Synthesis Of Ether-Based Functionalized Ionic Liquids [C_nOC₂mim][Thr]?n=1,2? And Study On The Vaporization Enthalpy

Ionic liquids are ecologically friendly solvents.As a new type of environmentally friendly functional material,ionic liquids have unique physical and chemical properties such as negligible vapor pressure,excellent electrical conductivity,high thermal stability,and designability.It has wide application prospects in the fields of life science,medicinal chemistry,environmental chemistry and chemical industry.The ionic liquids containing ether groups have more flexible alkoxy chains,so the ionic liquids containing ether groups has lower melting points.Ionic liquids' researches on thermodynamics and supplements of related data are not only indispensable basic data in practical applications,but also important for quantum chemical calculations.Among the current experimental techniques for determining the vapor pressure and vaporization enthalpy of ionic liquids,thermogravimetric analysis has advantages of high efficiency and high accuracy.This paper designed a two-step method to prepare ether-based functionalized threonine ionic liquids[CnOC2mim][Thr](n=1,2).First,[CnOC2mim][Cl](n=1,2)was prepared by the reaction of N-methylimidazole with CnOC2CI(n=1,2),and then passed through the processed basic anion exchange resin to obtain the hydroxide type intermediate.Finally,[CnOC2mim][Thr](n=1,2)was prepared by the acid-base neutralization reaction between the hydroxyl intermediate and threonine.The ionic liquids synthesized above were characterized by 1H NMR,13C NMR,and dynamic thermogravimetric analysis.Initial decomposition temperatures of ionic liquids[CnOC2mim][Thr](n=1,2)were determined by dynamic thermogravimetric analysis.Using benzoic acid as a reference material,the vapor pressure and average temperature vaporization enthalpy of the ionic liquid were measured by the isothermogravimetrical analysis method.Choosing the appropriate temperature range as the constant temperature interval The heat capacity was calculated using Verevkin's method,and the average temperature vaporization enthalpy was converted to a vaporization enthalpy of 298.15 K.Based on this,the Clausius-Clapeyron equation is used to estimate the assumed normal boiling point Tb of the ionic liquid,and the vaporization entropy at the assumed normal boiling point is calculated.The heat capacity can be used to calculate the enthalpy of vaporization,the entropy of vaporization and the Gibbs free energy at any temperature of the ionic liquid.Experimental results show that the enthalpy of vaporization of the ionic liquid decreases,and the vaporized Gibbs free energy decreases to zero until the temperature rises to the imaginary boiling point,and the value of the vaporization entropy increases with the increase of temperature with the increasing temperature.