title: Experimental and theoretical insights into the involvement of radicals in triclosan phototransformation.
abstract: The phototransformation of triclosan has been a matter of longstanding interest due to both its prevalence in the environment and the discovery of 2,8-dichlorodibenzodioxin as a photoproduct. In this study, photolysis of triclosan resulted in several primary photoproducts including the following: 2,8-dichlorodibenzodioxin (4%), 4,5'-dichloro-[1,1'-biphenyl]-2,2'-diol (10%), 5-chloro-2-(4-chlorophenoxy)phenol (0.5%), and 2,4-dichlorophenol (7%). Trapping studies using d8-isopropanol showed deuterium incorporation in 5-chloro-2-(4-chlorophenoxy)phenol, providing strong evidence for the involvement of organic radicals in this reaction. Density functional calculations of the excited states of triclosan support the involvement of a radical intermediate in the mechanisms responsible for the dioxin, biphenyl, and phenoxyphenol photoproducts. The pathways for C-Cl bond cleavage and cyclization reactions are discussed.
authors.affiliation: Institute for Biogeochemistry and Pollutant Dynamics, ETH Zurich, 8092 Zurich, Switzerland.
authors.forename: Sarah
authors.initials: S
authors.lastname: Kliegman
authors.forename: Soren N
authors.initials: SN
authors.lastname: Eustis
authors.forename: William A
authors.initials: WA
authors.lastname: Arnold
authors.forename: Kristopher
authors.initials: K
authors.lastname: McNeill
mesh_terms: D000891:Anti-Infective Agents, Local / Q000737:chemistry / Q000528:radiation effects*; D002733:Chlorophenols / Q000737:chemistry; D004147:Dioxins / Q000737:chemistry; D010782:Photolysis; D011078:Polychlorinated Biphenyls / Q000737:chemistry; D014260:Triclosan / Q000737:chemistry / Q000528:radiation effects*; D014874:Water Pollutants, Chemical / Q000737:chemistry / Q000528:radiation effects*
chemical_list: D000891:Anti-Infective Agents, Local; D002733:Chlorophenols; D004147:Dioxins; D014874:Water Pollutants, Chemical; D014260:Triclosan; D011078:Polychlorinated Biphenyls; C068993:2,8-dichlorodibenzo-4-dioxin