Ionic liquid -based

This chapter will concentrate on the preparation of ionic liquids based on 1,3-dialkylimidazolium cations, as these have dominated the area over the last twenty... 

Beckmann rearrangements of several ketoximes were performed in room-temperature ionic liquids based on l,3-dialkylimida2olium or alkylpyridinium salts containing phosphorus compounds (such as PCI5) by Deng and Peng [59] (Scheme 5.1-31, BP = 1-butylpyridinium). Turnover numbers of up to 6.6 were observed, but the authors did not mention whether the ionic liquid could be reused. 

Glycidyl methacrylate (purity 98 %) was purchased fiom Aldrich. Ionic liquids based on 1-n-ethyl-3-methyliinidazolium (EMIm), l-n-butyl-3-methylimidazolium (BMhn), 1-n-hexyl-3-methylimidaJ5Dlium (HMhn) with dififeent anions such as CT, BF4", PFg wo e prepared according to the procedures reported previously. Copolymerization of glycidyl methacrylate (GMA) and CO2 were carried out in a 50 mL stainless steel autoclave equipped with a... 

Besides the advantage of recyclability, reactions in ionic liquids are generally faster and are run under milder conditions than reactions with conventional solvents. Further activation may come from ultrasonic agitation.520 Since the majority of ionic liquids used are imidazolium salts, the effect of these solvents can be at least partly attributed to the in situ formation of carbene complexes (Section 9.6.3.4.10).521 Cross-coupling of ArB(OH)2 can also be efficiently performed in ionic liquids based on long-chain tetraalkylphosphonium salts, in which case aryl bromides and some aryl chlorides can be processed in the presence of the trivial ligand PPh3.522... 

The anodic oxidation of the tetrafluoroborate anion occurs at potentials higher than 2.1 V and the remaining hexafluorophosphate and imide anions are oxidised at potentials higher than 2.0 V. Hence, the stability window of the EMImBF4 and BMImBF4 is 4.2 V. Ionic liquids BMImPF6 and EMImN(Tf)2 shows a similar stability window of ca. 4.1 V. However, the window of the BMPyN(Tf)2, is considerably lower ca. 3.0 V. This is consistent with data (ca. 4.1-4.2 V) found for a series of ionic liquids based on EMIm+ and DMPIm+ (l,2-dimethyl-3-propylimidazolium) cations [12],... 

Using a similar protocol, Loupy and coworkers have reported the synthesis of chiral ionic liquids based on (ll ,2S)-(-)-ephedrinium salts under microwave irradiation conditions (Scheme 4.21a) [75]. Importantly, the authors were also able to demonstrate that the desired hexafluorophosphate salts could be prepared in a one-pot protocol by in situ anion-exchange metathesis (Scheme 4.21b). The synthesis and transformation of so-called task-specific ionic liquids is discussed in more detail in Section 7.4. 

Many of these problems may be overcome by using ionic liquids based on sugars [35] or deep eutectic mixtures. Deep eutectic mixtures such as that derived from choline chloride and urea (m. pt. 12°C [36]) or carboxylic acids [37] can be liquids and have very low vapour pressure. They have been successfully used as electrochemical solvents, but their use in catalysis remains little explored. Urea is a fertiliser and choline chloride (Vitamin B4) is a component of chicken feed so the mixture is environmentally acceptable. 

The physical properties of ionic liquids have been extensively studied and some trends are beginning to emerge. In particular, ionic liquids based on 1,3-dialkylimidazolium cations have been investigated in detail, partly due the their wide use as solvents to conduct synthesis and catalysis. The attraction of the imidazolium cation in synthetic applications is because the two substituent groups can be varied to modify the properties of the solvent. For example, Table 4.1... 

Ionic liquids based on imidazolium cations and either [BF4]- or [PF6] anions have been used to immobilize transition metal based oxidation catalysts developed... 

Sun, J. MacFarlane, D. R. Forsyth, M. A new family of ionic liquids based on the l-alkyl-2-methylpyrrolinium cation, Electrochim. Acta, 2003, 48(12), 1707-1711 Fors3dh, S. Golding, J. MacFarlane, D. R. Forsyth, M. A-methyl-iV-alkylpyrrolidinium tetrafluoroborate salts ionic solvents and solid electrolytes, Electrochim. Acta, 2001, 46(10-11), 1753-1757 Golding, J. J. Macfarlane, D. R. Spiccia, L. et al. Weak intermolecular interactions in sulfonamide salts structure of 1-ethyl-2-methyl-3-benzylimidazolium bis[(trifluoromethyl)sulfonyl]amide, Chem. Commun., 1998, 1593-1594. 

In SILP carbonylation we have introduced a new methanol carbonylation SILP Monsanto catalyst, which is different from present catalytic alcohol carbonylation technologies, by using an ionic liquid as reaction medium and by offering an efficient use of the dispersed ionic liquid-based rhodium-iodide complex catalyst phase. In perspective the introduced fixed-bed SILP carbonylation process design requires a smaller reactor size than existing technology in order to obtain the same productivity, which makes the SILP carbonylation concept potentially interesting for technical applications. 

Anodic limit, potential referred to Li+/Li, cutoff current density in parentheses. Scan rate 5 mV s. Activated carbon as working surface. Scan rate 10 mV s. Supporting electrolyte 0.1 M BU4NBF4. Scan rate 100 mV s . The solvent-free condition was realized by using an ionic liquid based on Imldazolium cation, at 80 °C. Scan rate 20 mV s . ... 

P. Kotianova and E. Matisova, Liquid-phase microextraction and its utilization for trace analysis of organic compounds in water matrix. Chemicke Listy, 2000,94(4), 220-225. Liu Jf, Chi Yg, Jiang Gb, C. Tai, Peng Jf and JT. Hu, Ionic liquid-based liquid-phase microextraction, a new sample enrichment procedure for liquid chromatography. Journal of Chromatography A, 2004,1026(1-2), 143-147. 

Various solid-supported perruthenate reagents have been designed for the oxidation of alcohols.Solid-supported NMO has also been used. A number of perruthenate systems employing O2 as the terminal oxidant have also been reported. The use of ionic liquids based upon substituted imidazolium cations as alternative solvent media for the selective oxidation of alcohols to aldehydes and ketones has also been investigated. ... 

Ionic liquids, having per definition a melting point below 100 °C, and especially room temperature ionic liquids (RTIL) have attracted much interest in recent years as novel solvents for reactions and electrochemical processes [164], Some of these liquids are considered to be green solvents [165]. The scope of ionic liquids based on various combinations of cations and anions has dramatically increased, and continuously new salts [166-168] and solvent mixtures [169] are discovered. The most commonly used liquids are based on imidazolium cations like l-butyl-3-methylimidazolium [bmim] with an appropriate counter anion like hexafluorophos-phate [PFg]. Salts with the latter anion are moisture stable and are sometimes called third generation ionic liquids. 

It is worth pointing out that, besides o-sorbitol 19 and D-mannitol 36, other low-molecular weight building blocks have been already obtained on the ton-scale from low cost or waste polymeric carbohydrates (starch, cellulose, hemicellulose, chitin) [80, 81]. Most of these compounds are densely functionalized enantiopure molecules that can be easily converted into high-value added products, including chiral ionic liquids. Therefore, further studies are required to develop other synthetic approaches to environmentally sustainable ionic liquids based on renewable raw materials. 

MacFarlane, D. et al.. Low viscosity ionic liquids based on organic salts of the dicyanamide anion, Chem. Commun., 1430, 2001. 

Table 3.2 Performance Characteristics of Ionic Liquid-Based Modified Electrodes...

Tao, W., Pan, D., Liu, Q., Yao, S., Nie, Z., and Han, B., Optical and bioelec-trochemical characterization of water-miscible ionic liquids based composites of multiwalled carbon nanotubes. Electroanalysis, 18,1681-1688,2006. 

Immobilized ionic liquid-based sfafionary phases... 

---