Registration Dossier
Registration Dossier
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EC number: 232-259-2 | CAS number: 7803-49-8
Hydrolysis
Administrative data
Link to relevant study record(s)
Description of key information
According to structural properties, hydrolysis is not expected/probable.
Key value for chemical safety assessment
Additional information
Hydroxylamine may occur as different chemical species dependent on pH (see also Chapter 4.21). For this substance, the transformation of the ammonium-ion and possible nitrification by microbial activity might be the decisive process for degradation.
The hydroxyl-ammonium ion is expected to dissociate to hydroxylamine (free base) and hydrogen ions. Hydroxyl-ammonium ion and hydroxylamine (free base) are in equilibrium according to the following reaction scheme:
[NH3 -OH] + --> NH2-OH + H+
The estimated pKa for this reaction is 5.8. The amount of hydroxylammonium ion decreases rapidly at pH-values above 5. Only in very acidic environment, the substance is present as hydroxyl-ammonium ion. At pH 7, the amount of hydroxyl-ammonium ion is approximately 6 %, and at pH 8 nearly only the free base is present.
The free hydroxylamine base is very reactive and, at environmental conditions, is expected to decompose further by abiotic processes and nitrification. The expected ultimate degradation products are ammonia, nitrogen and water (Hollemann-Wiberg, 1995).
2NH2OH → NH3 + HNO + H2O
2HNO → N2O + H2O
NH2OH + HNO → N2 + 2H2O
Reference:
ECB (2008). EU-RAR Draft, Bis-(hydroxylammonium)sulphate, CAS: 10039 -54 -0,14. May 2008
Hollemann-Wiberg (1995): Lehrbuch der Anorganischen Chemie, de Gruyter, p. 702-704
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