1H NMR Analysis of cellulose in ionic liquids

1H NMR spectroscopy of cellulose in a non-deuterated polar ionic liquid (IL) was carried out to analyze specific interaction between cellulose and ILs. We applied a polar IL, 1,3-dimethylimidazolium methyl methylphosphonate, as a cellulose solvent for 1H NMR spectroscopy. To prevent vanishing of the signals of hydroxyl groups (C-OHs) by hydrogen-deuterium exchange, a non-deuterated IL was utilized, and both signals for C-OHs and backbone protons were successfully detected with the aid of the no-deuterium NMR technique and a solvent suppression technique. It was confirmed that C-OHs interacted with ILs more strongly, rather than backbone protons. Furthermore, the signals of the C-OHs at 2-, 3-, and 6-position were independently observed. A strong interaction between C-OH at the 6-position and ILs was confirmed to be a key step for dissolution of cellulose.