Research on triamterene equilibrium solubility in mono-solvents and aqueous solutions according to solvent effect, models, thermodynamic analysis and quantum chemical calculation

Abstract

The equilibrium solubilities of triamterene in pure solvents {isopropanol, methanol, n-propanol, water, 1,2-dichloroethane, 2-methoxyethanol, ethyl acetate, acetonitrile, N-methylformamide (NMF), n-butanol, isobutanol and dimethylsulfoxide (DMSO)}, as well as solvent mixtures of methanol/DMSO + water, were determined by dint of the saturation shake-flask technique. Triamterene solubility (105x) rose as the determination temperature rose and fell in the order at 298.15 K: 2-methoxyethanol (453.9) > DMSO (281.3) > NMF (142.6) > methanol (8.424) > n-propanol (1.432) > n-butanol (1.152) > ethyl acetate (0.9441) > isobutanol (0.8738) > acetonitrile (0.7991) > isopropanol (0.7419) > 1,2-dichloroethane (0.5232) > water (0.1795). No crystal transition or solvation in the trial process was shown via X -ray power diffraction patterns. The solvent effects, in which the interactions of solvent–solvent and solvent–solute were considered, were studied via linear solvation energy relationship. Using equations such as Wilson, Apelblat, λh, and NRTL for mono-solvents and Jouyban-Acree as well as modified van't Hoff-Jouyban-Acree for solvent mixtures, the magnitudes of equilibrium solubility were associated. The greatest relative average deviation of 5.787 × 10−2 and the maximum deviation value of root mean square of 219.1 × 10−4 were computed for neat solvents. According to the solubility information in pure solvents, the Wilson equation was used to compute the mixing solution parameters. At 298.15 K, the inverse Kirkwood-Buff integral was utilized here to examine the preferred solvation of triamterene. In blends of DMSO/methanol + water with middle and rich DMSO/methanol compositions, the parameters of preferred solvation for DMSO/methanol were positive, indicating the preferential solvation of triamterene by DMSO/methanol. In addition, the electrostatic acidity-basicity properties were demonstrated using the lowest negative electrostatic potential in company with the minimum m local ionization energy of molecular surface. The N in ring of the triamterene is the preferential target for electrophilic assault; and –NH2 of the triamterene, for nucleophilic assault. The weak triamterene-solvent interactions were graphically displayed by the use of the independent gradient approach on the basis of Hirshfeld partition analysis.