Thermodynamics Research Center / ThermoML | Journal of Chemical Thermodynamics

ABSTRACT

The equilibrium solubility of 2,3-dihydro-6-propyl-2-thioxo-4(1H)-pyrimidinone in four neat solvents namely methanol, ethanol, n-propanol and isopropanol and co-solvent mixtures of methanol (1) + water (2), ethanol + water (2), n-propanol (1) + water (2) and isopropanol (1) + water (2) at temperature range from (278.15 to 333.15) K was reported. The experiment was carried out by the saturation shake-flask technique under atmosphere pressure (101.1 kPa). At the same composition of methanol, ethanol, n-propanol or isopropanol and temperature, the mole fraction solubility of 2,3-dihydro-6-propyl-2-thioxo-4(1H)-pyrimidinone was highest in methanol (1) + water (2) mixtures, and lowest in isopropanol (1) + water (2) mixtures. By using the Jouyban-Acree model, van't Hoff-Jouyban-Acree model and Apelblat-Jouyban-Acree model, 2,3-dihydro-6-propyl-2-thioxo-4(1H)-pyrimidinone solubility was well correlated obtaining RAD lower than 2.65% and RMSD lower than 1.85 * 10-4. The transfer Gibbs free energy (deltatrG.deg.), enthalpy (deltatrH.deg.), and entropy (deltatrS.deg.) were calculated, demonstrating that the solubilization capacity was more favorable with the increase in the alcohol concentration. Furthermore, quantitative values for the local mole fraction of methanol (ethanol, n-propanol or isopropanol) and water around the 2,3-dihydro-6-propyl-2-thioxo-4(1H)-pyrimidinone were computed by using the Inverse Kirkwood-Buff integrals method applied to the determined solubility data. 2,3-Dihydro-6-propyl-2-thioxo-4(1H)-pyrimidinone was preferentially solvated by water for the four solvent mixtures in water-rich compositions; while in intermediate and co-solvent-rich composition for alcohol (1) + water (2) mixtures, 2,3-dihydro-6-propyl-2-thioxo-4(1H)-pyrimidinone is preferentially solvated by the alcohol. The preferential solvation magnitude of 2,3-dihydro-6-propyl-2-thioxo-4(1H)-pyrimidinone was highest in isopropanol mixtures than in the other three co-solvent mixtures.