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(3-Chloropropyl)triethoxysilane (CAS 5089-70-3, EC No. 225-805-6) is a liquid at standard temperature and pressure, with a measured freezing point of <-20°C at 1013 hPa, and a measured boiling point of 221°C at 1071 hPa. It has a predicted density of 1.03 g/cm3 at 20°C, a predicted kinematic viscosity of 1.6 mm2/s at 20°C and a measured vapour pressure of 30.9 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 99°C at 1013 hPa and a measured boiling point of 221°C at 1013 hPa. It has a measured auto-ignition temperature of 231°C at 1013 hPa and it is not explosive and not oxidising on the basis of chemical structure.

In contact with water, the substance hydrolyses moderately rapidly (half-lives of <0.4 h at pH 4 at 20°C, 35 h at pH 7 and 2 h at pH 9 and 25°C) resulting in the formation of (3-chloropropyl)silanetriol (CAS 64426-41-4) and ethanol (CAS 64-17-5, EC No. 200-578-6) according to the following equation:

Cl(CH2)3Si(OCH2CH3)3 + 3H2O ¿ Cl(CH2)3Si(OH)+ 3CH2CH3OH


The properties of the parent submission substance have been determined using relevant methods. The substance has a measured log Kow value of 3.13 at 21°C and pH 7.02-7.61, it has a measured water solubility value of approximately 113 mg/L at 20°C and pH 4.7.

Ethanol is miscible with water, has low log Kow (-0.3) and high vapour pressure (7910 Pa at 25°C).

The saturation concentration in water of the silanol hydrolysis product, (3-chloropropyl)silanetriol, is limited by condensation reactions to approximately 1000 mg/L. However, it is very hydrophilic (calculated solubility is 1.0E+06 mg/L using a QSAR method) and it has a predicted log Kow of -1.1. (3-Chloropropyl)silanetriol is not surface active and is much less volatile than the parent substance, with a predicted vapour pressure of 2.5E-04 Pa at 25°C. The first dissociation constant of a structurally analogous silanetriol (phenylsilanetriol) has been reported to be around pKa of 10.

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