Studies by electron spin resonance of the reactions of alkylperoxy radicals. Part 1.—Absolute rate constants for the termination reactions of alkylperoxy radicals

Alkylperoxy radicals, produced by the photolysis of solutions of di-t-butyl peroxide in oxygen-saturated alkanes, have been detected by electron spin resonance spectroscopy. Tertiary alkylperoxy radicals terminate with second-order kinetics, and absolute termination rate constants have been measured over a range of temperatures (–60 to +20°C). The process has an unusually high activation energy (ca. 8 kcal mol–1) for a reaction involving two radicals. Secondary alkylperoxy radicals decay more rapidly by a reaction which has a smaller activation energy (ca. 2 kcal mol–1). The decay of primary radicals is so rapid that the radical concentration is too small to be detected. A new method is described for the measurement of cross-termination rate constants.