E. J. Pedersen, E. Urbansky, B. Mariñas
Oct 19, 1999
Citations
8
Influential Citations
67
Citations
Journal
Environmental Science & Technology
Abstract
Methanediol dehydrates to give formaldehyde, which reacts rapidly and reversibly with monochloramine to form N-chloroaminomethanol. Under drinking water conditions, N-chloroaminomethanol undergoes a relatively slow decomposition that eventually leads to the formation of cyanogen chloride (ClCN) in apparently stoichiometric amounts. The following reaction sequence is proposed: CH2(OH)2 ⇆ CH2O + H2O; CH2O + NH2Cl ⇆ CH2(OH)NHCl; CH2(OH)NHCl → CH2NCl + H2O; CH2NCl → HCl + HCN; CN- + NH2Cl + H+ → ClCN + NH3. These reactions were studied at 25.0 °C and an ionic strength of 0.10 M (NaClO4). Stopped-flow photometry was used to monitor rapid, reversible reactions, and photometry was used to study relatively slow decomposition reactions. Equilibrium and rate constants for the addition of formaldehyde to monochloramine were (6.6 ± 1.5) × 105 M-1 and (2.8 ± 0.1) × 104 M-1 s-1, respectively. The dehydration of N-chloroaminomethanol was catalyzed by both H+ and OH-, with respective rate constants of 277 ± 7 and 26.9 ±...