New insight into experimental and computational studies of Choline chloride-based ‘green’ ternary deep eutectic solvent (TDES)

Abstract

In this study, we have examined the influence of ternary component (n-butanol, iso-butanol, and butandiol) as hydrogen bond donor (HBD) on binary Deep eutectic solvents (BDES) as hydrogen bond acceptor (HBA) which is composed of Choline chloride (ChCl) and Malonic acid (MA) in equimolar ratio (1:1) also called as maline to understand the hydrogen bonding interactions involved therein. The physicochemical properties of such as density, sound velocity, refractive index, conductivity, and viscosity of maline and TDES were evaluated at 303.15 K. Fourier-transform infrared spectroscopy (FT-IR) validated the molecular structures of the components and the involvement of extensive hydrogen bonding. Here the combination of maline (ChCl: MA) with the mentioned alcohols was simulated using Gauss View 5.0.9 package. Study showed that maline and butandiol exhibited a well-established and high relative hydrogen bond networks between them leading to a larger melting point depression in comparison to n-butanol and iso-butanol. Such a response could be related to the stable homogeneous system formed by butandiol and not by n-butanol and iso-butanol. These findings are further supported and significantly validated by the evaluation of Total energy (T.E) which accounts for the involvement of molecular orbitals. Additionally, the 3D-molecular electrostatic potential (3D-MEP) description was performed to predict the coordination of electrophilic and nucleophilic sites between the HBA and HBD.