Solubility and solution thermodynamics of thymol in six pure organic solvents

• Solubility of thymol in six pure organic solvents was experimentally determined.
• Several solution thermodynamic properties of thymol were calculated.
• The experimental solubility data were correlated by five models.
• The studies of molecular modeling and solubility parameters were carried out.
• The TOPEM was employed to calculate the solubility of thymol.

The solubility of thymol in methanol, ethanol, 1-propanol, 2-propanol, 1-butanol and acetonitrile with the temperature ranging from (279.15 to 313.15) K at atmospheric pressure was measured by the gravimetric method. For the temperature range investigated, the solubility of thymol in the solvents increased with a rise of temperature. Results of these measurements were correlated by five thermodynamic models-modified Apellblat, λh, van’t Hoff, Wilson and NRTL, in which Wilson model achieved the best fitting results. The enthalpy, entropy and Gibbs free energy of dissolution were calculated with the van’t Hoff equation. The results indicated that the processes of solution in all selected solvents were endothermic, entropy-driven and non-spontaneous. The studies of molecular simulation and solubility parameters were carried out to give the explanation for the sequence of solubility in various solvents. The data of quasi-static heat capacity for both solid and liquid phases of thymol were investigated by stochastic temperature modulation DSC technique (TOPEM). The extent to which the assumptions of the differential molar heat capacity (ΔCP) in the regular solution equation influence the magnitude of the ideal solubility of thymol was examined.