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Physical & Chemical properties

Partition coefficient

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Endpoint:
partition coefficient
Data waiving:
study technically not feasible
Justification for data waiving:
the study does not need to be conducted because the substance decomposes
Justification for type of information:
JUSTIFICATION FOR DATA WAIVING
In accordance with Column 2 of Annex VII Section 7.8 and Section 2 of Annex XI of the REACH regulation the test cannot be performed as the substance decomposes.
Endpoint:
partition coefficient
Type of information:
(Q)SAR
Remarks:
Estimated by calculation
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
accepted calculation method
Justification for type of information:
1. SOFTWARE
EPI Suite

2. MODEL (incl. version number)
KOWWIN v1.67 Atom Fragment Contribution method

3. SMILES OR OTHER IDENTIFIERS USED AS INPUT FOR THE MODEL
O=C(CS[Sn](SCC(=O)OCC(CC)CCCC)(SCC(=O)OCC(CC)CCCC)C)OCC(CC)CCCC

4. SCIENTIFIC VALIDITY OF THE (Q)SAR MODEL
Current versions of EPIWIN, developed by Syracuse Research Corporation, have not been validated for estimating endpoints for chemicals that contain metals in their molecular structure; therefore, the estimated values derived from the EPIWIN models should be used with caution.
Qualifier:
according to
Guideline:
OECD Guideline 107 (Partition Coefficient (n-octanol / water), Shake Flask Method)
Deviations:
yes
Remarks:
, due to the several analytical difficulties the experimental determination was not performed.
Qualifier:
according to
Guideline:
OECD Guideline 117 (Partition Coefficient (n-octanol / water), HPLC Method)
Qualifier:
according to
Guideline:
EU Method A.8 (Partition Coefficient)
Principles of method if other than guideline:
Method (calculated): KOWWIN v1.67 Atom Fragment Contribution method
In principle, the log Pow can be determined experimentally by the flask shaking method (log Pow between -2 and 4, OECD guideline no. 107 and EEC Directive A.8) or alternatively by the HPLC-method as described in EEC Directive A.8 and OECD guideline no. 117 (log Pow between 0 and 6). For expected values Log Pow >6 no experimental methods are provided in the above mentioned guidelines so far. Therefore, during this study the estimation of the partition coefficient was performed by a model calculation.
GLP compliance:
no
Type of method:
other: calculation
Partition coefficient type:
octanol-water
Analytical method:
other: not applicable
Type:
log Pow
Partition coefficient:
11
Remarks on result:
other: As the value provided was estimated by calculation, no data are given for temperature and pH.
Details on results:
Neither the HPLC-method nor the flask shaking method were applicable for the determination of the partition coefficient, since the log Pow was expected to be >6. The partition coefficient was estimated by a model calculation.

As significant technical difficulties exist and the presence of the actual named test substance in aqueous solution is doubtful, the current OECD Guidelines 107 or 117 are not suitable for determining the octanol-water partition coefficient of this compound. Therefore, testing will not be conducted and data generated by property-estimation software (e.g., KOWWIN version 1.67) will be reported instead.

Calculated log Pow of parent substance: 11.0

Calculated log Pow of daughter product: 3.68

Conclusions:
The log Pow was estimated to be 11.0. However, because this substance will not exist in contact with water, the log Pow of the expected/stable daughter product (2-ethylhexylthioglycolate) was also calculated and was determined to be 3.68.

Description of key information

Waived: Study technically not feasible. Calculated values of log Pow for parent and expected/stable daughter product are given.

Key value for chemical safety assessment

Additional information

Until very recently, the substance was considered to exhibit properties such that a waiver has been submitted to address this end point based on data to suggest the substance rapidly hydrolysed. Taking account of the recently performed hydrolysis study it is no longer known if this is definitely the case and as this new information indicates the substance may in fact behave differently than originally thought a new partition coefficient study is being attempted on a structurally related substance to try and obtain a definitive result. This testing should be completed in the first half of 2020 and if this study proves to be successful then the registrant will look to also perform a new partition coefficient study on this substance to try and obtain a definitive result for the end point.

In accordance with Column 2 of REACh Annex VII, if the testing cannot be performed due to decomposition in water, a calculated value of log Pow should be provided as well as details fo the calculation method.

As significant technical difficulties exist and the presence of the actual named test substance in aqueous solution is doubtful, the current OECD Guidelines 107 or 117 are not suitable for determining the octanol-water partition coefficient of this compound. Therefore, testing was not conducted and data was generated by property-estimation software (e.g., KOWWIN version 1.67). During the preliminary test, the log Pow of the test item was estimated by a calculation method based on the theoretical fragmentation of the molecule into substructures for which reliable log Pow increments are known. The log Pow is obtained by summing the fragment values and the correction terms for intramolecular interactions. The log Pow was estimated to be 11.0. However, because this substance will not exist in contact with water, the log Pow of the expected/stable daughter product (2-ethylhexylthioglycolate) was also calculated and was determined to be 3.68.