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 (Δ sol G m o ) and the molar entropies of solution (Δ sol S m o ) were determined on the basis of the solubilities and previously determined molar enthalpies of solution (Δ sol H m o ). The thermodynamic parameters of sublimation (Δ sub G m o, Δ sub S m o ) were calculated from the previously determined molar enthalpies of sublimation Δ sub H m o . The values obtained were used for calculation of the thermodynamic parameters of solvation (Δ solv G m o, Δ solv S m o ). The thermodynamic functions of solvation and solution were correlated with the values of the surface-accessible areas, the partial molar volumes V 2 o, the molecular volumes V 2 M, and the parameters β of the compounds investigated.