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Partition coefficient

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Description of key information

The log octanol/water partition coefficient (log Kow) of isophthalic acid (IPA) was estimated using the KOWWIN v1.67 QSAR model available from the US EPA. The estimated log Kow of isophthalic acid is 1.76.  Additionally, KOWWIN provides a measured log Kow value of 1.66 for isophthalic acid, retrieved from the data base of experimental results used to construct the QSAR model.  
The octanol/water partition coefficient of isophthalic acid has also been determined according to the shake-flask procedure, in a system buffered to pH 7. The mean log Kow obtained under these conditions was -2.34. This value implies a much higher relative solubility of IPA in the aqueous phase than the log Kow indicated by KOWWIN QSAR and by the experimentally determined value for IPA that has been used in the construction of the KOWWIN model. This is likely to have been caused by the presence of the buffer used to maintain the test system at pH 7: IPA would have been converted under these conditions to salts with higher aqueous solubility than that of the free acid.
Wherever other models of the US EPA's EPISUITE QSAR programs have been used to generate estimates of physico-chemical or environmental fate and behaviour characteristics that require input of log Kow, these secondary models selected the database (measured) log Kow of 1.66 as the default value for isophthalic acid.

Key value for chemical safety assessment

Log Kow (Log Pow):
1.66
at the temperature of:
25 °C

Additional information