# Formation of 2,4-Dichlorophenol by free chlorine mediated oxidation of Triclosan

I cannot find much guidance in the literature. This is the reaction between free chlorine in water and triclosan. I understand ether cleavage and electrophilic aromatic substitution (maybe) involved. Any ideas as to what the mechanism of this reaction might be?

Just as ethers can be formed when alcohols are protonated, the reverse reaction, formation of alcohols from ethers can also occur in the presence of acid. In the case at hand, when chlorine is mixed with water hypochlorous acid is one of the compounds formed, and it can serve as the proton source for the following reaction. The nucleophile can be $\ce{OCl^-}$, or any other nucleophile present. In any case this mechanism explains the formation of 2,4-dichlorophenol from TCS, chlorine and water.
• It's similar, but the aromatic ring blocks the "rear-side approach" normally associated with a traditional $\ce{S_{N}2}$ mechanism. Instead, a $\ce{S_{N}Ar}$ mechanism is probably involved. For example, see en.wikipedia.org/wiki/Nucleophilic_aromatic_substitution – ron Sep 11 '14 at 17:16