STRUCTURE AND REACTIVITY OF CERTAIN ETHYLARENES IN REACTIONS WITH PEROXY-RADICALS

A study has been made of the liquid-phase initiated oxidation of 4-ethyl- and 4-isopropylpyridine-N-oxides by molecular oxygen. Rate constants have been determined for the reaction of the cumylperoxy radical with molecules of 4-ethylpyridine-N-oxide and ethylbenzene. It has been established that the reactivity in the reaction with peroxy radicals increases in the series 4-ethylpyridine < ethylbenzene << 4-ethylpyridine-N-oxide. In the MINDO-3 approximation, quantum-chemical calculations have been performed for the ethylarene molecules and the radicals formed from these molecules by rupture of alpha-CH bonds. It has been shown that the higher reactivity of the 4-ethylpyridine-N-oxide molecule in comparison with the other ethylarene molecules is due to the lower energy of the C-H bond that is ruptured, and to the higher level of electron-donor properties of the reaction center in the transition state.