Registration Dossier

Administrative data

Endpoint:
partition coefficient
Type of information:
(Q)SAR
Adequacy of study:
key study
Study period:
2010
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: A well documented non-GLP study
Justification for type of information:
QSAR prediction: migrated from IUCLID 5.6
Cross-referenceopen allclose all
Reason / purpose:
reference to same study
Reason / purpose:
reference to other study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2010
Report Date:
2010

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
other: ECHA (2008). Guidance on information requirements and chemical safety assessment- Chapter 7a: Endpoint specific guidance. European Chemicals Agency (ECHA), Helsinki, Finland. May 2008.
Principles of method if other than guideline:
Calculated using the U.S. EPA KOWWIN (v1.67a). US EPA. (2009) Estimation Programs Interface Suite™ for Microsoft® Windows, v 4.00. United States Environmental Protection Agency, Washington, DC, USA.
GLP compliance:
no
Type of method:
other: Calculated using the U.S. EPA KOWWIN (v1.67a)
Partition coefficient type:
octanol-water

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Name of test material: 6,6'-[[3,3',5,5'-tetrakis(1,1-dimethylethyl)-[1,1'- biphenyl]-2,2'-diyl] bis(oxy)]bis-dibenzo[d,f][1,3,2]-dioxaphosphepin
- Physical state: Solid, white powder

Study design

Analytical method:
not specified

Results and discussion

Partition coefficient
Type:
log Pow
Partition coefficient:
20.66
Remarks on result:
other: Estimation made using the USEPA program KOWWIN software (v1.67a)
Details on results:
The calculated log Pow value of 20.66 was calculated for 6,6'-[[3,3',5,5'-tetrakis(1,1-dimethylethyl)-[1,1'- biphenyl]-2,2'-diyl] bis(oxy)]bis-dibenzo[d,f][1,3,2]-dioxaphosphepin using the “fragment constant” methodology described above. The accuracy of this “fragment constant” estimation can be assessed by comparing the “fragment constant” estimations to measured values of log Pow for the reference substances. As shown in Attachement 1, these measured and estimated values agree within 0.22 log units for three reference substances whose structural features are also represented in the structure of the test material. Because each of these reference substances belongs to the training dataset for the KOWWIN program, it can be said that these reference substances and 6,6'-[[3,3',5,5'-tetrakis(1,1-dimethylethyl)-[1,1'- biphenyl]-2,2'-diyl] bis(oxy)]bis-dibenzo[d,f][1,3,2]-dioxaphosphepin itself are within the structural domain of the estimation method. However, it should be noted that the estimated log Pow of 20.66 falls well outside of the parametric domain of the KOWWIN training set, as the highest measured log Pow value among these training set substances is 8.18. This is not to suggest that the estimation for 6,6'-[[3,3',5,5'-tetrakis(1,1-dimethylethyl)-[1,1'- biphenyl]-2,2'-diyl] bis(oxy)]bis-dibenzo[d,f][1,3,2]-dioxaphosphepin is inaccurate, but rather is an indication that the expected log Pow of this substance is much higher than can be measured for typical organic substances.

Any other information on results incl. tables

The estimated log Pow value for the test material can be validated in a second way, using a more qualitative “molecular fragment” approach. Measured log Pow values are available for 2,4-di-tert-butyl phenol and for 2,2’-biphenol, the structures of which are directly represented in the structure of 6,6'-[[3,3',5,5'-tetrakis(1,1-dimethylethyl)-[1,1'- biphenyl]-2,2'-diyl] bis(oxy)]bis-dibenzo[d,f][1,3,2]-dioxaphosphepin. The contribution to log Pow from the phosphite group, which occurs twice in the structure of the test material, can be derived from the measured log Pow of tri-n-propyl phosphite and n-propanol. The log Pow of tri-n-propyl phosphite is 2.26, while that of n-propanol is 0.25. Since there are three n-propanol groups in tri-n-propyl phosphite, the contribution to log Pow from the P atom of the phosphite fragment can be estimated as 2.26 – 0.75 = 1.51 (Attachement 2). When the contributions to log Pow from these molecular fragments are added, an estimated log Pow of 20.1 is obtained, which is in good agreement with the value of 20.66 obtained by the “fragment constant” method.

Applicant's summary and conclusion

Conclusions:
The estimated log Pow value forthe test material using the USEPA program KOWWIN software (v1.67a) was 20.6.
Executive summary:

The octanol-water partition coefficient (log Pow) of 6,6'-[[3,3',5,5'-tetrakis(1,1-dimethylethyl)-[1,1'- biphenyl]-2,2'-diyl] bis(oxy)]bis-dibenzo[d,f][1,3,2]-dioxaphosphepin was estimated using the USEPA program KOWWIN software (v1.67a). KOWWIN uses a "fragment constant" methodology to predict log Pow. In a "fragment constant" method, 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 Pow estimate. The estimated log Pow value for the test material using this method was 20.6. To evaluate the reliability of this prediction, the log Pow of several structurally related reference substances, having reliable/measured values of log Pow, were also estimated. These measured and estimated values agree within 0.22 log units for three reference substances whose structural features are also represented in the structure of the test material. Because each of these reference substances belongs to the training dataset for the KOWWIN program, it can be said that these reference substances and 6,6'-[[3,3',5,5'-tetrakis(1,1-dimethylethyl)-[1,1'- biphenyl]-2,2'-diyl] bis(oxy)]bis-dibenzo[d,f][1,3,2]-dioxaphosphepin itself are within the structural domain of the estimation method. The predicted log Pow for the test material was also validated on the basis of a “molecular fragment” approach, where measured values of log Pow for molecular fragments of the test material were added to give a log Pow of 20.1; which is in good agreement with that resulting from the “fragment constant” method.

The results and analysis presented here confirm that the log Pow value for 6,6'-[[3,3',5,5'-tetrakis(1,1-dimethylethyl)-[1,1'- biphenyl]-2,2'-diyl] bis(oxy)]bis-dibenzo[d,f][1,3,2]-dioxaphosphepin is much higher than can be measured by any currently applicable experimental technique. This estimated value is validated on the basis of demonstrated accuracy of the applied “fragment constant” method for several structurally-related reference substances, and by a more qualitative “molecular fragment” method. Substances having log Pow > 8 are considered to be so hydrophobic that they are not bioavailable in the dissolved aquatic state, and therefore have very low potential for bioconcentration in aquatic organisms. Therefore, the same can be said for test material, that the substance is expected to be neither bio-available nor bio-accumulative in the aquatic environment.