Kinetics of radiation-chemical reactions in a nonuniform colloid particle

The decomposition of ionol (2,6-di-tert-butyl-4-methylphenol) by the action of gamma -radiation in nitrous oxide-saturated aqueous solutions of lecithin liposomes was studied. The ionol located in the nonpolar liposome layer was shown to be consumed upon irradiation, the consumption yield growing with increasing ionol concentration. This finding indicates that some portion of OH radicals penetrate across the polar to the nonpolar layer. The ratio of rate constants for reactions of OH radicals with the hydrocarbon moiety of long-chain Fatty acids containing 17 carbon atoms and ionol was found to be 0.11 +/- 0.03 as determined by the steady-state treatment. An equation for the flux of radicals passing through the reactive membrane (polar liposome layer) from the bulk of dispersion medium was obtained using the diffusion kinetic model. This equation describes the experimental data with the ratio of the diffusion coefficient of OH radical in the polar zone to that in the nonpolar zone equal to 6.5 +/- 2.5.