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Partition coefficient

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Reference
Endpoint:
partition coefficient
Type of information:
calculation (if not (Q)SAR)
Remarks:
Migrated phrase: estimated by calculation
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
Data estimated by KOWWIN v 1.67 using EPISUITE v 4 which uses a valid estimation method. However, as the test substance contains isocyanate groups which rapidly hydrolyse the log Pow QSAR estimation is questionable. Hence, additionally the Kow values of the hydrolytic products have been determined.
Reason / purpose:
reference to other study
Qualifier:
according to
Guideline:
other: REACH guidance on QSARs: Chapter R.6. QSARs and grouping of chemicals
Principles of method if other than guideline:
The logarithmic octanol-water partition coefficient (log Kow) was estimated by using KOWWIN v1.67 program of EPIWEB v 4.0.


GLP compliance:
no
Type of method:
other: estimated using EPIWEB v 4.0.
Partition coefficient type:
octanol-water
Key result
Type:
log Pow
Partition coefficient:
4.74
Remarks on result:
other: Data estimated by KOWWIN v1.67 for m-TMXDI; However, as m-TMXDI contains isocyanate groups which rapidly hydrolyse the log Pow QSAR estimation is questionable.
Key result
Type:
log Pow
Partition coefficient:
3.53
Remarks on result:
other: Data estimated by KOWWIN v1.67 for hydrolysed product 1,3-bis(2-{3-[2-(carbamoylamino)propan-2-yl]phenyl}propan-2-yl)urea
Key result
Type:
log Pow
Partition coefficient:
1.89
Remarks on result:
other: Data estimated by KOWWIN v1.67 for hydrolysed product tetramethyl-m-xylylene diamine
Details on results:
m-TMXDI:
SMILES : O=C=NC(c1cc(ccc1)C(N=C(=O))(C)C)(C)C
CHEM : Benzene, 1,3-bis(1-isocyanato-1-methylethyl)-
MOL FOR: C14 H16 N2 O2
MOL WT : 244.30
-------+-----+--------------------------------------------+---------+--------
TYPE | NUM | LOGKOW FRAGMENT DESCRIPTION | COEFF | VALUE
-------+-----+--------------------------------------------+---------+--------
Frag | 4 | -CH3 [aliphatic carbon] | 0.5473 | 2.1892
Frag | 6 | Aromatic Carbon | 0.2940 | 1.7640
Frag | 2 | -tert Carbon [3 or more carbon attach] | 0.2676 | 0.5352
Frag | 2 | -N=C=O [isocyanate, aliphatic attach] | 0.0100**| 0.0200
Const | | Equation Constant | | 0.2290
-------+-----+--------------------------------------------+---------+--------
NOTE | | Isocyanates hydrolyze....estimate questionable! |
NOTE | | An estimated coefficient (**) used |
-------+-----+--------------------------------------------+---------+--------
Log Kow = 4.7374

 The Kow estimation for m-TMXDI is questionable because of  the hydrolysis potential of the isocyanate groups present. Under environmentally relevant conditions (i.e. low concentrations of m-TMXDI, pH = 7),urea (i.e.,1,3-bis(2-{3-[2-(carbamoylamino)propan-2-yl]phenyl}propan-2-yl) urea)and to a minor degree, polyurea are formed (Cytec, pers. comm.; Pemberton and Tury, 2004; Heimbachet al., 1996; Yakabeet al., 1999; Turyet al., 2003; cited in Environment Canada/Health Canada, 2008). In specific cases (i.e. high dispersion combined with low concentrations), tetramethyl-m-xylene diamine (diamine; m-TMXDA) may also be produced (Sopac and Boltromejuk, 1974; cited in Environment Canada/Health Canada, 2008).

Hence, the Kow value of m-TMXDI is not relevant, instead the hydrolytic products i.e.,urea anddiamines (TMXDA) are more relevant for safety assessment.The estimated Kow values of the urea and the diamine were 3.53 and 1.89 respectively and this QSAR estimation was found to lie within the applicability domain described for the KOWWIN model(see below for details on results):

Urea: 1,3-bis(2-{3-[2-(carbamoylamino)propan-2-yl]phenyl}propan-2-yl)urea

SMILES : C(C)(C)(c1cc(C(C)(C)NC(=O)NC(C)(C)c2cc(C(C)(C)NC(=O)(N))ccc2)ccc1)NC(

=O)(N)

MOL FOR: C27 H40 N6 O3

MOL WT : 496.66

-------+-----+--------------------------------------------+---------+--------

TYPE | NUM | LOGKOW FRAGMENT DESCRIPTION | COEFF | VALUE

-------+-----+--------------------------------------------+---------+--------

Frag | 8 | -CH3 [aliphatic carbon] | 0.5473 | 4.3784

Frag | 2 | -NH2 [aliphatic attach] |-1.4148 | -2.8296

Frag | 4 | -NH- [aliphatic attach] |-1.4962 | -5.9848

Frag | 12 | Aromatic Carbon | 0.2940 | 3.5280

Frag | 3 | -NC(=O)N- [urea] | 1.0453 | 3.1359

Frag | 4 | -tert Carbon [3 or more carbon attach] | 0.2676 | 1.0704

Const | | Equation Constant | | 0.2290

-------+-----+--------------------------------------------+---------+--------

Log Kow = 3.5273

diamine: Tetramethyl-m-xylylene diamine:

SMILES : NC(c1cc(ccc1)C(N)(C)C)(C)C

CHEM : Benzene, 1,3-bis(1-isocyanato-1-methylethyl)-

MOL FOR: C12 H20 N2

MOL WT : 192.31

-------+-----+--------------------------------------------+---------+--------

TYPE | NUM | LOGKOW FRAGMENT DESCRIPTION | COEFF | VALUE

-------+-----+--------------------------------------------+---------+--------

Frag | 4 | -CH3 [aliphatic carbon] | 0.5473 | 2.1892

Frag | 2 | -NH2 [aliphatic attach] |-1.4148 | -2.8296

Frag | 6 | Aromatic Carbon | 0.2940 | 1.7640

Frag | 2 | -tert Carbon [3 or more carbon attach] | 0.2676 | 0.5352

Const | | Equation Constant | | 0.2290

-------+-----+--------------------------------------------+---------+--------

Log Kow = 1.8878

Conclusions:
According to KOWWIN v 1.67 (EPISUITE v 4), the estimated value for the log Pow (octanol-water partition coefficient) of the test substance was found to be 4.74. However, as the test substance rapidly hydrolyses under environmentally relevant conditions to 1,3-bis(2-{3-[2-(carbamoylamino)propan-2-yl]phenyl}propan-2-yl)urea (urea) as well as to tetramethyl-m-xylylene diamine (diamine; m-TMXDA) in specific cases, these hydrolytic products are more relevant for safety assessment. The estimated Kow values of the urea and the diamine were 3.53 and 1.89 respectively and this QSAR estimation was found to lie within the applicability domain described for the KOWWIN model.


Executive summary:

According to KOWWIN v 1.67 (EPISUITE v 4), the estimated value for the log Pow (octanol-water partition coefficient) of the test substance was found to be 4.74. However, as the test substance rapidly hydrolyses under environmentally relevant conditions to 1,3-bis(2-{3-[2-(carbamoylamino)propan-2-yl]phenyl}propan-2-yl)urea (urea) as well as to tetramethyl-m-xylylene diamine (diamine; m-TMXDA) in specific cases, these hydrolytic products are more relevant for safety assessment. The estimated Kow values of these hydrolytic products were determined to be 3.53 for the urea and 1.89 for diamine and the QSAR estimation was found to lie within the applicability domain described for the KOWWIN model.

Description of key information

The log Pow was estimated using the KOWWIN v 1.67 model of EPI SUITE v 4 (US EPA, 2010).

Key value for chemical safety assessment

Log Kow (Log Pow):
4.74

Additional information

According to KOWWIN v 1.67 (EPI SUITE v 4), the estimated value for the log Pow (octanol-water partition coefficient) of the test substance was found to be 4.74. However, as the test substance rapidly hydrolyses under environmentally relevant conditions to 1,3-bis(2-{3-[2-(carbamoylamino)propan-2-yl]phenyl}propan-2-yl)urea (urea) as well as to tetramethyl-m-xylylene diamine (diamine; m-TMXDA) in specific cases, these hydrolytic products are more relevant for safety assessment. The estimated Kow values of these hydrolytic products were determined to be 3.53 for the urea and 1.89 for diamine.