Registration Dossier
Registration Dossier
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EC number: 203-137-6 | CAS number: 103-71-9
Hydrolysis
Administrative data
Link to relevant study record(s)
Description of key information
The stability of an other isocyanate, isopropyl isocyanate, was tested in an aqueous test solution showing a rapid degradation (half live less than 1 hour). Further the stability of 1-chloro-4-isocyanatobenzene in a second test yielded a half-life of 7.3 h. The only hydrolysis products of both isocyanates were found to be the corresponding amines. These results can be taken as read-across for the isocyanate examined here, a rapid hydrolysis in water with the corresponding amine as degradation product.
A study was conducted with phenyl isocyanate which examined just the first stage of the hydrolysis to carbamic acids. The half-life of this reaction was reported as 20 s.
Key value for chemical safety assessment
- Half-life for hydrolysis:
- 1 h
- at the temperature of:
- 25 °C
Additional information
According to handbook data, isocyanates react rapidly with water forming aminic structures as well as carbamic acids, which are mostly unstable, and ureas under release of carbon dioxide. Monitoring the amine formation in hydrolysis studies gives a picture of the degradation of the isocyanate. This behaviour of isocyanates has been used in studies to determine the rate of degradation*. In Guidance on IR & CSA Chapter R.6 it is mentioned that degradation products instead of parent substance can be investigated for ecotoxicological effects if the hydrolysis is very rapidly (t1/2 <1 h), OECD Guidance Document on Aquatic Toxicity Testing of Difficult Substances and Mixtures (2000) and Guidance on IR & CSA Chapter R.7b state the same. As phenyl isocyanate hydrolyses to aniline this is the ecotoxicological relevant species. Concluding, tests performed using the corresponding amine can equally be used to assess the ecotoxicological hazards of phenyl isocyanate. An underestimation of environmental hazards is thus avoided supporting a conservative and thus protective hazard assessment.
* Bayer Industry Services (2004), 4-chlorophenyl-isocyanate: Investigation on Stability in Aqueous Test Solutions. Project No: 200300181. Leverkusen, Germany.
Bayer Industry Services (2003), Isopropyl isocyanate: Investigation on Stability in Aqueous Test Solutions. Project No: 200300095. Leverkusen, Germany.
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