Theoretical study of the reaction of chitosan monomer with 2,3-epoxypropyl-trimethyl quaternary ammonium chloride catalyzed by an imidazolium-based ionic liquid.
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 -CH2OH groups, and the graft reaction on the -NH2 group is calculated to be exothermic by 20.5kcal/mol with a free energy barrier of 42.6kcal/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 36.5kcal/mol and the barrier is reduced to 29.3kcal/mol, which are further corrected to 28.0 and 29.1kcal/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.
Key Lab of Colloid and Interface Chemistry, Ministry of Education, Institute of Theoretical Chemistry, Shandong University, Jinan 250100, PR China.
Xueli
X
Mu
Key Laboratory of Fine Chemicals (Shandong Provence), Qilu University of Technology, Jinan 250553, PR China.
Xiaodeng
X
Yang
Key Lab of Colloid and Interface Chemistry, Ministry of Education, Institute of Theoretical Chemistry, Shandong University, Jinan 250100, PR China. Electronic address: zhangdj@sdu.edu.cn.
Dongju
D
Zhang
Key Lab of Colloid and Interface Chemistry, Ministry of Education, Institute of Theoretical Chemistry, Shandong University, Jinan 250100, PR China. Electronic address: cbliu@sdu.edu.cn.
Chengbu
C
Liu
D000498:Allyl Compounds / Q000737:chemistry; D000643:Ammonium Chloride / Q000737:chemistry*; D048271:Chitosan / Q000737:chemistry*; D007093:Imidazoles / Q000737:chemistry; D052578:Ionic Liquids / Q000737:chemistry*; D008956:Models, Chemical
C544334:1-allyl-3-methylimidazolium; D000498:Allyl Compounds; D007093:Imidazoles; D052578:Ionic Liquids; D000643:Ammonium Chloride; D048271:Chitosan
2,3-Epoxypropyltrimethyl ammonium chloride; Catalyze; Chitosan; DFT; Imidazolium-based ionic liquid