title: Theoretical studies on the dissolution of chitosan in 1-butyl-3-methylimidazolium acetate ionic liquid.
abstract: In this work, the dissolution mechanism of chitosan in imidazolium acetic-based ionic liquid (IL) 1-butyl-3-methylimidazolium acetate was investigated by density functional theory (DFT). Chitobiose is considered to symbolize chitosan during the DFT calculations. [Bmim]OAc is supposed to be the best suitable IL among the investigated ILs for the dissolution of chitosan since the complex formed between [Bmim]OAc and chitobiose has the lowest energy. The hydrogen bonds formed by IL and chitobiose were studied by discussing the geometric parameter variations and the vibration mode analyses. Four strong hydrogen-bond patterns C1-H1 ⋯ O16, C2-H2 ⋯ O16, O38-H39 ⋯ O1 and O40-H41 ⋯ O2 were found, which means the existence of strong interaction between chitosan and [Bmim]OAc. In addition, natural bond orbital (NBO) analysis was used to study the second order perturbation stabilization energies (E(2)) that denotes the intensity of the interactions between chitobiose with H2O and ILs. The E(2) of chitobiose with [Bmim]OAc is larger than that of chitobiose with other ILs and solvents studied, which proves that chitobiose can be dissolved in [Bmim]OAc but cannot in water and other solvents. Atom in molecules (AIM) theory shows that hydrogen bonds between chitobiose and [Bmim]OAc are stronger than that between chitobiose and other solvents. It means that the interactions between [Bmim]OAc and chitobiose interrupt the initial hydrogen bonds in the chitobiose due to the formation of new hydrogen bonds in the complexes. The calculation data provide the interaction mechanism of the dissolution of chitosan in [Bmim]OAc.
authors: School of Chemistry, Qufu Normal University, Qufu 273165, China. Electronic address: tianqingqing1988@163.com.
authors: Qingqing
authors: Q
authors: Tian
authors: School of Chemistry, Qufu Normal University, Qufu 273165, China. Electronic address: liushuangyue0919@163.com.
authors: Shuangyue
authors: S
authors: Liu
authors: Department of Chemistry, Renmin University of China, Beijing 100872, China. Electronic address: sxf07wldxx@ruc.edu.cn.
authors: Xiaofu
authors: X
authors: Sun
authors: School of Chemistry, Qufu Normal University, Qufu 273165, China. Electronic address: sunhaitaojwc@126.com.
authors: Haitao
authors: H
authors: Sun
authors: College of Materials Science and Technology, Beijing Forestry University, Beijing 100083, China. Electronic address: zmxue@bjfu.edu.cn.
authors: Zhimin
authors: Z
authors: Xue
authors: Department of Chemistry, Renmin University of China, Beijing 100872, China. Electronic address: tcmu@chem.ruc.edu.cn.
authors: Tiancheng
authors: T
authors: Mu
mesh_terms: D002236:Carbohydrate Conformation; D048271:Chitosan / Q000737:chemistry*; D006860:Hydrogen Bonding; D007093:Imidazoles / Q000737:chemistry*; D052578:Ionic Liquids / Q000737:chemistry*; D008962:Models, Theoretical; D012995:Solubility; D012997:Solvents / Q000737:chemistry; D014867:Water / Q000737:chemistry
chemical_list: C525963:1-butyl-3-methylimidazolium; D007093:Imidazoles; D052578:Ionic Liquids; D012997:Solvents; D014867:Water; D048271:Chitosan
keywords: Acetic-based ionic liquid; Atom in molecules analysis; Chitobiose; Natural bond orbital analysis; Vibration mode analysis