Isotope effect in diffusion of methyl radicals in glassy ethanol-1,2 d5 at low temperatures

Abstract

The kinetics of methyl radicals decay has been studied at 77 K and at 90 K in glassy mixtures 0.9( xC 2H 5OH+(1− x)C 2D 5OH)+0.1H 2O. It has been shown that in matrices with a small content of H-component ( x≲0.02) the decay rate of CD 3 radicals is noticeably higher than that of CH 3. Upon H/D substitution in the methyl radical the rate of radical migration and the rate of deuterium atom abstraction from matrix molecules change simultaneously. As the fraction of C 2H 5OH in the mixture increases, the difference in the rates of the decay of methyl radical isotopomers vanishes. The unusual “inverse” isotope effect in the methyl radical diffusion is considered in the framework of the transition state theory.