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Vapour pressure

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Endpoint:
vapour pressure
Type of information:
(Q)SAR
Adequacy of study:
key study
Reliability:
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 MBBPVPWIN 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.:
#1
Temp.:
25 °C
Vapour pressure:
3.5 Pa
Conclusions:
A vapour pressure value of 3.5 Pa at 25°C has been determined for the substance using an appropriate estimation method, the result is considered reliable.
Endpoint:
vapour pressure
Type of information:
(Q)SAR
Adequacy of study:
supporting study
Reliability:
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 MBBPVPWIN 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
Test no.:
#1
Temp.:
25 °C
Vapour pressure:
0 Pa
Conclusions:
A vapour pressure of 2.7E-05 Pa at 25°C was determined for octylsilanetriol which is the hydrolysis product of the registered substance using a reliable QSAR estimation method. The result is considered to be reliable.

Description of key information

Vapour pressure [trichloro(octyl)silane]: 3.5 Pa at 25°C (QSAR)


Vapour pressure [octylsilanetriol]: 2.7E-05 Pa at 25°C (QSAR)


Key value for chemical safety assessment

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

Additional information

A predicted vapour pressure of 3.5 Pa at 25°C was determined for the registered substance using a validated QSAR estimation method. The result is considered to be reliable and is selected as key study.

The key study is supported by measured vapour pressure values of 0.2 Pa at 20°C and 8.4 Pa at 50°C which was determined for the substance using the dynamic method in accordance with OECD Test Guideline 104 and in compliance with a known quality system (ISO 9001:2008).

 

In contact with water, trichloro(octyl)silane hydrolyse very rapidly to form octylsilanetriol and hydrochloric acid.

 

The vapour pressure of the silanol hydrolysis product, octylsilanetriol was determined to be 2.7E-05 Pa at 25°C using a validated QSAR estimation method.