Equations for the Partition of Neutral Molecules, Ions and Ionic Species from Water to Water–Methanol Mixtures

We have constructed equations for the transfer of neutral molecules, ions and ionic species from water to water–methanol mixtures across the entire composition range, in terms of water to solvent partition coefficients, as log10P. We have obtained the required partition coefficients for neutral molecules from solubilities in water and water–methanol mixtures, and partition coefficients for ions from literature data. Log10P values for ionic species, that are deprotonated acid anions and protonated base cations, were calculated from known data on pKa values in water and water–methanol mixtures, and we list these new partition coefficients. We have also used the pKa method to determine log10P for the transfer of the hydrogen ion from water to water–methanol mixtures. Our equations can describe the transfer of neutral molecules, ions and ionic species with a standard deviation in log10P from 0.06 to 0.18 log units for a total of 118 species.