Characterizing the Solvation Interactions of Choline Chloride-based Deep Eutectic Solvents Employed in Separations

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Solvent visuals and plot of hydrogen bond basicity versus dispersive-type interactions
Plot illustrating the relation of hydrogen bond basicity versus dispersive-type interactions at 40 ℃ for 5 out of 25 DESs evaluated in this study. (blue square), [Ch+][Cl-] : 2 Urea; (red triangle), [Ch+][Cl-] : 2 Malonic acid; (green circle), [Ch+][Cl-] : 2 (1,4-Butane diol); (orange diamond), [Ch+][Cl-] : 4 (1,6-Hexane diol); and (purple triangle), 4 tetrabutylammonium chloride : Triethylene glycol
Scientific Achievement

Solvation properties of choline chloride-based deep eutectic solvents (DESs) were thoroughly characterized using gas chromatography for the first time. Solvation models were constructed for various DESs to describe their individual solvation interactions and used to interpret and explain DES behavior in previously reported catalysis, separations, and organic synthesis studies.

Significance and Impact

The models developed in this study enable us to predict the performance of DESs in catalysis and separation systems based on their solvation characteristics. This advancement provides a framework for the selection of optimal DESs in various applications that could result in significant cost savings in energy-intensive separation processes.

Research Details
  • Choline salts form DESs with isomers of butane diol and hexane diol that possess higher hydrogen bond basicity and dispersive-type interactions compared to those composed of urea, acetamide, and organic acids.
  • Employing organic acids as hydrogen bond donor significantly enhances the hydrogen bond acidity of choline chloride ([Ch+][Cl-]) DESs.
  • Substituting chloride anion with acetate in choline salts decreases dipolar interactions while enhancing the hydrogen bond basicity.
  • Employing different structural isomers of butane diol as hydrogen bond donor can significantly influence hydrogen bonding interactions.

Abbasi, N.M., Farooq, M.Q., Anderson, J.L. “Investigating the Variation in Solvation Interactions of Choline Chloride-Based Deep Eutectic Solvents Formed Using Different Hydrogen Bond Donors.” ACS Sustainable Chem. Eng. 2021, 9, 35, 11970-11980.