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Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.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

The substance, 3-(trimethoxysilyl)propane-1-thiol is a colourless liquid at standard temperature and pressure, with a measured melting point of < -80 °C, and a predicted boiling point of 200 °C. It has a relative density of 1.015 at 25 °C and a predicted vapour pressure of 8.1 Pa at 25 °C. The substance has a predicted viscosity of 1.8 mm2/s at 20°C.


The substance is not classified for flammability according to Regulation (EC) No. 1272/2008 on the basis of a measured flash point of 95 °C and a predicted boiling point of 200 °C. It has a measured auto-ignition temperature of 243 °C and is not explosive and not oxidising on the basis of structural examination.


In contact with water, 3-(trimethoxysilyl)propane-1-thiol reacts rapidly (half-life of 0.2 h at pH 4, 0.3 h at pH 5, 2.6 hours at pH 7 and 0.1 hours at pH 9, between 20-25 °C) to produce 3-(trihydroxysilyl)propanethiol and methanol according to the following equation:




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-(trihydroxysilyl)propanethiol and methanol are assessed instead.


However, the key physicochemical properties of 3-(trimethoxysilyl)propane-1-thiol was predicted with the use of a validated QSAR estimation method. The substance has a predicted log Kow value of 1.7 at pH 7 and 20 °C, and water solubility value of 2800 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 silanol hydrolysis product, 3-(trihydroxysilyl)propanethiol is limited by condensation reactions that can occur over time at loadings above approximately 1000 mg/l. However, it is very hydrophilic (calculated solubility is 1.0E+06 mg/l at 20 °C using a QSAR method) and has a low log Kow (-1.4 at pH 7 and 20 oC, predicted). It is not expected to be surface active and it is much less volatile than the parent substance with a predicted vapour pressure of 1.1E-04 Pa at 25°C. The silanol hydrolysis product is not expected to undergo significant dissociation within the environmentally-relevant range. The first dissociation constant of a structurally analogous silanetriol (phenylsilanetriol) has been reported to be around pKa of 10.



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





Additional information