Reactions of Monobromamine and Dibromamine with Phenolic Compounds and Organic Matter: Kinetics and Formation of Bromophenols and Bromoform.

Monobromamine (NH 2 Br) and dibromamine (NHBr 2 ) produced from reactions of hypobromous acid (HOBr) with ammonia can react with phenolic structures of natural organic matter (NOM) to produce disinfection byproducts such as bromoform (CHBr 3 ). The reactivity of NH 2 Br was controlled by the reaction of the bromoammonium ion (NH 3 Br + ) with phenolate species, with specific rate constants ranging from 6.32 × 10 2 for 2,4,6-tribromophenol to 1.22 × 10 8 M -1 s -1 for phenol. Reactions of NHBr 2 with phenol and bromophenols were negligible compared to its self-decomposition; rate constants could be determined only with resorcinol for pH > 7. At pH 8.1-8.2, no formation of CHBr 3 was observed from the reaction of NH 2 Br with phenol while the reaction of NH 2 Br with resorcinol produced a significant concentration of CHBr 3 . In contrast to NH 2 Br, a significant amount of CHBr 3 produced with an excess of NHBr 2 over phenol was explained by the reactions of HOBr produced from NHBr 2 decomposition. A comprehensive kinetic model including the formation and decomposition of bromamines and the reactivity of HOBr and NH 2 Br with phenolic compounds was developed at pH 8.0-8.3. Furthermore, the kinetic model was used to evaluate the significance of the NH 2 Br and NHBr 2 reactions with the phenolic structures of two NOM isolates.