US EPA

1609851 

Journal Article 

Experimental and theoretical insights into the involvement of radicals in triclosan phototransformation 

Kliegman, S; Eustis, SN; Arnold, WA; Mcneill, K 

2013 

1 

Environmental Science & Technology
ISSN: 0013-936X
EISSN: 1520-5851 

47 

13 (Jul 2 

6756 

English 

23282071 

10.1021/es3041797 

WOS:000321521400007 

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 d(8)-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. 

Chemical reactions; Dioxins; Chemical bonds; Free radicals; 2013)