Solubility and Solution Thermodynamics of 3,4-Bis(4-aminofurazan-3-yl)furoxan in Pure Solvents and Binary Solvent Mixtures

The solubility of 3,4-bis(4 '-aminofurazan-3 '-yl)furoxan (BAFF) was determined in ten pure solvents (dichloromethane, 1,2-dichloroethane, cyclohexane, water, methanol, ethanol, n-propanol, isopropanol, n-butanol, and ethyl acetate) as well as three binary solvent mixtures (methanol/water, ethanol/water, ethyl acetate/1,2-dichloroethane) over various temperature ranges (283.15 to 353.15 K). The measurements were conducted by using a static analytical method under atmospheric pressure. During the temperature ranges investigated, it was observed that the solubility of BAFF increased with the increase in the temperature in all selected solvents. Among the ten pure solvents, ethyl acetate has the highest solubility, while methanol, ethanol, n-butanol, and isopropanol have moderate solubilities. Water, 1,2-dichloroethane, and dichloromethane have relatively low solubilities, while in the binary solvent systems, the solubility of BAFF decreased with increasing the mole fraction of antisolvent (water or 1,2-dichloroethane) at given temperature. Moreover, the experimental solubility data in pure solvents were correlated using the modified Apelblat equation, the lambda h equation, and two local composition models (Wilson model and NRTL model). Additionally, the modified Apelblat equation, CNIBS/R-K model, Jouyban-Acree model, and multicomponent NRTL model were successfully employed to correlate the experimental solubility in mixed solvent systems. Furthermore, based on the experimental data and the NRTL model, the dissolution thermodynamic properties of BAFF in both pure and binary solvents were calculated and analyzed. These properties include the dissolution Gibbs energy, enthalpy, and entropy. These data indicate that the dissolution process of BAFF is endothermic and spontaneous.