Tricyclo[8.2.2.24,7]hexadeca-1(12),4,6,10,13,15-hexaene

Adsorption / desorption

Link to relevant study record(s)

Reference

Endpoint:

adsorption / desorption: screening

Type of information:

(Q)SAR

Adequacy of study:

key study

Study period:

2017

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 limited documentation / justification

Justification for type of information:

1. SOFTWARE
KOCWIN v2.00 (US EPA)

2. MODEL (incl. version number)
Estimation using log Kow (octanol-water partition coefficient)

3. SMILES OR OTHER IDENTIFIERS USED AS INPUT FOR THE MODEL
c(ccc(c1)CCc(ccc(c2)C3)c2)(c1)C3


4. SCIENTIFIC VALIDITY OF THE (Q)SAR MODEL
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 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

6. ADEQUACY OF THE RESULT
The estimate value has been generated by a valid model. The model is applicable to Dibenzetano with the necessary level of reliability and is sufficiently relevant for the regulatory purpose.

Principles of method if other than guideline:

- Software tool(s) used including version: KOKOCWIN v2.00 (US EPA)
- Model(s) used: Estimation using log Kow (octanol-water partition coefficient)
- Model description: see field 'Justification for type of information'
- Justification of QSAR prediction: see field 'Justification for type of information'

Type:

log Koc

Value:

4.461 dimensionless

Validity criteria fulfilled:

yes

Conclusions:

Estimated Log Koc for Dibenzetano was 4.46, which indicated that the substance is hardly mobile in soil and sewage sludge.

Description of key information

Estimated Log Koc for Dibenzetano was 4.46, which indicated that the substance is hardly mobile in soil and sewage sludge.

Key value for chemical safety assessment

Koc at 20 °C:

28 840

Additional information

[LogKoc: 4.46]