Solubilities of Cinnamic Acid Esters in Ionic Liquids

Abstract

The solubilities of three cinnamic acid esters, namely, methyl ferulate, methyl p-coumarate, and methyl sinapate, in eight imidazolium-based ionic liquids composed of the PF6 − and BF4 − anions have been measured at (30, 39, and 48) °C. Higher solubilities of the three esters were observed in the ionic liquids composed of the BF4 − anion than those composed of the PF6 − anion. Also, higher solubilities are observed in alkyl-substituted (on the imidazolium cation moiety) ILs than in polar-substituted ILs, whereas, as the alkyl chain length on the cation moiety increases, the solubility increases as well. Moreover, using the van’t Hoff equations, the apparent Gibbs energy, enthalpy, and entropy of solution were calculated. Positive values of the three thermodynamic functions were found in all cases. Finally, successful correlations of the experimental data were achieved with the UNIQUAC and the NRTL activity coefficient models.

Thermodynamic Models and Central Composite Design for Calcium Sulfate Dihydrate Solubility

“…T hm is the harmonic mean of the experimental temperatures. [26]. These values decrease with increasing both HCl and additive concentrations, which means that the dissolution process occurred with less energy.…”

“…The positive ΔG o sol values suggest that the dissolution process is spontaneous [24,26]. The positive value of ΔS o sol points to an unfavorable solubilization entropy for the solute in solution [26]. The negative value of ΔS o sol is due to more order in the solution [27].…”

Thermodynamic Parameters of Solutions of Sildenafil Citrate in Some Organic Solvents at Different Temperatures

“…were obtained from equation [8,11] [12,13]. The Gibbs energy of dissolution (Gsol) is also positive for the studied solvents suggesting that the dissolution process is spontaneous [14].…”

Measurement and Correlation for Solubility of Some Pyrimidine Derivatives in Different Solvents

“…When stronger bonds are broken and weaker bonds are formed, energy is consumed. So, Δ sol becomes positive [12] which indicates endothermic dissolution of compounds [15]. The positive value of Δ sol indicates that the dissolution process is not spontaneous [12,15].…”

“…So, Δ sol becomes positive [12] which indicates endothermic dissolution of compounds [15]. The positive value of Δ sol indicates that the dissolution process is not spontaneous [12,15]. The positive entropy change indicates that the entropy of solubilization is unfavorable for solute in solution [15], whereas negative entropy is due to more order in solutions [16].…”