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Physical & Chemical properties

Partition coefficient

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Administrative data

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, but not (completely) falling into its applicability domain, with adequate and reliable documentation / justification
Justification for type of information:
1. SOFTWARE
EPISuite v4.0 (2009)

2. MODEL (incl. version number)
KOWWIN v1.67

3. SMILES OR OTHER IDENTIFIERS USED AS INPUT FOR THE MODEL
The model considers the substance to be "ion pairs", therefore it only provides estimates for the ionised fatty acids and benzoic acid rather than the salts.

4. SCIENTIFIC VALIDITY OF THE (Q)SAR MODEL
The principle models used in EPISuite, are incorporated into the OECD toolbox (a computer database of QSARs and a flow system to allow for prediction of endpoints based on the incorporated models, data and similar structures) which is supported by the OECD, the EU and ECHA (as well as individual countries). It is expected, therefore, that Regulators are sufficiently aware of the EPISuite models, their development, methods and performance, that a detailed discussion on the scientific validity of EPISuite is not required.

5. APPLICABILITY DOMAIN
The predictive accuracy of KOWWIN has been tested on an external validation dataset of 10,946 compounds with a diverse selection of chemical structures. Currently there is no universally accepted definition of model domain, though property estimates are potentially less accurate for compounds outside the Molecular Weight range of the training set compounds, and/or compounds with more of a given fragment than the maximum for all training set compounds. When interpreting results, it should also be considered whether a compound may have a functional group(s) or other structural features not represented in the training set, and for which no fragment coefficient was developed.

6. ADEQUACY OF THE RESULT
The partition coefficients were estimated by QSAR but the results are considered not to be relevant to the substances themselves. As aluminum, (octadecanoato-O)oxoaluminium is an ionisable salt. the partition coefficient can vary greatly depending on pH and the pKa of the substance. In order to compare partition coefficient values of different, ionizable compounds on a relative basis, partition coefficient values are sometimes reported as "corrected for ionization", indicating that the value represents the partition coefficient at a pH where a compound exists primarily in the non-ionized form. However, KOWWIN considers (octadecanoato-O)oxoaluminium to be “ion pairs” and as such only provides estimates for the ionised fatty acids and benzoic acid rather than the salts. The partition coefficient values for the salt itself therefore could not be determined.

Data source

Reference
Reference Type:
other: QSAR
Title:
KOWWIN v1.67
Author:
United States Environmental Protection Agency
Year:
2009
Bibliographic source:
Estimation Programs Interface (EPI) Suite, v4.00 developed by the US Environmental Protection Agency's Office of Pollution Prevention and Toxics and Syracuse Research Corporation (SRC)

Materials and methods

Principles of method if other than guideline:
The partition coefficient was estimated using EPISuite v4.0 (US EPA 2009) using KOWWIN v1.67. KOWWIN uses a "fragment constant" methodology in which a structure is divided into fragments (atom or larger functional groups) and coefficient values of each fragment or group are summed together to yield the log P estimate. Coefficients for individual fragments and groups were derived by multiple regression of 2447 reliably measured log P values. The predictive accuracy of KOWWIN has been tested on an external validation dataset of 10,946 compounds with a diverse selection of chemical structures. Currently there is no universally accepted definition of model domain, though property estimates are potentially less accurate for compounds outside the Molecular Weight range of the training set compounds, and/or compounds with more of a given fragment than the maximum for all training set compounds. When interpreting results, it should also be considered whether a compound may have a functional group(s) or other structural features not represented in the training set, and for which no fragment coefficient was developed.
GLP compliance:
not specified
Type of method:
calculation method (fragments)
Partition coefficient type:
octanol-water

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
not specified
Details on test material:
No data reported

Study design

Analytical method:
not specified

Results and discussion

Partition coefficient
Key result
Type:
log Pow
Partition coefficient:
7.78
Temp.:
20 °C
pH:
7
Remarks on result:
other: Standard conditions assumed
Details on results:
The partition coefficient of the substance is estimated by QSAR to give a log Pow of 7.78. However, as the substance is considered to be an “ion pair”, the value was estimated on the basis of the ionised fatty acids rather than the salt. The partition coefficient values for the salt therefore could not be determined.

Applicant's summary and conclusion

Conclusions:
The partition coefficient of the substance is estimated to give a log Kow of 7.78.
Executive summary:

The partition coefficient of the substance was estimated using a QSAR model (KOWWIN v1.67 in EPISuite v4.00, US EPA 2009), following the Atom/Fragment Contribution method. The substance is considered by KOWWIN to be “ion pairs” and as such, KOWWIN only provides estimates for the ionised acids rather than the salt itself.