Li-7 NMR as probe for solvent-cellulose interactions in cellulose dissolution

Molten salt hydrates proved to be alternative solvents to cellulose. To investigate the reasons for this dissolving ability, information about the solvent-cellulose interactions is essential. As well as C-13 HR NMR, Li-7 NMR was used to obtain further insight into this problem. After comparing several molten salt hydrates, the Li-7 NMR spectra revealed a smaller shielding of the lithium cation for not dissolving than for dissolving and swelling cellulose systems. In most solvent systems the shielding at the Li-7 nuclei increases with the cellulose concentration. 2D Li-7-H-1 HOESY NMR was successfully applied to verify the presence of cellobiose, used as a model compound for cellulose, in the first co-ordination sphere of the lithium cation.