(222l) Choline Chloride-Based Eutectic Mixtures: An Experimental and Molecular Simulation Study

Deep eutectic solvents (DES), considered readily available and relatively inexpensive ILs analogues, show promise for many engineering applications compared to typical ionic liquids (IL)¹. A large portion of the eutectic mixtures that have been thus far studied experimentally as novel solvents use choline chloride as their ammonium salt component while varying the hydrogen bond donor (HBD) of the system at different compositions. The eutectic point of these mixtures can vary depending on the HBDs used and can thus be difficult to predict.

In this work, molecular simulations and experimental infrared spectroscopy are used to characterize hydrogen bonding and ionic interactions within each system to determine how the HDB affects choline chloride-based eutectic solvents. This combined experimental and computational approach is used to obtain atomistic detail of the hydrogen bonding interactions in the system at its eutectic point. Since only the HBD type is changed, conclusions are based on the ability of these HBD’s ability to interact with choline chloride.

Experimental IR spectra are reported for choline chloride-malonic acid mixture and its pure components since this technique is very sensitive to hydrogen bonding. Our previous method²for modeling choline chloride-urea was implemented on this and two other systems, one having ethylene glycol and the other glycerol, to determine force field applicability for other DES.  Through atomistic molecular dynamics, force field validation is conducted for each system by comparing experimental and simulated data, when possible. Detailed structure and hydrogen bond analyses between moieties show the greatest interactions for each system. Through this work, it is suggested that the anion-HBD and HBD-HBD are crucial interactions (based on RDFs and a hydrogen bond analysis) responsible for the behavior of these eutectic mixture.

1. Abbott, A.P., Capper, G., Davies, D.L., Rasheed, R.K. & Tambyrajah, V. Chem Commun. 2003, 70-71

2. Perkins, S.P., Painter, P., Colina, C.M. J. Phys. Chem. B. 2013, submitted for publication.