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Partition coefficient

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Description of key information

The log octanol/water partition coefficients of constituents of Alcohols, C12-15, branched and linear are in the range 5.15-6.55 at 20°C and pH 7 (HPLC method)

Key value for chemical safety assessment

Additional information

The n-octanol/water partition coefficient has been measured for the constituents of Alcohols, C12-15, branched and linear with the use of an HPLC method in accordance with OECD 117 Test Guideline. Log Kow values in the range 5.15 - 6.55 at 20°C and pH 7 were obtained for the constituents. The result is considered to be reliable.

Although, a weighted average partition coefficient value of 5.81 at 20°C and pH 7 was obtained for the whole substance, partition coefficient for a multi-constituent or UVCB substance is not meaningful scientifically for the purpose of assessment of exposure or risk.

Exposure and risk are assessed on the basis of log Kow of the individual constituents. Dodecan-1-ol has a reported log Kow value of 5.13 (Hansch 1995); tetradecan-1-ol has a reported log Kow value of 6.03 (Burkhard 1985) and pentadecan-1-ol has a predicted log Kow value of 6.43 at 25°C.

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.