception of cobalt salt, which gave α-methylstyrene oxide in considerable yield even at 760 mmHg of oxygen pressure, where little α-methylstyrene oxide was formed in the presence of other metal salts or in the absence of catalysts.