Solubility, Hansen solubility parameter, molecular simulation and thermodynamic analysis of N-methyl-3,4,5-trinitropyrazole at various temperatures

The solubility of N-methyl-3,4,5-trinitropyrazole (MTNP) in (isopropanol + ethanol) mixtures at T = 283. 15 K-323.15 K was tested by a laser monitoring method. The solubility of MTNP increases with the increasing temperature in (isopropanol + ethanol) mixtures. The solubility of MTNP decreases with the increasing isopropanol mass fraction ranging from 0.10 to 0.90. Besides, supersolubility (the metastable zone width) of MTNP was determined by a laser monitoring method. The experimental results showed that the solubility of MTNP in (isopropanol + ethanol) solvent mixtures increases with increasing temperature and the metastable zone width decreases with increasing temperature. Additionally, the values were correlated by the modified Apelblat equation, van't Hoff equation, CNIBS/R-K model and Ma model. In addition, Hansen solubility parameters were used to explain the solubility order. Solubility order of MTNP in (isopropanol + ethanol) solvent mixtures was interpreted by comparing the interaction energy (E-inter) between MTNP and binary solvent. The apparent thermodynamic properties of Gibbs energy, enthalpy and entropy were calculated by the van't Hoff and Gibbs equations. The enthalpy-entropy relationship for MTNP was discussed. Finally, solid-liquid surface tension and surface entropy factor were obtained by the solubility data. (C) 2022 Elsevier B.V. All rights reserved.

Automated summary

In this study, the solubility of N-methyl-3,4,5-trinitropyrazole (MTNP) in (isopropanol + ethanol) mixtures was investigated using a laser monitoring method. The results showed that the solubility of MTNP increased with temperature and decreased with the increase of isopropanol mass fraction. The metastable zone width was also determined, and its relationship with temperature was analyzed. The solubility order was explained using interaction energy and solvent parameters. The thermodynamic properties of MTNP were calculated and discussed, and the solid-liquid surface tension and surface entropy factor were obtained.