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Physical & Chemical properties

Dissociation constant

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Description of key information

pKa 15.75; no dissociation at pH 4-9.

Key value for chemical safety assessment

Additional information

A weight-of-evidence approach was chosen for the dissociation constant of 2 -ethylhexan-1-ol, consisting of the following information:

1) Using the SPARC online calculator, the pKa of 2 -ethylhexan-1-ol was estimated to be 15.75 at 25 °C.

2) 2 -Ethylhexanol is reported in the literature a) to be a neutral liquid and b) with pH = 7 (at 1 g/L water), which means that the substance does not dissociate in water at ambient conditions.

3) pKa values of several simple aliphatic alcohols as listed in the literature (e.g. in the CRC Handbook of Chemistry and Physics):

methanol and ethanol have a pKa value of 15.5 at 25 °C, isopropyl alcohol of 16.5 and t-butyl alcohol of 17.

Considering these data, the pKa for 2 -ethylhexan-1-ol is given as 15.75.

Therefore, the neutral form accounts for >99.999% under normal environmental conditions (pH 4 -9 according to the ECHA Guidance R.7a), i.e. 2 -ethylhexan-1-ol does not dissociate at environmentally relevant pH values. This conclusion is also valid if the general standard deviation for values estimated with the SPARC pKa calculator (±0.25 pKa units for simple molecules, ±0.36 pKa units for most other organic structures) is considered.