Infinite dilution partial molar excess entropy–enthalpy compensation for thiophene, carbon dioxide and water in ionic liquids

Infinite dilution partial molar excess entropy–enthalpy compensation for polar solutes in an ionic liquid (IL) is investigated using the literature data of infinite dilution activity coefficient, ln γ1∞. Entropy–enthalpy compensation holds for the polar solutes, such as thiophene and CO2, and non-polar solutes, such as heptane and toluene. For the water + IL binaries, a converged linear relationship between infinite dilution partial molar excess entropy and enthalpy holds. Using the compensation rule, it is shown that, for the efficient removal of thiophene and CO2 from non-polar solutes with IL solvents, ILs having weaker molecular interactions with thiophene and CO2 are advantageous, because the entropy terms control the ln γ1∞ values.

► S,H-compensation rule enhances the development of solution models for ILs.
► Infinite dilution activity coefficient data are used to study S,H-compensation.
► Entropy–enthalpy-compensation holds for the polar solutes thiophene and CO2 in ILs.
► For water in ILs a linear relationship between partial molar S and H holds.
► ILs for the removal of thiophene and CO2 from non-polar solutes are proposed.