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Partition coefficient

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Endpoint:
partition coefficient
Type of information:
(Q)SAR
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: scientifically accepted calculation method
Justification for type of information:
QSAR prediction
Qualifier:
according to
Guideline:
other: REACH guidance on QSARs Chapter R.6 , May 2008
Deviations:
not applicable
Principles of method if other than guideline:
The computer program KOWWIN v1.68 (EPIWIN software by US-EPA) uses the chemical structure of a compound to estimate of the contributions from individual molecular fragments and summing them up to predict the logarithmic octanol-water partition coefficient (logPow).
GLP compliance:
no
Remarks:
QSAR
Type of method:
other: logarithmic octanol-water partition coefficient estimate from KOWWIN 1.68
Partition coefficient type:
octanol-water
Key result
Type:
log Pow
Partition coefficient:
9.18
Remarks on result:
other: estimated by KOWWIN
Details on results:
The substance Octadecane falls in the applicability domain of the model.

TYPE | NUM | LOGKOW FRAGMENT DESCRIPTION | COEFF | VALUE

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

Frag | 2 | -CH3 [aliphatic carbon] | 0.5473 | 1.0946

Frag | 16 | -CH2- [aliphatic carbon] | 0.4911 | 7.8576

Const | | Equation Constant | | 0.2290

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

Log Kow = 9.1812

Conclusions:
log Pow = 9.18 (estimated by KOWWIN 1.68)
Executive summary:

The logarithmic octanol-water partition coefficient of octadecane has been estimated by KOWWIN v1.68 (EPIWIN software). The obtained value is 9.18.

Endpoint:
partition coefficient
Type of information:
other: handbook data
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: peer-reviewed handbook
Qualifier:
according to
Guideline:
other: no data
Deviations:
not specified
GLP compliance:
no
Remarks:
data from handbook
Type of method:
HPLC method
Partition coefficient type:
octanol-water
Key result
Type:
log Pow
Partition coefficient:
9.32
Remarks on result:
other: exp. HPLC-k′ correlation (Coates et al. 1985)
Key result
Type:
log Pow
Partition coefficient:
9
Remarks on result:
other: calculated-fragment const. (Wang et al. 1992)
Key result
Type:
log Pow
Partition coefficient:
8.13
Remarks on result:
other: calculated-molar volume correlation (Wang et al. 1992)
Conclusions:
- log Pow = 9.32 (HPLC-k′ correlation, Coates et al. 1985)
- log Pow = 9.00; 8.13 (calculated-fragment const.; calculated-molar volume correlation, Wang et al. 1992)
Executive summary:

According to the Handbook of Physical-Chemical Properties and Environmental Fate for Organic Chemicals, the partition coefficient of Octadecane is

- log Pow = 9.32 (exp. HPLC-k′ correlation, Coates et al. 1985)

- log Pow = 9.00; 8.13 (calculated-fragment const.; calculated-molar volume correlation, Wang et al. 1992)

Description of key information

- log Pow = 9.32 (exp. HPLC-k′ correlation, Coates et al. 1985)

- log Pow = 9.00; 8.13 (calculated-fragment const.; calculated-molar volume correlation, Wang et al. 1992)

- log Pow = 9.18 (estimated by US-EPA software KOWWIN v1.68)

Key value for chemical safety assessment

Log Kow (Log Pow):
9.32
at the temperature of:
20 °C

Additional information

The log Pow of 9.32 was chosen as the key value since it was the only experimental value available. It is assumed that the value of Pow was measured at room temperature (20°C). In this context it is important to emphasise that the effect of temperature on log Pow is not great - usually on the order of 0.001 to 0.01 Iog Kow units per degree - and may be either positive or negative.

The estimated values are in the same range, allowing the conclusion that the key value can be considered sufficiently reliable.