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

Abstract

Molten salt hydrates proved to be alternative solvents to cellulose. Toinvestigate the reasons for this dissolving ability, information about thesolvent–cellulose interactions is essential. As well as ¹³CHR NMR, ⁷Li NMR was used to obtain further insight into thisproblem.After comparing several molten salt hydrates, the ⁷Li NMR spectrarevealed a smaller shielding of the lithium cation for not dissolving than fordissolving and swelling cellulose systems. In most solvent systems theshieldingat the ⁷Li nuclei increases with the cellulose concentration. 2D⁷Li-¹H HOESY NMR was successfully applied to verify thepresence of cellobiose, used as a model compound for cellulose, in the firstco-ordination sphere of the lithium cation.