Prediction of Thermophysical Properties of Acetate-Based Ionic Liquids Using Semiempirical Methods

Abstract

Five acetate-based ionic liquids (AcAILs) [C n mim][OAc](n = 2, 3, 4, 5, 6) (1-alkyl-3-methylimidazolium acetate) were prepared by the neutralization method and characterized by 1H NMR spectroscopy and differential scanning calorimetry (DSC). Their density, surface tension, and refractive index were measured at 298.15 to 338.15 K. Since the AcAILs can form strong hydrogen bonds with water, small amounts of water are difficult to remove by common methods. In order to eliminate the effect of the impurity water, the standard addition method (SAM) was applied to these measurements. On the basis of the experimental data, the molecular volume (sum of positive and negative ion volumes), V m, of [C n mim][OAc](n = 2, 3, 4, 5, 6), the entropy of surface formation, S a, the Gibbs energy of surface formation E a, the parachor, P, and the molar refraction, R m, the polarization coefficient, αp, were calculated. The results show that E a, P, and R m are approximately temperature-independent and the contribution to these properties per methylene (−CH2−) on alkyl chain of [C n mim][OAc](n = 2, 3, 4, 5, 6) was discussed. According to both Kabo’s and Rebelo’s methods, the molar enthalpy of evaporation of the [C n mim][OAc](n = 2, 3, 4, 5, 6) was estimated using surface tension and molar volume. In the same time, the surface tension of the AcAILs may be estimated using the parachor and the refractive index. The estimated values of the surface tension and the corresponding experimental one are extremely similar.

Vaporization enthalpy and the molar surface Gibbs free energy for ionic liquids [C n Dmim][NTF 2 ] ( n = 2, 4)

“…In order to obtain k E of the two ILs, the reported values γ and V [28] were When the temperature of the solution reaches the critical temperature, T c , the molar surface Gibbs energy g = 0, and a = bT c , so that Eq. (14) can be changed into a new Eӧtvӧs equation as follow: In order to test the reliability and objectivity about the molar surface enthalpy is a temperature-independent constant, using above mentioned method and literature data [27,46], literatures [27,46]. γ exp = -0.00342 + 0.9995γ pre r 2 = 0.999, SD = 0.1.…”

“…Hence, in order to study these ILs on the thermodynamics and aslo continue our previous investigation [25][26][27], this paper reports the following: (1) The preparation of ionic liquids {1-alkyl-2,3-dimethyimidazolium-N,N-bis(trifluoromethyl sulfonyl)imide} [C n Dmim][NTF 2 ] (n = 2, 4) using the neutralization method and confirmation by 1 H NMR spectroscopy, 13 …”

“…Plot γ exp vs γ pre for [C n Dmim][NTF 2 ] (n = 2, 4). γ exp = -0.8657 + 1.030γ pre r 2 = 0.99, SD = 0.05 Using the above same method, we predicted the surface tension, γ pre , of ILs [C n mim][BF 4 ] and [C n mim][OAc](n = 2, 3, 4, 5, 6) using the literature data[27,46] and the predicted values of γ pre are listed inthe table S4 and table S5, respectively.Plotting the experimental values of γ exp intable S4 and table S5 vs the corresponding…”

Study on the thermodynamic properties for ionic liquid [C6mim][OAc](1-hexyl-3-methylimidazolium acetate)

“…The density, surface tension, and other physicochemical properties for the homologue of AcAILs were previously reported [7][8][9]. As a continuation of our previous investigation [7][8][9][10][11][12][13], this paper sol H Â m , for [C 6 mim] [OAc] in the temperature range of (288.15 to 308.15 ± 0.01) K were obtained according to of Archer's method [14], and the hydration enthalpy of cation and anion in infinite dilution aqueous [C 6 …”

The molar surface Gibbs free energy and its application for aqueous solutions of ionic liquid N-butyl-pyridinium dicyanamide [C4py][DCA]

“…As our continual investigation [17][18][19][20][21][22][23], the followings were reported in this work: (1) The values of density and surface tension for aqueous solutions of [C 4 py] [DCA] were determined at T = (288. 15-318.15) K with an interval of 5 K. (2) On the basis of thermodynamics, a semi-empirical model-molar surface Gibbs free energy model of the IL solution was put forward, which can predict the surface tension of the solutions.…”