Heat capacities at 298.15K of the extended [CnC1im][Ntf2] ionic liquid series

Rocha, Marisa A.A.; Bastos, Margarida; Coutinho, João A. P.; Santos, Luı́s M. N. B. F.

doi:10.1016/j.jct.2012.04.025

Cited by 68 publications

(44 citation statements)

References 21 publications

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“…Moreover, this macroscopic segregation behaviour has been shown to be a major feature in the ionic liquid bulk phase and as reflected in the thermophysical properties of ILs. [66][67][68][69][70][71][72][73] Similar trend shifts were observed in the IL viscosity, [66][67] surface tension, 68 vapour pressure, 69,70 heat capacity, 71 among others. 72,73 It is, however, thought-provoking to highlight that different trends on the IL acidity with increasing alkyl chain length have also been reported.…”

Section: Experimental Kamlet-taft Solvatochromic Parameterssupporting

confidence: 67%

Hydrogen-bond acidity of ionic liquids: an extended scale

Kurnia

Lima

Cláudio

et al. 2015

Phys. Chem. Chem. Phys.

102

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One of the main drawbacks comprising an appropriate selection of ionic liquids (ILs) for a target application is related to the lack of an extended and well-established polarity scale for these neoteric fluids. Albeit considerable progress has been made on identifying chemical structures and factors that influence the polarity of ILs, there still exists a high inconsistency in the experimental values reported by different authors. Furthermore, due to the extremely large number of possible ILs that can be synthesized, the experimental characterization of their polarity is a major limitation when envisaging the choice of an IL with a desired polarity. Therefore, it is of crucial relevance to develop correlation schemes and a priori predictive methods able to forecast the polarity of new (or not yet synthesized) fluids. In this context, and aiming at broadening the experimental polarity scale available for ILs, the solvatochromic Kamlet-Taft parameters of a broad range of bis(trifluoromethylsulfonyl)imide-([NTf 2 ] − )-based fluids were determined. The impact of the IL cation structure on the hydrogen-bond donating ability of the fluid was comprehensively addressed. Based on the large amount of novel experimental values obtained, we then evaluated COSMO-RS, COnductor-like Screening MOdel for Real Solvents, as an alternative tool to estimate the hydrogen-bond acidity of ILs. A three-parameter model based on the cation-anion interaction energies was found to adequately describe the experimental hydrogen-bond acidity or hydrogen-bond donating ability of ILs. The proposed three-parameter model is also shown to present a predictive capacity and to provide novel molecular-level insights into the chemical structure characteristics that influence the acidity of a given IL. It is shown that although the equimolar cation-anion hydrogen-bonding energies (E HB ) play the major role, the electrostaticmisfit interactions (E MF ) and van der Waals forces (E vdW ) also contribute, admittedly in a lower extent, towards the hydrogen-bond acidity of ILs. The new extended scale provided for the hydrogen-bond acidity of ILs is of high value for the design of new ILs for task-specific applications. † Electronic supplementary information (ESI) available: Comparison between experimental and literature solvatochromic values; correlation between experimental and predicted hydrogen-bond acidity; equation to calculate the absolute relative deviation. See

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Section: Experimental Kamlet-taft Solvatochromic Parameterssupporting

confidence: 67%

Hydrogen-bond acidity of ionic liquids: an extended scale

Kurnia

Lima

Cláudio

et al. 2015

Phys. Chem. Chem. Phys.

102

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“…As mentioned before, similar trends were observed for the thermophysical properties of ILs, such as viscosity [23,24], surface tension [25], vapour pressures [26,27] and heat capacities [28] among others [29,30]. Although those studies focused on the physical properties of pure ILs with symmetric and asymmetric alkyl side chains, the two basic conclusions might also be extended to the water solubility on these series of ILs that are: (i) ILs are highly structured fluids with high-charge density areas permeated by low-charge density regions (the alkyl side chain); and (ii) the topology of the nonpolar domains is strongly dependent on the relative volumes occupied by the polar and nonpolar moieties.…”

Section: Resultssupporting

confidence: 83%

“…Similar trends were observed at other temperatures as shown in Figures S2-S3 in the Supporting Information. Figure 3 clearly shows that for the set of studied ILs, various regions and trend shifts can be observed as function of the cation alkyl chain length, as previously remarked for various thermophysical properties [23][24][25][26][27][28][29][30]. The first region, here called "Region A", consists of the series of short alkyl chain length ILs with N < 6, and where the decrease (slope) on the mole fraction solubility of water is higher than that observed in "Region B".…”

Section: Resultssupporting

confidence: 60%

“…The symmetry of the cation provides a different structural organization which can be used to tune the physical properties of IL [23][24][25][26][27][28][29][30] and, ultimately, contribute to better design of ILs for a given task. To complement the experimental data, additional quantum chemical Density Functional theory (DFT) calculations were carried out, via computational simulations, namely by the COnductor-like Screening Model for Real Systems (COSMO-RS) [31] and Electrostatic potential-derived CHelpG [32].…”

Section: Introductionmentioning

confidence: 99%

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Comprehensive study on the impact of the cation alkyl side chain length on the solubility of water in ionic liquids

Kurnia

Neves

Freire

et al. 2015

Journal of Molecular Liquids

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A comprehensive study on the phase behaviour of two sets of ionic liquids (ILs) and their interactions with water is here presented through combining experimental and theoretical approaches. The impact of the alkyl side chain length and the cation symmetry on the water solubility in the To complement the experimental data and to further investigate the molecular-level mechanisms behind the dissolution process, Density Functional Theory calculations, using the Conductor-like Screening Model for Real Solvents (COSMO-RS) and the Electrostatic potential-derived CHelpG, were performed. The COSMO-RS model is able to qualitatively predict water solubility as function of temperature and alkyl chain lengths of both symmetric and asymmetric cations. Furthermore, the model is also capable to predict the somewhat higher water solubility in the asymmetric cation, as well as the trend shift as function of alkyl chain lengths experimentally observed. Both COSMO-RS and the electrostatic potential-derived CHelpG show that the interactions of water and the IL cation take place on the IL polar region, namely on the aromatic head and adjacent methylene groups what explains the differences in water solubility observed for cations with different chain lengths. Furthermore, the CHelpG calculations for the isolated cations in the gas phase indicates that the trend shift of water solubility as function of alkyl chain lengths and the difference of water solubility in symmetric may also result from the partial positive charge distribution/contribution of the cation.

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“…Most of the heat-capacity values on [C18mim][NTf2] [5] were presented graphically and, therefore, they are of limited use. Rocha et al [7] used a drop calorimeter [8] to determine heat capacities at T = 298.15 K for [Cnmim][NTf2] (n = 2 to 12). Dzyuba and Bartsch [9] determined parameters of a solid-phase transition and fusion for [C10mim]NTf2 with DSC.…”

mentioning

confidence: 99%

Thermodynamics of long-chain 1-alkyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ionic liquids

Paulechka

Blokhin

Rodrigues

et al. 2016

The Journal of Chemical Thermodynamics

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The heat capacities in the temperature range (5 to 370) K and the parameters of solid-phase phase transitions and fusion were determined for three [Cnmim][NTf2] (n = 10, 14, 16) ILs. The temperature-dependent vapour pressures of [C14mim][NTf2] and [C16mim][NTf2] were measured with a Knudsen effusion apparatus combined with a quartz crystal microbalance. Thermodynamic properties of these compounds in the crystal, liquid, and gas states were derived from the obtained data. The results obtained in this work were combined to those available in the literature for the short-chain homologues to discuss regularities in thermodynamic properties of the series. While some properties demonstrate simple linear dependence on the alkyl chain length, a more complicated behaviour with strong nonlinearity or a break at n = 6 is observed for others.

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Heat capacities at 298.15K of the extended [CnC1im][Ntf2] ionic liquid series

Cited by 68 publications

References 21 publications

Hydrogen-bond acidity of ionic liquids: an extended scale

Hydrogen-bond acidity of ionic liquids: an extended scale

Comprehensive study on the impact of the cation alkyl side chain length on the solubility of water in ionic liquids

Thermodynamics of long-chain 1-alkyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ionic liquids

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