The solid-liquid equilibrium behavior of 2,7-dihydroxynaphthalene in eleven organic solvents: Thermodynamic analysis and molecular simulation understanding

Abstract

2,7-Dihydroxynaphthalene (DHN), one of the most important aromatic compounds, was selected to study its differences of solubility in eleven mono organic solvents from 283.15 to 323.15 K through the gravimetric experiments and theoretical simulations. It was found that the DHN has the highest solubility in isopropanol among alcohol solvents, while in non-alcohol solvents, it has the highest solubility in ethyl acetate. Furthermore, four well-known thermodynamic equations were utilized for correlating and modeling the experimental solubility data. All the value of ARD is very small, no more than 2%, proving that these models are applicable and effective. In addition, the result of mixing thermodynamic functions underlined that the dissolution process is spontaneous and exhibits an exothermic mechanism. We also did the crystal structure stacking pattern, Hirshfeld surface, and the molecular electrostatic potential surface (MEPs) analysis to evaluate the molecular interactions of the DHN and predict the possible hydrogen bond interaction sites. Further, we did molecular dynamic (MD) simulations to illustrate and explain the diverse solubility of DHN in selected solvents from molecular perspective. Solvation free energy and radial distribution function (RDF) analysis results indicate that the molecular interactions are the decisive factors that determine the mixing process of DHN, which successfully explained the reason for the diversity in dissolution behavior. We believe that all the results in this article can provide a reference for the further purification and process development of DHN.