FT-EPR Study of the Photolysis of 4-Chlorophenol

摘要

Fourier transform electron paramagnetic resonance (FT-EPR) has been used to identify the transient free radicals formed in the photolysis of 4-chlorophenol (4CP) dissolved in alcohols and to get information on their precursor from CIDEP effects. It is found that photolysis of 4-diazo-2,5-cyclohexadienone in 2-propanol produces the same FT-EPR spectrum as that produced by photolysis of 4CP. The results lend strong support to the recent proposal that the photochemistry of 4CP in aqueous and alcohol solutions involves formation of the carbene 4-oxocyclohexa-2,5-dienylidene. A number of publications have been concerned with the photolysis of 4-chlorophenol (4CP). The interest in the photochemistry of 4CP, and halogenated phenols in general, stems from efforts to develop a method for the photodegradation of these important pollutants. The primary products formed upon photolysis of 4CP depend strongly on reaction conditions. For instance, in oxygenated aqueous solution the reaction produces benzoquinone, whereas hydroquinone is the major product under anaerobic conditions. In the presence of hydrogen donors or in alcohol solution phenol is formed.