Solubility determination and thermodynamic dissolution functions of 1,3-diphenylguanidine in nine organic solvents at evaluated temperatures

• Solubility of 1,3-diphenylguanidine in nine organic solvents were determined.
• The solubility were correlated with four thermodynamic models.
• Apparent dissolution enthalpy and excess enthalpy of solution were obtained.

The solubility of 1,3-diphenylguanidine was determined in ethanol, isopropanol, n-propanol, n-butanol, i-butanol, ethyl acetate, toluene, acetone and acetonitrile by a high performance liquid chromatography (HPLC) within temperature range from (273.15 to 313.15) K under pressure of 101.3 kPa. The solubility of 1,3-diphenylguanidine in the selected solvents increased with the increase in temperature. On the whole, the solubility of 1,3-diphenylguanidine in these solvents followed the order: acetone > ethyl acetate > n-butanol > n-propanol > ethanol > i-butanol > acetonitrile > isopropanol > toluene. The acquired solubility of 1,3-diphenylguanidine were correlated with the Apelblat equation, λhλh equation, Wilson model and NRTL model, and the corresponding model parameters were obtained. The Apelblat equation provided better results than the other three models. Furthermore, the apparent dissolution enthalpy and excess enthalpy of solution were obtained from the experimental solubility. The solubility would be helpful in optimising the purification process of 1,3-diphenylguanidine on the industrial scale.

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