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Vapour pressure

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vapour pressure
Type of information:
Adequacy of study:
key study
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
results derived from a valid (Q)SAR model and falling into its applicability domain, with adequate and reliable documentation / justification
Justification for type of information:
See attached QMRF/QPRF
Principles of method if other than guideline:
The result was obtained using an appropriate QSAR method (see attached QMRF and QPRF for details).

The model is an adaptation of the existing SRC model MPBPVPWIN v 1.43, which is a component of the EPI Suite. This existing model uses the normal boiling point as input. Whilst this method is good in principle, the model was developed using a wide range of organic chemicals and only a few organosilicon compounds. Therefore, a validation procedure was undertaken to assess the applicability of the model to organosilicon compounds. It was noted that the MPBPVPWIN model gave a systematic error; therefore, the current model was developed to correct this. The current model is a linear regression based QSAR, with the vapour pressure prediction from MPBPVPWIN as the descriptor. The adapted model applies to organosilicon substances.
Key result
Test no.:
25 °C
Vapour pressure:
< 0 Pa
A predicted vapour pressure of <1E-06 Pa at 25°C was determined for the substance using an appropriate estimation method. The result is considered to be reliable.

Description of key information

Vapour pressure: <1E-06 Pa at 25°C (QSAR)

Key value for chemical safety assessment

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

Additional information

The registration substance, octaphenylcyclotetrasiloxane is a solid with a melting temperature of >200°C and predicted boiling point of >700°C at standard atmospheric pressure. A predicted vapour pressure of 7.4E-15 Pa at 25°C was determined for the substance, however, this predicted result is outside the lower end of the descriptor range. According to the ECHA Guidance R7.a (version 6.0, July 2017); if the melting point is between 200 -300°C, a limit value for the vapour pressure is sufficient. Therefore, the vapour pressure of the submission substance is reported as <1E-06 Pa at 25°C. The predicted result is considered to be reliable and sufficient for assessment purposes.