Structure Confirmation, Reactivity, Bacterial Mutagenicity and Quantification of 2,2,4-Tribromo-5-Hydroxycyclopent-4-Ene-1,3-Dione in Drinking Water

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.