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The application of different ionic liquids (IL), namely 1-N-butyl-3-methylimidazolium chloride ([C(4)mim](+)Cl(-)), 3-methyl-N-butyl-pyridinium chloride and benzyldimethyl(tetradecyl)ammonium chloride were investigated as solvents for cellulose. The ILs used have the ability to dissolve cellulose with a degree of polymerization in the range from 290 to 1 200 to a very high concentration. Using [C(4)mim](+)Cl(-), no degradation of the polymer appears. By (13)C NMR measurement it was confirmed that this IL is a so-called non-derivatizing solvent. [C(4)mim](+)Cl(-) can be applied as a reaction medium for the synthesis of carboxymethyl cellulose and cellulose acetate. Without using any catalyst, cellulose derivatives with high degree of substitution could be prepared.(13)C NMR spectrum of cellulose dissolved in the IL [C(4)mim](+)Cl(-) (top). The (13)C NMR spectrum of cellulose dissolved in DMSO/tetrabutylammonium fluoride trihydrate is shown for comparison (bottom).

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.