Registration Dossier
Registration Dossier
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EC number: 246-377-7 | CAS number: 24636-31-5
Endpoint summary
Administrative data
Description of key information
The substance, 3-(chlorodimethylsilyl)propyl methacrylate, is not stable in water, which affects the approach to the determination of physicochemical properties.
3-(Chlorodimethylsilyl)propyl methacrylate is a liquid at standard temperature and pressure, with a melting point of <-80°C, and a predicted boiling point of 210°C at 1013 hPa. It has a predicted density of 1.0 g/cm3 at 20°C and a predicted vapour pressure of 9.6 Pa at 25°C.
The substance is not classified for flammability according to Regulation (EC) No. 1272/2008 on the basis of a measured flash point of 112 ± 1.0°C at 1013 hPa and a predicted boiling point of 210°C at 1013 hPa. It has a measured auto-ignition temperature of 301°C at 1013 hPa, and is not explosive and not oxidising on the basis of structural examination.
In contact with water, 3-(chlorodimethylsilyl)propyl methacrylate reacts rapidly (half-life of <1 minute at pH 4, pH 7 and pH 9 and 25°C) to produce 3-[hydroxy(dimethyl)silyl]propyl methacrylate and hydrochloric acid according to the following equation:
CH2=C(CH3)C(=O)OCH2CH2CH2Si(CH3)2Cl + H2O → CH2=C(CH3)C(=O)OCH2CH2CH2Si(CH3)2OH+ HCl
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 silanol hydrolysis product, 3-[hydroxy(dimethyl)silyl]propyl methacrylate are assessed instead.
The silanol hydrolysis product, 3-[hydroxy(dimethyl)silyl]propyl methacrylate, may undergo condensation reactions in solution to produce the siloxane dimer and establish a dynamic equilibrium. The overall rate of condensation is dependent on nominal loading, temperature, and pH of the system, as well as what else is present in the solution.
The condensation reactions of monosilanols may be modelled as an equilibrium between monomer and dimer. The reaction is reversible unless the dimer concentration exceeds its solubility; in this case, the dimer forms a separate phase, driving the equilibrium towards the dimer. For 3-[hydroxy(dimethyl)silyl]propyl methacrylate, at loadings above about 30 mg/l the concentration of the dimer is predicted to exceed its solubility, resulting in formation of a separate phase. In addition, the dimer is expected to have a high volatility from water and this may cause losses from water under some conditions. Further information is given in a supporting report (PFA 2016am) attached in Section 13.
The saturation concentration in water of the silanol hydrolysis product, 3-[hydroxy(dimethyl)silyl]propyl methacrylate is limited by condensation reactions that can occur over time at loadings above approximately 30 mg/l. However, it has a predicted water solubility of 330 mg/l at 20°C using a validated QSAR method and has a log Kow 2.6. It is not expected to be surface active and it is much less volatile than the parent substance (vapour pressure = 4.8E-02 Pa at 25°C, predicted).
Reference:
PFA (2016am). Peter Fisk Associates, Silanols and aquatic systems, 404.105.003
Additional information
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