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

Abstract

Aqueous methylphenol ( o-, m- and p-isomers) solutions were treated with hypochlorite at 20°C under various experimental conditions. Changes in the compositions of the chlorination products in water were determined by using gas chromatographic (GC) and GC—mass spectrometric analyses of diethyl ether extracts. The chlorination of methylphenols in dilute aqueous solutions produced a series of highly chlorinated compounds, including chloromethylphenols, chloromethylbenzoquinones and chlorinated carboxylic acids. Tentative identifications were also made for other compounds with following molecular formulae: C 14H 5Cl 2O 2, C 14H 4Cl 3O 2 and C 14H 3Cl 4O 2. On the basis of the thin-layer chromatographic and GC behaviour and mass fragmentation patters, the compounds are considered to be chlorinated methylphenoxymethylphenols. The production of some of these compounds is dependent on the number of equivalents of chlorine per mol of compound and the reaction pH. These results show that treatment with chlorine of water contaminated with phenolic compounds leads to the production of chlorinated phenoxyphenols (predioxins), which are precursors of the highly toxic chlorinated dibenzo- p-dioxins.