Ionic Liquids as Reaction Medium in Cellulose Functionalization

Abstract Summary: The application of different ionic liquids (IL), namely 1‐N‐butyl‐3‐methylimidazolium chloride ([C4mim]+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 [C4mim]+Cl−, no degradation of the polymer appears. By 13C NMR measurement it was confirmed that this IL is a so‐called non‐derivatizing solvent. [C4mim]+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. 13C NMR spectrum of cellulose dissolved in the IL [C4mim]+Cl− (top). The 13C NMR spectrum of cellulose dissolved in DMSO/tetrabutylammonium fluoride trihydrate is shown for comparison (bottom). magnified image 13C NMR spectrum of cellulose dissolved in the IL [C4mim]+Cl− (top). The 13C NMR spectrum of cellulose dissolved in DMSO/tetrabutylammonium fluoride trihydrate is shown for comparison (bottom).