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Environmental fate & pathways

Adsorption / desorption

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Reference
Endpoint:
adsorption / desorption: screening
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).
Key result
Sample No.:
#1
Type:
log Koc
Value:
2.5
pH:
7
Temp.:
20 °C
Remarks on result:
other: for the parent substance
Conclusions:
Log Koc value of 2.5 was obtained for the substance using a validated QSAR method. The result is considered to be reliable.

Description of key information

Adsorption/desorption:

log Koc [cyclohexyl(dimethoxy)methylsilane]: 2.5 (QSAR)

 

log Koc [cyclohexylmethylsilanediol]: 2.0 (calculation)

Key value for chemical safety assessment

Koc at 20 °C:
320

Additional information

A predicted log Koc value of 2.5 was obtained for cyclohexyl(dimethoxy)methylsilane using a validated QSAR estimation method. The result is considered to be reliable and used for assessment purposes.

In addition, adsorption has been estimated using two separate estimation methodologies: (1) KOCWIN (version 2) estimation using first-order Molecular Connectivity Index (MCI) and (2) estimation based on log Kow using TGD (Technical Guidance Document) non-hydrophobics equation. Koc predictions based on log Kow and on MCI are both presented as neither method had been validated fully for this class of substance. The calculated log Koc values are 3.3 based log Kow estimation and 3.6 based on MCI estimation.

The substance hydrolyses moderately rapidly to form cyclohexylmethylsilanediol and methanol which have low log Koc and low potential for adsorption.

For environmental exposure assessment, adsorption is predicted for the silanol hydrolysis product using the‘non-hydrophobics’ log Kow-based prediction method for log Koc (Sabljic et al., 1995).

The relevant equation is:

Log Koc = 0.52 log Kow + 1.02

Therefore, log Koc for the silanol hydrolysis product is 2.0.

Reference:

Sabljić A and Güsten H (1995). QSARs for soil sorption. in: overview of structure-activity relationships for environmental endpoints. Hermens JLM (ed), report prepared within the framework of the project "QSAR for prediction of fate and effects of chemicals in the environment", an international project of the Environmental Technologies RTD programme (DG XII/D-1) of the European Commission under contract number EV5V-CT92-0211.