Diisooctyl 2,2'-[(dioctylstannylene)bis(thio)]diacetate

Adsorption / desorption

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

adsorption / desorption: screening

Data waiving:

study technically not feasible

Justification for data waiving:

other:

Justification for type of information:

The study does not need to be conducted because the HPLC method is not technically feasible for the organotin substances. On this basis, adsorption/desorption testing has been omitted.

The adsorption coefficient of the test material was calculated using KOCWIN v2.00 2000 U.S. Environmental Protection Agency. Given that the substance is slightly greater than the molecular weights in the training set, the estimate is less accurate.
The adsorption Koc of the test material was estimated to be 1.925e+009 L/kg.

Reference 2

Endpoint:

adsorption / desorption, other

Remarks:

QSAR

Type of information:

(Q)SAR

Adequacy of study:

supporting study

Study period:

26 March 2018

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

results derived from a valid (Q)SAR model, but not (completely) falling into its applicability domain, with adequate and reliable documentation / justification

Justification for type of information:

1. SOFTWARE
EPI Suite Version 4.11

2. MODEL (incl. version number)
KOCWIN v2.00

3. SMILES OR OTHER IDENTIFIERS USED AS INPUT FOR THE MODEL
O=C(CS[Sn](SCC(=O)OC(CCCCCC)C)(CCCCCCCC)CCCCCCCC)OC(CCCCCC)C

4. SCIENTIFIC VALIDITY OF THE (Q)SAR MODEL
- Estimation Using Molecular Connectivity Index
PCKOCWIN (version 1) estimated Koc solely with a QSAR utilizing Molecular Connectivity Index (MCI).  This QSAR estimation methodology is described completely in a journal article (Meylan et al, 1992) and in a report prepared for the US EPA (SRC, 1991).  PCKOCWIN (version 2) utilizes the same methodology, but the QSAR has been re-regressed using a larger database of experimental Koc values that includes many new chemicals and structure types.
- QSAR Derivation
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. 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.

- Results Using Molecular Connectivity Index
The equation derived by the non-polar (no correction factor) regression is:
log Koc  =  0.5213 MCI  +  0.60
(n = 69, r2 = 0.967, std dev = 0.247, avg dev = 0.199)

for comparison, the previous version of PCKOCWIN used a very similar equation:
log Koc  =  0.53 MCI  +  0.62

Adding in the correction factor regression yields the final MCI equation:
log Koc  =  0.5213 MCI  +  0.60 + ΣPfN  

where ΣPfN 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.

- Estimation Using Log Kow
A traditional method of estimating soil adsorption Koc involves correlations developed with log octanol-water partition coefficient (log Kow) (Doucette, 2000).  Since an expanded experimental Koc database was available from the new MCI regression, it was decided to develop a log Kow estimation methodology that was potentially more accurate than existing log Kow QSARs for diverse structure datasets.
Effectively, the new log Kow methodology simply replaces the MCI descriptor with log Kow and derives similar equations.  The derivation uses the same training and validation data sets.  The training set is divided into the same non-polar (no correction factors) and correction factor sets.  The same correction factors are also used.

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 + ΣPfN  

where ΣPfN 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.


5. APPLICABILITY DOMAIN
The minimum and maximum values for molecular weight are the following:

Training Set Molecular Weights:
Minimum MW:  32.04
Maximum MW:  665.02
Average MW:  224.4

Validation Molecular Weights:
Minimum MW:  73.14
Maximum MW:  504.12
Average MW:  277.8

Currently there is no universally accepted definition of model domain.  However, users may wish to consider the possibility that log Koc estimates are less accurate for compounds outside the MW range of the training set compounds, and/or that have more instances of a given fragment than the maximum for all training set compounds.  It is also possible that a compound may have a functional group(s) or other structural features not represented in the training set, and for which no fragment coefficient or correction factor was developed.  These points should be taken into consideration when interpreting model results.

6. ADEQUACY OF THE RESULT
Given that the substance is slightly greater than the molecular weights in the training set, the estimate is less accurate.

Qualifier:

according to guideline

Guideline:

other: REACH Guidance on QSARs R.6

Version / remarks:

May/July 2008

Deviations:

no

GLP compliance:

no

Type of method:

other: calculation

Specific details on test material used for the study:

- Molecular weight: 751.80

Type:

Koc

Value:

1 925 000 000 L/kg

KOCWIN v2.00 Results

Koc Estimate from MCI:

First Order Molecular Connectivity Index: 20.818

Non-Corrected Log Koc (0.5213 MCI + 0.60): 11.4522

Fragment Correction(s): 2 Ester (-C-CO-O-C-) or (HCO-O-C): -2.5939

Corrected Log Koc: 8.8583

Estimated Koc: 7.216e+008 L/kg

Koc Estimate from Log Kow:

Log Kow (Kowwin estimate): 15.35

Non-Corrected Log Koc (0.55313 logKow + 0.9251): 9.4156

Fragment Correction(s): 2 Ester (-C-CO-O-C-) or (HCO-O-C): -0.1312

Corrected Log Koc: 9.2845

Estimated Koc: 1.925e+009 L/kg

Conclusions:

The adsorption Koc of the test material was estimated to be 1.925e+009 L/kg.

Executive summary:

The adsorption coefficient of the test material was calculated using KOCWIN v2.00 2000 U.S. Environmental Protection Agency. Given that the substance is slightly greater than the molecular weights in the training set, the estimate is less accurate.

The adsorption Koc of the test material was estimated to be 1.925e+009 L/kg.

Description of key information

The study does not need to be conducted because the HPLC method is not technically feasible for the organotin substances. On this basis, adsorption/desorption testing has been omitted.

Additional information

QSAR

The adsorption coefficient of the test material was calculated using KOCWIN v2.00 2000 U.S. Environmental Protection Agency. Given that the substance is slightly greater than the molecular weights in the training set, the estimate is less accurate.

The adsorption Koc of the test material was estimated to be 1.925e+009 L/kg.