Mechanism of Heterogeneous Alkaline Deacetylation of Chitin: A Review

Mechanism of Heterogeneous Alkaline Deacetylation of Chitin: A Review

This review provides an analysis of experimental results on the study of alkaline heterogeneous deacetylation of chitin obtained by the authors and also published in the literature. A detailed analysis of the reaction kinetics was carried out considering the influence of numerous factors: reaction r...

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Bibliographic Details
Published in:Polymers Vol. 15; no. 7; p. 1729
Main Authors: Novikov, Vitaly Yu, Derkach, Svetlana R, Konovalova, Irina N, Dolgopyatova, Natalya V, Kuchina, Yulya A
Format: Journal Article
Language:English
Published: Switzerland MDPI AG 30-03-2023
MDPI
Subjects:
Analysis
Biopolymers
Chemical reaction, Rate of
Chitin
Chitosan
Crustaceans
deacetylation
Energy consumption
Hydration
Hydroxides
Hypotheses
Kinetics
Molecular weight
Polymers
Proteins
Reaction kinetics
reaction mechanism
Review
Netherlands
chitosan
reaction mechanism
kinetics
deacetylation
hydration
chitin
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Summary:This review provides an analysis of experimental results on the study of alkaline heterogeneous deacetylation of chitin obtained by the authors and also published in the literature. A detailed analysis of the reaction kinetics was carried out considering the influence of numerous factors: reaction reversibility, crystallinity and porosity of chitin, changes in chitin morphology during washing, alkali concentration, diffusion of hydroxide ions, and hydration of reacting particles. A mechanism for the chitin deacetylation reaction is proposed, taking into account its kinetic features in which the decisive role is assigned to the effects of hydration. It has been shown that the rate of chitin deacetylation increases with a decrease in the degree of hydration of hydroxide ions in a concentrated alkali solution. When the alkali concentration is less than the limit of complete hydration, the reaction practically does not occur. Hypotheses have been put forward to explain the decrease in the rate of the reaction in the second flat portion of the kinetic curve. The first hypothesis is the formation of "free" water, leading to the hydration of chitin molecules and a decrease in the reaction rate. The second hypothesis postulates the formation of a stable amide anion of chitosan, which prevents the nucleophilic attack of the chitin macromolecule by hydroxide ions.
Bibliography:ObjectType-Article-2
SourceType-Scholarly Journals-1
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content type line 23
ObjectType-Review-1
ISSN:2073-4360
2073-4360
DOI:10.3390/polym15071729