Solubility and Mixing Thermodynamics Properties of p-Toluenesulfonamide and o-Toluenesulfonamide in Seven Monosolvents at Different Temperatures

The solubility of p-toluenesulfonamide and o-toluenesulfonamide in seven monosolvents of methanol, ethanol, n-propanol, isopropanol, n-butanol, acetonitrile, and ethyl acetate were measured by using the isothermal saturation method at temperatures ranging from 283.15 to 318.15 K under 101.3 kPa. The mole fraction solubility of p-toluenesulfonamide and o-toluenesulfonamide in those selected monosolvents increased with the increase in temperature. The maximum mole fraction solubility of o-toluenesulfonamide was observed in ethyl acetate (0.07748 at 318.15 K), followed by that in acetonitrile (0.07368 at 318.15K), methanol (0.05790 at 318.15 K), ethanol (0.04564 at 318.15 K), n-propanol (0.04271 at 318.15 K), isopropanol (0.04142 at 318.15 K), and n-butanol (0.03879 at 318.15 K). For p-toluenesulfonamide + solvents systems, the maximum mole fraction solubility was observed in acetonitrile (0.1588 at 318.15 K), followed by that in ethyl acetate (0.1329 at 318.15K), methanol (0.1043 at 318.15 K), ethanol (0.09142 at 318.15 K), n-propanol (0.06888 at 318.15 K), isopropanol (0.05092 at 318.15 K) and n-butanol (0.05645 at 318.15 K). The measured solubility data were correlated and calculated by using the modified Apelblat equation, Buchowski–Ksiazaczak λh equation, Wilson model, and NRTL model. The largest values of relative average deviations (RAD) and the root-mean-square deviations (RMSD) between the experimental and calculated solubility were 0.87 × 10–2 and 8.46 × 10–4, respectively. On the basis of the obtained solubility, the standard enthalpy of solution (ΔHsolo), the standard Gibbs energy (ΔGsolo) of solution, and the standard entropy of solution (ΔSsolo) of p-toluenesulfonamide and o-toluenesulfonamide dissolved in monosolvents were calculated. The results show that the dissolution of p-toluenesulfonamide and o-toluenesulfonamide in these monosolvents is a spontaneous process. The correlation and curve fitting results indicated good correlation of the experimental solubility data of p-toluenesulfonamide and o-toluenesulfonamide with the modified Apelblat model. Therefore, the experimental solubility and correlation equations established in this study can be useful in the crystallization, purification in laboratories, and related industries.