Study on solid-liquid equilibrium behavior of oxadiazine dissolved in 12 pure solvents: Solubility determination, model correlation and molecular simulation

Abstract

The dissolution mechanism of oxadiazine was comprehensively explored by model calculation and molecular simulation. The solubility of oxadiazine in 12 pure solvents was measured by static method in the temperature range of 293.15– 323.15 K under standard atmospheric pressure. The measured data show that the solubility in different solvents varies greatly, and oxadiazine has the maximum solubility in N, N-dimethylformamide (0.113 mol∙mol−1) and the minimum solubility in isopropanol (0.00130 mol∙mol−1) at 298.15 K. Subsequently, the solubility data were correlated with modified Apelblat model, van’t Hoff model and Wilson model, where the modified Apelblat model showed the most appropriate fitting effect. The calculated mixing thermodynamic properties including ΔmixG (−933 ∼ −10.9 J·mol−1) and ΔmixS (0.0680 ∼ 2.35 J·mol−1·K−1), indicates that the dissolution of oxadiazine in 12 pure solvents was spontaneous and entropy-driven. Hansen solubility parameter was used to explain and analyze the miscibility between oxadiazine and 12 pure solvents, which showed that the dissolution of oxadiazine was the contribution of volume-dependent. Solvent effect analysis was carried out on the dissolution of oxadiazine using KAT-LSER model, and it was concluded that the solute–solvent interactions are much stronger than the solvent–solvent interactions. The solvation free energy of oxadiazine dissolved in 12 pure solvents was calculated by molecular simulation. The results show that absolute value of solvation free energy is consistent with the solubility order of oxadiazine.