Ionization of Cellobiose in Aqueous Alkali and the Mechanism of Cellulose Dissolution

Cellulose, one of the most abundant renewable resources, is insoluble in most common solvents but dissolves in aqueous alkali under a narrow range of conditions. To elucidate the solubilization mechanism, we performed electrophoretic NMR on cellobiose, a subunit of cellulose, showing that cellobiose...

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Published inThe journal of physical chemistry letters Vol. 7; no. 24; pp. 5044 - 5048
Main Authors Bialik, Erik, Stenqvist, Björn, Fang, Yuan, Östlund, Åsa, Furó, István, Lindman, Björn, Lund, Mikael, Bernin, Diana
Format Journal Article
LanguageEnglish
Published United States American Chemical Society 15.12.2016
Subjects
Anhydroglucose unit
binding
Cellulose
Cellulose chain
Cellulose Derivatives
Cellulose dissolutions
charge
Chemical Sciences
Chemical shift
chemical-shifts
Common solvents
complexes
Deprotonation
Dissociation
Dissolution
Electrophoresis
electrophoretic nmr
Fysikalisk kemi
Hemiacetals
hydroxides
Kemi
MD simulation
mixtures
Natural Sciences
Naturvetenskap
Nuclear magnetic resonance spectroscopy
Physical Chemistry
Renewable resource
Renewable Resources
Solubility
Solvents
state
Sustainable materials
Synthesis
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Summary:Cellulose, one of the most abundant renewable resources, is insoluble in most common solvents but dissolves in aqueous alkali under a narrow range of conditions. To elucidate the solubilization mechanism, we performed electrophoretic NMR on cellobiose, a subunit of cellulose, showing that cellobiose acts as an acid with two dissociation steps at pH 12 and 13.5. Chemical shift differences between cellobiose in NaOH and NaCl were estimated using 2D NMR and compared to DFT shift differences upon deprotonation. The dissociation steps are the deprotonation of the hemiacetal OH group and the deprotonation of one of four OH groups on the nonreducing anhydroglucose unit. MD simulations reveal that aggregation is suppressed upon charging cellulose chains in solution. Our findings strongly suggest that cellulose is to a large extent charged in concentrated aqueous alkali, a seemingly crucial factor for solubilization. This insight, overlooked in the current literature, is important for understanding cellulose dissolution and for synthesis of new sustainable materials.
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ISSN:1948-7185
1948-7185
DOI:10.1021/acs.jpclett.6b02346