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Related Concept Videos

Cationic Chain-Growth Polymerization: Mechanism00:57

Cationic Chain-Growth Polymerization: Mechanism

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The cationic polymerization mechanism consists of three steps: initiation, propagation, and termination. In the initiation step of the polymerization process, the π bond of a monomer gets protonated by the Lewis acid catalyst, which is formed from boron trifluoride and water. The protonation of the π bond generates a carbocation stabilized by the electron‐donating group. In the propagation step, the π bond of the second monomer acts as a nucleophile and attacks the...
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Anionic Chain-Growth Polymerization: Mechanism01:04

Anionic Chain-Growth Polymerization: Mechanism

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The mechanism for anionic chain-growth polymerization involves initiation, propagation, and termination steps. In the initiation step, a nucleophilic anion, such as butyl lithium, initiates the polymerization process by attacking the π bond of the vinylic monomer. As a result, a carbanion, stabilized by the electron‐withdrawing group, is generated. The resulting carbanion acts as a Michael donor in the propagation step and attacks the second vinylic monomer, which acts as a Michael...
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Complexation Equilibria: The Chelate Effect01:19

Complexation Equilibria: The Chelate Effect

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In complexation reactions, metal atoms or cations interact with ligands to form donor-acceptor adducts called metal complexes. Ligands that bind through one donor site are monodentate, ligands with two donor sites are bidentate, and those with more than two donor sites are polydentate ligands. For example, ethylene diamine is a bidentate ligand that binds through two nitrogen donor atoms, forming a five-membered ring. EDTA is a polydentate ligand that binds through four oxygen and two nitrogen...
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Ziegler–Natta Chain-Growth Polymerization: Overview01:17

Ziegler–Natta Chain-Growth Polymerization: Overview

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Ziegler–Natta polymerization is another form of addition or chain‐growth polymerization used for synthesizing linear polymers over branched polymers. The catalyst used for polymerization is the Ziegler–Natta catalyst, named after Karl Ziegler and Giulio Natta, who developed it in 1953. This catalyst is an organometallic complex of titanium tetrachloride and triethyl aluminum, with the active form of the catalyst being an alkyl titanium compound. Using the Ziegler–Natta...
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Regioselectivity and Stereochemistry of Acid-Catalyzed Hydration02:34

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The rate of acid-catalyzed hydration of alkenes depends on the alkene's structure, as the presence of alkyl substituents at the double bond can significantly influence the rate.
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Radical Chain-Growth Polymerization: Mechanism01:09

Radical Chain-Growth Polymerization: Mechanism

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The radical chain-growth polymerization mechanism consists of three steps: initiation, propagation, and termination of polymerization. The polymerization initiates when a free radical generated from the radical initiator adds to the unsaturated bond in the monomer. The unpaired electron of the free radical and one π electron in the unsaturated bond creates a σ bond between the free radical and the monomer. As a result, the other π electron in the unsaturated bond converts this species into...
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Preparation of Expanded Chitin Foams and their Use in the Removal of Aqueous Copper
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Mechanistic insights into controlled depolymerization of Chitosan using H-Mordenite.

A Pandit1, C Deshpande1, S Patil1

  • 1Department of Chemical Engineering, Institute of Chemical Technology, Matunga, Mumbai-19, India.

Carbohydrate Polymers
|January 1, 2020
PubMed
Summary

The addition of H-Mordenite (H-MOR) to acetic acid solutions facilitates controlled chitosan depolymerization. This process reduces impurities like 5-Hydroxy Methyl Furfural (5-HMF) and glucosamine, yielding desired molecular weights.

Keywords:
ChitosanDepolymerizationH-MordeniteReaction kineticsSolid acid

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Area of Science:

  • Materials Science
  • Chemical Engineering
  • Polymer Chemistry

Background:

  • Chitosan, a biopolymer, undergoes depolymerization in acidic conditions.
  • Controlling chitosan depolymerization is crucial for obtaining specific molecular weights and reducing byproducts.
  • H-Mordenite (H-MOR) is an acidic zeolite with potential catalytic properties.

Purpose of the Study:

  • To investigate the kinetics of chitosan depolymerization in dilute acetic acid.
  • To evaluate the effect of H-Mordenite (H-MOR) on chitosan depolymerization rate and mechanism.
  • To assess the impact of H-MOR on the formation of impurities such as 5-Hydroxy Methyl Furfural (5-HMF) and glucosamine.

Main Methods:

  • Chitosan depolymerization kinetics were studied in dilute acetic acid with varying concentrations of H-Mordenite (H-MOR).
  • Molecular weight changes were measured using Gel Permeation Chromatography (GPC).
  • Adsorption studies, Infra-red spectroscopy, and rheological assessments were employed to understand the interaction between chitosan and H-MOR.

Main Results:

  • H-Mordenite (H-MOR) altered the depolymerization rate of chitosan.
  • The energy of activation for depolymerization increased slightly from 20.54 kJ/mol to 23.25 kJ/mol with maximum H-MOR concentration.
  • Spectroscopic and adsorption data suggested chitosan adsorption/grafting onto the H-MOR surface facilitated depolymerization.
  • H-MOR significantly reduced 5-Hydroxy Methyl Furfural (5-HMF) formation by three-fold and glucosamine content by over ten times.

Conclusions:

  • H-Mordenite (H-MOR) plays a crucial role in the controlled cleavage of chitosan.
  • The presence of H-MOR enables the production of chitosan with desired molecular weights and reduced impurities.
  • The mechanism involves the adsorption and grafting of chitosan onto the porous H-MOR surface.