Chloramide

Hydrolysis

Description of key information

Hydrolysis of monochloramine (NH2Cl) has been studied in various conditions in several studies. Studies available were not performed according to standardized method and were not in compliance with GLP but studies were used in a weight of evidence approach.

Margerum (1978) has shown that hydrolysis of monochloramine results in the release of active chlorine in the form of HOCl in slightly basic and slightly acidic solutions which are considered as representative of environmental conditions. In these conditions, the rate constant equals 1.9E-5 s-1 which corresponds to a T1/2 of 10 hours. The study is considered reliable with restrictions. Indeed, the study is published in a peer-reviewed journal, it is considered well documented and meets generally accepted scientific principles. Thus, the T1/2 value of 10 hours was considered as the key value for hydrolysis.

Key value for chemical safety assessment

Half-life for hydrolysis:

10 h

at the temperature of:

25 °C

Additional information

Hydrolysis of monochloramine (NH2Cl) has been studied in various conditions in several studies. Studies available were not performed according to standardized method and were not in compliance with GLP. Nevertheless, studies were published in peer-reviewed journals and it is considered that they meet generally accepted scientific principles. Thus, studies were used in a weight of evidence approach.

 Margerum (1978) has shown that hydrolysis of monochloramine is relatively slow by comparison with other chlorine species. Hydrolysis of monochloramine results in the release of active chlorine in the form of HOCl in slightly basic and slightly acidic solutions which are considered as representative of environmental conditions. In these conditions, the rate constant equals 1.9E-5 s-1 which corresponds to a T1/2 of 10 hours. The study is considered reliable with restrictions. Indeed, the study is published in a peer-reviewed journal, it is considered well documented and meets generally accepted scientific principles. Thus, the T1/2 value of 10 hours was considered as the key value for hydrolysis.

This constant rate is confirmed by a study of Vikesland (2001) which mentioned a previous study of Morris and Isaac (1981) and a constant rate of 7.6 x 10E-2 h-1 equivalents to a T1/2 of 9 hours, following the reaction NH2Cl + H2O -> HOCl + NH3. No further details are available regarding hydrolysis and thus the study has to be considered as not assignable for this endpoint.

Finally, Lin (1983) studied the dissipation of chlorine residuals in water under different light conditions but at a constant pH of 7.4. The rate constant obtained in first order reaction is influence by pH as well as temperature and it was shown that kinetics of monochloramine in water are different under dark conditions or light conditions (transport of chlorine residuals was found to be quite extensive under dark conditions).