Experimental and Computational Studies of Choline Chloride-Based Deep Eutectic Solvents

Abstract

Choline-chloride based deep eutectic solvents (DES) have been used for several different applications (e.g., solubility, electrochemistry, and purifications) due to their relative inexpensive and readily available nature. In this work, three choline chloride-based DESs are simulated using molecular dynamics to study the hydrogen bonding interactions of the system. Three hydrogen bond donors (HBD) are studied in order to determine the changes in the hydrogen bonding interactions when the HBD is different in the DES. One dicarboxylic acid and two polyols (with different number of OH groups) were chosen as the HBDs of interest. First, the simulations are validated by comparing simulated and experimental thermodynamic and transport properties, when possible. Then, for maline (choline chloride/malonic acid), the more anomalous system studied here, molecular simulations complement results obtained from an FTIR spectroscopic study in order to further understand this unique system. Good agreement with experimental values was obtained for simulated density, heat capacity, and transport properties. A high relative percent of hydrogen bonding is observed for interactions between the anion and the HBD for the three main systems studied here, consistent with the nature of how these moieties interact in DESs. Comparison is also done with a previous DES studied in our group. From the infrared spectroscopic study conducted on maline films, band assignments were discussed highlighting a “free” carbonyl group of the carboxylic acid group in the eutectic mixture when the OH group is hydrogen bonded to something else. Additionally, a band is assigned to a hydrogen bonded carbonyl group. These band assignments are consistent with findings in the molecular simulations and highlight the predominant interactions of the system.

Vibrational analysis and formation mechanism of typical deep eutectic solvents: An experimental and theoretical study

“…[12][13][14][15][16][17][18][19][20][21][22][23][24][25] To date, although researches on DESs have made tremendous progress, there are few theoretical studies on DESs, especially the physicochemical properties of DESs, such as the formation mechanism, spectra properties, etc. [26][27][28][29][30][31][32][33][34] It is well known that the physicochemical properties of DESs have quite significance for further researches. Compared with other liquids, the interaction inside the DESs is more complicated due to diverse components.…”

“…[35][36][37][38][39] Over the past years, there have been a few studies on vibrational analysis of DESs. [29][30][31] Yue et al…”

“…[40] Perkins et al studied on vibrational modes by experiments and formation mechanism of three kinds of DESs (ChCl/ethylene glycol 1:2; ChCl/glycerol 1:2; ChCl/malonic acid 1:1) by molecular dynamics. [30,31] Most noteworthy point is that Zhang et al measured the FTIR spectrum of choline chloride/magnesium chloride hexahydrate compared with theoretical IR spectra calculated at the B3LYP/6-311++G(d) level. [29] In the present work, we firstly employed DFT methods to study the structures and predict the vibrational frequencies of three typical kinds of DESs (ChCl/glycerol, ChCl/acetic acid and ChCl/urea).…”

The impact of charges in force field parameterization for molecular dynamics simulations of deep eutectic solvents

“…In spite of this relevance, studies reporting computational chemistry analyses on DES properties are almost absent in the literature. Molecular dynamics studies on CH_Cl + urea (1:2) DES were reported [20][21][22][23] whereas studies for CH_Cl + magnesium chloride hexahydrate using Density Functional Theory (DFT) approach were also published [24]. Regarding the full characterization of DES, classic molecular dynamics, MD, provides a direct connection between nanoscopic features and macroscopic physicochemical properties, and thus, it would be one of the most suitable approach for DES analysis and development.…”

Green Separation of Bioactive Natural Products Using Liquefied Mixture of Solids

“…Ethaline has two interactions. The first is between the chlorine anion and the hydroxyl hydrogen atom of choline, and the second is between the anion and the hydroxyl hydrogen atoms in ethylene glycol [28]. Ethaline has a strong interaction with unreacted oil (DG, MG and FFA) and unsaponifiable matter (bioactive compounds) from crude RBO-based biodiesel due to the presence of hydroxyl groups on those compounds.…”