STRUCTURE CONFIRMATION, REACTIVITY, BACTERIAL MUTAGENICITY AND QUANTIFICATION OF 2,2,4-TRIBROMO-5-HYDROXYCYCLOPENT-4-ENE-1,3-DIONE IN DRINKING WATER

17 May 2024, Version 2

Abstract

Non-target chemical analysis of drinking water revealed the presence of two new disinfectant by-product (DBP) groups in the UK, halogenated-hydroxycyclopentenediones and halogenated-methanesulfonic acids. We unequivocally identified 2,2,4-tribromo-5-hydroxycyclopent-4-ene-1,3-dione (TBHCD), and quantified it together with dibromomethanesulfonic acid at 122±34 and 326±157 ng L-1 in London drinking water, respectively (N=21). We found TBHCD to be photolabile and unstable in tap water and at alkaline pH. Furthermore, spectral and computational data for TBHCD and three other halogenated-hydroxycyclopentenediones indicated they could act as a source of radicals and form other DBPs as a result. Importantly, TBHCD was calculated to have a 14.5 kcal mol-1 lower C-Br bond dissociation enthalpy than the N-Br bond of N-bromosuccinimide, a common radical substitution reagent used in organic synthesis. TBHCD was mutagenic in Salmonella/microsome assays using strains TA98, TA100 and TA102. This work reveals the unique features, activity and toxicity of trihalogenated hydroxycyclopent-4-ene-1,3-diones, prompting a need to more comprehensively assess their risks.

Keywords

non-target screening
disinfectant by products
halogenated cyclopentenedione
chemical stability
chemical pollutant reactivity
chemical toxicity
drinking water contamination

Supplementary materials

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Supplementary Information
Description
The details of the instruments used for the characterization of the compound after synthesis are reported, as well as the details of X-ray Christal structure of 2,2,4-tribromo-5-hydroxycyclopent-4-ene-1,3-dione characterization and the cartesian coordinates of optimized structure for bond dissociation enthalpies and energies calculations. Supplementary figures and tables are included below.
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