Solubility Determination, Hansen Solubility Parameter, Molecular Simulation, and Thermodynamic Properties of 1,3-Diaminoguanidine Monohydrochloride in 12 Monosolvents from 273.15 to 323.15 K

The solubility of 1,3-diaminoguanidine monohydrochloride (DAMG) was determined in 12 monosolvent systems, including water, methanol, ethanol, n -propanol, n -butanol, isopropanol, isobutanol, tetrahydrofuran (THF), ethyl acetate, acetonitrile, hexane, and heptane using a gravimetric method within the temperature range of 273.15–323.15 K under 101.3 kPa. DAMG exhibited the highest solubility in water followed by methanol and ethanol, which were significantly higher than other selected solvents, and the solubility of DAMG increases with temperature rises in all selected solvent systems. The obtained solubility data were correlated with modified Apelblat model, Van’t Hoff model, λ h equation, and Wilson model, and the Van’t Hoff model and the λ h equation show the excellent fitting performance. The Hansen solubility parameter (HSP) analysis revealed that van der Waals forces mainly affected the dissolution behavior of DAMG, while polarity had a significant effect on it. In addition, the intermolecular energies calculated by the molecular dynamics simulation (MD) and the radial distribution functions (RDF) derived from the MD trajectories support this conclusion. Moreover, the thermodynamic properties were evaluated using Van’t Hoff model, which indicated that the mixing process was mainly driven by enthalpy.