Theoretical Calculation Of Thermodynamic Properties Of 20 Amino Acid Ionic Liquids

From the last few decades,ionic liquids?ILs?have been subject to growing concern in the chemical laboratories and industrial areas because of their application in“green”chemistry.For example,as replacement of organic compounds and volatile organic solvents in chemical industry.However,the potential hazards that may exist to the environment in practical application.Based on modifiable ILs,amino acids have been used as precursors in order to reduce the toxicity and prepare the chiral ILs.Because of the presence of amino and carboxyl groups in amino acids,amino acid ionic liquids?AAILs?can be used to capture greenhouse gases such as SO₂ and CO₂.It has shown that AAILs have a strong hydrogen bonding ability that is useful for dissolving biomaterials,such as cellulose and DNA.AAILs have a broad development prospect,the demand for it's thermodynamic properties is widespread.To tailor the properties of ILs and design novel ILs for specific tasks,it is critically important to understand the relationship between structures and thermodynamic properties of ILs.In this paper,the thermodynamic properties of AAILs containing 1-ethyl-3-methylimidazolium?[Emim]⁺?and 20 amino acids?[AA]^-?were studied systematically in combination with quantum chemical calculation,molecular dynamic simulation,Born-Haber cycle and isodesmic reactions.The main studying contents of this paper are as follows:?1?Quantum chemistry methods,especially M06-2X/TZVP method was applied to obtain the dissociation enthalpies of 20[Emim][AA].The influences of dispersion interaction and the structure of AAILs on the dissociation enthalpies were analyzed.?2?Tinker 4.3 program was used to study the dynamic properties of 20 kinds of AAILs.Then,according to the dynamics simulation results,the densities,molar volumes,vaporization enthalpies,cohesive energy densities and solubility parameters of 20[Emim][AA]were calculated.In addition,the vaporization enthalpies of 20[Emim][AA]were also calculated by krossing empirical method.The relationship between the structure of AAILs and vaporization enthalpies was explored.?3?Based on BH cycle,quantum chemical calculation,molecular dynamics simulation and isodesmic reactions were combined to predict the formation enthalpy of20[Emim][AA].The calculation results provide some initial hints as to the relationship between the formation enthalpies and the structures of AAILs.