Abstract
The translational diffusion coefficients of ketyl radicals produced by a hydrogen abstraction reaction in ethanol, methanol, and cyclohexane are investigated by the transient grating (TG) method, from liquid phase to the medium-density region in wide temperature ranges. It is found that the diffusion coefficient of the radical (Dr) is smaller than that of a stable molecule with a similar size (Ds) even under supercritical conditions. In the medium-density region, the values of Dr in alcohols are differently dependent on temperature over viscosity from those in cyclohexane. The activation energy of Dr was determined and compared with that of solvent viscosity. We found that Dr/Ds decreases with decreasing density in the medium-density region for cyclohexane. This tendency is explained in terms of the local density enhancement in the medium-density region. In alcohols, the density dependence of Dr/Ds is not significant.
Published Version
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