Acylation and carbanilation of cellulose in ionic liquids

Abstract

Ionic liquids (ILs) namely 1-N-butyl-3-methylimidazolium chloride ([C₄mim]⁺Cl⁻), 1-N-ethyl-3-methylimidazolium chloride ([C₂mim]⁺Cl⁻), 1-N-butyldimethylimidazolium chloride ([C₄dmim]⁺Cl⁻) and 1-N-allyl-2,3-dimethylimidazolium bromide ([Admim]⁺Br⁻) were investigated as solvent for the homogeneous acylation and carbanilation of the biopolymer cellulose. Cellulose acetates with a degree of substitution (DS) in the range from 2.5 to 3.0 are accessible within 2 h at 80 °C in a complete homogeneous procedure. The acylation of cellulose with the fatty acid chloride lauroyl chloride leads to cellulose laurates with DS from 0.34 to 1.54. The reaction starts homogeneously and continues heterogeneously. The synthesis of cellulose carbanilates succeeds in the ionic liquid [C₄mim]⁺Cl⁻ without any catalyst. The new homogeneous path gives pure cellulose carbanilates. All reactions are carried out under mild conditions, low excess of reagent and a short reaction time. The reaction media applied can be easily recycled and reused.