The effect of solvents on solid-liquid phase equilibrium of 1,3-Di-o-tolylguanidine

The crystal structure of 1,3-Di-o-tolylguanidine (DOTG) were investigated, as well as the thermodynamic properties about the solid-liquid phase equilibrium. The intermolecular interactions examined by Hirshfeld surface analysis demonstrate that the N-H···N and C-H···C interactions are dominant in the solid-state structure of DOTG. The solubility of DOTG in thirteen pure solvents (ethanol, 1-propanol, 2-propanol, 1-butanol, isobutanol, 2-butanol, 1-pentanol, propyl acetate, isopropyl acetate, acetone, butanone, acetonitrile, 1,4-dioxane) was measured by a gravimetric method from 283.15 K to 323.15 K at atmospheric pressure. According to the experimental results, the solubility of DOTG in all solvents increase with the increase of temperature. The determined solubility data were correlated using the Apelblat equation, λh equation, van't Hoff equation and the NRTL model. Additionally, the effects of solvent properties on the solubility of DOTG were discussed in terms of solvent polarity, hydrogen bond and cohesive energy density. Furthermore, the mixing thermodynamic properties of DOTG were studied in selected solvents based on the NRTL model, showing that the process of DOTG dissolving is spontaneous and entropy-driving.