Thermochemical behavior of dissolved carboxylic acid solutes: Solubilities of 3-methylbenzoic acid and 4-chlorobenzoic acid in organic solvents

Abstract

The Abraham general solvation model is used to correlate the solubility behavior of 3-methylbenzoic acid and 4-chlorobenzoic acid in alcohol and ether 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; R2 is the solute excess molar refraction; Vx is the McGowan volume of the solute; ΣαH2 and ΣβH2 are measures of the solute hydrogen-bond acidity and hydrogen-bond basicity; πH2 denotes the solute dipolarity–polarizability descriptor; and L(16) is 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 general solvation model was found to describe the experimental solubility data and published literature partitioning data of 3-methylbenzoic acid and 4-chlorobenzoic acid to within overall standard deviations of 0.079 log units and 0.085 log units, respectively. Key words: 3-methylbenzoic acid solubilities, 4-chlorobenzoic acid solubilities, alcohol solvents, partition coefficients, molecular solute descriptors, solubility predictions.