Cyclohexyldimethoxymethylsilane

Partition coefficient

Link to relevant study record(s)

Reference

Endpoint:

partition coefficient

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 KOWWIN v1.67, which is a component of the EPIWIN Suite. The model is based on fragment values. That is, the chemical structure is broken down into its constituent functional groups, and the contribution of each group toward the overall partition coefficient is calculated. The constants used within KOWWIN have been derived by SRC from a wide range of organic chemicals. 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 alkoxysilane compounds. It was noted that the model under-predicted log Kow for alkoxysilanes; therefore, a correction factor is applied when this structural feature is present. The adapted model applies to di- and tri-alkoxysilanes.

Partition coefficient type:

octanol-water

Key result

Type:

log Pow

Partition coefficient:

4.3

Temp.:

20 °C

pH:

ca. 7

Conclusions:

A log Kow value of 4.3 at 20°C was obtained for the substance using a validated QSAR method. The result is considered to be reliable.

Description of key information

Log K_ow [Cyclohexyl(dimethoxy)methylsilane]: 4.3 at 20°C (QSAR)

Log K_ow [cyclohexylmethylsilanediol]: 1.9 at 20°C (QSAR)

Log K_ow [methanol] = -0.82 to -0.64

Key value for chemical safety assessment

Log Kow (Log Pow):

4.3

at the temperature of:

20 °C

Additional information

A predicted log K_ow value of 4.3 at 20°C was obtained for the parent substance using a validated QSAR estimation method. The result is considered to be reliable and is selected as key study. The predicted log K_ow value is supported by a measured log K_ow of 4.25 which was determined for the parent substance using a relevant form of the HPLC test method, but lacking some corrective adjustment that would be necessary to validly interpret the result. For organosilicon substances of this type, validation studies have been conducted to develop appropriate HPLC estimation methodology to determine log K_ow. In addition to non-standard mobile phase, a specific adjustment must be applied to correct the resulting log K_ow.

In contact with water, the substance hydrolyses moderately rapidly to form cyclohexylmethylsilanediol and methanol.

The log K_ow of the silanol hydrolysis product was determined to be 1.9 using a validated estimation method. A shake-flask test (which would have assessed the partially- or fully-hydrolysed organosilane products of the alkoxysilane) is notable for the close correspondence of the resulting log K_ow to the predicted value for the hydrolysis product; however it is not possible to fully interpret this study in view of the lack of supporting analytical work.

In another study to which reliability could not be assigned, the log K_ow of the hydrolysis product was reported to be 1.45.

Methanol has a reported log K_ow of -0.82 to -0.64 (OECD 2004).

Reference:

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