Equations for the Correlation and Prediction of Partition Coefficients of Neutral Molecules and Ionic Species in the Water–Isopropanol Solvent System

We use literature data on solubilities of 46 compounds in the water–isopropanol (IPA) system to obtain the corresponding partition coefficients, P, for transfer from water to water–IPA mixtures. We have then used our previously constructed linear free energy equation to obtain equations that correlate log10 P at water–IPA intervals across the entire water–IPA system. These equations can then be used to predict partition coefficients and solubilities of further compounds in the water–IPA systems at 298 K. The coefficients in our linear free energy equation encode information on the physicochemical properties of the water–IPA mixtures. We show that the hydrogen bond basicity of the water–IPA mixtures only increases slightly from water to IPA, but that the hydrogen bond acidity of the mixtures decreases markedly from water to IPA in a smooth continuous manner. We have also used data on ions and on ionic species to set out equations for the estimation of their partition coefficients from water to water–IPA mixtures. We find that for partition from water to IPA itself, log10 P =  − 1.81 for H+.