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Partition coefficient

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Reference
Endpoint:
partition coefficient
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Study acceptable for assessment
Qualifier:
according to guideline
Guideline:
OECD Guideline 107 (Partition Coefficient (n-octanol / water), Shake Flask Method)
Principles of method if other than guideline:
The amount of adipic acid in water- and octanol-phase was measured titrimetrically.
GLP compliance:
no
Type of method:
shake-flask method to: flask method
Partition coefficient type:
octanol-water
Analytical method:
titration method
Type:
log Pow
Partition coefficient:
0.093
Temp.:
25 °C
pH:
3.3
Details on results:
The Pow was calculated bei Pow = c(octanol) / c(water), where c is the concentration of adipic acid in the solvent.
The pH of the aqueous phase was 3.3. Since in the examined mixture a protolytic equilibrium is established, the distribution coefficient Pow is strongly pH-dependent. A Pow determination in which the mixture was adjusted to pH 7 with 0.1 mol / L NaOH, gives log Pow <-3.

Measurement results:

 c (Octanol) g/L  c (Water) g/L  Pow  Log Pow
 2.53 2.05   1.23  0.091
 5.07  4.07  1.25  0.095
 mean value    1.24  0.093

The log Kow is dependent on the pH, based upon the pKa values of adipic acid. At pH 7 (NaOH addition) the log Kow  was < -3.

Executive summary:

The measured log Kow of adipic acid is 0.093 (BASF, 1988).

Description of key information

The measured log Kow of adipic acid is 0.093 (BASF, 1988).

Key value for chemical safety assessment

Log Kow (Log Pow):
0.09
at the temperature of:
25 °C

Additional information

The logarithmic octanol-water partition coefficient (log Kow) for adipic acid was predicted using the QSAR calculation of the Estimation Program Interface (EPI) Suite v 4.11. The log Kow was estimated to be 0.23. Thus the predicted and measured value both show a low logKow for the substance.