Solubility and dissolution thermodynamics of 5-fluorouracil in (ethanol + water) mixtures

Abstract

Equilibrium mole fraction solubility of 5-fluorouracil (5-FU) in 19 aqueous-ethanolic mixtures, as well as in neat water and neat ethanol, was determined at seven temperatures from (293.15 to 323.15) K. 5-FU solubility in these mixtures was adequately correlated with several well-known correlation models. The respective apparent thermodynamic functions (Gibbs energy, enthalpy, and entropy) for the dissolution, mixing and solvation processes were computed using the van’t Hoff and Gibbs equations. The enthalpy–entropy relationship for 5-FU was non-linear in the plot of enthalpy vs. Gibbs energy of solution with variant but positive slope in almost all the composition regions. Thus, the driving mechanism for 5-FU transfer processes was the enthalpy. In addition, by means of the inverse Kirkwood-Buff integrals is observed that apparently 5-FU is preferentially solvated by water molecules in water-rich mixtures but preferentially solvated by ethanol molecules in ethanol-rich mixtures.