H-atom abstraction from alcohols by alkyl radicals. Cooperative effects in the reactions of alkyl radicals in glassy methanol-d3 Original Research Article

The ESR technique has been used to study the kinetics of the reaction of methyl and ethyl radicals with the additives of hydrogen-substituted alcohols CH3OH, C2H5OH, and CH3CD2OH, dissolved in glassy methanol-d3 within the temperature range 77–92 K. It has been demonstrated that the number of radical-accesible matrix molecules increases with temperature reaching N = 100 at 90 K, and is actually independent of radical type and strongly dependent on the type of H-substituted additive. Upon subtitution CH3CH2OH by CH3CD2OH at 90 K the number of methyl radical-accessible molecules decreases from N = 100 to N = 5. Using the data obtained it has been concluded that the large number of radical-accessible matrix molecules is not determined by its migration throughout the matrix as well as by the peculiarities of glass structure (the existence of the regions with high molecular mobility and/or with the large free volume). The model has been proposed for the elementary reaction of hydrogen atom abstraction in solids, according to which the atom transfer becomes possible due to the fluctuation rearrangement of molecular radical environment.