Registration Dossier
Registration Dossier
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EC number: 216-467-0 | CAS number: 1591-02-2
Endpoint summary
Administrative data
Description of key information
Additional information
Dibutoxy(dimethyl)silane is a liquid at standard temperature and pressure, with a measured melting point of -81.4±0.5°C at 1013 hPa, and a measured boiling point of 191.4±0.5°C at 1013 hPa . It has a predicted density of 0.87 g/cm3 at 20°C and a predicted vapour pressure of 30 Pa at 25°C.
The substance is not classified as a flammable liquid according to Regulation (EC) No. 1272/2008 on the basis of a measured flash point of 72°C and a measured boiling point of 191.4±0.5°C at 1013 hPa. It has a measured auto-ignition temperature of 210°C at 1013 hPa, and is not explosive and not oxidising on the basis of structural examination.
In contact with water, dibutoxy(dimethyl)silane reacts rapidly (half-life of 1.4 hours at pH 7 and 25°C, 0.59 hours at pH 9 and 25°C and <8 minutes at pH 4 and 19.6°C) to produce dimethylsilanediol and n-butanol according to the following equation:
C10H24O2Si + 2H2O → C2H8O2Si + 2C4H9OH
Therefore, requirements for testing of water-based physicochemical properties for the substance are waived on the basis of instability in water. The properties of the hydrolysis products, dimethylsilanediol and n-butanol, are assessed instead.
However, the physicochemical properties of the parent substance have been predicted using validated QSAR estimation methods. Dibutoxy(dimethyl)silane has a predicted log Kow value of 4.9 at 20°C and water solubility value of 9.4 mg/l at 20°C (predicted).
n-Butanol has a reported water solubility value of 7.7E+04 mg/l at 20°C, low log Kow (0.88) and vapour pressure of 560 Pa at 25°C (OECD 2001).
The saturation concentration in water of the silanol hydrolysis product, dimethylsilanediol, is limited by condensation reactions that can occur over time at loadings above approximately 1000 mg/l. However, it is very hydrophilic (calculated solubility is 1.0E+06 mg/l at 20°C using a QSAR method) and has a measured log Kow value of -0.38 ± 0.04 at 20.2± 0.3°C and log Kaw value of -6.94 ± 0.33 at 20.2± 0.3°C.
Dimethylsilanediol is not expected to be surface active and it has a predicted vapour pressure of 7 Pa at 25°C.
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