Unexpected selective alkaline periodate oxidation of chitin for the isolation of chitin nanocrystals

• Published in: Green chemistry : an international journal and green chemistry resource : GC 2021-02, Vol.23 (2), p.745-751
• Main Authors: Liu, Peiwen, Liu, Huan, Schäfer, Timmy, Gutmann, Torsten, Gibhardt, Holger, Qi, Houjuan, Tian, Lin, Zhang, Xizhou Cecily, Buntkowsky, Gerd, Zhang, Kai
• Format: Article
• Language: English
• Subjects: Chitin; Crystals; Deacetylation; Green chemistry; Nanocrystals; Oxidation; Polysaccharides
• ISSN: 1463-9262; 1463-9270
• DOI: 10.1039/d0gc04054a

Periodate oxidation reaction occurring directly on chitin has been neglected in polysaccharide chemistry so far. Herein, we present the first direct alkaline periodate oxidation of chitin, which demonstrates at the same time a novel approach for the preparation of chitin nanocrystals (ChNCs). This oxidation is based on an unprecedented selective reaction of non-ordered domains of chitin by the dimeric orthoperiodate ions (H 2 I 2 O 10 4− ) as the major species in alkaline surroundings. Nearly 50 wt% of non-ordered regions are dissolved after sequential accelerated partial deacetylation, periodate oxidation and β-alkoxy fragmentation, which allows the isolation of up to 50 wt% of uniform anisotropic zwitterionic ChNCs. No periodate oxidation on chitin? For the first time, direct selective alkaline periodate oxidation of chitin led to the isolation of ordered domains as uniform anisotropic and zwitterionic ChNCs after simultaneous removal of non-ordered domains.