Solubilities in Water of Uracil and Its Halogenated Derivatives

The solubilities of crystalline compounds, uracil, 5-fluorouracil, 5-chlorouracil, 6-chlorouracil, 5-bromouracil, 5-iodouracil, and 5-(trifluoromethyl)uracil, in water have been determined at 25 °C by the isothermal saturation method. The molar standard Gibbs energies (ΔsolGmo) and the molar entropies of solution (ΔsolSmo) were determined on the basis of the solubilities and previously determined molar enthalpies of solution (ΔsolHmo). The thermodynamic parameters of sublimation (ΔsubGmo, ΔsubSmo) were calculated from the previously determined molar enthalpies of sublimation ΔsubHmo. The values obtained were used for calculation of the thermodynamic parameters of solvation (ΔsolvGmo, ΔsolvSmo). The thermodynamic functions of solvation and solution were correlated with the values of the surface-accessible areas, the partial molar volumes V2o, the molecular volumes V2M, and the parameters β of the compounds investigated.