Institute for Biogeochemistry and Pollutant Dynamics, ETH Zurich, 8092 Zurich, Switzerland.
Environ Sci Technol. 2013 Jul 2;47(13):6756-63. doi: 10.1021/es3041797. Epub 2013 Jan 15.
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.
三氯生的光转化一直是人们长期关注的问题，这不仅是因为它在环境中普遍存在，还因为发现 2,8-二氯二苯并-对-二恶英是其光产物之一。在本研究中，三氯生的光解导致了几种主要的光产物，包括以下几种：2,8-二氯二苯并-对-二恶英（4%）、4,5'-二氯-[1,1'-联苯]-2,2'-二醇（10%）、5-氯-2-(4-氯苯氧基)苯酚（0.5%）和 2,4-二氯苯酚（7%）。使用氘代异丙醇进行的捕获研究表明，5-氯-2-(4-氯苯氧基)苯酚中存在氘原子掺入，这为有机自由基在该反应中的参与提供了有力证据。三氯生激发态的密度泛函计算支持在导致二恶英、联苯和苯氧基苯酚光产物的机制中存在自由基中间体。讨论了 C-Cl 键断裂和环化反应的途径。
