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Adsorption / desorption

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adsorption / desorption, other
Type of information:
Adequacy of study:
key study
Study period:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
accepted calculation method
Justification for type of information:
As a screening tool the US-EPA model KOCWIN v2.00 was used. According the the result with the MCI method it was considered not necessary to carry out an experimental study.
Principles of method if other than guideline:
This section is a excerpt from PCKOCWIN documentation. More details are available in the user guide integrated in the software.

PCKOCWIN (version 2) estimates Koc with two separate estimation methodologies:
(1) estimation using first-order Molecular Connectivity Index (MCI)
(2) estimation using log Kow (octanol-water partition coefficient)

(1) The same methodology as described in (Meylan et al, 1992) was used to develop the QSAR equations utilizing Molecular Connectivity Index (MCI).  Two separate regressions were performed.  The first regression related log Koc of non-polar compounds to the first-order MCI.  As noted above, non-polar compounds are now designated as "compounds having no correction factors" which simply means the MCI descriptor alone can adequately predict the Koc.  Measured log Koc values were fit to a simple linear equation of the form:
 log Koc  = a MCI  + b
where a and b are the coefficients fit by least-square analysis.
The second regression included the 447 compounds having correction factors.  Correction factors are specific chemical classes or structural fragments.  The regression coefficients were derived via multiple linear regression of the correction descriptors to the residual error of the prediction from the non-polar equation.
final MCI equation:
 log Koc  =  0.5213 MCI  +  0.60 + SPfN  
where SPfN is the summation of the products of all applicable correction factor coefficients from Appendix D multiplied by the number of times (N) that factor is counted for the structure.

(2) Separate equations correlating log Koc with log Kow were derived for nonpolar and polar compounds because it was statistically more accurate to do so than to use the approach taken with the MCI-based method.  The equation derived by the non-polar (no correction factor) regression is:
 log Koc  =  0.8679 Log Kow  -  0.0004
    (n = 68, r2 = 0.877, std dev = 0.478, avg dev = 0.371)
One non-polar compound was removed from the regression (hexabromobiphenyl) because it was the only compound without a recommended experimental log Kow and the accuracy of its estimated log Kow (9.10) is suspect.  This equation is used for any compound having no correction factors.
For the multiple-linear regression using correction factors, log Kow was included as an individual descriptor.  For compounds having correction factors, the equation is:
 log Koc  =  0.55313 Log Kow  +  0.9251 + SPfN  
where SPfN is the summation of the products of all applicable correction factor coefficients from Appendix D multiplied by the number of times (N) that factor is counted for the structure.

Overall, the MCI methodology is somewhat more accurate than the Log Kow methodology, although both methods yield good results.
Key result
Sample No.:
450 L/kg
25 °C
Transformation products:
not measured


CHEM   : 2-Propenoic acid, 3,3,5-trimethylcyclohexyl ester

MOL FOR: C12 H20 O2

MOL WT : 196.29

---------------------------  KOCWIN v2.00 Results  ---------------------------

 Koc Estimate from MCI:


        First Order Molecular Connectivity Index  ........... :  6.427

        Non-Corrected Log Koc (0.5213 MCI + 0.60)  .......... :  3.9500

        Fragment Correction(s):

                 1   Ester  (-C-CO-O-C-) or (HCO-O-C) ......  : -1.2970

        Corrected Log Koc  .................................. :  2.6531

                        Estimated Koc:  449.8  L/kg   <===========

 Koc Estimate from Log Kow:


        Log Kow  (User entered   )  ......................... :  4.60

        Non-Corrected Log Koc (0.55313 logKow + 0.9251)  .... :  3.4695

        Fragment Correction(s):

                 1   Ester  (-C-CO-O-C-) or (HCO-O-C) ......  : -0.0656

        Corrected Log Koc  .................................. :  3.4039

                        Estimated Koc:  2535  L/kg   <===========

Validity criteria fulfilled:
not applicable
Based on PCKOCWIN v2.00, Koc is calculated according to 2 equations: according to MCI (Molecular Connectivity Indices) or to correlation with Kow. The former is considered to provide more accurate results, so according to MCI, the potentail for adsorption is estimated to be: Koc = 450 (logKoc = 2.65)
Executive summary:

As a screening for this property, it has been made use of US-EPA's QSAR software PCKOCWIN v2.00, part of EPISUITE.

According to the MCI method koc is estimated as equal to 450 (logKoc = 2.65). Considering the result suggesting a fairly low potential for adsorption no further experiment has been carried out.

Description of key information

The adsorption/desorption coefficient of 3.3.5-TRIMETHYLCYCLOHEXYL ACRYLATE (CAS 86178-38-3) was estimated using the recommended QSAR model KOCWIN v2.00, via the MCI method.

The estimated Koc value was equal to 450 L/kg and the log Koc is therefore equal to 2.65.

Key value for chemical safety assessment

Koc at 20 °C:

Additional information

[LogKoc: 2.65]