Modification of Chitosan by Zincke Reaction: Synthesis of a Novel Polycationic Chitosan-Pyridinium Derivative

Abstract

Chitosan is a biodegradable aminopolysaccharide produced by deacetylation of acetamide groups of chitin, one of the most abundant organic materials in nature. Many different types of organic reactions have been described to modify the functional groups of chitosan and produce materials with applications in a large number of areas. However, the Zincke reaction, an old method which is commonly used to convert primary amine in pyridinium salts, has not been reported to transform the chitosan amino group at C-2 position in glucosamine units. In this paper, our efforts are described to carry out this reaction, employing different conditions to covalently anchor pyridinium salts on the polymer surface. Optimized synthesis conditions using water/ethanol as solvent, triethylamine and Zincke salt excess yielded a novel polycationic chitosan-pyridinium derivative with a weight gain of 52% after 48 h of reaction. The modified biopolymer is water insoluble and exhibits a high degree of chemical modification. The 13 C solid state nuclear magnetic resonance (SS-NMR) spectrum of chitosan-pyridinium derivative showed signals at 147.0, 142.0 and 129.0 ppm, attributed to aromatic carbons, confirming the presence of a quaternary pyridinium ring directly attached to the biopolymer. The Zincke reaction was employed for the first time to modify the chitosan backbone.

Exploring the Antimicrobial and Antitumoral Activities of Naphthoquinone-Grafted Chitosans

“…The naphthoquinone-grafted CS were prepared employing three different reaction conditions to evaluate final polymer formation. Inspired by Freitas (2019) [ 33 ], the first approach was evaluated using ethanol and water as solvent (EtOH:H 2 O method), whereas the second method was inspired by Greco et al (2015) [ 34 ], employing triethylamine as base (EtOH:H 2 O + Et 3 N method). In order to improve CS solubility, a third approach was tested by using dimethylformamide as solvent (DMF method).…”

Ionic Liquid Functionalized Chitosan Catalyst with Optimized Hydrophilic/Hydrophobic Structural Balance for Efficient CO2 Fixation

“…Chitosan shows four prominent peaks at 106.4, 85.1, 61.9, and 58.4 ppm characteristics to C1, C4, C6, and C2 carbon of pyranose ring, respectively in the 13 C NMR spectrum (Supporting Information, Figure S2). The peak at 77 ppm is assigned to the C5 and C3 carbon of the ring [37] . Pyridine modified chitosan shows four additional peaks in the aromatic region at 164.5, 151, 144.4, and 124.1 ppm corresponding to C7 carbon atom of imine bond, C10, C8, and C9 carbon atoms of the pyridine ring, respectively (Supporting Information, Figure S3).…”

“…The (020) plane at 2θ = 10.3°is assigned to the crystal plane which is parallel to the chitosan fiber and perpendicular to the glucosamine ring. 37 The observed shift in the 2θ value corresponding to (020) plane to the lower angle suggests the increase in the distance between the two fibres of chitosan. This can be explained as the attached pyridine ring on the side chain occupies the space between two fibres resulting in the increased distance between the (020) planes.…”

“…The peak at 77 ppm is assigned to the C5 and C3 carbon of the ring. [37] Pyridine modified chitosan shows four additional peaks in the aromatic region at 164.5, 151, 144.4, and 124.1 ppm corresponding to C7 carbon atom of imine bond, C10, C8, and C9 carbon atoms of the pyridine ring, respectively (Supporting Information, Figure S3). The 13 C NMR spectrum of IL-CS-8, shows peaks corresponding to the pyranose ring, pyridine ring and additional peaks in the aliphatic region (Supporting Information, Figure S4).…”

Growth of complex crystal on biopolymer surface: Synthesis and characterization

“…Chitosan is a carbohydrate biopolymer classified as a semi-crystalline cationic copolymer composed of two monomeric β (1→4) linked units of N-acetyl-D-glucosamine and D-glucosamine. 8 The application of this polymer is wide, such as in agriculture, 9 biomedicine, 10 chemistry 11 and food products 12 among others. The capacity of this biopolymer is most evident associated with other materials, such as in polymer blends and metal ions, to promote synergistic properties.…”