Free radical chemistry

Abstract

During the past two decades important advances have been made in some areas of free radiacal research in the People's Republic of China, i. e. single electron transfer reactions, the establishment. of spin-delocalization substituent constants, and the study of thermodynamic stabilities of radicals. It has been shown through kinetic studies that the reactions between piperidine nitroxides with some biological small molecules, e. g. cysteine, glutathione, ascorbic acid, in solution or micelles proceed by electron transfer mechanism. Piperidine oxoammonium salts oxidize aromatic amines and N, Scontaining heterocycles to the corresponding radical cations, and the isotope effects in electron transfer reactions between thianthrene and N-methylphenothiazine radical cations and their respective neutral parent molecules have been reported for the first time. Through kinetic studies on the thermal cycload- dition reactions of Y-substituted α, β, β-trifluorostyrenes, a new scale σjj of spin-delocalization substituent constants is established, which is separated from the substituent polar effect, and a dual-parameter equation is used for correlation analysis of a number of free radical reactions with success. By study of the effects of EWG and EDG substituents on the thermodynamic stabilities of free radicals, the existence of Class O radicals has been proved.