The widely used antimicrobial agent triclosan (5-chloro-2-(2,4-dichlorophenoxy)phenol) readily reacts with free chlorine under drinking water treatment conditions. Overall second-order kinetics were observed, first-order in free chlorine and first-order in triclosan. Over the pH range of 4−11.5, the kinetics were pH sensitive as a result of the pH dependent speciation of both triclosan and free chlorine. Using a Marquardt−Levenberg routine, it was determined that this pH effect indicates that the dominant reaction in this system is between the ionized phenolate form of triclosan and hypochlorous acid (HOCl). The overall second-order rate coefficient was determined to be kArO- = 5.40 (±1.82) × 103 M-1 s-1. Three chlorophenoxyphenols and two chlorophenols were identified by gas chromatographic−mass spectroscopic analysis. The chlorophenoxyphenol compounds include two monochlorinated triclosan derivatives (5,6-dichloro-2-(2,4-dichlorophenoy)phenol and 4,5-dichloro-2-(2,4-dichlorophenoxy)phenol) and one dichl...

Formation of chloroform and chlorinated organics by free-chlorine-mediated oxidation of triclosan.

To assess the estrogenic activity potentially stemming from bisphenol A (BPA) in drinking water, APCI/LC/MS and NMR were used to identify the products of its aqueous chlorination under the following conditions: 500 microg/L bisphenol A and 1.46 mg/L sodium hypochlorite (pH 7.5) at 25 degrees C. The 13 products (4-chloro-BPA; 2,6'-dichloro-BPA; 2,6-dichloro-BPA; 2,2',6'-trichloro-BPA; 2,2',6,6'-tetrachloro-BPA; trichlorophenol; 4-isopropyl-2'-hydroxylphenol; and six kinds of polychlorinated phenoxyphenols (PCPPs)) were found in the chlorinated BPA solution. Three main pathways are proposed: (1) chlorine-substitution reactions on the aromatic ring, followed by dehydration to form the chlorine-substituted BPA, (2) chlorine substitution reactions followed by cleavage of the alpha-C on the isopropyl moiety with positive partial charge and beta'-C on the benzene moiety with a negative partial charge to form trichlorophenol and 4-isopropyl-2'-hydroxylphenol, and (3) the formation of PCPPs. Especially for pathway 2, the reaction mechanism was clarified based on semiempirical quantum mechanical calculations. The reaction proceeded by attack of the OH and Cl (from HOCl) on the alpha-C on the isopropyl moiety with a positive partial charge and on the beta'-C with a negative partial charge on the benzene moiety. The activation energies forthe HOCl/4-chloro-BPA and 2,2',6,6'-tetrachloro-BPA reactions were 0.14 and 0.15 kcal/mol, respectively. Finally, the estrogenic activity of the aqueous chlorinated BPA solution was assessed by an estrogen receptor binding assay and a yeast two-hybrid system. It was found that the binding affinity of the chlorinated aqueous BPA at 60 min was 24 times that before chlorination. The transcriptional activation-induced by products were detected by a yeast two-hybrid system based on the ligand-dependent interaction of two proteins, a human ER and a coactivator, suggesting that the chlorinated BPA solution elicits an ability to mimic the effect of the estrogen hormone.

Products of Aqueous Chlorination of Bisphenol A and Their Estrogenic Activity

Chlorination of bisphenol A in aqueous media: formation of chlorinated bisphenol A congeners and degradation to chlorinated phenolic compounds.

Occurrence of PCDD and PCDF in different kinds of paper

Chemical changes of organic compounds in chlorinated water. XIII: Gas chromatographic−mass spectrometric studies of the reactions of irgasan DP 300 [5-chloro-2-(2,4-dichlorophenoxy)phenol] with chlorine in dilute aqueous solution

Chemical changes of organic compounds in chlorinated water : IX. Formation of polychlorinated phenoxyphenols during the reaction of phenol with hypochlorite in dilute aqueous solution

Chemical changes of organic compounds in chlorinated water : X. Formation of polychlorinated methylphenoxymethylphenols (predioxins) during chlorination of methylphenols in dilute aqueous solution

Kaori Yamada

Papers

Chemical changes of organic compounds in chlorinated water : IX. Formation of polychlorinated phenoxyphenols during the reaction of phenol with hypochlorite in dilute aqueous solution

Chemical changes of organic compounds in chlorinated water : X. Formation of polychlorinated methylphenoxymethylphenols (predioxins) during chlorination of methylphenols in dilute aqueous solution