Prediction of the thermodynamic properties of 1-alkyl-3-methylimidazolium lactate ionic liquids [C n mim][Lact] (n = 2, 3, 4, 5, and 6) by parachor

Abstract

An ionic liquid (IL) based on lactate, 1-butyl-3-methylimidazolium lactate ([C 4 mim][Lact]), has been prepared and characterized by 1 H nuclear magnetic resonance (NMR) spectroscopy and differential scanning calorimetry (DSC). Since the IL can form strong hydrogen bonds with water, trace water is a problematic impurity in the IL. Using the standard addition method (SAM), the density, refractive index and surface tension of [C 4 mim][Lact] were measured in the temperature range (308.15 to 343.15 ± 0.05) K. On the basis of the experimental data, the parachor and molar volume for [C 4 mim][Lact], and the molecular volume V m , surface tension , molar enthalpy of vaporization  l g H m 0 , refractive index n D , and the thermal expansion coefficients , for the homologues [C n mim][Lact] (n = 2, 3, 4, 5, and 6) were estimated using semi-empirical methods. The estimated values are in good agreement with the experimental data.parachor, lactate, ionic liquid, density, surface tension, refractive index

Determination and Prediction for the Polarity of Ionic Liquids

“…As listed in the table, the values of δ μ decrease with increasing number of methylene (−CH 2 −) groups in the alkyl chains of the ILs, that is the order: δ μ [C 2 mim]­[AcO] > δ μ [C 4 mim]­[AcO] > δ μ [C 5 mim]­[AcO] > δ μ [C 6 mim]­[AcO] > δ μ [C 2 mmim]­[NTf 2 ] > δ μ [C 4 mmim]­[NTf 2 ]. In addition, the reported values of refractive index n D , molar mass M , density ρ, molar refraction R m , the contribution part from the average permanent dipolmoment Δ l g H m n o , enthalpy of vaporization Δ l g H m o (298), contribution part from the induced dipole moment Δ l g H mμ o , and the new scale of polarity δ μ for [C n mim]­[Lact]­( n = 2,3,4,5), [C n mim]­[NTf 2 ]­( n = 2,4,6,8,10), and others at 298 K have been collected from the literature, − and on the basis of eq , δ μ values were predicted and listed in Table . From the table, it can been seen that anions have a great effect on the polarity of δ μ for ionic liquids, and the quantitative relation will continue to be investigated in future work.…”

Estimation of Properties of Ionic Liquids 1-Alkyl-3-methylimidazolium Lactate Using a Semiempirical Method

“…In order to further verify the reliability of this method, using [C 2 mim] + as a reference ion, the values of the ionic parachor for [Ala] − , [Pro] − , [Gly] − , [BF 4 ] − , and [OAc] − were calculated using experimental data in the literature ,,,− and are listed in Table S2 in the Supporting Information. According to the data in Table S2, the values of the parachor, P (Cal), of the ILs [C n mim][Ala], [C n mim][Pro], [C n mim][Ala], [C n mim][BF 4 ], and [C n mim][OAc] (for n = 3, 4, 5, 6) were estimated and are listed in Table S4 in the Supporting Information.…”

“…These data show that the use of the SAM is appropriate in this work. 3,4,5,6). From the experimental values of the density, the molecular volume (the sum of the volumes of the positive and negative ions), V m , of [C 2 mim][Lact] and [C 5 mim][Lact] were calculated from the following equation:…”

“…In order to expand the application of this method, using [C 2 mim] + as a reference ion, the values of ionic contribution to molar refraction R m for [Ala] − , [Pro] − , [Gly] − , and [OAc] − were calculated using experimental data in the literature 6,13,14,22,24 and are listed in Table S2 in the Supporting Information. According to the data in Table S2 The linear fitting parameters are listed in Table S3 in the Supporting Information.…”

“…The ionic liquids based on lactic acid (LAILs), which is a naturally generated organic acid and plays an important role inside the human body, are typical CILs and have strong hydrogen bonding ability. Thus, LAILs have been expected to be applied in various fields, such as industrial chemistry and pharmaceutical chemistry; thus, they have attracted increasing attention from both academical and industrial communities as a greener solvent and a new functional material. − …”