The transfer of neutral molecules, ions and ionic species from water to wet octanol

TLDR: It is shown that differences in partition coefficients between neutral species and the corresponding ionic species, as log P(oct), are not at all constant.

Abstract: Partition coefficients for transfer from water to wet octanol have been set out for permanent ions, and for ionic species derived from neutral molecules by loss or acceptance of a proton. A previous equation for the partition of neutral compounds from water to wet octanol has been extended to include the partition of permanent ions, and ionic species; the only additional descriptors required are J+ for cations and J− for anions. Fourteen cations and twelve anions are included in the equation. It is shown that differences in partition coefficients between neutral species and the corresponding ionic species, as log P(oct), are not at all constant. For carboxylic acids and the corresponding anion, differences are about 5.0 log units, for phenols and the corresponding anion differences range from 2.2 to 4.9 log units, and for amines and the corresponding protonated cations there is an enormous range of differences from 0.6 to 7.1 log units.