Determination of the Polarities of Some Ionic Liquids Using 2-Nitrocyclohexanone as the Probe

Angelini, Guido; Chiappe, Cinzia; Maria, Paolo De; Fontana, Antonella; Gasparrini, Francesco; Pieraccini, Daniela; Pierini, Marco; Siani, Gabriella

doi:10.1021/jo050288g

Cited by 66 publications

(76 citation statements)

References 43 publications

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“…However, one particularly thorough study of polarity using reaction dynamics bears special mention. Angelini et al [40] observed the tautomerization of a nitroketone complex in a series of five imidazolium-based ionic liquids, and conducted a linear free energy analysis of the behavior of the equilibrium constant. The results indicate an overall polarity comparable to that of acetonitrile, and the details of the linear free energy relationship analysis seem consistent with the partitioning and spectroscopic studies above.…”

Section: The Chemical Environment Of Ionic Liquidsmentioning

confidence: 99%

Understanding Organic Processes in Ionic Liquids: Achievements So Far and Challenges Remaining

Harper¹,

Kobrak

2006

MROC

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The use of ionic liquids as alternatives to traditional molecular solvents is a rapidly expanding field. Their many advantages, including negligible vapor pressures, tunable miscibilities and the ease of product isolation, mean that they have been considered (and shown to be effective) as solvents for a range of reactions. However, the outcomes of many of these organic processes differ on changing solvent to an ionic liquid. For these ionic liquid media to be truly considered as alternative solvents, these differences must be understood. This article seeks to extend this understanding by reviewing the variations in the outcome of organic processes along with the fundamental physical properties of ionic liquids that differ from molecular liquids. A case study on nucleophilic substitutions is used to demonstrate the usefulness of our approach.

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Section: The Chemical Environment Of Ionic Liquidsmentioning

confidence: 99%

Understanding Organic Processes in Ionic Liquids: Achievements So Far and Challenges Remaining

Harper¹,

Kobrak

2006

MROC

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“…Probe based analysis have included both single parameter studies based on, for example, pyridinium Nphenolate betaine dye, 8,9 nile red 10,11 and 2-85 nitrocycloexanone 12 and multiparameter studies using the Kamlet-Taft parameters 5,[13][14][15] . Solvatochromic methods are based on the fact that these dyes interact with the solvent into which they are added and the extent of these interactions is shift in the energy levels associated with the dye electronic transitions in the visible region and a corresponding shift in the absorbance of the dye 9 .…”

mentioning

confidence: 99%

Thermal reversion of spirooxazine in ionic liquids containing the [NTf2]− anion

Coleman

Byrne

Minkovska

et al. 2009

Phys. Chem. Chem. Phys.

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We have compared the rate of thermal reversion of Spirooxazine (SO) from its merocyanine (MC) form within ionic liquids and molecular solvents. E t (30) and Kamlet-Taft parameter studies indicate ILs are comparable to polar protic and aprotic solvents. The observed reversion kinetics within the ionic liquids were slower than that of molecular solvents with similar polarity, 15 indicating a greater degree of interactions between the ionic liquid ions and the zwitterionic MC isomer, which led to increased lifetimes for the MC-ion complexes. Pre-metathesis cleaning of precursor salts was found to be necessary in order to obtain spectroscopic grade ILs for physiochemical analysis using solvatochromic probe dyes.

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“…8 The degree of order may also influence solvation and organic reactivity by ordering the reactants. 9,10 In a previous paper, 11 we have shown that the keto−enol interconversion of 2-nitrocyclohexanone (2-NCH) is a suitable probe reaction for investigating the complexity of the effects of RTILs at the molecular level.…”

Section: ■ Introductionmentioning

confidence: 99%

“…11 The tautomeric equilibrium is displaced toward the keto form upon transfer from apolar organic solvents to RTILs as the cavitational and nonspecific electrostatic effects that stabilize the ketone overwhelm the specific electrostatic contributions that stabilize the enol.…”

Section: ■ Introductionmentioning

confidence: 99%

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Thermodynamic Analysis of Anion and Cation Effects on the Keto–Enol Equilibrium in Ionic Liquids. A Comparative Study with Conventional Solvents

et al. 2015

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A comparative thermodynamic investigation of the keto-enol interconversion reaction has been performed in several organic solvents and room-temperature ionic liquids (RTILs) to evaluate the role of the solvent and the effect of the ionic composition of RTILs. The tautomeric constant (KT) values at different temperatures have been analyzed in terms of the van't Hoff relationship to give the relevant thermodynamic parameters. The ΔG° values are the results of quite different combinations of the ΔH° and ΔS° values depending on the nature of the solvent. As expected, in conventional solvents, the tautomeric equilibrium is enthalpically disfavored and entropically favored by the increase in solvent polarity. In ionic liquids, the nature of the anion seems to play a primary role in the thermodynamics of the reaction that is endothermic and enthalpically driven in PF6- and TF2N-based RTILs and exothermic but entropically driven in BF4-based RTILs. The cation effect on the thermodynamics of the reaction is more complex and is consistent with a prevalence of the alkyl side chain segregation in the organization of the ILs.

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Determination of the Polarities of Some Ionic Liquids Using 2-Nitrocyclohexanone as the Probe

Cited by 66 publications

References 43 publications

Understanding Organic Processes in Ionic Liquids: Achievements So Far and Challenges Remaining

Understanding Organic Processes in Ionic Liquids: Achievements So Far and Challenges Remaining

Thermal reversion of spirooxazine in ionic liquids containing the [NTf2]− anion

Thermodynamic Analysis of Anion and Cation Effects on the Keto–Enol Equilibrium in Ionic Liquids. A Comparative Study with Conventional Solvents

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