Applications of Ionic Liquids in Carbohydrate Chemistry:  A Window of Opportunities

Abstract

Ionic liquids (ILs) are composed only of ions. Of special interest to this review are those where at least one ion (the cation) is organic and whose melting points are below or not far above room temperature. ILs are designated as "green" solvents because they have extremely low vapor pressure, are non-inflammable, and thermally and chemically stable. Therefore, many of them can be, in principle, recycled into the process indefinitely. The objective of the present review is to discuss different aspects of the use of ILs in carbohydrate chemistry, in particular, dissolution and functionalization of simple sugars, cyclodextrins, cellulose, starch, and chitin/chitosan. The molecular structure and synthesis of ILs most frequently employed in carbohydrate chemistry are discussed with an emphasis on imidazolium and pyridinium cations with different counterions. The physicochemical properties of ILs that are relevant to the dissolution and functionalization of carbohydrates, in particular their polarities and hydrogen-bonding abilities, are discussed. Dissolution of simple saccharides and biopolymers in ILs is presented with an emphasis on the mechanism of carbohydrate--IL interactions. Finally, the very interesting novel applications of the solutions obtained are addressed. These include, inter alia, spinning of the dissolved biopolymer into fibers, extrusion into slabs and rods, formation of matrixes for a myriad of substrates, including biomacromolecules, formation of nanocomposites, and functionalization to produce important derivatives. The use of ILs in many branches of science is expanding fast; it is hoped that this review will draw the attention of researchers to the "window of opportunities" that these green solvents open into carbohydrate chemistry.

Ionic liquids as coagents for sulfur vulcanization of butadiene–styrene elastomer filled with carbon black

“…The large size and conformational flexibility of the ILs ions lead to small lattice enthalpies and large entropy changes [2,3]. Therefore, the liquid state of ILs is thermodynamically favorable.…”

Effect of Ionic Liquids on Oil Palm Biomass Fiber Dissolution

“…As for 1-butyl-3-methylimidazolium chloride ([bmim][Cl]), Remsing et al (2006) and Moulthrop et al (2005) have reported that the chloride anion is much more involved than the cation in the disruption of the hydrogen bond system (18 to 25 wt.%) and the solubilization of the chains. The postulated Cl-OH-cellulose interaction is comparable to the structure discussed for the cellulose/DMAc/LiCl system, but it should be more efficient because the anion is free due to its looser binding with the large asymmetric cation (El Seoud et al 2007).…”

Applications of Ionic Liquids for the Development of Optical Chemical Sensors and Biosensors

“…Cellulose, a biocompatible, biodegradable, nontoxic, and inexpensive natural material, is well soluble in [BMIm]Cl and other ILs with melting points below 100 C. 100 Theoretical aspects of the interaction of cellulose and some cellulose-based materials with ILs have been discussed in previous reviews. [29][30][31][32]101 The solubility of cellulose in ILs depends on the origin, extent of polymerization, temperature of the dissolution, and water content in the system, in particular. [30][31][32]102 Cellulose can be regenerated from the cellulose-IL solutions in a variety of forms (films, fibers, beads, sponges, etc.)…”

“…ILs can dissolve inorganic gases (O2, CO2, CO, SO2, NO2, H2S, etc. ), 24,27 silicon alkoxides (tetramethoxysilane, TMOS; tetraethoxysilane, TEOS; methyltrimethoxysilane, MTMOS), 28 mono-and polysaccharides (carbohydrates, starch, cellulose, chitin, chitosan, guar gum, and xanthan gum), 10,[29][30][31][32] natural organic materials (silk 17 and wood 29,33,34 ), some synthetic polymers, 35,36 enzymes, [37][38][39] etc. The listed substances can serve either as matrix materials (natural and synthetic polymers) or recognition elements (dyes, complexes, and biocatalysts), and target compounds (gases) for optical sensing platforms.…”