Solubility of crystalline nonelectrolyte solutes in organic solvents — Mathematical correlation of 2-methoxybenzoic acid and 4-methoxybenzoic acid solubilities with the Abraham solvation parameter model

Abstract

The Abraham solvation parameter model is used to calculate the numerical values of the solute descriptors for 2-methoxybenzoic acid and 4-methoxybenzoic acid from experimental solubilities in organic solvents. The mathematical correlations take the form of [Formula: see text] [Formula: see text] where CS and CW refer to the solute solubility in the organic solvent and water, respectively, CG is a gas phase concentration, E is the solute excess molar refraction, V is the McGowan volume of the solute, A and B are measures of the solute hydrogen-bond acidity and hydrogen-bond basicity, S denotes the solute dipolarity–polarizability descriptor, and L is the logarithm of the solute gas phase dimensionless Ostwald partition coefficient into hexadecane at 298 K. The remaining symbols in the above expressions are known solvent coefficients, which have been determined previously for a large number of gas–solvent and water–solvent systems. The Abraham solvation parameter model was found to describe the experimental solubility data and published literature partitioning data of 2-methoxybenzoic acid and 4-methoxybenzoic acid to within overall standard deviations of 0.146 log units and 0.114 log units, respectively.Key words: 2-methoxybenzoic acid solubilities, 4-methoxybenzoic acid solubilities, partition coefficients, molecular solute descriptors, solubility predictions.