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Chitin Deacetylation Using Deep Eutectic Solvents: Ab Initio-Supported Process Optimization

[Image: see text] Chitin is the most abundant marine biopolymer, being recovered during the shell biorefining of crustacean shell waste. In its native form, chitin displays a poor reactivity and solubility in most solvents due to its extensive hydrogen bonding. This can be overcome by deacetylation....

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Autores principales: Vicente, Filipa A., Huš, Matej, Likozar, Blaž, Novak, Uroš
Formato: Online Artículo Texto
Lenguaje:English
Publicado: American Chemical Society 2021
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8025712/
https://www.ncbi.nlm.nih.gov/pubmed/33842102
http://dx.doi.org/10.1021/acssuschemeng.0c08976
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author Vicente, Filipa A.
Huš, Matej
Likozar, Blaž
Novak, Uroš
author_facet Vicente, Filipa A.
Huš, Matej
Likozar, Blaž
Novak, Uroš
author_sort Vicente, Filipa A.
collection PubMed
description [Image: see text] Chitin is the most abundant marine biopolymer, being recovered during the shell biorefining of crustacean shell waste. In its native form, chitin displays a poor reactivity and solubility in most solvents due to its extensive hydrogen bonding. This can be overcome by deacetylation. However, this process requires a high concentration of acids or bases at high temperatures, forming large amounts of toxic waste. Herein, we report on the first deacetylation with deep eutectic solvents (DESs) as an environmentally friendly alternative, requiring only mild reaction conditions. Biocompatible DESs are efficient in disturbing the native hydrogen-bonding network of chitin, readily dissolving it. First, quantum chemical calculations have been performed to evaluate the feasibility of different DESs to perform chitin deacetylation by studying their mechanism. Comparing these with the calculated barriers for garden-variety alkaline/acidic hydrolysis, which are known to proceed, prospective DESs were identified with barriers around 25 kcal·mol(–1) or lower. Based on density functional theory results, an experimental screening of 10 distinct DESs for chitin deacetylation followed. The most promising DESs were identified as K(2)CO(3):glycerol (K(2)CO(3):G), choline chloride:acetic acid ([Ch]Cl:AA), and choline chloride:malic acid ([Ch]Cl:MA) and were subjected to further optimization with respect to the water content, process duration, and temperature. Ultimately, [Ch]Cl:MA showed the best results, yielding a degree of deacetylation (DDA) of 40% after 24 h of reaction at 120 °C, which falls slightly behind the threshold value (50%) for chitin to be considered chitosan. Further quantum chemical calculations were performed to elucidate the mechanism. Upon the removal of 40% N-acetyl groups from the chitin structure, its reactivity was considerably improved.
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spelling pubmed-80257122021-04-08 Chitin Deacetylation Using Deep Eutectic Solvents: Ab Initio-Supported Process Optimization Vicente, Filipa A. Huš, Matej Likozar, Blaž Novak, Uroš ACS Sustain Chem Eng [Image: see text] Chitin is the most abundant marine biopolymer, being recovered during the shell biorefining of crustacean shell waste. In its native form, chitin displays a poor reactivity and solubility in most solvents due to its extensive hydrogen bonding. This can be overcome by deacetylation. However, this process requires a high concentration of acids or bases at high temperatures, forming large amounts of toxic waste. Herein, we report on the first deacetylation with deep eutectic solvents (DESs) as an environmentally friendly alternative, requiring only mild reaction conditions. Biocompatible DESs are efficient in disturbing the native hydrogen-bonding network of chitin, readily dissolving it. First, quantum chemical calculations have been performed to evaluate the feasibility of different DESs to perform chitin deacetylation by studying their mechanism. Comparing these with the calculated barriers for garden-variety alkaline/acidic hydrolysis, which are known to proceed, prospective DESs were identified with barriers around 25 kcal·mol(–1) or lower. Based on density functional theory results, an experimental screening of 10 distinct DESs for chitin deacetylation followed. The most promising DESs were identified as K(2)CO(3):glycerol (K(2)CO(3):G), choline chloride:acetic acid ([Ch]Cl:AA), and choline chloride:malic acid ([Ch]Cl:MA) and were subjected to further optimization with respect to the water content, process duration, and temperature. Ultimately, [Ch]Cl:MA showed the best results, yielding a degree of deacetylation (DDA) of 40% after 24 h of reaction at 120 °C, which falls slightly behind the threshold value (50%) for chitin to be considered chitosan. Further quantum chemical calculations were performed to elucidate the mechanism. Upon the removal of 40% N-acetyl groups from the chitin structure, its reactivity was considerably improved. American Chemical Society 2021-03-05 2021-03-15 /pmc/articles/PMC8025712/ /pubmed/33842102 http://dx.doi.org/10.1021/acssuschemeng.0c08976 Text en © 2021 The Authors. Published by American Chemical Society Permits the broadest form of re-use including for commercial purposes, provided that author attribution and integrity are maintained (https://creativecommons.org/licenses/by/4.0/).
spellingShingle Vicente, Filipa A.
Huš, Matej
Likozar, Blaž
Novak, Uroš
Chitin Deacetylation Using Deep Eutectic Solvents: Ab Initio-Supported Process Optimization
title Chitin Deacetylation Using Deep Eutectic Solvents: Ab Initio-Supported Process Optimization
title_full Chitin Deacetylation Using Deep Eutectic Solvents: Ab Initio-Supported Process Optimization
title_fullStr Chitin Deacetylation Using Deep Eutectic Solvents: Ab Initio-Supported Process Optimization
title_full_unstemmed Chitin Deacetylation Using Deep Eutectic Solvents: Ab Initio-Supported Process Optimization
title_short Chitin Deacetylation Using Deep Eutectic Solvents: Ab Initio-Supported Process Optimization
title_sort chitin deacetylation using deep eutectic solvents: ab initio-supported process optimization
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8025712/
https://www.ncbi.nlm.nih.gov/pubmed/33842102
http://dx.doi.org/10.1021/acssuschemeng.0c08976
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