New natural deep eutectic solvents based on aromatic organic acids

Abstract

It is imminent to explore new types of starting materials for natural deep eutectic solvents (NADESs). Herein, a series of natural aromatic organic acids as the hydrogen bond donor (HBD) and coumarin as the model hydrogen bond acceptor (HBA) were used to design and prepare NADESs. They are characterized by nuclear magnetic resonance (NMR) and attenuated total reflection flourier transformed infrared spectroscopy (ATR-FTIR), supported by quantum chemistry (QC) calculations. The liquid phase of the mixture is attributed to the non-ideal behavior of both components at most of the ratios. In addition, — ${\rm \Delta }E$ presented the energy dynamic equilibrium of eutectic systems. Using solid–liquid phase diagrams and mean interaction energies obtained by the conductor like screening model for real solvent model (COSMO-RS), the predicting formability of DESs can be achieved by choosing the proper HBAs and HBDs. Finally, five green solvents, including mandelic acid-coumarin, salicylic acid-coumarin, benzoic acid-coumarin, hydroxybenzoic acid-coumarin, and cinnamic acid-coumarin, were obtained. Thus, the aromatic organic acid studied in this work is vital for the development of novel green eutectic systems.

Keywords

• green solvent
• aromatic organic acid
• physicochemical property
• non-covalent interaction