A tracer study of the m‐methoxybenzoyloxy radical

The polymerization of styrene initiated by bis(m‐methoxybenzoyl)peroxide has been studied at 60°C. and 80°C. using peroxide labelled with carbon‐14. The ratio of the numbers of m‐methoxybenzoyloxy and m‐methoxyphenyl end‐groups in the polymers has been determined for polymers prepared under various conditions. The results have been used to compare the stabilities and reactivities of various aroyloxy radicals. It is shown that the introduction of a methoxy group into the meta position of a benzoyloxy radical causes an increase in the stability of the radical; the effect is not so marked as when this group is introduced into the para position.