Ionic liquids, literature reviews

For the results reported in both Table 7.2-3 and Table 7.2-4, the only reported detail concerning the ionic liquid was that it was [EMIM][C1-A1C13]. No details of the aluminium(III) chloride content were forthcoming. As with most of the work presented in this chapter, data are taken from the patent literature and not from peer reviewed journals, and so many experimental details are not available. This lack of clear reporting complicates issues for the synthetic polymer chemist. Simpler and cheaper chloroaluminate(III) ionic liquids prepared by using cations derived from the reaction between a simple amine and hydrochloric acid (e.g., Me3N-E3Cl and... 

From reviewing much of the literature it is easy to conclude that ionic liquids are excellent solvents for catalysts and reagents but not for products, which is obviously not the case. Whilst some products can be decanted from the liquid and others can be recovered by distillation, there are many useful reactions in which removal of the product (or residual reactants) from the ionic liquid is challenging. Extraction with an organic solvent, or even water, would reduce the overall eco-efficiency. Initial... 

Solid polymer and gel polymer electrolytes could be viewed as the special variation of the solution-type electrolyte. In the former, the solvents are polar macromolecules that dissolve salts, while, in the latter, only a small portion of high polymer is employed as the mechanical matrix, which is either soaked with or swollen by essentially the same liquid electrolytes. One exception exists molten salt (ionic liquid) electrolytes where no solvent is present and the dissociation of opposite ions is solely achieved by the thermal disintegration of the salt lattice (melting). Polymer electrolyte will be reviewed in section 8 ( Novel Electrolyte Systems ), although lithium ion technology based on gel polymer electrolytes has in fact entered the market and accounted for 4% of lithium ion cells manufactured in 2000. On the other hand, ionic liquid electrolytes will be omitted, due to both the limited literature concerning this topic and the fact that the application of ionic liquid electrolytes in lithium ion devices remains dubious. Since most of the ionic liquid systems are still in a supercooled state at ambient temperature, it is unlikely that the metastable liquid state could be maintained in an actual electrochemical device, wherein electrode materials would serve as effective nucleation sites for crystallization. 

The literature of room temperature ionic liquids (RTILs) was reviewed to select and report on those RTILs involved directly in chemical reactions either as a solvent for a catalyst, a conversion agent, or a task specific ionic liquid. Special emphasis was placed on manuscripts appearing in the literature in the last ten years. 

We begin with a brief summary of some of the review articles that have been written on the subject of ionic liquids. Wilkeswrote a short history of ionic liquids describing the chronological development of ionic liquids with an emphasis on listing the names and pictures of those involved in the research. Holbrey and Seddon and Earle and Seddon reviewed the literature of ionic liquids composed entirely of ions which were mainly of interest to electrochemists. Recently, however, it has become apparent that, inter alia, their lack of measurable vapor pressure characterizes them as green solvents, and that a wide range of chemical reactions (reviewed here) can be performed in them. Wassercheid and Keim reviewed the literature of ionic liquids, not only the synthesis and physical properties of the ILs, but also their use as... 

Keeping these facts in mind, there is an obvious interest in being able to apply NMR to the chemistry of and in ionic liquids (ILs). This chapter focuses on the main achievements in the field, giving a tutorial-like approach to NMR spectroscopy in ILs. If you prefer a more review-like source of information that aims at completeness and a more historical style, please refer to the recent literature [2]. 

Following up this initial work a large number of reactions have been published by academic and industrial groups wherein a Lewis-acidic chloroaluminate ionic liquid is used as the acidic catalyst. A comprehensive overview on these research activities can be found in several reviews on this topic and the literature cited therein [18, 22, 37]. 

The modem world of chemical synthesis is unthinkable without NMR spectroscopy. Especially in organic synthesis, the information content of a combination of various NMR techniques is tremendeous and unmatched by any other spectroscopic method. Thus, since ionic liquids ( ILs for short) are predominantly used as solvents these days, the application of magnetic resonance spectroscopy to ionic solvents has become very important. None the less, the unique properties of this modem solvent class has put quite some challenge to researchers trying to apply NMR for ILs. In this review, I will describe the development of NMR in modem (i.e. air- and moisture-stable, predominantly imidazolium-based) ILs of the last 8 years historically from an experimental perspective. If you are looking for a more substrate-specific point of view or are interested in the early developments with chloroaluminate ILs, you are kindly asked to refer to the recent literature [1],... 

In the previous sections the use of catalysts dissolved in ionic liquids has been documented with a variety of examples from the most recent literature. They were classified are catalytic systems based on the adoption of Strategies A, B and C, when solvent-less conditions were not adopted. In an ideal liquid-liquid biphasic system, the IL must dissolve the catalytic intermediates and, in part, the substrate to avoid that mass transfer limits reaction rates. Moreover, products should have a limited solubility in the IL to allow a facile product removal or extraction, and, possibly, the recycle of the ionic liquid-trapped catalyst. The separation of the catalyst from the products is made easier if solid support-immobilised ILs are used. The preference for a solid catalyst is dictated not only by the easier separation but also, as outlined by Mehnert in an excellent review article, " by (i) the possible use of fixed bed reactors, and (ii) the use of a limited amount of IL, a generally expensive chemical which can limit the economic viability of the process. In this section attention will be focused only on the most recent examples of solid-phase assisted catalysis using ionic liquids, following Strategy D. Examples prior to 2006 are covered in recent reviews and will not be discussed here. " ... 

Reviewing the so far published literature about transition metal catalysis in ionic liquids it becomes quite clear that by far the greatest part of the work has been carried out in the form ofliquid-liquid biphasic catalysis. There are three convincing arguments for the choice of this reaction mode. 

Polymers are essential to modem society. They are found in every household as plastics, fibers, coatings, detergents, adhesives etc. So, it is not surprising that the use of ionic liquids as solvents for polymerization reactions is now being extensively explored. This is the subject of this chapter and reviews in the literature have already covered aspects of this field in some detail [1]. 

This book reviews reactions in which ionic liquids, fluorous media and supercritical CO2 are used, as these solvents are the most promising new types of green reaction media. Sufficient details are provided to allow researchers to explore the use of these solvents in specific reactions. Typical examples of reaction conditions and workup procedures are included at the end of each chapter to allow chemists to utilize these new technologies with confidence, and extensive references to the literature are listed. Other standard green reaction media such as water, ethanol, aqueous surfactant micelles and polymers, as well as solvent-free conditions, are outside the scope of this book. 

The novice reader may think that the subject is an emerging field however, the green chemistry name is an umbrella for many well-established ideas and techniques that already exist in the literature. None of the techniques under the green technology label can therefore be considered new. For example, the first room-temperature ionic liquid, ethylammonium nitrate [EtNH3] [N03] , which melts at 12°C was discovered by Paul Walden in 1914 [40], Ionic liquids were also observed in Friedel-Crafts acylation and alkylation reactions [41,42], The reader is directed to two reviews that chronicle the historical development of ionic liquids [43,44]. Microwave-assisted synthesis was developed by Gedeye and Westaway at Laurentian University in Sudbury, Canada [45-48],... 

As far as specific ion effects in nonaqueous solutions (including Ionic Liquids) are concerned, the literature is scarce and no general conclusions have been drawn so far. Mostly, solubility data are given and sometimes also conductivity or osmotic coefficients. A collection of data can be found in [25], but there is no review on specific if effects in nonaqueous systems. 

Geldbach, T.J., Organometallics in Ionic Liquids-Catalysis and Coordination Chemistry , in Organometallic Chemistry, Vol. 34 A Review of the Literature Published between January 2004 and December 2005, Eds. I.J.S. Fairlamb and J. Lynam, Royal Society of Chemistry, Cambridge (2008), pp. 58-73. 

A recent review by Tang et al. (2012) describes methods of preparation of ionic liquids in which either the cation or the anion beas functional groups such as hydroxyl, ethers (including PEG -(CH2-CH2-0) -CH3 with up to 16), thiols, and others. They discuss their physical, including electrochemical, properties, toxicity and biodegradability, and applications as solvents for organic and enzymatic reactions, as media for capture of CO and SO and for separation of gaseous mixtures. They list 406 references to literature. 

The behavior of liquid primary alcohols in various surfactant systems is of course not universally the same. It can depend on the type of surfactant and/or of the other components in the microemulsion system [7,8,18,19,106-132] the latter fact justifies and increases the importance of the previous sections, which reveal the properties of pure alcohols and alcohol/water systems. The effects of alcohols also strongly depend on their partition between the water phase, oil phase, and interface surfactant film. Alcohol partition behavior in ionic surfactant systems was thoroughly reviewed by Zana [7]. In the following we focus more on their different roles and the variety of effects on the structure and intermolecular interactions in microemulsion systems. These phenomena will be presented for the example of a ternary system composed of the nonionic surfactant Brij 35 at moderate concentrations, water and one of the simple alcohols from ethanol to 1-decanol, and will be supported with an additional literature review [7,109-119]. 

John Wilkes insightful review of the history of ionic liquids up to 2002, he showed that these neoteric compounds are not so new after all. In fact, their history dates back to the nineteenth century, where probably the first documented case of an ionic liquid was recorded when a red oil was observed to form during a Friedel-Crafts reaction. Work in the early twentieth century demonstrated that simple ammonium salts could be liquids below room temperature. For example, ethylammonium nitrate has a melting point of 12°C. Even though ionic liquids have been known for many years, it took a long time for them to become popular in the research community. As shown in Figure 1, very little publication activity on ionic liquids existed prior to 2000. From 1980 to 1989, one finds from a Web of Science search that only 35 articles appeared that used the term ionic liquid. Perhaps if we expand the search a bit and include those studies that used the term molten salt to mean ionic liquid as defined here, we may have retrieved a few more examples. Still, at one time in the recent past it was possible for a person to read every article published on the topic and still have time to eat, sleep, and carry out his or her own research. Everybody working in the field knew one another, and each of those researchers was familiar with the complete literature. What a difference a few years make ... 

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