Revealing Solid-Liquid Equilibrium Behavior of 4-Fluorobenzoic Acid in 12 Pure Solvents from 283.15 to 323.15 K by Experiments and Molecular Simulations

The solubility of 4-fluorobenzoic acid (4FBA) in 12 pure solvents (methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, isobutanol, 1-pentanol, ethyl formate, methyl acetate, ethyl acetate, acetonitrile, and acetone) from 283.15 to 323.15 K at atmospheric pressure was determined using the gravimetric method. Within the experimental temperature range, the solubility of 4FBA increased with increasing temperature in all solvents. Four thermodynamic models (modified Apelblat model, NRTL model, Van't Hoff model, and lambda h model) were selected to correlate the experimental solubility data of 4FBA and assess the goodness of fit. The results revealed that the modified Apelblat equation exhibited the highest fitting accuracy. Furthermore, the mixing thermodynamic properties (mixing Gibbs free energy, mixing enthalpy, and mixing entropy) derived from the NRTL equation indicated that the mixing process of 4FBA in the selected solvents is spontaneous and entropy-driven. To elucidate the solid-liquid equilibrium behavior of 4FBA in pure solvents, the structural properties of the solute-solvent molecules were investigated. The physicochemical properties of solvents, solvation free energies, and radial distribution functions were studied to explain the solid-liquid equilibrium behavior of 4FBA.