Photosensitized dechlorination of polychlorinated benzenes. 1. Carbazole-photosensitized dechlorination of hexachlorobenzene

Photosensitized dechlorination of hexachlorobenzene (HCBz) in hexane and in acetonitrile (MeCN) solutions as well as in aqueous solutions of poly(sodi um styrenesulfonate-co-N-vinylcarbazole) (PSSS-VCz) copolymer has been stud ied. It was found that the reaction was photosensitized by both molecular a nd polymeric carbazole (Cz) chromophores. The products have been identified using GC, NMR and MS analyses. The detected products were: pentachlorobenz ene, tetrachlorobenzenes, trichlorobenzenes, dichlorobenzenes, chlorobenzen e and benzene. It was postulated that dechlorination process is mediated by an electron transfer from the excited carbazole chromophores to the molecu le of chlorinated benzene with subsequent heterolytic cleavage of the C-Cl bond. The photosensitized by Cz dechlorination process is a stepwise reacti on. The rate of photosensitized degradation of HCBz in aqueous PSSS-VCz sol ution was considerably higher than in organic solvents. (C) 1999 Elsevier S cience Ltd. All rights reserved.