Mathematical correlation of 4-aminobenzoic acid solubilities in organic solvents with the abraham solvation parameter model

Abstract

The Abraham solvation parameter model is used to calculate the numerical values of the solute descriptors for 4-aminobenzoic acid from experimental solubilities in organic solvents. The mathematical correlations take the form of where C S and C W refer to the solute solubility in the organic solvent and water, respectively, C G is a gas phase concentration, R 2 is the solute excess molar refraction, V x is McGowan volume of the solute, and are measures of the solute hydrogen-bond acidity and hydrogen-bond basicity, 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. We estimate R 2 as 1.0750 and calculate V x as 1.0315, and then solve a total of 26 equations to yield , and . These descriptors reproduce the observed log(C S/C W) values with a standard deviation of only 0.120 log units. The log(C S/C G) correlation could not be used in the present study because of lack of experimental vapor pressure data for 4-aminobenzoic acid at 298.15 K.