Registration Dossier

Data platform availability banner - registered substances factsheets

Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.

The new ECHA CHEM database has been released by ECHA, and it now contains all REACH registration data. There are more details on the transition of ECHA's published data to ECHA CHEM here.

Diss Factsheets

Physical & Chemical properties

Endpoint summary

Administrative data

Description of key information

3-[Dimethoxy(methyl)silyl]propanethiol is a liquid at standard temperature and pressure, with a measured melting point of <-80°C, and a predicted boiling point of 190°C. It has a predicted density of 1.0 g/cm³ at 20°C and a predicted vapour pressure of 23 Pa at 25°C.

The substance is not classified for flammability in accordance with Regulation (EC) No 1272/2008; this is on the basis of a measured flash point of 76°C and predicted boiling point of 190°C. It has a measured auto-ignition temperature of 235°C and is not explosive and not oxidising on the basis of structural examination.

In contact with water, 3-[dimethoxy(methyl)silyl]propanethiol reacts rapidly (half-life 1.4 h at 25°C and pH 7, 0.1 h at 25°C and pH 4, and 0.03 h at 25°C and pH 9) to produce 3-(dihydroxymethylsilyl)propanethiol and methanol according to the following equation:

Si(CH3)(OCH3)2C3H6SH + 2H2O → Si(CH3)(OH)2C3H6SH + 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 silanol hydrolysis product, 3-(dihydroxymethylsilyl)propanethiol and methanol are assessed instead.

Methanol is miscible with water, has low log Kow (-0.82 to -0.64) and high vapour pressure (12,790 Pa at 20°C) (OECD 2004).

The saturation concentration in water of the silanol hydrolysis product, 3-(dihydroxymethylsilyl)propanethiol, is limited by condensation reactions to approximately 45 mg/l. However, it is very hydrophilic (calculated solubility is 47000 mg/l at 20°C using a QSAR method) with predicted low log Kow of 0.5 at 20°C. It is not surface active. The hydrolysis product is much less volatile than the parent substance (predicted vapour pressure = 0.0092 Pa at 25°C).

The molecular weight of 3-[dimethoxy(methyl)silyl]propanethiol is 180.34 g/mol. The molecular weight of 3-(dihydroxymethylsilyl)propanethiol is 152.28. One mole of the parent substance generates one mole of the silanol hydrolysis product plus two moles of methanol.


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

Additional information