LAUSR

Abstract Knowledge of solubility and thermodynamic properties of 3,4-dinitro-1H-pyrazole (DNP) within different solvents are essential in the processes of crystallization and further theoretical studies. In this study, the solubility of DNP in 12 pure solvents (i.e., water, n-propanol, isobutyl alcohol, n-pentanol, isoamyl alcohol, xylene, ethyl acetate, epichlorohydrin, chloroform, acetonitrile, tetrahydrofuran and 2-butanone) has been determined by using gravimetric method within the temperature range of (283.15–323.15) K under atmospheric pressure. Good dissolution ability was found for DNP in the organic solvents we studied. The sequence of the mole fraction solubility is tetrahydrofuran >2-butanone > n-propanol > n-pentanol > isobutyl alcohol > isoamyl alcohol > acetonitrile > ethyl acetate > epichlorohydrin > xylene > water > chloroform. Solubility of DNP increased with the increasing temperature in each pure solvent. In addition, solubility data was correlated by four models including the modified Apelblat equation, NRTL model, Wilson model and Two-Suffix Margules model. The maximum root-mean-square deviation (104RMSD) was 715.47. Basically speaking, values of R2 and 104RMSD between experimental and calculated solubility showed that NRTL model provided most satisfactory fitting results in this work. Moreover, Hansen solubility parameters (δd, δp, δh, δt, δv and Δδt) were used to describe the dissolution characteristics of solid in different solvents. Then, the Kamlet-Taft parameters (α, β and π*) were explained to investigate the solvent effect on DNP solubility. Furthermore, other parameters, including mixing enthalpy (ΔmixH), mixing entropy (ΔmixS) and mixing Gibbs energy (ΔmixG) were calculated according to the Wilson model, and their results have been discussed on the basis of experimental data. It has been found that all mixing Gibbs energy are less than zero, hence, the dissolution of DNP is a spontaneous process.