Registration Dossier
Registration Dossier
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EC number: 217-370-6 | CAS number: 1825-62-3
Endpoint summary
Administrative data
Description of key information
Additional information
The registered (parent)substance ethoxytrimethylsilane (CAS 1825-62-3) hydrolyses rapidly under environmental relevant conditions (DT50 = 2.2 min at pH 7 and 25 °C; EU Method C.7) to the hydrolysis products trimethylsilanol (CAS 1066-40-6) and ethanol (CAS 64-17-5). The ECHA guidance R.16 states that “for substances where hydrolytic DT50 is less than 12 h, environmental effects are likely to be attributed to the hydrolysis products rather than to the parent itself” (ECHA, 2016). The ECHA guidance R.16 also suggests that in cases where the hydrolysis half-life is less than 12 h, the breakdown products, rather than the parent substance, should be evaluated for aquatic toxicity. Thus, the environmental fate assessment in this dossier is based on the hydrolysis products.
The parent substance is characterized by a predicted water solubility of 0.302 g/l (at 20 - 25 °C, QSAR) and is not readily biodegradable (OECD 310). It has a measured vapour pressure of 118 hPa at 20°C (Dynamic method, EU Method A.4) and thus is expected to be volatile. Therefore, indirect photodegradation in air is a possible degradation pathway. Furthermore, it has a predicted log Kow of 3.7 (QSAR), indicating a moderate potential for adsorption to soil and sediment. Considering the rapid hydrolysis, the moderate potential for adsorption to soil and sediment, and the good water solubility, the main compartment for environmental distribution will be water.
Silanol hydrolysis product trimethylsilanol (CAS No. 1066-40-6)
The silanol hydrolysis product is characterized by a water solubility of 995 mg/L (at 20°C, OECD 105) and a vapour pressure of 19 hPa (at 25°C, OECD 104), indicating a potential for volatility. Therefore, indirect photodegradation in air is a possible degradation pathway. However, with a half-life of 4.1 days (publication) due to photodegradation, the silanol hydrolysis product will degrade slowly in air. There is no evidence of any significant biodegradation (0% after 28 days, OECD 310). However, its potential for bioaccumulation and its affinity to soil and sediment is low based on its low log Kow of 1.19 ( at 25 °C and pH 7; OECD 107).
Ethanol
The alcohol hydrolysis product ethanol is well characterized in the public domain. In the environment, it is expected to distribute into air (57%), water (34%) and soil (9%). It is fully water miscible at ambient temperatures and is characterized by a low partition coefficient (log Kow = -0.31) and a low adsorption coefficient (Koc = 1) and is considered to have a low overall environmental hazard profile (OECD SIDS, 2004).
Reference:
OECD (2004): SIDS Initial Assessment Report for SIAM 19, Berlin, Germany, 19-22 October 2004, Ethanol, CAS 64-17-5.
Information on Registered Substances comes from registration dossiers which have been assigned a registration number. The assignment of a registration number does however not guarantee that the information in the dossier is correct or that the dossier is compliant with Regulation (EC) No 1907/2006 (the REACH Regulation). This information has not been reviewed or verified by the Agency or any other authority. The content is subject to change without prior notice.
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