N,N′-Dihydroxyethanediamide (DHG) is an energetic material used as a corrosion inhibitor and burning rate suppressant in solid propellants. However, as a critical parameter in synthesis and crystallization, solubility has been insufficient in existing research. In this work, the mole fraction solubility of DHG in 11 pure solvents (dimethylformamide, dimethylacetamide, pyridine, water, methanol, ethanol, n-propanol, isopropanol, n-butanol, ethyl acetate, and acetonitrile) and DHG-DMSO solvate in DMSO was determined from 293.15 to 333.15 K by the isothermal saturation method. Results showed that the solubility of DHG increased with temperature in 10 solvents but decreased in pyridine, while that of the DHG-DMSO solvate also increased. The dissolution behavior was analyzed by solvent property parameters, molecular electrostatic potential surface, and Hirshfeld surface, revealing that hydrogen bonding is the dominant factor. Four models (the polynomial empirical, modified Apelblat, Yaws, and van’t Hoff) were utilized to correlate the solubility data. The Apelblat equation and the Yaws model showed similarly satisfactory performance. The apparent thermodynamic properties of DHG dissolution were calculated using the van’t Hoff equation. The results indicate that the dissolution process is endothermic in all 10 solvents except pyridine, where it is exothermic. This study provides essential fundamental data for the solvent selection in DHG recrystallization.
Xie et al. (Wed,) studied this question.