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Physical & Chemical properties

Vapour pressure

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Description of key information

Vapour pressure [triethoxy(2,4,4-trimethylpentyl)silane]: 0.14 and 0.22 Pa at 20 and 25°C respectively (OECD 104)


Vapour pressure [(2,4,4-trimethylpentyl)silanetriol]: 1.2E-04 Pa at 25°C (QSAR)


Vapour pressure [ethanol]: 7910 Pa at 25°C

Key value for chemical safety assessment

Vapour pressure:
0.22 Pa
at the temperature of:
25 °C

Additional information

Vapour pressure values of 0.14 and 0.22 Pa at 20 and 25°C respectively were determined using the effusion method in accordance with OECD 104 and in compliance with GLP (Wieser 2010). The results are considered to be reliable and selected as key study.

In another reliable study using the dynamic method in accordance with OECD 104 test method and in compliance with GLP (Tognucci 2001), a vapour pressure value of 9 Pa at 25°C was determined for the substance. The result at ambient temperature was taken from the extrapolation of data measured in the range 100 -181°C. In another study using the dynamic method (Bimsner 2006), vapour pressure values of 1260 Pa and 4100 Pa at 20°C and 50°C respectively were determined for the substance. However, there was no information on purity of the sample tested. In a further study (Haas 2015), vapour pressure values of 6 Pa at 20°C and 53 Pa at 50°C were determined for the substance using an effusion method (Knudsen cell) method in accordance with relevant test method and in compliance with a known quality system (ISO 9001:2008).

The key study was selected because of the following reasons:

- The purity of the substance used for the key study was 99% compared to 94.5% (Tognucci 2001a), 93.2% (Haas 2015)

- The result in the key study was from a lower temperature range of 20 - 35°C. Therefore, the error associated with extrapolation was avoided

- The presence of volatile impurities and method used can influence measured vapour pressure of a substance

The key study is supported by a predicted vapour pressure of 0.5 Pa at 25°C using a validated QSAR estimation method. In a secondary source to which reliability could not be assigned, a vapour pressure value of 600 Pa at 25°C was reported for the substance.

In contact with water, the substance hydrolyses at a moderate rate to form (2,4,4-trimethylpentyl)silanetriol and ethanol.

A vapour pressure value of 1.2E-04 Pa at 25°C was determined for the silanol hydrolysis product using an accepted calculation method.

The measured vapour pressure of ethanol is 7910 Pa at 25°C (Daubert, T E and Danner R P (1985).Physical and Thermodynamic properties of Pure Chemicals. Data Compilation).