Solubility determination, Hansen solubility parameter, molecular simulation and thermodynamic properties of 2-anilino-6-(dibutylamino)-3-methylfluoran in four binary solvent mixtures from 283.15 K to 323.15 K

Abstract

The laser monitoring method was used to assess the solubility of 2-Anilino-6-(dibutylamino)-3-methylfluoran (ODB-2) in four binary solvent systems (methyl acetate, ethyl acetate, n-propyl acetate, n-butyl acetate + acetonitrile) at temperatures ranging from 283.15 K to 323.15 K. The results indicated that the solubility of ODB-2 increased with the increasing temperature and molar fraction of the ester solvent. Five models, including the Apelblat model, λh model, CNIBS/R-K model, Ma model, and Sun model, were applied to fit the experimental ODB-2 solubility data. Among these models, the Apelblat model and CNIBS/R-K model performed significantly better than the other models. Moreover, it was found that the Hansen solubility parameter played a significant role in explaining the dissolving behavior of ODB-2 in the four binary solvents. The intermolecular interactions between solute and solvent, as well as between solvent molecules themselves, were studied using the radial distribution function obtained through molecular dynamics simulations. The findings suggested that the dissolving behavior of ODB-2 was closely related to the intermolecular forces among solute–solvent and solvent–solvent. The thermodynamic properties of the dissolution process, including enthalpy and entropy changes, were calculated using the modified van't Hoff equation. These results demonstrated that the dissolution of ODB-2 was an endothermic process driven by entropy.