Despite decades of research on the formation of disinfection by-products (DBPs) during chlorination of phenols, there is still considerable uncertainty about the relevance and nature of ring cleavage products. To address this knowledge gap, we investigated the reaction of hypochlorous acid (HOCl) with a variety of phenolic compounds, including commonly used personal care product ingredients, plasticizers and pharmaceuticals as well as naturally occurring phenols. Formation of DBPs was investigated using liquid chromatography-high resolution mass spectrometry using both positive and negative electrospray ionization. In addition, a novel amino acid reactivity assay that utilizes the nucleophilic amino acid N-alpha-acetyl-lysine (NAL) was used to detect electrophilic DBPs. As expected, the reaction of HOCl with phenolic compounds initially led to the formation of chlorophenols which is attributable to electrophilic aromatic substitution. This was followed by the formation of ring cleavage products such as chlorinated carboxylic acids. In addition, results from the amino acid reactivity assay further revealed the formation of several electrophilic ring cleavage products, including 2-butene-1,4-dial (BDA), its chlorinated analogue chloro-2-butene-1,4-dial (Cl-BDA) as well as several other alpha,beta-unsaturated dialdehyde compounds. For BDA we were able to demonstrate that the formation and yields are strongly dependent on the ring substituents, in particular of those in para-position to the phenolic hydroxyl group. Furthermore, the formation of BDA and other ring cleavage products was also impacted by the composition of the aqueous media including the buffer that was used to maintain a stable pH during the chlorination experiments. The application of in-silico toxicity prediction models indicated the formation of several DBPs that are of toxicological concern.

Identification and quantification of unsaturated C4-dicarbonyl ring cleavage products from chlorination of phenolic compounds: Structure-activity relationships

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.