Theoretical study of the reaction of chitosan monomer with 2, 3-epoxypropyl-trimethyl quaternary ammonium chloride catalyzed by an imidazolium-based ionic liquid. (1st August 2016)

• Record Type: Journal Article
• Authors: Mu, Xueli; Yang, Xiaodeng; Zhang, Dongju; Liu, Chengbu
• Is Part Of: Carbohydrate polymers. Volume 146(2016)
• Page Start: 46
• Page End: 51
• Publication Date: 2016-08-01
• Subjects: Imidazolium-based ionic liquid -- Chitosan -- Catalyze -- 2, 3-Epoxypropyltrimethyl ammonium chloride -- DFT; Polysaccharides -- Periodicals; Polysaccharides -- Periodicals; Polysaccharides -- Périodiques; Electronic journals; 547.78
• DOI: 10.1016/j.carbpol.2016.03.032
• Languages: English
• ISSNs: 0144-8617

Abstract

Highlights: DFT calculations illustrate the mechanism of the graft reaction of chitosan with the epoxy compound. The polar environment of [Amim]Cl ionic liquid favors the graft reaction. The ionic liquid also serves a catalyst of the reaction to promote the ring-opening of the epoxy compound. Abstract: The molecular mechanism of the graft reaction of 2, 3-epoxypropyl-trimethyl quaternary ammonium chloride with chitosan monomer was investigated by performing density functional theory (DFT) calculations. The calculated results show that the −NH2 group of chitosan monomer is more reactive than its −OH and −CH2 OH groups, and the graft reaction on the −NH2 group is calculated to be exothermic by 20.5 kcal/mol with a free energy barrier of 42.6 kcal/mol. The reaction cannot benefit from the presence of the intruded water molecule, but can be considerably assisted by 1-allyl-3-methylimidazolium chloride ([Amim]Cl) ionic liquid. The reaction catalyzed by the ion-pair is calculated to be exothermic by 36.5 kcal/mol and the barrier is reduced to 29.3 kcal/mol, which are further corrected to 28.0 and 29.1 kcal/mol by considering the solvent effect of [Amim]Cl ionic liquid. Calculated results verified the experimental finding that imidazolium-based ionic liquids can promote the reaction of chitosan with epoxy compounds.