Photoreduction of 3,6-Di-tert-Butyl-o-Benzoquinones in the Presence of N,N-Dimethylanilines in Binary Solvent Mixtures

Resumo

The effect of the composition and dielectric characteristics of binary solvent mixtures on the photoreduction rate constant (k_H) of 3,6-di-tert-butyl-o-benzoquinone and its 4-cyano derivative in the presence of three N,N-dimethylanilines has been studied. It has been found that for the pair 3,6-di-tert-butyl-o-benzoquinone–N,N-dimethylaniline, the free energy electron transfer of which is ΔG_e = +0.11 eV, ln k_H is proportional to the difference of the reciprocals of experimentally determined optical and static permittivities for the toluene–acetonitrile and benzene–N,N-dimethylformamide blends. For quinone–amine pairs, which have ΔG_e ≠ +0.11 eV, k_H is maximal in toluene and benzene and decreases with the increasing amount of the polar component in the solvent mixture, with lnk_H being inversely proportional to the permittivity of the medium.