Measurement, correlation of solubility and thermodynamic properties analysis of 2,4,6-trinitroresorcinol hydrate in pure and binary solvents

The solubility of 2,4,6-trinitroresorcinol hydrate (TNR center dot 2/3H(2)O) in the pure solvents (methanol, ethanol, isopropanol and water) and the binary mixed solvents (methanol-water, ethanol-water and isopropanol-water) was measured by the laser dynamic method from 298.15 K to 323.15 K under the atmospheric pressure. The TNR center dot 2/3H(2)O do not change before and after the solubility measurement in the selected solvents. The solubility increases with the increase of the temperature, and methanol is more suitable for the cooling crystallization of TNR center dot 2/3H(2)O. In the pure solvents, the solubility order at the same temperature is: methanol > ethanol > isopropanol > water, which may be affected by the properties (such as hydrogen bond, polarity, dielectric constant, cohesive energy density etc.) of the alcohol solvents, self-association of water molecules, the hydrophobic wing of the TNR center dot 2/3H(2)O and so on. In the mixed solvents, the solubility has different sensitivity to the content of organic components (x(2)) in the solvent. The possible reason is that: the interaction between solvent and solvent plays an important role (the formation of azeotropic mixtures of alcohols and water, the interaction between water and alcohol solvents, the properties of the solvents etc.). The solubility data of TNR center dot 2/3H(2)O were compared with that of 2,4,6-trinitrophenol (TNP) that have been reported. It can be found that the solubility of TNP is always greater than that of TNR center dot 2/3H(2)O with the same solvent and temperature, and x(2)= 0.63-0.69 (ethanol-water) and x(2) approximate to 0.73 (isopropanol-water) are more suitable as the solvents for solution crystallization to separate TNR center dot 2/3H(2)O from the mixture of TNP and TNR center dot 2/3H(2)O. The experimental mole fraction solubility data (xexp) of TNR center dot 2/3H(2)O were correlated by the modified Apelblat, Van't Hoff, CNIBS R-K, and Jouyban-Acree-modified Apelblat model. All of these models give satisfactory results, and the Van't Hoffmodel has better correlation and helps to expand the solubility data of TNR center dot 2/3H(2)O. The thermodynamic properties during the dissolution process were analyzed based on the Van't Hoff. And the dissolution of TNR center dot 2/3H(2)O in the solvents used is considered to be an endothermic, non-spontaneous and entropy-driven process and the enthalpy is the main contributor to the Gibbs free energy in the process of dissolution. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

The solubility of TNR center dot 2/3H(2)O was studied in different solvents, showing an increase with temperature and the highest solubility in methanol in pure solvents. The solubility in mixed solvents is sensitive to the organic content, and interactions between alcohols and water also play a significant role in solubility.