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 degrees C by the isothermal saturation method. The molar standard Gibbs energies (Delta(sol)G(m)degrees) and the molar entropies of solution (Delta S-sol(m)degrees) were determined on the basis of the solubilities and previously determined molar enthalpies of solution (Delta H-sol(m)degrees). The thermodynamic parameters of sublimation (Delta(sub)G(m)degrees, Delta S-sub(m)degrees) were calculated from the previously determined molar enthalpies of sublimation Delta H-sub(m)degrees. The values obtained were used for calculation of the thermodynamic parameters of solvation (Delta(solv)G(m)degrees, Delta S-solv(m)degrees). The thermodynamic functions of solvation and solution were correlated with the values of the surface-accessible areas, the partial molar volumes V-2 degrees, the molecular volumes V-2(M), and the parameters P of the compounds investigated.