Solubility Measurement, Correlation, and Hansen Solubility Parameter of 1,3-Dinitropyrazole in Twelve Solvents

Abstract

1,3-Dinitropyrazole serves as a crucial intermediate in pharmaceutical synthesis and is also recognized as a high-energy density material. Its purity can affect the yield, safety, and stability of the product. Recrystallization is a pivotal step in its purification. This study investigates the solubility of 1,3-dinitropyrazole in twelve solvents, offering guidance for the selection of appropriate solvents. The solubility of 1,3-dinitropyrazole in a selection of twelve solvents, including water, methanol, ethanol, acetonitrile, hexane, cyclohexane, dichloromethane, dichloroethane, benzene, toluene, ethyl acetate, and acetone, was measured by the gravimetric technique across a temperature spectrum from 278.15 to 318.15 K at atmospheric pressure. Under ambient conditions at 298.15 K, the order of solubility was as follows: acetonitrile (48.201 × 10^–2) > acetone (45.012 × 10^–2) > dichloromethane (37.019 × 10^–2) > ethyl acetate (36.088 × 10^–2) > dichloroethane (33.244 × 10^–2) > benzene (19.563 × 10^–2) > methylbenzene (15.221 × 10^–2) > methanol (5.531 × 10^–2) > ethyl alcohol (3.078 × 10^–2) > cyclohexane (0.060 × 10^–2) > hexane (0.053 × 10^–2) > water (0.051 × 10^–2). Additionally, the solubility in these 12 pure solvents increases as the temperature rises. The efficacy of four established thermodynamic models, including the Apelblat equation, Jouyban–Acree model, van’t Hoff model, and λh model, was evaluated via R², ARD and RMSD criteria. Notably, the Apelblat equation and Jouyban–Acree models demonstrated exceptional accuracy, with the Jouyban–Acree model emerging as the optimal choice for predicting the solubility of 1,3-dinitropyrazole. Meanwhile, the application of Hansen solubility parameters in predicting and analyzing solubility also has its limitations. The data pertaining to the solid–liquid equilibrium of 1,3-dinitropyrazole across a range of solvents are indispensable for the initial assessment of its utility in industrial contexts.