The kinetics and mechanism of the decomposition of Nchloroalanine (a rapidly formed chlorination product of the common amino acid, alanine) have been investigated. The decomposition products have been shown to be acetaldehyde, ammonia, carbon dioxide, and chloride ion or, depending on pH, pyruvic acid, ammonia, and chloride ion. The kinetics were studied by UV-visible spectrophotometry and by the DPD-FAS titrimetric technique. The reaction is first order in N-chloroalanine and independent of alanine concentration over three orders of magnitude of concentration. There is a complex dependence on pH (however, there is no pH dependence over the range in most natural water, pH 5 to 9). The half-life of the reaction in the 5-9 pH range is 46 min at 25 °C. The rate constant shows a marked temperature dependence at all pH values, changing by a factor of more than three for a 10 °C temperature change. The pH dependence of the first-order rate constant and the molar excitation coefficient have been used to infer the ionic state of the reactants and the mechanism.

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Dechlorination of some organic chloramines with aqueous sulfite solutions does not take place instantaneously as previously assumed. Field dechlorination times on the order of hours for some compounds that are found in chlorinated effluents appear likely on the basis of laboratory studies. These chlorinated compounds are not detected by standard analytical methods in the presence of sulfite ion.