Bromide is ubiquitous in aqueous environmental systems. Recent increases in anthropogenic discharges of bromide (e.g., from wastewater effluents, hydraulic fracturing, and road salts) into sources of drinking water have renewed concerns over the formation of brominated disinfection by-products (DBPs) during drinking water treatment. When bromide-containing waters are disinfected with free chlorine, bromide is readily oxidized into free bromine, primarily as HOBr (pKa= 8.7) at near-neutral pH. Free bromine can subsequently react with organic compounds in the water to form potentially toxic brominated DBPs.The vast majority of previous research on mechanisms of DBP-precursor bromination assumes HOBr is �the� active brominating agent. We present evidence that other brominating agents (including BrCl, BrOCl, and Br2O) in equilibrium with HOBr can significantly influence regiospecific bromination rates of methoxy-substituted benzenes, employed herein as model DBP precursors (Figure 1 ).  Our results suggest that the greater electrophilicities of BrCl, BrOCl, and Br2O can more than compensate for their lower concentrations relative to HOBr during bromination of aromatic compounds of somewhat modest nucleophilicity. Equilibrium concentrations of BrCl, BrOCl, and Br2O are proportional to the concentrations of Cl-, HOCl, and HOBr, respectively. Accordingly, we also discuss how changes in solution chemistry can influence bromination rates, particularly during chlorination of drinking water and wastewater. We also explore how the structure of aromatic compounds influences the relative importance of BrCl, BrOCl, and Br2O as active brominating agents.

Contributions of BrCl, BrOCl, and Br<sub>2</sub>O toward bromination rates of aromatic compounds in solutions of aqueous free bromine: Implications for water disinfection

247th National Meeting (2014)

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Contributions of BrCl, BrOCl, and Br2O toward bromination rates of aromatic compounds in solutions of aqueous free bromine: Implications for water disinfection

Contributions of BrCl, BrOCl, and Br₂O toward bromination rates of aromatic compounds in solutions of aqueous free bromine: Implications for water disinfection