Glycerol eutectics as sustainable solvent systems

Physicochemical properties of betaine monohydrate-carboxylic acid mixtures

“…In this work, if the molar ratio of salt to acid decrease thus the hydrogen bonding ability also increased and thus leading to increase in the polarity (or decrease in polarity scale). Similar result also reported by Abbot et al [14] that the polarity scale E T (30) (using Reichardt's dye) of choline chloride-glycerol DES decrease with an increase in glycerol concentration. The viscosity of betaine monohydrate-carboxylic acid mixtures in the range of 6.4-73 cSt at a temperature of 40°C (Figure 1b).…”

“…However, viscosity of the mixture tends to similar with decrease in the mole ratio of salt to acid. The high viscosity of DES is often attributed to the presence of an extensive hydrogen bond network between salt and hydrogen bond donor which causing the lack of free volume within the DES [14]. The betaine monohydrate-propionic acid mixture has greater stability than betaine monohydrate-acetic acid mixture at the eutectic composition [10].…”

Low melting mixtures in organic synthesis – an alternative to ionic liquids?

“…7 A DES is defined as a mixture of hydrogen bond donor (HBD) systems with simple halide salts which produce liquids. 8 Their physicochemical properties resemble those of ionic liquids. Abbott's fundamental work inspired other researchers to exploit the unusual properties of this system.…”

“…In the last few years, different (uncharged) hydrogen bond donors of natural and synthetic origin were used in combination with choline chloride. [8][9][10][11][12] As in the case of ILs, the melting point of the mixtures is not predictable, but some general trends can be derived. Abbott hypothesised that the melting point depression is caused by charge delocalisation due to hydrogen bonding between the halide anion and the hydrogen bond donor.…”

“…7 The preparation of deep eutectic solvents is very simple: the mixed components are stirred under heating (∼80°C) until a homogeneous, clear liquid has been formed. 8,12 A subtype of DES are metal-based eutectics made from metal salts like ZnCl 2 , FeCl 3 , SnCl 2 , AlCl 3 , and simple organic alcohols or amides as HBDs. 13,14 The donor molecule serves as a complexing agent and coordinates to the cation.…”