title: Thermodynamic properties of chloramine formation and related reactions during water treatment: a G4MP2, G4, and W1BD theoretical study.
abstract: A high-level gas and aqueous phase theoretical thermodynamic study was conducted on the primary and related chemical reactions which occur during chloramination for water treatment using the G4MP2, G4, and W1BD composite methods with the SMD, PCM, and CPCM solvation models. The standard state (298.15 K, 1 atm or 1M) formation of mono-, di-, and tri-chloramines from their precursors via hypochlorous acid chlorination is substantially exothermic and exergonic in both the gas and aqueous phases. The excellent agreement between experimental and theoretical values for a range of structural and thermodynamic calculations on a suite of calibration compounds suggests that the G4MP2, G4, and W1BD calculations meet or exceed criteria for thermochemical accuracy. The temperature influence on the thermodynamics of chloramine formation is projected to be negligible regardless of phase between 0 and 100°C. Additional thermodynamic calculations were undertaken on associated chloramination reactions involving the disproportionation of monochloramine, the decomposition of di- and tri-chloramine, and the reactions of trichloramine with ammonia and dichloramine. The results from these investigations not only provide a better understanding of the reaction thermodynamics, they also allow for a more rigorous interpretation of proposed chloramination mechanisms.
authors.affiliation: a Chemologica Research , Mortlach , Saskatchewan , Canada.
authors.forename: Sierra
authors.initials: S
authors.lastname: Rayne
authors.forename: Kaya
authors.initials: K
authors.lastname: Forest
mesh_terms: D002700:Chloramines / Q000138:chemical synthesis*; D054879:Halogenation; D006997:Hypochlorous Acid / Q000737:chemistry; D008956:Models, Chemical; D015394:Molecular Structure; D013816:Thermodynamics; D014732:Vibration; D018508:Water Purification / Q000379:methods*
chemical_list: D002700:Chloramines; D006997:Hypochlorous Acid; C030816:chloramine