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Partition coefficient

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Reference
Endpoint:
partition coefficient
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2010-01-13
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
test procedure in accordance with national standard methods with acceptable restrictions
Remarks:
Test procedure in accordance with national standard methods (ASTM) without GLP.
Qualifier:
according to
Guideline:
other: ASTM E 1147
Deviations:
no
GLP compliance:
no
Type of method:
HPLC method
Partition coefficient type:
octanol-water
Analytical method:
high-performance liquid chromatography
Key result
Type:
log Pow
Partition coefficient:
8.3
Remarks on result:
other: The temperature of the measurement is not reported.

Measurement

Log Kow: 8.3

Conclusions:
A log Kow value of 8.3 at 20°C and pH 7 was determined for the substance using a relevant test method. The result is considered to be reliable.
Executive summary:

Docosan-1-ol was determined according ASTM E 1147 . The partition coefficient was determined to be log Pow 8.3 at 20°C and pH 7.

Description of key information

The log octanol-water partition coefficient of a commercial sample of docosan-1-ol is 8.3 (by HPLC method) at 20°C and pH 7. A log Kow value of 7.75 would be predicted for the pure linear alcohol based on category trends.

Key value for chemical safety assessment

Log Kow (Log Pow):
8.3
at the temperature of:
20 °C

Additional information

The log octanol/water partition coefficient of 8.3 at 20°C and pH 7 was determined for docosan-1-ol in accordance with ASTM E 1147. The result is considered to be reliable.

Trends in the value of log Kow across the category have been examined across the homologous series covered by the C6 -24 Alcohols category based on reliable literature for pure alcohol samples. A predictive equation based on the carbon chain length has been derived. This shows that the value of log Kow derived by the equation reaches a peak at around C20 and then begins to drop again. It would be expected that, experimentally, values of log Kow reach a plateau and that the values would not drop again. Therefore for docosan-1-ol, the log Kow value for a pure alcohol is predicted to be 7.75, the same as the reliable literature measurement for the neighbouring alcohol, icosan-1-ol C20.

Discussion of trends in the Category of C6-24 linear and essentially-linear aliphatic alcohols:

As chain length increases, the free energy required for a molecule to dissolve becomes less favourable for larger molecules. The octanol-water partition coefficient increases with molecular weight because each additional -CH2- group makes the octanol phase more preferred over water in terms of relative solvation energy.