Solubility and solution thermodynamics of p-toluenesulfonamide in 16 solvents from T = 273.15 to 324.75 K

The solid-liquid equilibrium data and solution thermodynamics of chemicals are indispensable for the synthesis and purification of crystalline products in industry. The selection of a solvent directly influences the yield and purity of a product. In this work, the solubility of p -toluenesulfonamide ( p -TSA) in 16 pure solvents, methanol, ethanol, n -propanol, isopropanol, n -butanol, isobutanol , n -pentanol, isopentanol, acetone, ethyl acetate , acetonitrile , cyclohexanone , cyclopentanone , methyl acetate , ethyl formate and dichloromethane , was determined by a static gravimetric method at temperatures ranging from 273.15 to 324.75 K under atmospheric pressure. The results indicate that the mole fraction solubility of p -TSA increased with increasing temperature in all 16 solvents. The solubility value in the selected alcohols ranks in the following order: methanol > ethanol > n -propanol > isopropanol > n -butanol > n -pentanol > isopentanol > isobutanol , and the polarity of a solvent seems to be an important factor influencing the solubility of p -TSA in alcohols. In the other eight solvents, the solubility sequence is cyclopentanone > acetone > cyclohexanone > (acetonitrile, methyl acetate) >  ethyl acetate > ethyl formate > dichloromethane , which strongly deviates from the order of solvent polarities. Then, the measured solubility data were correlated with four thermodynamic models, i.e., the modified Apelblat equation, λh equation, non-random two-liquid (NRTL) equation and the Wilson equation. Overall, the NRTL model provided the most satisfactory fitting results. Furthermore, the dissolution thermodynamic parameters, Gibbs energy (△ dis G ), molar enthalpy (△ dis H ) and molar entropy (△ dis S ) were calculated according to the Wilson model. The values of △ dis H and △ dis S are positive in all selected solvents, showing that the dissolution process of p -TSA in the selected solvents is endothermic and entropy-driven. The △ dis G values are negative in all selected solvents and decrease with increasing temperature, which demonstrates that dissolution of p -TSA in the selected solvents is favorable and spontaneous.