A method involving flow microcalorimetry is described for determination of the enthalpy of transfer of acidic or basic molecules from water-immiscible organic solvents to water. In this first paper the method is illustrated by application to the transfer of n-butyric acid from toluene to water at 25°. Distribution experiments were performed to permit evaluation of the free energy of transfer. Detailed consideration was given to the enthalpy and free-energy contributions arising from dimerization of the solute in the organic solvent. The thermodynamic parameters for the process involving monomeric solute n- C3H7COOH (toluene) = n-C3H7COOH (H2O) are ΔG°298 = (-1220 ± 50) cal mol-1, ΔH298 = (-3520 ± 150) cal mol-1, and ΔS°298 = (-7.7 ± 0.5) cal deg-1 mol-1.
All Science Journal Classification (ASJC) codes
- Physical and Theoretical Chemistry