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On the Electronic Structure Origin of Mechanochemically Induced Selectivity in Acid-Catalyzed Chitin Hydrolysis

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Title: On the Electronic Structure Origin of Mechanochemically Induced Selectivity in Acid-Catalyzed Chitin Hydrolysis
Authors: De Chavez, Danjo Browse this author
Kobayashi, Hirokazu Browse this author →KAKEN DB
Fukuoka, Atsushi Browse this author →KAKEN DB
Hasegawa, Jun-ya Browse this author →KAKEN DB
Issue Date: 14-Jan-2021
Publisher: American Chemical Society
Journal Title: The Journal of Physical Chemistry A
Volume: 125
Issue: 1
Start Page: 187
End Page: 197
Publisher DOI: 10.1021/acs.jpca.0c09030
Abstract: Recently, mechanical ball milling was applied to chitin depolymerization. The mechanical activation afforded higher selectivity toward glycosidic bond cleavage over amide bond breakage. Hence, the bioactive N-acetylglucosamine (GlcNAc) monomer was preferentially produced over glucosamine. In this regard, the force-dependent mechanochemical activation-deactivation process in the relaxed and pulled GlcNAc dimer undergoing deacetylation and depolymerization reactions was studied. For the relaxed case, the activation energies of the rate-determining steps (RDS) proved that the two reactions could occur simultaneously. Mechanical forces associated with ball milling were approximated with linear pulling and were introduced explicitly in the RDS of both reactions through force-modified potential energy surface (FMPES) formalism. In general, as the applied pulling force increases, the activation energy of the RDS of deacetylation shows no meaningful change, while that of depolymerization decreases. This result is consistent with the selectivity exhibited in the experiment. Energy and structural analyses for the depolymerization showed that the activation can be attributed to a significant change in the glycosidic dihedral at the reactant state. A lone pair of the neighboring pyranose ring O adopts a syn-periplanar conformation relative to the glycosidic bond. This promotes electron donation to the sigma*-orbital of the glycosidic bond, leading to activation. Consequently, the Bronsted-Lowry basicity of the glycosidic oxygen also increases, which can facilitate acid catalysis.
Rights: This document is the Accepted Manuscript version of a Published Work that appeared in final form in [The Journal of Physical Chemistry A], copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see
Type: article (author version)
Appears in Collections:触媒科学研究所 (Institute for Catalysis) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

Submitter: 長谷川 淳也

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