Registration Dossier

Diss Factsheets

Physical & Chemical properties

Endpoint summary

Administrative data

Description of key information

(3-Chloropropyl)trimethoxysilane, (CAS 2530-87-2, EC No. 219-787-9) is a liquid at standard temperature and pressure, with a glass transition temperature of -138°C at 1013 hPa, and a measured boiling point of 199°C at 1013 hPa. It has a predicted density of 1.05 g/cm3 at 20°C, a predicted kinematic viscosity of 1.9 mm2/s at 20°C and a vapour pressure of 52.2 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 79°C at 1013 hPa and a measured boiling point of 199°C. It has a measured auto-ignition temperature of 235°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 rapidly (half-lives of <0.083 h at pH 4, 3.1 h at pH 7 and <0.1 h at pH 9 and 25°C) resulting in the formation of (3-chloropropyl)silanetriol (CAS 64426-41-4) and methanol (CAS 67-56-1) according to the following equation:

Cl(CH2)3Si(OCH3)3 + 3H2O → Cl(CH2)3Si(OH)+ 3CH3OH

 

Therefore, requirements for testing of water-based physicochemical properties for the substance are waived on the basis of instability in water.

However, the properties of the parent submission substance have been estimated using appropriate QSAR methods. Log Kow value of 2.0 and water solubility value of 3500 mg/L at 20°C were predicted for the substance.

Methanol is miscible with water, has low log Kow (-0.82 to -0.64) and high vapour pressure (12790 Pa at 20°C) (OECD 2004).

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.

Reference:

OECD (2004): SIDS Initial Assessment Report for SIAM 19, Berlin, Germany, 18 - 20 October 2004, Methanol, CAS 67-56-1).

Additional information

Categories Display