Solution‐State One‐ and Two‐Dimensional NMR Spectroscopy of High‐Molecular‐Weight Cellulose

Abstract

High-molecular-weight celluloses (which even include bacterial cellulose) can be dissolved fully in methyltrioctylphosphonium acetate/[D6 ]DMSO solutions to allow the measurement of resonance-overlap-free 1 D and 2 D NMR spectra. This is achieved by a simple and non-destructive dissolution method, without solvent suppression, pre-treatment or deuteration of the ionic component. We studied a range of cellulose samples by using various NMR experiments to make an a priori assignment of the cellulose resonances. Chain-end resonances are also visible in the (1) H NMR spectrum. This allows the rough determination of the degree of polymerisation (DP) of a sample for low-DP celluloses by the integration of non-reducing chain ends C1 versus polymeric cellobiose C1. Low-DP celluloses show a good agreement with the gel-permeation chromatography (GPC) values, but high-DP pulps show more deviation. For high-purity pulps (pre-hydrolysis kraft and sulfite), residual xyloses and mannoses can also be identified from the (1) H-(13) C heteronuclear single-quantum coherence (HSQC) spectra. Resonances are thus assigned for the common polymeric polysaccharides found in chemical pulps.

Crystallinity reduction and enhancement in the chemical reactivity of cellulose by non-dissolving pre-treatment with tetrabutylphosphonium acetate

“…ILs have already been well studied as novel solvents for cellulose dissolution and biomass processing (Swatloski et al 2002;Lasse et al 2013;Holding et al 2014Holding et al , 2016Holding et al , 2017. ILs are often defined as 'molten organic salts' with melting points below 100°C (Skoda-Földes 2014; Chowdhury et al 2007;Siódmiak et al 2012), whose chemical and physical properties can be tuned by varying the cations, homologous substituents and anions.…”

Efficiency of hydrophobic phosphonium ionic liquids and DMSO as recyclable cellulose dissolution and regeneration media

“…65 Proton NMR spectra of the ionic liquid before dissolution, aer dissolution of 5 wt% cellulose in 60 : 40 wt% [P 8888 ]…”

WtF‐Nano: One‐Pot Dewatering and Water‐Free Topochemical Modification of Nanocellulose in Ionic Liquids or γ‐Valerolactone

“…Therefore, we also recorded a multiplicity‐edited 1 H– 13 C heteronuclear single quantum correlation (HSQC)– NMR spectrum for the AcCNF film (Figure ). Expansion of the cellulose biopolymer region clearly shows that at least cellulose C6 and C2 and xylan C2 and C3 are acetylated, using previously reported assignments for acetylated cellulose,, and xylan, for comparison. Assignments for the acetylated xylan resonances were also performed by taking the AcCNF film and heating in [D 6 ]DMSO at 80 °C for 1 h (see the Supporting Information, S11).…”

“…The initial sample, prepared from [emim][OTf] according to sequence C/procedure 1, was dissolved in [P 4444 ][OAc]/[D 6 ]DMSO (ca. 6 wt % CNF in a 1:4 w/v solvent ratio), at 100 °C for 30 min and was introduced to a 5 mm NMR tube for analysis. The NMR measurements included 1 H, 13 C, and quantitative 13 C NMR spectroscopy, as well as two‐dimensional heteronuclear single quantum correlation (HSQC)– and diffusion‐ordered spectroscopy (DOSY), utilizing the bipolar pulse pair stimulated echo (BPPSTE), pulse sequence (see the Supporting Information, S6–S11).…”