One-electron photooxidation of carbazole in the presence of carbon tetrachloride. Part I. Carbon tetrachloride and ethanol used as reaction media

Abstract

The photochemical reaction products of carbazole with carbon tetrachloride in ethanol have been isolated and identified along with photoproducts in the irradiated solution of carbazole in pure CCl4 using water and ethanol added after the irradiation. This allowed us to discuss the complex mechanism of secondary photochemical changes in the carbazole–CCl4 system. We propose that the electron transfer from carbazole to CCl4 molecule in the excited CT complex, [Formula: see text] is the primary photochemical reaction followed by an heterolytic dissociation of a C—Cl bond which gives rise to the primary photoproducts in the solvent cage [C+•Cl−ĊCl3]. Secondary photochemical reactions initiate transformation of the radical cation of carbazole in the solvent cage giving rise to the following intermediate species:[Formula: see text]The probability of formation and further transformations of these Transient products: α, β, and γi, depends strongly on the nature of the reaction media. Thermodynamically stable products are formed depending on the reaction media; (carboethoxy)carbazoles, (carbo-N-carbazyl)carbazoles, and carbazole – carboxylic acids can serve as a proof for the formation of the above listed intermediates. All the results reported on the secondary photochemical reactions strongly support the electron-transfer primary mechanism used to explain the fluorescence quenching of carbazole by CCl4.These results also explain the changes observed in the fluorescence spectrum of carbazole when the ethanol solution of carbazole in the presence of CCl4 is irradiated.