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Partition coefficient

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Reference
Endpoint:
partition coefficient
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Study period:
2012
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 adequate and reliable documentation / justification
Justification for type of information:
Due to hydrolysis the calculated logKow of 3.56 for m-Trifluormethylphenylisocyanate is from theoretical interest only. For the assessment of m-Trifluormethylphenylisocyanat the calculated logKow of 2.04 for m-Trifluormethylanilin, the hydrolysis product should be taken into account.
Reason / purpose:
read-across: supporting information
Guideline:
other: REACH guidance QSARs R6, May/July 2008
Principles of method if other than guideline:
Estimation Program Interface EPI-Suite version 4.1: KOWWIN for estimating the logarithmic octanol-water partition coefficient (log Kow).
The Estimation Programs Interface was developed by the US Environmental Agency's Office of Pollution Prevention and Toxics and Syracuse Research Corporation (SRC).© 2000 - 2011 U.S. Environmental Protection Agency for EPI SuiteTM (Published online in January 2011).
GLP compliance:
no
Type of method:
other: QSAR
Partition coefficient type:
octanol-water
Key result
Type:
log Pow
Partition coefficient:
2.04
Remarks on result:
other: QSAR calculation

Validity of model:

1. Defined Endpoint: Octanol-water partition coefficient

2. Unambiguous algorithm: The molecule is separated into distinct atom/fragments using an Atom/Fragment Contribution method. Based on structure of the molecule, the following fragments were applied: aliphatic carbon, fluorine (aliphatic attach), Aromatic Carbon, aliphatic N (one aromatic attach) and one equation constant. The number of times of the fragments that occurs in the structure of the substance applied by the program is verified.

3. Applicability domain: With a molecular weight of 161.13 g/mole the substance is within the range of the training set (18.02 - 719.92) as well as in the range of the validation set (27.03 - 991.15).

4. Statistical characteristics: Correlation coefficient of the total training set r² = 0.982; Correlation coefficient of the total validation set r² = 0.943.

5. Mechanistic interpretation: The structural fragments used as descriptors reflect the lipophilic or hydrophobic properties of the substances, and so the octanol-water partition coefficient.

6. Adequacy of prediction: The result for m-Trifluormethylanilin falls within the applicability domain described above and the estimation rules applied for the substance appears appropriate. Therefore the predicted value can be considered reliable yielding a useful result for further assessment.

Conclusions:
The hydrolysis product of m-Trifluormethylphenylisocyanate, m-Trifluormethylaninline (CAS : 98 -16 -8), has a calculated logKow of 2.04.
Executive summary:

The hydrolysis product, m-Trifluormethylaninline (CAS : 98 -16 -8) has a calculated logKow of 2.04.

Isocyanates are known to rapidly hydrolyse under the formation of the corresponding amine as well as solid polyurea compounds *. However, the insoluble inert polyurea is not assumed to cause environmental hazards due to the reduced uptake of high molecular mass compounds, whereas the amine is assumed to be the ecotoxicological relevant species. Concluding, tests performed using the corresponding amine can equally be used to assess the ecotoxicological hazards of isocyanates assuming the complete transfer of the isocyanate into the corresponding amine while neglecting the formation of a certain fraction ecotoxicological not active polyurea compounds. An underestimation of environmental hazards is thus avoided supporting a conservative and thus protective hazard assessment.

* Bayer Industry Services (2004). 4-chlorophenyl-isocyanate: Investigation on Stability in Aqueous Test Solutions. Project No: 200300181. Leverkusen, Germany. Bayer Industry Services (2003). Isopropylisocyante: Investigation on Stability in Aqueous Test Solutions. Project No: 200300095. Leverkusen, Germany.

Description of key information

The partition coefficient (log Kow) of m-Trifluormethylphenylisocyanat is 3.56 (estimated by Currenta, 2012).
The partition coefficient (log Kow) of the corresponding hydrolysis product m-Trifluormethylanilin is 2.04 (estimatet by Currenta, 2012).

Key value for chemical safety assessment

Log Kow (Log Pow):
2.04

Additional information

Due to hydrolysis the calculated logKow of 3.56 is from theoretical interest only. For the assessment of m-Trifluormethylphenylisocyanat the calculated logKow of 2.04 for m-Trifluormethylanilin, the hydrolysis product should be taken into account.

Isocyanates are known to rapidly hydrolyse under the formation of the corresponding amine as well as solid polyurea compounds *. However, the insoluble inert polyurea is not assumed to cause environmental hazards due to the reduced uptake of high molecular mass compounds, whereas the amine is assumed to be the ecotoxicological relevant species. Concluding, tests performed using the corresponding amine can equally be used to assess the ecotoxicological hazards of isocyanates assuming the complete transfer of the isocyanate into the corresponding amine while neglecting the formation of a certain fraction ecotoxicological not active polyurea compounds. An underestimation of environmental hazards is thus avoided supporting a conservative and thus protective hazard assessment.

* Bayer Industry Services (2004). 4-chlorophenyl-isocyanate: Investigation on Stability in Aqueous Test Solutions. Project No: 200300181. Leverkusen, Germany. Bayer Industry Services (2003). Isopropylisocyante: Investigation on Stability in Aqueous Test Solutions. Project No: 200300095. Leverkusen, Germany.