Solubility, dissolution thermodynamics and preferential solvation of 4-nitroaniline in (ethanol + water) mixtures

Abstract

ABSTRACT In this research, the equilibrium mole fraction solubility of 4-nitroaniline (4-NA) in some aqueous-ethanolic mixtures was determined at seven temperatures from (293.15 to 323.15) K. The respective apparent thermodynamic functions (Gibbs energy, enthalpy, and entropy) of the dissolution processes were computed using the van’t Hoff and Gibbs equations. The enthalpy-entropy relationship for 4-NA was non-linear in the plot of enthalpy vs. Gibbs energy of solution with negative slopes from neat water to the mixture w 1 = 0.10 and from w 1 = 0.20 to neat ethanol but positive slope from w 1 = 0.10 to w 1 = 0.20. Therefore, the driving mechanism for 4-NA transfer processes is the entropy in water-rich mixtures. Additionally, by means of the inverse Kirkwood-Buff integrals is observed that 4-NA is preferentially solvated by water molecules in water-rich mixtures but preferentially solvated by ethanol molecules in the mixtures of 0.23 ≤ x 1 ≤ 1.00.