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Selected Publication:

Hosoya, T; Sakaki, S.
(2013): Levoglucosan Formation from Crystalline Cellulose: Importance of a Hydrogen Bonding Network in the Reaction
CHEMSUSCHEM. 2013; 6(12): 2356-2368. FullText FullText_BOKU

Levoglucosan (1,6-anhydro--D-glucopyranose) formation by the thermal degradation of native cellulose was investigated by MP4(SDQ)//DFT(B3LYP) and DFT(M06-2X)//DFT(B3LYP) level computations. The computational results of dimer models lead to the conclusion that the degradation occurs by a concerted mechanism similar to the degradation of methyl -D-glucoside reported in our previous study. One-chain models of glucose hexamer, in which the interchain hydrogen bonds of real cellulose crystals are absent, do not exhibit the correct reaction behavior of levoglucosan formation; for instance, the activation enthalpy (E-a=approximate to 38kcalmol(-1)) is considerably underestimated compared to the experimental value (48-60kcalmol(-1)). This problem is solved with the use of two-chain models that contain interchain hydrogen bonds. The theoretical study of this model clearly shows that the degradation of the internal glucosyl residue leads to the formation of a levoglucosan precursor at the chain end and levoglucosan is selectively formed from this levoglucosan end. The calculated E-a (56-62kcalmol(-1)) agrees well with the experimental value. The computational results of three-chain models indicate that this degradation occurs selectively on the crystalline surface. All these computational results provide a comprehensive understanding of several experimental facts, the mechanisms of which have not yet been elucidated.
Authors BOKU Wien:
Hosoya Takashi

Find related publications in this database (Keywords)
chain structures
conformation analysis
density functional calculations
hydrogen bonds

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