title: Free radical chemistry of disinfection-byproducts. 1. Kinetics of hydrated electron and hydroxyl radical reactions with halonitromethanes in water.
abstract: Halonitromethanes are disinfection-byproducts formed during ozonation and chlorine/chloramine treatment of waters that contain bromide ion and natural organic matter. In this study, the chemical kinetics of the free-radical-induced degradations of a series of halonitromethanes were determined. Absolute rate constants for hydroxyl radical, *OH, and hydrated electron, e(aq)-, reaction with both chlorinated and brominated halonitromethanes were measured using the techniques of electron pulse radiolysis and transient absorption spectroscopy. The bimolecular rate constants obtained, k (M(-1) s(-1)), for e(aq)-/*OH, respectively, were the following: chloronitromethane (3.01 +/- 0.40) x 10(10)/(1.94 +/- 0.32) x 10(8); dichloronitromethane (3.21 +/- 0.17) x 10(10)/(5.12 +/- 0.77) x 10(8); bromonitromethane (3.13 +/- 0.06) x 10(10)/(8.36 +/- 0.57) x 10(7); dibromonitromethane (3.07 +/- 0.40) x 10(10)/(4.75 +/- 0.98) x 10(8); tribromonitromethane (2.29 +/- 0.39) x 10(10)/(3.25 +/- 0.67) x 10(8); bromochloronitromethane (2.93 +/- 0.47) x 10(10)/(4.2 +/- 1.1) x 10(8); bromodichloronitromethane (2.68 +/- 0.13) x 10(10)/(1.02 +/- 0.15) x 10(8); and dibromochloronitromethane (2.95 +/- 0.43) x 10(10) / (1.80 +/- 0.31) x 10(8) at room temperature and pH approximately 7. Comparison data were also obtained for hydroxyl radical reaction with bromoform (1.50 +/- 0.05) x 10(8), bromodichloromethane (7.11 +/- 0.26) x 10(7), and chlorodibromomethane (8.31 +/- 0.25) x 10(7) M(-1) s(-1), respectively. These rate constants are compared to recently obtained data for trichloronitromethane and bromonitromethane, as well as to other established literature data for analogous compounds.
authors.affiliation: Department of Chemistry and Biochemistry, California State University at Long Beach, 1250 Bellflower Boulevard, Long Beach, California 90840, USA. smezyk@csulb.edu
authors.forename: Stephen P
authors.initials: SP
authors.lastname: Mezyk
authors.forename: Teresa
authors.initials: T
authors.lastname: Helgeson
authors.forename: S Kirkham
authors.initials: SK
authors.lastname: Cole
authors.forename: William J
authors.initials: WJ
authors.lastname: Cooper
authors.forename: Robert V
authors.initials: RV
authors.lastname: Fox
authors.forename: Piero R
authors.initials: PR
authors.lastname: Gardinali
authors.forename: Bruce J
authors.initials: BJ
authors.lastname: Mincher
mesh_terms: D004128:Dimethylnitrosamine; D004202:Disinfectants / Q000737:chemistry*; D004583:Electrons; D005609:Free Radicals / Q000737:chemistry*; D006846:Hydrocarbons, Halogenated / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D017665:Hydroxyl Radical / Q000737:chemistry*; D007700:Kinetics; D008956:Models, Chemical; D009602:Nitrosamines / Q000737:chemistry*; D011675:Pulse Radiolysis; D013696:Temperature; D014867:Water / Q000737:chemistry*
chemical_list: D004202:Disinfectants; D005609:Free Radicals; D006846:Hydrocarbons, Halogenated; D009602:Nitrosamines; D014867:Water; D017665:Hydroxyl Radical; D004128:Dimethylnitrosamine