Photochemistry of halogenated benzene derivatives. Part VI. Photoreactions of tetra-and pentachlorophenols in water-acetonitrile mixtures

Laboratory photochemical studies of aqueous acetonitrile solutions of some polychlorinated phenols (PCPs) such as 2,3,4,5-tetrachlorophenol (2,3,4,5-Cl 4 -Pn) ( 1 ), 2,3,4,6-Cl 4 -Pn ( 2 ), 2,3,5,6-Cl 4 -Pn ( 3 ), and pentachlorophenol (Cl 5 -Pn) ( 4 ) at λ > 285 nm have been carried out for 6 and 24 h exposure times. All the investigated PCPs underwent reductive dechlorination. This process was dependent not only upon the position of OH group but also upon the relative positions of the Cl substituents on the benzene ring. The Cl 4 -Pn 2 (and 3 ) and Cl 5 -Pn ( 4 ) also yielded photoproducts of molecular formulae C 8 H 4 Cl 3 NO (M +* = 235) and C 8 H 3 Cl 4 NO (M +* = 269), respectively. Furthermore, phenol 3 is unique amongst the investigated PCPs; in addition to the above mentioned photoproducts, it yielded hexa-, hepta-, and octachlorodihydroxybiphenyl(s) as well as heptachlorohydroxydiphenyl ether.