Ionic Liquids: Solvents for the Twenty-First Century

Earle, Martyn J.

doi:10.1021/bk-2002-0818.ch007

Cited by 12 publications

(1 citation statement)

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“…Ionic liquids (ILs) have arisen as new alternative solvents to volatile organic solvents, being considered in principle environmentally friendly mainly because they are non‐flammable and non‐volatile . In recent decades, the synthesis, characterization, and applications of ILs became an exciting field of research.…”

Section: Introductionmentioning

confidence: 99%

Understanding the Role of Protic Ionic Liquids (PILs) in Reactive Systems: Rational Selection of PILs for the Design of Green Synthesis Strategies for Allylic Amines and β‐Amino Esters

et al. 2019

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The reactive behaviour of protic ionic liquids (PILs) has been shown to be governed not only by their chemical structures but also by their global compositions, which include the presence of free acids and bases at equilibrium with ionic pairs. Six PILs composed of primary, secondary, or tertiary alkyl ammonium cations with two couterions, nitrate or acetate, were tested in model reactions with unsaturated substrates. The free species that were naturally present in these liquids were identified by cyclic voltammetry. Only tributylammonium nitrate was found to be mostly composed just of the ionic pair; the other five PILs also contain variable amounts of free acid and amine. In reactive systems, these free species determine the products of the reaction. In particular, allylic amines and β‐amino esters were obtained in good yields (91 and 75 %, respectively) by reaction of conjugated dienes and acrylates in the presence of PILs. By taking into account the actual composition of each PIL, it was possible to direct the reaction path towards a specific product with good yields, to ensure acid catalysis, to avoid polymerization of the substrate, and to promote phase transfer of products. These results establish some useful guidelines for the rational design of new PIL‐based one‐step synthetic strategies.

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Section: Introductionmentioning

confidence: 99%

Understanding the Role of Protic Ionic Liquids (PILs) in Reactive Systems: Rational Selection of PILs for the Design of Green Synthesis Strategies for Allylic Amines and β‐Amino Esters

et al. 2019

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Ionic Liquids

Meindersma

Maase

Haan

2007

Ullmann's Encyclopedia of Industrial Chemistry

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The article contains sections titled: 1. Introduction 2 Physical and Chemical Properties 2.1. Introduction 2.2. Melting Point 2.3. Density 2.4. Viscosity 2.5. Thermal Stability 2.6. Electrochemical Window 3 Synthesis/Production 3.1. Introduction 3.2. Synthesis 3.2.1. Lewis Acid‐Based ILs 3.2.2. Anion Metathesis 3.2.3. Synthesis of Chloride Free ILs 3.2.4. Preparation with Microwaves 3.3. Producers of Ionic Liquids 4 Applications 4.1 Potential Applications 4.1.1. Solvents for Synthesis and Catalysis 4.1.1.2 Solvents for Catalysis 4.1.1.3 Polymer Synthesis 4.1.1.4 Biocatalysis 4.1.2. Electrochemical Applications 4.1.3. Analytical Applications 4.1.4. Separations 4.1.4.1 Liquid Separations 4.1.4.2 Gas Separations 4.1.5. Fluid Applications: Thermal Fluids and Lubricants 4.2. Applications in Pilot Plants and Industry 4.2.1. Reactions 4.2.1.1. Acid Scavenging 4.2.1.2. Production of 2,5‐dihydrofuran 4.2.1.3. Chlorination of Alcohols/Cleavage of Ethers 4.2.1.4. Hydrosilylation 4.2.1.5. Fluorination 4.2.1.6. Dimerization and Oligomerization of Olefins 4.2.2. Separations 4.2.2.1 Extractive Distillation 4.2.2.2. Extraction of Aromatic Hydrocarbons 4.2.3. Electroplating/Polishing 4.2.4. ILs as Performance Chemicals 4.2.4.1 Compatibilizers for Pigment Pastes 4.2.4.2. Antistatic Additives for Cleaning Fluids 4.2.5. ILs in Gas Processing 4.2.5.1. Storage of Gases 4.2.5.2. Ionic Compressor 5 Analysis 6 Toxicology and Occupational Health 6.1. (Eco)toxicology 6.2. Mutagenicity 6.3. Safety and Corrosion 7 References The common definition of an ionic liquid (IL), or a room temperature ionic liquid (RTIL), is that it is a liquid composed entirely of ions, which is fluid below 100 °C. Ionic liquids are generally much denser (ρ = 1 − 1.6 g/cm 3 ) and more viscous (η = 10 − 500 mPa · s) than conventional solvents. Ionic liquids can be stable up to temperatures of 500 °C. They can easily be synthesized and the variability of the cation and anion may be used to adjust the properties of the ionic liquids. Therefore, the possibility arises to optimize an ionic liquid for a specific application by stepwise tuning the relevant solvent properties. For this reason ionic liquids have been referred to as “designer solvents”. The potential to use ionic liquids as novel solvents or fluids for a diverse range of applications has become increasingly apparent. The intrinsic nonvolatile nature of ILs provides an opportunity to reduce, or even completely eliminate, hazardous and toxic emissions to the atmosphere, thus providing the promise for significant environmental benefits. In synthesis and catalysis, ILs have been used as solvents (or solvents and catalysts), with the greatest current effort on using the ILs as alternatives to volatile organic compounds (VOCs). Electrochemical studies have utilized the fact that ILs are liquids rather than solids to provide liquid electrolytes without needing to add an additional solvent. Ionic liquids are also used in separations, replacing volatile solvents. The number of applications on pilot‐plant and commercial scale is still limited, but growing. Although ionic liquids are also known as “green solvents”, this is not always true. They can be corrosive, flammable, or toxic. Due to their nonvolatile nature, ionic liquids are generally considered as having a low impact on the environment and human health, and thus recognized as solvents for green chemistry. However, the impact of ionic liquids on aquatic ecosystems is important given their mild to high solubility in water. Before ionic liquids will be widely used in industry, the effects of ILs on the aquatic environment must be known.

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