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Dissociation constant

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Description of key information

Several data on pKa are available
- pka=4,75 (SPARC)
- pKa = 4,4 - 4,89 at 25°C (handbook data - HSDB)

Key value for chemical safety assessment

pKa at 20°C:
4.8

Additional information

The pKa of heptanoic acid has been estimated by SPARC (a QSAR method) which is a recommended software program to predict pKa by ECHA

(the Guidance on information requirements and chemical safety assessment Chapter R.7a: Endpoint specific guidance, table R.7 -36).

The pKa estimated is 4,75. This data is consistent with data coming from handbook : range of pKa between 4,4 and 4,89.

According to the Guidance on information requirements and chemical safety assessment Chapter R.7a: Endpoint specific guidance, R.7.1.17.3 (ECHA, 2008), if the estimated pKa by QSPR method is not in the environmentally-relevant pH range (5 -9), then a test is not necessary.

Therefore, heptanoic acid is considered to be almost entirely in the anion form.