Study On Thermodynamic Properties Of Functionalized Ionic Liquid Dilute Solution Of[COC₂MIM][Ala] And [G_nMIM][OAc]（n=3,5）

Due to the higher viscosity,the applications of Ionic liquids have been limited in chemical engineering.Deploy them into dilute solutions can greatly improve this shortcoming and expand its application range.The datas of physicochemical properties about dilute solutions for ionic liquids are the basic and important for the study and application.Therefore,it is necessary and important to effectively measure the physicochemical properties.Functionalized ionic liquids are a kind of novel green solvents,and the hydrophobic properties can be altered by introducting the ether and carboxyl functional groups into the ionic liquids.In this paper,a dilute solution of ether-based and carboxyl-functionalized ionic liquids with various molarities,0.0100-0.500 mol·kg^-1,were measured at 288.15-318.15 K with interval 5 K.The surface tension and density for dilute solution of ionic liquid 1-methoxyethyl-3-methylimidazolium alanine[COC₂MIM][Ala],1-propyl-3-methylimidazolium acetate[C₃MIM][OAc],1-pentyl-3-methylimidaz-olium acetate[C₅MIM][OAc]was tested.We further improved the traditional model theory of Li Yigui,and derived a new physical function-the molar surface Gibbs free energy（g_s）,on the basis of the original theory.The molar surface of the dilute solution of 1-methoxyethyl-3-methylimidazolium alanine,1-propyl-3-methylimidazolium-acetic acid and 1-pentyl-3-methylimidazoliumacetic acid ionic liquid was calculated respectively.The linear empirical equation between the molar concentration of the dilute solution and the Gibbs energy of the molar surface was established;The surface tension values for dilute solutions of[COC₂MIM][Ala],[C₃MIM][OAc]and[C₅MIM][OAc]was predicted by used empirical equations.Using the empirical equation,the surface tension of the solution was predicted,and the predicted values and the corresponding experimental one are highly correlated and extremely similar.Therefore,the molar surface Gibbs energy can be used as a new semi-empirical method to predict the physicochemical properties of dilute solutions of ionic liquids.According to the molar surface Gibbs energy,derived a new E?tv?s equation,in which each parameter had a clearer physical significance.We can clearly know that the molar surface entropy is the main factor that determines the polarity of the liquid and the larger the value,the smaller the polarity of the liquid.