Solubilities of Cinnamic Acid Esters in Organic Solvents

The solubilities of three cinnamic acid esters, namely, methyl ferulate, methyl p-coumarate, and methyl sinapate, have been measured in tert-butanol, tert-pentanol, ethyl acetate, and n-hexane, at the temperature range of (303.15 to 321.15) K. It is shown that tert-pentanol is the best solvent for methyl p-coumarate and methyl ferulate and ethyl acetate for methyl sinapate, while the nonpolar n-hexane is the worst solvent. Using the experimentally measured solubilities, the thermodynamic properties of dissolution of the three esters have been calculated. To better understand the solubilization process, the melting temperatures and the enthalpies of fusion of the three esters were determined by differential scanning calorimetry. Finally, successful correlation of the experimental data was achieved with the UNIQUAC and the nonrandom two-liquid (NRTL) activity coefficient models.