Registration Dossier
Registration Dossier
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EC number: 442-070-9 | CAS number: 329039-38-5
Phototransformation in air
Administrative data
Link to relevant study record(s)
Description of key information
DT50 (24h-day) = 31 h
Key value for chemical safety assessment
Additional information
No experimental data evaluating the potential for photodegradation of methyldiacetoxyisopropoxy silane (CAS No. 329039-38-5) in air are available. Based on its vapour pressure value (199 Pa at 25 ºC), this substance can be expected to show potential for volatilization into air. Nevertheless, once present in the atmosphere, it is susceptible to undergo indirect photodegradation with an estimated half-life of 31 hours (QSAR calculation, AOPWIN v1.92, reaction with OH-radicals, 24h-day) (Dr. Knoell Consult, 2012). Since methyldiacetoxyisopropoxy silane is hydrolytically unstable (half-lives in water < 4 h), an assessment of the photodegradation potential of the main transformation products is included as well. Isopropanol (CAS No. 67-63-0) and acetic acid (CAS No. 64-19-7) are highly volatile substances, with vapour pressure values of 43 hPa and 20.9 hPa respectively (at 20 and 25 °C)(OECD SIDS, 1997; HSDB, 2012). QSAR calculations performed with the AOPWIN v1.92 indicate that indirect photodegradation of these substances in air can be expected, with estimated half-lives of 53 hours and 25.7 days respectively. On the other hand, the estimated half-life of methylsilanetriol (CAS No. 2445-53-6) was determined to be 36.7 hours. Nevertheless, this is not expected to be a relevant degradation pathway for this metabolite since, based on its vapour pressure value (0.153 Pa at 25 °C), volatilization into air to a significant degree is unlikely.
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