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 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.

Subject headings

NATURVETENSKAP  -- Kemi -- Fysikalisk kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences -- Physical Chemistry (hsv//eng)

NATURVETENSKAP  -- Kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences (hsv//eng)

Keyword

Chemical shift

Deprotonation

Dissociation

Dissolution

Nuclear magnetic resonance spectroscopy

Solubility

Anhydroglucose unit

Cellulose chain

Cellulose dissolutions

Common solvents

Hemiacetals

MD simulation

Renewable resource

Sustainable materials

Cellulose

Cellulose Derivatives

Electrophoresis

Renewable Resources

Solvents

Synthesis

electrophoretic nmr

chemical-shifts

solvents

charge

hydroxides

complexes

mixtures

binding

state

Publication and Content Type

ref (subject category)

art (subject category)