Kinetics of -oxyl Radicals' Decay.

-oxyl radicals of various structures were generated by oxidation of corresponding -hydroxy compounds with iodobenzene diacetate, [bis(trifluoroacetoxy)]iodobenzene, and ammonium cerium(IV) nitrate in acetonitrile. The decay rate of -oxyl radicals follows first-order kinetics and depends on the structure of -oxyl radicals, reaction conditions, and the nature of the solvent and oxidant. The values of the self-decay constants change within 1.4 × 10 s for the 3,4,5,6-tetraphenylphthalimide--oxyl radical to 1.4 × 10 s for the 1-benzotriazole--oxyl radical. It was shown that the rate constants of the phthalimide--oxyl radicals' self-decay with different electron-withdrawing or -donor substituents in the benzene ring are higher than that of the unsubstituted phthalimide--oxyl radical in most cases. The solvent effect on the process of phthalimide--oxyl radical self-decomposition was investigated. The dependence of the rate constants on the Gutmann donor numbers was shown.