Chlorine is the most common disinfectant used in drinking water treatment. Despite its important role in preventing waterborne disease, the reaction of chlorine with organic and inorganic water constituents can also result in the formation of (potentially) carcinogenic disinfection by-products (DBPs). Phenolic compounds are of particular relevance as DBP precursors because they are found in many anthropogenic chemicals, including pesticides, flame retardants, plasticizers, pharmaceuticals and personal care products, as well as in natural organic matter. Although the fate of phenols during reaction with chlorine has been investigated for decades, a mass balance for product formation has not been established and the identity and toxicity of ring cleavage products formed at elevated chlorine exposures (i.e., under conditions typically encountered during disinfection of drinking water and wastewater) are unknown. To address this knowledge gap, we used a novel approach to identify reactive electrophiles by measuring the formation of adducts with nucleophilic biomolecules.<br/>Using the amino acid N-a-acetyl-lysine as nucleophilic target, we identified the formation of previously unknown electrophilic dicarbonyl compounds during the reaction of phenol with chlorine. Experiments with a variety of alkyl-, chlorine- and bromine-substituted phenols revealed that the formation of these ring cleavage products depends on the position of the substituents relative to the hydroxyl group with yields varying between 0 - 45%. The high genotoxicity and mutagenicity of the formed dicarbonyls compounds suggests that they can contribute substantially to the overall toxicity of chlorinated waters if phenolic compounds are present. The results further highlight the suitability of this approach to electrophilic transformation products that are formed during chlorination.

Chlorination of phenols revisited: Formation of electrophilic dicarbonyl ring cleavage products

2019 Spring National Meeting

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