An overview of the mutual solubilities of water–imidazolium-based ionic liquids systems (original) (raw)
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Green Chemistry, 2001
A series of hydrophilic and hydrophobic 1-alkyl-3-methylimidazolium room temperature ionic liquids (RTILs) have been prepared and characterized to determine how water content, density, viscosity, surface tension, melting point, and thermal stability are affected by changes in alkyl chain length and anion. In the series of RTILs studied here, the choice of anion determines water miscibility and has the most dramatic effect on the properties. Hydrophilic anions (e.g., chloride and iodide) produce ionic liquids that are miscible in any proportion with water but, upon the removal of some water from the solution, illustrate how sensitive the physical properties are to a change in water content. In comparison, for ionic liquids containing more hydrophobic anions (e.g., PF 6 2 and N(SO 2 CF 3 ) 2 2 ), the removal of water has a smaller affect on the resulting properties. For a series of 1-alkyl-3-methylimidazolium cations, increasing the alkyl chain length from butyl to hexyl to octyl increases the hydrophobicity and the viscosities of the ionic liquids increase, whereas densities and surface tension values decrease. Thermal analyses indicate high temperatures are attainable prior to decomposition and DSC studies reveal a glass transition for several samples. ILs incorporating PF 6 2 have been used in liquid/liquid partitioning of organic molecules from water and the results for two of these are also discussed here. On a cautionary note, the chemistry of the individual cations and anions of the ILs should not be overlooked as, in the case of certain conditions for PF 6 2 ILs, contact with an aqueous phase may result in slow hydrolysis of the PF 6 2 with the concomitant release of HF and other species.
Journal of Physical Chemistry B, 2008
Physical properties of 4 room-temperature ionic liquids consisting of the 1-butyl-3-methylimidazolium cation with various perfluorinated anions and the bis(trifluoromethylsulfonyl)imide (Tf 2 N -) anion with 12 pyrrolidinium-, ammonium-, and hydroxyl-containing cations are reported. Electronic structure methods are used to calculate properties related to the size, shape, and dipole moment of individual ions. Experimental measurements of phase-transition temperatures, densities, refractive indices, surface tensions, solvatochromic polarities based on absorption of Nile Red, 19 F chemical shifts of the Tf 2 Nanion, temperature-dependent viscosities, conductivities, and cation diffusion coefficients are reported. Correlations among the measured quantities as well as the use of surface tension and molar volume for estimating Hildebrand solubility parameters of ionic liquids are also discussed.
2014
The knowledge of the liquid-liquid equilibria (LLE) between ionic liquids (ILs) and water is of utmost importance for environmental monitoring, process design and optimization. Therefore, in this work, the mutual solubilities with water, for the ILs combining the 1-methylimidazolium, [C 1 im] + ; 1-ethylimidazolium, [C 2 im] + ; 1-ethyl-3-propylimidazolium, [C 2 C 3 im] + ; and 1-butyl-2,3-dimethylimidazolium, [C 4 C 1 C 1 im] + cations with the bis(trifluoromethylsulfonyl)imide anion, were determined and compared with the isomers of the symmetric 1,3-dialkylimidazolium bis(trifluoromethylsulfonyl)imide ([C n C n im][NTf 2 ], with n = 1-3) and of the asymmetric 1-alkyl-3methylimidazolium bis(trifluoromethylsulfonyl)imide ([C n C 1 im][NTf 2 ], with n = 2-5) series of ILs. The results obtained provide a broad picture of the impact of the IL cation structural isomerism, including the number of alkyl side chains at the cation, on the water-IL mutual solubilities. Despite the hydrophobic behaviour associated to the [NTf 2 ] − anion, the results show a significant solubility of water in the IL-rich phase, while the solubility of ILs in the water-rich phase is much lower. The thermodynamic properties of solution indicate that the solubility of ILs in water is entropically driven and highly influenced by the cation size. Using the results obtained here in addition to literature data, a correlation between the solubility of [NTf 2 ]-based ILs in water and their molar volume, for a large range of cations, is proposed. The COnductor like Screening MOdel for Real Solvents (COSMO-RS) was also used to estimate the LLE of the investigated systems and proved to be a useful predictive tool for the a priori screening of ILs aiming at finding suitable candidates before extensive experimental measurements.
Journal of the Brazilian Chemical Society, 2008
Uma série de líquidos iônicos 1-alquil éter (e 1-alquil)-3-metilimidazólio 2-4 ([C x O y MIm] + [Ânion] ou [C x MIm] + [Ânion] , onde MIm = 3-metilimidazólio; C x O y = 1-alquil éter, C 7 O 3 = -(CH 2 ) 2 O(CH 2 ) 2 O(CH 2 ) 2 OCH 3 (A), C 3 O 1 = -(CH 2 ) 2 OCH 3 (B); C x = 1-alquil, C 10 = C 10 H 21 (C), C 4 = C 4 H 9 (D); e [Ânion] = H 3 CSO 3 (2), BF 4 (3) ou PF 6 (4)) foram preparados e caracterizados. A força da ligação de hidrogênio entre o cátion e o ânion dos líquidos iônicos 2-4 depende principalmente do ânion e diminui na ordem H 3 CSO 3 > BF 4 > PF 6 . Todos os líquidos iônicos metanosulfonatos 2 possuem uma forte desblindagem para o próton H 2 do ciclo imidazólio. Os líquidos iônicos funcionalizados com um grupo 1-alquil éter mostram densidades mais altas em comparação com seus equivalentes do grupo 1-alquil. Os sais 2a-b, 3a-d e 4a-b são líquidos iônicos à temperatura ambiente. E, todos os líquidos iônicos 1-alquil éter funcionalizados (exceto 4b) são completamente amorfos. As maiores faixas líquidas foram obtidas com os líquidos iônicos tetrafluoroborato devido as suas solidificações a temperaturas baixas e excelente estabilidade térmica. Estes dados fornecem informações importantes para o entendimento sobre possíveis aplicações e a preparação de líquidos iônicos com tarefas específicas.
On the solid, liquid and solution structural organization of imidazolium ionic liquids
Journal of the Brazilian Chemical Society, 2004
Sais derivados do cátion 1,3-dialquilimidazólio são uma das mais populares e investigadas classes de líquidos iônicos a temperatura ambiente. Embora, em vários casos, suas propriedades físico-químicas e/ou o resultado dos processos que ocorrem nesses líquidos diferem significantemente daqueles obtidos em solventes orgânicos dipolares, estes ainda podem ser descritos como simples solventes orgânicos. Nesta revisão, será introduzido o conceito que líquidos iônicos derivados do cátion 1,3-dialquilimidazólio são mais convenientemente descritos como estruturas poliméricas supramoleculares do tipo {[(DAI) x (X) x-n)] n+ [(DAI) x-n (X) x)] n-} n onde DAI representa o cátion 1,3dialquilimidazólio e X o ânion. Este padrão estrutural é observado geralmente em sólidos e mantido em grande extensão no estado líquido e mesmo em fase gasosa. A introdução de outras moléculas ou macromoléculas no líquido iônico provoca a perturbação da rede de ligações de hidrogênios podendo gerar, em alguns casos, nano-estruturas com regiões polares e apolares onde compostos de inclusão podem ser formados. 1,3-dialkyl imidazolium salts are one of the most popular and investigated classes of room temperature ionic liquids. Although in various cases the physical-chemical properties and/or the outcome of the processes in these liquids significantly differ from those performed in "classical" dipolar organic solvents, they are still regarded as merely homogeneous solvents. In this brief overview it is developed the concept that pure 1,3-dialkylimidazolium ionic liquids are better described as hydrogen-bonded polymeric supramolecules of the type {[(DAI) x (X) x-n)] n+ [(DAI) x-n (X) x)] n-} n where DAI is the 1,3-dialkylimidazolium cation and X the anion. This structural pattern is a general trend for the solid phase and is maintained to a great extent in the liquid phase and even in the gas phase. The introduction of other molecules and macromolecules occurs with a disruption of the hydrogen bond network and in some cases can generate nano-structures with polar and non-polar regions where inclusion-type compounds can be formed.
The Journal of Physical Chemistry B, 2013
Ionic liquids (ILs) composed of two different pyrazolium cations with dicyanamide and bis(trifluoromethanesulfonyl)imide anions have been synthesized and characterized by NMR, Kamlet-Taft solvatochromic parameters, conductivity and rheological measurements, as well as ab initio calculations. Density functional calculations for the two pyrazolium cations, 1-2 butyl-2-methylpyrazolium [bmpz] and 1-butyl-2,3,5-trimethylpyrazolium [bm 3 pz] provide a full picture of their conformational states. Homo-and heteronuclear NOE show aggregation motives sensitive to steric hindrance and anions' nature. Self-diffusion coefficients D for the anion and the cation have been measured by pulsed field gradient spin-echo NMR (PGSE-NMR). The ionic diffusivity is influenced by their chemical structure and steric hindrance giving the order D cation > D anion for all the examined compounds. The measured ion diffusion coefficients, viscosities and ionic conductivity follow the Vogel-Fulcher-Tammann (VFT) equation for the temperature dependencies and the best fit parameters have been determined. Solvatochromic parameters indicate an increased ion association on going from bis(trifluoromethanesulfonyl)imide to dicyanamide-based pyrazolium salts, as well as specific hydrogen bond donor capability of H atoms on the pyrazolium ring. All these physical properties are compared to those of an analogous series of imidazolium-based ILs.
European Chemical Bulletin, 2013
Chromatographic retention factor data were measured for a chemically diverse set of thirty-seven organic solutes on a 1-(2-hydroxyethyl)-3methylimidazolium tris(pentafluoroethyl)trifluorophosphate ([EtOHMIm] + [FAP] -) ionic liquid stationary phase at both 323 K and 353 K. The measured retention factors were combined with published gas-to-liquid partition coefficient data for solutes dissolved in ([EtOHMIm] + [FAP] -) and with published gas-to-water partition coefficient data to yield gas-to-anhydrous ionic liquid and water-toanhydrous ionic liquid partition coefficients. The three sets of partition coefficients were correlated with the Abraham solvation parameter model. The derived Abraham model correlations describe the experimental gas-to-ionic liquid and water-to-ionic liquid partition coefficient data to within an average standard deviation of 0.12 log units.
Fluid Phase Equilibria, 2015
Adsorption of three long-chain imidazolium ionic liquids (ILs) at toluene-water interface was studied along with their micelle formations at temperatures within (293.2-313.2) K. The used ILs act as excellent surfactants and under the same conditions, their interfacial activity is reasonably appeared in the order of [C 16 mim][Br] > [C 16 mim][Cl] > [C 12 mim][Cl]. The experimental data were satisfactorily reproduced by the Frumkin adsorption isotherm for concentrations less than critical micelle concentration (CMC). Accordingly, the highest maximum interface excess and adsorption equilibrium constant were for [C 16 mim][Br] because of its long alkyl chain as well as more polarizable anion. In this regard, the balance between electrostatic repulsion and van der Waals attraction provides a stronger attractive interaction for this IL. On the other hand, by rising temperature, the interface excess concentration, adsorption tendency and electrostatic repulsion between adsorbed molecules increase. The results show that, within the same concentration ranges, the maximum interfacial tension reduction were 72% for [C 12 mim][Cl] and [C 16 mim][Br] ILs, compared with 68% for similarly structure DTMAC and CTAB surfactants. Also, these ILs, respectively, have the CMC values about 81% and 63% of related surfactants. 2014 Elsevier B.V. All rights reserved.