Liquids, ionic

Ionic liquids posses some remarkable properties  

Ionic liquids (ILs) are organic salts composed of cations and anions that exist as liquids at ambient temperatures. Their unique and environmentally attractive properties, such as nonvolatUity, nonflammability, and excellent chemical and thermal stability have made them a promising alternative to conventional organic solvents for applications in biocatalysis. In addition, the physicochemical properties 

Water-miscible ionic liquids are usually toxic to microorganisms, but some microorganisms tolerate small amounts of water-miscible ionic hquids. For ejomple, Pichia 

In another type of application, water-immiscible ILs can form biphasic systems, where the enzyme and the cofactor dissolved in the aqueous phase is physically separated from the substrates and products mainly in the IL phase. The first report of enzymatic ketone reduction in an IL-buffer biphasic system described the IfoADH-catalyzed enantioselective reduction of 2-octanone in a biphasic system containing buffer and [BMIM][Tf2N], which showed higher reaction rates than that in buffer-methyl tert-butyl ether biphasic system [53]. 

In another example, the advantage of ILs used as solvent phase was clearly demonstrated during the reduction of 4-chloroacetophenone by I. k r. The reaction produced (JJ)-l-(4-chlorophenyl)ethanol in 46.2% yield in aqueous medium and hardly proceeded in aqueous-organic solvent (e.g., decane, tert-butyl methyl ether) biphasic system. However, the addition of 20% [BMIM][Tf2N] doubled the chemical yield of the alcohol product to 92.8% and pushed the product purity to an excellent 99.7% ee. The result was explainable that [BMIM][Tf2N] serves as a substrate reservoir and in situ extracting agent without destructive effects on the cell membranes [57]. 

The term ionic liquids refers to liquids that exclusively contain ions. They are liquid salts which do not need to be dissolved in a solvent such as water. As a rule, the term ionic liquids is used when the corresponding salts are liquid at temperatures lower than 100 °C. Examples of suitable cations are alkylated imidazolium, pyridin-ium, ammonium or phosphonium ions. The size and the symmetry of the participating ions prevents the formation of a strong crystal lattice, meaning that only small amounts of thermal energy are needed to overcome the lattice energy and break up the solid crystal structure. 

Ionic liquids should also be very suitable for use as monopropellants, but the salts used must contain either the oxidizer and fuel combined, or salt mixtures which contain both oxidizing and reducing salts. Since these mixtures are homogeneous systems which contain both the oxidizer and fuel, they can be labeled as monopropellants, just as hydrazine is. Particularly interesting are salt mixtures which are less toxic and have a lower vapor pressure than hydrazine. Such mixtures are also known as green propellants . Suitable anions are the nitrate or dinitram-ide ions [58], A combination which has already been studied intensively as an oxidizer is the HAN, hydroxylammonium nitrate system. ADN, ammonium nitrate (AN) and hydrazinium nitrate (HN) have also been investigated. As fuels, hydroxylammonium azide (HAA), ammonium azide (AA) or hydrazinium azide (HA) may be appropriate. As a rule, these salt mixtures are not used as pure substances on safety grounds, but with 20 or 40 % water added they then decom- 

In the future, 1,4,5-substituted tetrazolium salts with the general formula depicted in Eig. 9.25 should be synthesized and evaluated. Due to the introduction of hydrophobic side chains (except for NH2) one would expect these compounds to have melting points below 100 °C. 

It should be advantageous to introduce methyl-, ethyl-, ethylazide- and amino-groups, on the 1- and 4-position of the tetrazole ring system as well as hydrogen, 

The use of ionic liquids (also called molten salts) as reaction media is a relatively new area, although molten conditions have been well established in industrial processes (e.g. the Downs process, Fig. 11.2) for many years. While some molten salts are hot as the term suggests, others operate at ambient temperatures and the term ionic liquids is more appropriate. Although the terms ionic liquids and molten salts are sometimes used interchangeably, we make a clear distinction between them, using ionic liquid only for a salt with a melting point 373 K. 

When an ionic salt such as NaCl melts, the ionic lattice (see Fig. 6.16) collapses, but some order is still retained. Evidence for this comes from X-ray diffraction patterns, from which radial distribution functions reveal that the average coordination number (with respect to cation-anion interactions) of each ion in liquid NaCl is 4, compared with 6 in the crystalline lattice. For cation-cation or anion-anion interactions, the coordination number is higher, although, as in the solid state, the intemuclear distances are larger than for cation-anion separatirais. The solid-to-liquid transition is accompanied by an increase in volume of 10-15%. 

The term eutectic is commonly encotmtered in molten salt systems. The reason for forming a eutectic mixture is to provide a molten system at a convenient working temperature. For example, the melting point of NaCl is 1073 K, but is lowered if CaCl2 is added as in the Downs process. 

A eutectic is a mixture of two substances and is characterized by a sharp melting point lower than that of either of the components a eutectic behaves as though it were a single substance. 

Other alkali metal halides behave in a similar manner to NaCl, but metal halides in which the bonding has a significant covalent contribution (e.g. Hg(ll) halides) form melts in which equilibria such as 9.80 are established. In the solid state, HgCl2 forms a molecular lattice, and layer structures are adopted by HgBr2 (distorted Cdl2 lattice) and Hgl2. 

Room temperature ionic liquids arc currently receiving considerable attention as environmentally friendly alternatives to conventional organic solvents in a variety of contexts.The ionic liquids have this reputation because of their high stability, inertness and, most importantly, extremely low vapor pressures. Because they are ionic and non-conducting they also possess other unique properties that can influence the yield and outcome of organic transformations, Polymerization in ionic liquids has been reviewed by Kubisa. Commonly used ionic liquids are tetra-alkylammonium, tetra-alkylphosphonium, 3-alkyl-l-methylimidazolium (16) or alkyl pyridinium salts (17). Counter-ions are typically PF and BFT, though many others are known. 

Harrison et have used PLP (Section 4.5.2) to examine the kinetics of 

MMA polymerization in the ionic liquid 18 (bmimPFf,). They report a large (ca 2-fold) enhancement in kp and a reduction in Af This property makes them interesting solvents for use in living radical polymerization (Chapter 9). Ionic liquids have been shown to be compatible with ATRP and RAFT. However, there are mixed reports on compatibility with NMP. Widespread use of ionic liquids in the context of polymerization is limited by the poor solubility of some polymers (including polystyrene) in ionic liquids. 

There is also some evidence that the ionic liquid medium affects polymer structure. Uiedron and Kubisa reported that the tacticity of PM A prepared in the chiral ionic liquid 19 is different from that prepared in conventional solvent. It is also reported that reactivity ratios tor MMA-S copolymerization in the ionic liquid 18 differ from those observed for bulk copolymerization. 

Lewis acids are known to form complexes both with monomers and with propagating species. Their addition to a polymerization medium, even in catalytic amounts, can bring about dramatic changes in rate constants in homopolymerization (Section 8.3.4.1) and reactivity ratios in copolymerizalion (Section 8.3.4.2). Early work in this area has been reviewed by Bamford and Barton and Borsig. fhere is significant current interest in using Lewis Acids in establishing tacticity control in homopolymerization (see 8.3.4.1). 

The development of ionic liquids (ILs) was a significant addition to the range of chemical tools and is of particular interest here because many of them are heterocycles. The name is self-explanatory and can include a vast range of types, but is usually taken to mean salts that are liquid at or slightly above room 

Their normal laboratory applications are as specific solvents, catalysts and phase tags (5.1.5.2). 

Their abbreviations, for use in reaction schemes, are not universally defined, but amongst the common styles are, for example, l-n-butyl-3-methylimidazolium chloride = [BMIM][C1] or [bmim][Cl]. 

While it can be questioned how green ILs are, they are certainly useful chemically. They have numerous uses as Lewis or protic acid catalysts, for example aluminium chloride in [emim][Cl] is a superior catalyst for the Friedel-Crafts acylation of indoles bearing electron-withdrawing groups and of azaindoles.  

Ionic liquid bisulfate salts are good catalysts for the esterification of acids with neopentanol, where the starting materials are soluble in the ionic liquid, but the ester insoluble, allowing an easy isolation of the product.  

In the next section ionic liquids will be discussed briefly, some of which can also be considered as carbocation-based salts. They are far more stable but, on the other hand, have a lower catalytic activity. 

Ionic Uquids are salts that have, per definition, a melting point below 100 °C. If their melting point is below room temperature they are called room temperature ionic liquids (RTIL). The latter have attracted much interest in recent years as novel solvents for reactions and electrochemical processes [116]. Some of these liquids are considered to be green solvents [117]. The most commonly used liquids are based on imidazolium cations like 1-butyl-3-methylimidazoHum [bmim] with an appropriate counter anion like hexafluorophosphate [PFg]. Many ionic liquids are known to accelerate reactions. In most cases, achiral ionic liquids are applied and have been reviewed [116]. Here, the few examples of chiral ionic liquids (CILs) as catalysts are discussed. 

it would be possible to consider imidazolium-based ionic liquids as hydrogen bond activator organocatalysts, which will be discussed in another chapter. 

Chiral ionic liquids have also been applied in the Baylis-HUhnan reaction [131, 132]. Since they were used as co-catalyst and the asymmetric induction is considered to be achieved by the formation of ion pairs, they will not be discussed in detail here. 

Examples of enantiopure ionic Hquids appHed successfully as asymmehic catalytic reaction media are stiU very hmited. However, considering the large number of possible applications in combination with the advantages of easy recoverability, it is an important task to develop this research further. 

The scope of the thesis is to study and develop small-scale processes for ionic liquid-based extractions that can intensify the liquid-liquid separations of the spent nuclear fuel reprocessing cycle. In addition, modeUing methodologies are proposed to evaluate the applicability of the small-scale extractors in reprocessing large volumes of nuclear waste in industrial scale. 

Micro-technology is an important area in process intensification, which offers numerous potential benefits for the process industries. The pressing demands for sustainable, efficient, and safer flow processes make micro-fluidic devices an 

Tsaoulidis, Studies of Intensified Small-scale Processes 

Franke, R., GeiBelmann, A., Hahn, H. (2009). An industrial view of process intensification. Chemical Engineering and Processing Process Intensification, 48, 329-332. Cross, W., Ramshaw, C. (1986). Process intensification Laminar flow heat transfer. Chemical Engineering Research and Design, 64, 293-301. 

Gavriilidis, A., Angeli, P., Cao, E., Yeong, K., Wan, Y. (2002). Technology and applications of microengineered reactors. Chemical Engineering Research and Design, 80, 3-30. 

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. 

Clays modified with thermally stable ionic liquids 

In recent years, the surge of interest in ionic liquids has established phosphonium salts as favoured catonic components (Chapter 6.9). Phosphorus-containing anionic components of ionic liquids have also been found in, for example, R4P (RO)2S(0)0, R4P(R0)2P(0)0 , R4F(RO), (R )P(0)0 and R4F(R )2P(0)0-[95,96], 

3-Triazolium Salts as a Versatile New Class of Ionic Liquids 

Zekarias Yacob and Jurgen Liebscher Humboldt-University Berlin Germany 

Most of the 1,2,3-triazolium based ionic liquids are room temperature ionic liquids (RTILs) (Fletcher, Keeney et al. 2010 Khan, Hanelt et al. 2009). So far, not so many physical constants have been reported. Viscosity measurements and differential thermogravimetry (TGA) measurements of some 1,3,4-trisubstituted 1,2,3-triazolium ionic liquids counter-ions Qeong and Ryu 2010 Khan, Hanelt et al. 2009). These reports indicated good thermal stability up to 355 °C, which is strongly dependent on several variables such as the kind of counter-ion and the nature of substituents on the triazolium ring. One can tune the stability of 1,2,3- 

Since 1,2,3-triazolium ionic liquids have not been commercially available, their application as mere solvent is rare. l,3-Dialkyl-l,2,3-triazolium ionic liquids have been developed as stable and recyclable solvents for the Baylis-Hillman reaction. The Baylis-Hillman reaction between p-chlorobenzaldehyde and methyl acrylate was conducted in 1,2,3-triazolium ionic liquids at room temperature in the prescence of DABCO. Interestingly the reaction furnished improved yields within shorter reaction time in the triazolium ionic liquids as compared to analogous imidazolium ionic liquids (feong and Ryu 2010). 

1 Application of 1,2,3-triazolium ionic liquids in catalyst tagging 

According to the complexing ability of their anions, ionic liquids are classified as basic, neutral and acidic [50]. Some examples of neutral ionic liquids are reported in Table 6.9. 

Room temperature ionic liquids are air stable, non-flammable, nonexplosive, immiscible with many Diels-Alder components and adducts, do not evaporate easily and act as support for the catalyst. They are useful solvents, especially for moisture and oxygen-sensitive reactants and products. In addition they are easy to handle, can be used in a large thermal range (typically —40 °C to 200 °C) and can be recovered and reused. This last point is particularly important when ionic liquids are used for catalytic reactions. The reactions are carried out under biphasic conditions and the products can be isolated by decanting the organic layer. 

Room temperature ionic liquids have been found to be excellent solvents for a number of reactions [50b] such as the isomerization [51], hydrogenation [52] and Friedel-Crafts reactions [53]. A number of Diels-Alder reactions were recently investigated in these systems. 

Earle and coworkers [54] have performed Diels-Alder reactions in neutral ionic liquids. The results of reactions of cyclopentadiene with dimethyl maleate, ethyl acrylate and acrylonitrile are reported in Table 6.10. The cycloadditions proceeded at room temperature in all of the ionic liquids tested, except [BMIMJPF4, and gave almost quantitative yields after 18-24h. The endo/exo selectivity depends on dienophile. No enantioselectivity was observed in the [BMIM] lactate reaction. 

The use of Lewis acids (ZnU, BF3 Et20) in ionic liquids, tested in the cycloaddition of but-3-en-2-one with isoprene, increases both the rate and selectivity of the reaction. The ionic liquid remains catalytically active after the work-up and can be reused. 

An ionic liquid (IL) is literally an ionic compound (a salt) that is a liquid. Of most current interest are salts that are liquids at room temperature (RTILs), or at least below 100 °C. There is a range of compounds that form room temperature ionic liquids dating back to ethanolammonium nitrate, (EtNH3)+(N03) (m.p. 14 °C), synthesised by Walden in 1914. Perhaps the most popular and well-studied are those based on the l-butyl-3-methylimidazolium (bmim) cation, such as brnim PFg (13.20) and bmim+BF4 which melts at ca. -80 °C. The imidazolium ionic liquids were initially used as their halogenoaluminate salts but they have a major drawback in that they are highly moisture sensitive. 

In 1992, Zaworotko used weakly coordinating anions such as hexafluorophosphate and tetrafluo-roborate, greatly expanded the range of ionic liquids available. Modern ionic liquids that are air- and moisture stable based on non-coordinating anions has meant that the field has attracted tremendous 

Pharmaceuticals - 8000 Optical Fluids Magnetic Fluids ILs in Solar Cells ILs In Ion propulsion ILs in Fuel Cells Fleat Transfer Fluids Energetic Materials ILs for Electro-optics ILs for Biomass Processing Entrainers Acid Scavengers Flydraulic Fluids Lubricants Catalysts 

With the exception of fhe mosf studied ionic liquid, the EtMelm+BF4 imid-azolium salt, the major drawback of ionic liquids is their low conductivity at room temperature in aqueous and acetonitrile-based systems [112]. Table 4.7 illustrates that even EtMeIm+BF4 suffers from increased resistivity (lower conductivity) compared to aqueous or organic electrolytes. The correlation 

SCHEME 8.8 A cation that is protected by a ring and two carbon chains (shown by wiggly lines emanating from N). This protection of the positively charged site prevents the anion Br from packing well with the cation. Together, they form an ionic liquid. 

Acetylation reactions which could be of use in the transformation of bio-sourced alcohols and sugars have been performed in bmim-derived ionic liquids (Forsyth el al., 2002 Alleti el al., 2005). If the dicyanamide anion is incorporated into the liquid, mild acetylations of carbohydrates can be performed at room temperature, in good yields, without any added catalyst (Forsyth el al., 2002). The ionic liquid acts as an efficient base catalyst. 

Related to ionic liquids are substances known as deep eutectic solvents or mixtures. A series of these materials based on choline chloride (HOCH2CH2NMe3Cl) and either zinc chloride or urea have been reported (Abbott et al., 2002 2003). The urea/choline chloride material has many of the advantages of more well-known ionic liquids (e.g. low volatility), but can be sourced from renewable feedstocks, is non-toxic and is readily biodegradable. However, it is not an inert solvent and this has been exploited in the functionalisation of the surface of cellulose fibres in cotton wool (Abbott et al, 2006). Undoubtedly, this could be extended to other cellulose-based materials, biopolymers, synthetic polymers and possibly even small molecules. 

4 Other Alternatives to YOCs Solventless , Biphasic and Bio-Sourced Solvents 

Throughout the chemical industry, many products, such as poly(propylene) are made without the use of a solvent or are performed in the gas phase. In many cases, one of the reactants also acts as the solvent. As the field of green chemistry has grown, so has the number of so-called solventless reactions, including 

Microwave heating has also been applied in the solvent-free phosphorylation of microcrystalline cellulose (Gospodinova et al., 2002). In the isolation step of this procedure, only water and ethanol were used as additional solvents. Wax esters have been produced from vegetable oils using a solvent-free enzymatic process (Petersson et al, 2005) this is particularly noteworthy as enzymes are often intolerant to high concentrations of substrates. The examples of solvent-free procedures described here show that solvents are not always required in the transformation of naturally sourced biopolymers and also in the chemistry of small molecules that can be obtained from a biorefinery. 

Before 2001, only a few pure component properties (densities, viscosities, etc.) and mixture properties (phase equilibrium behavior, excess properties) involving ionic liquids were available. For a better understanding of their behavior and for the 

The large miscibility gap observed for an ionic liquid mixed with an aliphatic compound (without the addition of water as in the case of NMP) can be directly used for the separation of aromatic from aliphatic hydrocarbons by liquid-liquid extraction. Besides the miscibility gap, there are other requirements necessary for a successful extractant, such as high selectivity, high capacity, a low solubility of the extractant in the raffinate phase, a simple separation of the extract and the raffinate phase, low viscosity, high chemical and thermal stability and a sufficient density difference. Nearly all these requirements are met by the ionic liquids that have so far been investigated. However, our present knowledge of the thermal and chemical stability of ionic liquids is limited. For example, for some ionic liquids (largely dependent on the anion), hydrolysis does occur. 

The high solubility of aromatic compounds in ionic liquids can also be used for the removal of the different dibenzothiophenes using liquid-liquid extraction. These are the compounds that are usually difficult to convert by hydro-treating in desulfurization processes. 

For the industrial application of ionic liquids, as selective solvents for separation processes or other applications, a reliable knowledge of the pure component properties and mixture data (phase equilibria, excess properties) is required. Although 

An ionic liquid is a liquid that consists only of ions. However, this term includes an additional special definition to distinguish it from the classical definition of a molten salt. While a molten salt generally refers to the liquid state of a high-melting salt, such as molten sodium chloride, an ionic liquid exists at much lower temperatures (approx. 100 °C). The most important reported ionic liquids are composed of the following cations and anions  

The development of ionic liquids has revealed that the ions possess the following structural features  

The physical and chemical properties of the ionic liquids that make them interesting as potential solvents and in other applications are listed below. 

Salt/ionic liquid mp (°C) Salt/ionic liquid mp(°C) 

The aspects of medium engineering summarized so far were a hot topic in biocatalysis research during the 1980s and 1990s [5]. Nowadays, all of them constitute a well-established methodology that is successfully employed by chemists in synthetic applications, both in academia and industry. In turn, the main research interests of medium engineering have moved toward the use of ionic liquids as reaction media and the employment of additives. 

Ionic liquids, which can be defined as salts that do not crystallize at room temperature [46], have been intensively investigated as environmentally friendly solvents because they have no vapor pressure and, in principle, can be reused more efficiently than conventional solvents. Ionic liquids have found wide application in organometallic catalysis as they facilitate the separation between the charged catalysts and the products. 

In recent years ionic liquids have also been employed as media for reactions catalyzed both by isolated enzymes and by whole cells, and excellent reviews on this topic are already available [47]. Biocatalysis has been mainly conducted in those room-temperature ionic liquids that are composed of a 1,3-dialkylimidazolium or N-alkylpyridinium cation and a noncoordinating anion [47aj. 

The polarity of common ionic liquids is in the range of the lower alcohols or formamide, and their miscibility with water varies widely and unpredictably and is 

Several reports deal also with the effects of ionic liquids on enzyme enantioselectivity, which is the subject of this chapter. Although in several cases there was no change or even a decrease in enantioselectivity compared to organic solvents [47], in other cases improved enantioselectivity was observed [47,49-56]. In the following text, the latter cases will be examined in some detail. 

From overall environmental emissions and toxicity viewpoints the systems discussed so far (solvent free, SCCO2 and water) offer obvious advantages compared to the use of organic solvents, but the case is not quite so clear 

1-ethyl-3-methylimiclazolium chloride-aluminium(iii) chloride ([emimJAIC ) 

In principle, many other solvent combinations could be used in biphasic chemistry although the main driving force in this area is to provide environmental benefits. 

Supercritical fluids (e.g. supercritical carbon dioxide, scCCb) are regarded as benign alternatives to organic solvents and there are many examples of their use in chemical synthesis, but usually under homogeneous conditions without the need for other solvents. However, SCCO2 has been combined with ionic liquids for the hydroformylation of 1-octene [16]. Since ionic liquids have no vapour pressure and are essentially insoluble in SCCO2, the product can be extracted from the reaction using CO2 virtually uncontaminated by the rhodium catalyst. This process is not a true biphasic process, as the reaction is carried out in the ionic liquid and the supercritical phase is only added once reaction is complete. 

Although beyond the scope of this book, a vast amount of work has been directed to supporting homogeneous catalysts on solid supports including silica, alumina and zeolites, and functionalized dendrimers and polymers [19]. These give rise to so-called solid-liquid biphasic catalysis and in cases where the substrate and product are both liquids or gases then co-solvents are not always required. In many ways solvent-free synthesis represents the ideal method but currently solvent-free methods can only be applied to a limited number of reactions [20], 

One of the most advantageous properties of ILs is their very low vapor pressure. This is why they cannot contaminate the atmosphere and are a potential candidate for green chemistry. Reaction products can be separated from ILs by distillation. ILs can dissolve many organic, inorganic, and organometallic compounds. Compared with 

Thiazole and its derivatives are useful compounds in medicinal and agricultural chemistry. The thiazolium ring is present in vitamin B1 and its coenzyme form is important for the decarboxylation of a-keto acids [74]. This heterocyclic system has broad application in drug development for the treatment of inflammation [75] and bacterial [76] and HIV infections [77]. Hence the thiazole nucleus has been much studied in organic and medicinal chemistry. Originally it was synthesized by the Hantzsch reaction (a-halo ketones with thioamides or thioureas) (Equation 4.38) [78]. 

With a simple one-pot reaction of 2-chloro-l,3-dicarbonyl compounds with thioureas or thioamides in the presence of 1-butyl-3-methylimidazolium trifluorometha- 

The basic IL l-butyl-3-methylimidazolium hydroxide ([bmimJOH) efficiently catalyzes the condensation reaction of aldehydes and ketones with hydroxylamine hydrochloride with ultrasound irradiation (Equation 4.41). Compared with conventional methods, the main advantages of this procedure are milder conditions, shorter reaction times, and higher yields [81]. 

A series of halomethylated P-enaminones were synthesized using the IL [bmim] BF4 at room temperature (Equation 4.43). It was demonstrated that this IL is suitable as a reaction medium for the amination of P-alkoxyvinyl halomethyl ketones. This method is advantageous because of the absence of solvents, short reaction times, and good yields [84]. These compounds are now widely used as important materials in research, having interesting functionalities for use in medicinal and agricultural sciences [85]. 

In terms of the solvent-oriented description of acid-base chemistry in a non-aqueous solvent, equation 8.77 illustrates that, in molten HgBr2, species producing [HgBr] ions may be considered to act as acids, and those providing [HgBr3] ions function as bases. In most molten salts, however, the application of this type of acid-base definition is not appropriate. 

Anastas and Warner (see further reading) have developed 12 principles of green chemistry and these clearly illustrate the challenges ahead for research and industrial chemists  

Reaction of nraninm metal with N2O4 in N204/MeN02 solvent leads to the formation of [U02(N03)3 in which the U centre is 8-coordinate. Snggest (a) a strncture for the [U02(N03)3l anion, and (h) the identity of the counterion. 

Write an equation for the reaction of Na metal in liquid N2O4. 

Poliakoff, MW. George, and S.M. Howdle, in Chemistry Under Extreme or Non-Classical Conditions, R. van Eldik, and C.D. Hubbard, Eds., Wiley, New York, 1997, pp. 189-218. 

Nakamura, in Supercritical Fluid Processing of Food and Biomaterials, S.S,H. Rizvi, Ed., Blackie Academic Professional, London, 1994, pp. 54-61. 

Debedenetti, in Supercritical Fluids, Fundamentals for Application, E. Kiran, and J.M.H. Levent Sengers, EAs., Kluver Academic Publishers, Dordrecht, 1994, pp. 719-729. 

Murphy, E. Hansen, J. Jones, B. Mierau, S. G. Sunol, in Proceedings of the 5th International Symposium on Supercritical Fluids, Tome 1, ISAFS, Nice, 1998. 

Schmitt, R.A. Grieger-Bloc T.W. Chapman, in Chemical Engineering at Supercritical Fluid Conditions, M.E. Paulatis, J.M.L. Peiminger, R.D. Gray, and P. Davidson, Eds., Ann Arbor Science, Ann Abor, MI, 1983, p.445-460. 

The equilibrium constant for this reaction is strongly temperature dependent and somewhat influenced by the nature of the cation. Chum and Osteryoung report values of of 1.06x10 in AlClj/NaCl, 1.19x10 in AlCyA-n-butylpyridinium chloride (RCl) at 175°C, and 3.8 x 10 in the latter system at 30°C. They show what 

Anions other than the very water-sensitive and reactive haloaluminates have been added to the repertoire, including nitrate, phosphate, hexafluorophosphate, hexafluoroanti-monate, tetrafluoroborate, trifluoromethanesulfonate ( triflate ), and bis (trifluoro-methanesulfonyljimide, Examples of cations that are used include mraio- to 

Room-temperature ionic liquids have recently attracted a great deal of industrial interest (Carmichael, 2000 Guterman, 1999 see also the brief overview by Earle et al. (2003) and the extensive and detailed review by Olivier-Bourbigou et al. (2010). They are versatile as solvents or nonsolvents for organic substances, and some exhibit strongly temperature-dependent water solubility. They are nonvolatile. Some, notably those containing haloaluminate anions, have widely variable Lewis and Brpnsted acidity (into the superacid range). Others, such as those with tetrafluoroborate or hexafluorophosphate 

Ionic liquids, owing to their stability and nonvolatility, contribute to green chemistry. In many applications they are easily recovered and recycled, and volatile organic substances can be recovered from them by distillation under mild conditions in vacuo. For instance, the ability of l-butyl-3-methylimidazolium hexafluorophos-phate to dissolve both the organic reagent (chloromethyl)-benzene and the salt potassium cyanide has been exploited (Wheeler et al 2001) in a successful 

The use of ionic liquids in synthesis is the subject of a monograph by Wasserscheid and Welton (2008). A number of reaction types may be advantageously carried out in room-temperature ionic liquids. They include the following  

Room-temperature IL (RTILs) are a novel class of materials that can be utilized, for instance, as bulk solvents in biphasic operations, separations, and electrochemistry. The key features of these neoteric solvents are as follows generally, RTILs have a negligible or at least a very low vapor pressure in most cases, they are considered nonflammable RTILs are recyclable and possess unique solvation properties (high concentrations of solute, up to 2 1 some of them can dissolve cellulose and mineral rock) they have a wide liquidus range (from around — 100°C to -E400°C) and selective stabilization properties (immobilization of catalytically active species and nanoparticles) they are tunable in terms of polarity and co-miscibility with molecular solvents many have high solubility of various industrially important gases such as H2, O2, and CO2 and supercritical CO2 is often infinitely soluble in ILs, whereas ILs do not dissolve in SC-CO2 (separation aspect). 

The first IL was discovered in the early twentieth century, soon to be followed by the chloroaluminates, which were primarily targeted for improved battery technology. The problem with chloroaluminates is that they are both moisture and oxygen sensitive, and they are only stable in an inert atmosphere. Much later, at the beginning of the 1990s, Wilkes et al. discovered the first moisture- and air-stabile ILs. Until today, the scope of possible cation-anion combinations and as a new trend, zwitterionic compounds, has expanded tremendously for example, various alkyl-imidazolium, alkyl-pyridium, quaternary phosphonium, quaternary ammonium, and thiazolinium cations can be coupled with a multitude of anions such as [PFe] , [BF4] , [Cl] , [Br], and [A1C1] . Moreover, deep 

1-ethyl-3-methylimidazolium chlorjde-alumjnium(iii) chloride ([emimlAICU) 

1-butyl-3-methylimidazolium fluoride-boron trifluoride ([bmim]BF4) PFa- 

While polymeric plasticizers may cause a reduced flexibility in plastic materials, they can also be used in combination with traditional plasticizers to improve the leaching resistance. 

A poly(ester) plasticizer has been described, condensed from 2-methyl-l,3-propanediol, 3-methyl-l,5-pentanediol, adipic acid, and isononanol. The poly (ester) plasticizer exhibits high plasticization efficiency and imparts excellent oil resistance to synthetic resins (27). 

Some ionic liquids, suitable as plasticizers are shown in Table 

Ionic liquids have low volatility, low melting points and a high boiling point. They are high-temperature stable, non-flammable and are compatible with a wide variety of organic and inorganic materials. A number of ionic liquids are capable of to plasticize PVC in the same manner as DOP. 

Most ILs are based on quaternary ammonium cations such as 1,3-diaIkyHmidazoHum, N,N,N,N-tetraalkylammonium, N,N-dialkylpyrrolidinium, N-alkylpyridinium, or N-alkylpiperidinium. Other options are, for example, P,P,P,P-tetraaIkylphosphonium and S,S,S-trialkylsulfonium cations. Preferred anions can be either organic anions such as dicyanamide (DCA ), triflate 

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Gillan M 1980 Upper bound on the free energy of the restricted primitive model for ionic liquids Mol. Phys. 41 75... 

Haksjold B and Stell G 1982 The equilibrium studies of simple ionic liquids The Liquid State of... 

USING OF ION SELECTIVE ELECTRODES FOR THE DETERMINATION OF THE IONIC LIQUIDS SOLUBILITY... 

Theoretical and applied aspects of microwave heating, as well as the advantages of its application are discussed for the individual analytical processes and also for the sample preparation procedures. Special attention is paid to the various preconcentration techniques, in part, sorption and extraction. Improvement of microwave-assisted solution preconcentration is shown on the example of separation of noble metals from matrix components by complexing sorbents. Advantages of microwave-assisted extraction and principles of choice of appropriate solvent are considered for the extraction of organic contaminants from solutions and solid samples by alcohols and room-temperature ionic liquids (RTILs). 

The drermodynamic data for CuaS-FeS (Krivsky and Schuhmann, 1957) show that drese sulphides mix to form approximately ideal ionic liquids. These are molten salts in which the heat of mixing is essentially zero, and die entropy of mixing is related to the ionic fractions of die cations and anions. In the present case die ionic fractions yield values for the activities of the two sulphides... 

Commonly used ionic liquids are N-alkylpyridinium, N,N -dialkylimidazolium, alkylammonium and alkylphosphonium salts. 

To date a number of reactions have been carried out in ionic liquids [for examples, see Dell Anna et al. J Chem Soc, Chem Commun 434 2002 Nara, Harjani and Salunkhe Tetrahedron Lett 43 1127 2002 Semeril et al. J Chem Soc Chem Commun 146 2002 Buijsman, van Vuuren and Sterrenburg Org Lett 3 3785 2007]. These include Diels-Alder reactions, transition-metal mediated catalysis, e.g. Heck and Suzuki coupling reactions, and olefin metathesis reactions. An example of ionic liquid acceleration of reactions carried out on solid phase is given by Revell and Ganesan [Org Lett 4 3071 2002]. 

T. Welton, Room temperature ionic liquids. Solvents for synthesis and catalysis, Chem Rev 99 2071-2083 1999. C.M. Gordon, New developments in catalysis using ionic liquids, Appl. CatalA General 222 101-117 2001. 

R. Sheldon, Catalytic reactions in ionic liquids, J Chem Soc, Chem Commun 2399-2407 2001. 

Chapters 1 and 2 have been reorganised and updated in line with recent developments. A new chapter on the Future of Purification has been added. It outlines developments in syntheses on solid supports, combinatorial chemistry as well as the use of ionic liquids for chemical reactions and reactions in fluorous media. These technologies are becoming increasingly useful and popular so much so that many future commercially available substances will most probably be prepared using these procedures. Consequently, a knowledge of their basic principles will be helpful in many purification methods of the future. 

The singlet multidensity Ornstein-Zernike approach for the density profile described in this section has also been applied to study the role of association effects in the ionic liquid at an electrified interface [22]. 

Room-temperature ionic liquids, salts with A,A-dialkylimidazolium cations in synthesis and catalysis 99CRV2071. 

Ionic Liquids in Synthesis. Edited by Peter Wasserscheid, Thomas Welton Copyright 2002 Wiley-VCH Verlag GmbH Co. KGaA ISBNs 3-527-30515-7 (Hardback) 3-527-60070-1 (Electronic)... 

Ionic liquids may be viewed as a new and remarkable class of solvents, or as a type of materials that have a long and useful history. In fact, ionic liquids are both, depending on your point of view. It is absolutely clear though, that whatever ionic liquids are, there has been an explosion of interest in them. Entries in Chemical Abstracts for the term ionic liquids were steady at about twenty per year through 1995, but had grown to over 300 in 2001. The increased interest is clearly due to the realization that these materials, formerly used for specialized electrochemical applications, may have greater utility as reaction solvents. 

There are many synonyms used for ionic liquids, which can complicate a literature search. Molten salts is the most common and most broadly applied term for ionic compounds in the liquid state. Unfortunately, the term ionic liquid was also used to mean molten salt long before there was much literature on low-melting salts. It may seem that the difference between ionic liquids and molten salts is just a matter of degree (literally) however the practical differences are sufficient to justify a separately identified niche for the salts that are liquid around room temperature. That is, in practice the ionic liquids may usually be handled like ordinary solvents. There are also some fundamental features of ionic liquids, such as strong... 

None of the interesting materials just described are the direct ancestors of the present generation of ionic liquids. Most of the ionic liquids responsible for the burst of papers in the last several years evolved directly from high-temperature molten salts, and the quest to gain the advantages of molten salts without the disadvantages. It all started with a battery that was too hot to handle. 

U.S. Air Force Academy in 1961. He was an early researcher in the development of low-temperature molten salts as battery electrolytes. At that time low temperature meant close to 100 °C, compared to many hundreds of degrees for conventional molten salts. His work led directly to the chloroaluminate ionic liquids. 

The allcylpyridinium cations suffer from being relatively easy to reduce, both chemically and electrochemically. Charles Hussey (Figure 1.3) and I set out a program to predict cations more resistant to reduction, to synthesize ionic liquids on the basis of those predictions, and to characterize them electrochemically for use as battery electrolytes. 

Mary s University in Halifax, Nova Scotia. He was a visiting professor at the U.S. Air Force Academy in 1991, where he first prepared many of the water-stable ionic liquids popular today. 

We had no good way to predict if they would be liquid, but we were lucky that many were. The class of cations that were the most attractive candidates was that of the dialkylimidazolium salts, and our particular favorite was l-ethyl-3-methylimid-azolium [EMIM]. [EMIMJCl mixed with AICI3 made ionic liquids with melting temperatures below room temperature over a wide range of compositions [8]. We determined chemical and physical properties once again, and demonstrated some new battery concepts based on this well behaved new electrolyte. We and others also tried some organic reactions, such as Eriedel-Crafts chemistry, and found the ionic liquids to be excellent both as solvents and as catalysts [9]. It appeared to act like acetonitrile, except that is was totally ionic and nonvolatile. 

The pyridinium- and the imidazolium-based chloroaluminate ionic liquids share the disadvantage of being reactive with water. In 1990, Mike Zaworotko (Eigure 1.4) took a sabbatical leave at the Air Eorce Academy, where he introduced a new dimension to the growing field of ionic liquid solvents and electrolytes. 

It seems obvious to me and to most other chemists that the table of cations and anions that form ionic liquids can and will be extended to a nearly limitless number. The applications will be limited only by our imagination. 

For a review of salts formerly thought of as low-temperature ionic liquids, see Mamantov, G., Molten salt electrolytes in secondary batteries, in Materials for Advanced Batteries (Murphy, D. W., Broadhead, J., and Steele, B.C. H. eds.). Plenum Press, New York, 1980,... 

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