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Physical & Chemical properties

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Description of key information

[3-(2,3-Epoxypropoxy)propyl]dimethoxy(methyl)silane is a liquid at standard temperature and pressure, with a melting point of <-80°C, and a predicted boiling point of 220°C. It has a predicted density of 0.95 g/cm3 at 20°C and a predicted vapour pressure of 3.0 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 118°C and a predicted boiling point of 220°C. It has a measured auto-ignition temperature of 227±3°C at 1013 hPa and is not oxidising on the basis of chemical structure. The substance is not explosive based on read-across from a structural analogue.

In contact with water, [3-(2,3-epoxypropoxy)propyl]dimethoxy(methyl)silane undergoes rapid hydrolysis (half-life of 1.6 hours at pH 7, 0.1 hours at pH 4 and 0.03 hours at pH 9 and 20-25°C) to produce [3-(2,3-epoxypropxy)propyl]methylsilanediol and methanol according to the following equation:

CH3Si(OCH3)2(C3H6OC3H5O) + 2H2O → CH3Si(OH)2(C3H6OC3H5O) + 2CH3OH


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, [3-(2,3-epoxypropoxy)propyl]methylsilanediol and methanol are assessed instead.

However, the key physicochemical properties of [3-(2,3-epoxypropoxy)propyl]dimethoxy(methyl)silane were predicted with the use of validated QSAR estimation methods. The substance has a predicted log Kow value of 1.7 at 20°C and water solubility value of 1.2E+04 mg/L at 20°C.


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 hydrolysis product, [3-(2,3-epoxypropoxy)propyl]methylsilanediol 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 has a low log Kow (-0.7, predicted).

It is not expected to be surface active and it is much less volatile than the parent substance (vapour pressure = 2.8E-04 Pa at 25°C, predicted).


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



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