Further study of the decomposition of benzoyl peroxide in the presence of styrene

Styrene has been polymerized at 80°C. using as sensitizer benzoyl peroxide labeled with carbon‐14 in the benzene rings. From the specific activities of the polymers before and after hydrolysis, it has been possible to compare the velocity constants for the alternative reactions of the benzoyloxy radical, viz., addition to monomer or decomposition into a phenyl radical and carbon dioxide. By combining these results with those obtained at 60°C., the difference between the activation energies for the two reactions of the benzoyloxy radical has been calculated. Assuming normal values for the activation energy of the addition reaction and for the frequency factor of the decomposition reaction, the rate constant for the latter has been calculated.