2-methylimidazolium

In general, isotopic exchange is both expensive and difficult. In the case of many room-temperature ionic liquids, however, the manufacture of deuterated ionic liquids is relatively easily achievable. For example, the general synthesis of l-allcyl-3-methylimidazolium salts is shown in Scheme 4.1-1 [2]. This methodology allows maximum flexibility in the deuteration on the imidazolium cation that is, it can be either ring or side chain deuteration or both. 

Figure 4.2-1 shows the calculated ab initio molecular structure of the ionic liquid [BMIM][PFg] (l-butyl-3-methylimidazolium hexafluorophosphate). 

Davis and co-workers have carried out the first examples of the Knoevenagel condensation and Robinson annulation reactions [61] in the ionic liquid [HMIM][PFg] (HMIM = l-hexyl-3-methylimidazolium) (Scheme 5.1-33). The Knoevenagel condensation involved the treatment of propane-1,3-dinitrile with a base (glycine) to generate an anion. This anion added to benzaldehyde and, after loss of a water molecule, gave l,l-dicyano-2-phenylethene. The product was separated from the ionic liquid by extraction with toluene. 

The first successful hydrogenation reactions in ionic liquids were studied by the groups of de Souza [45] and Chauvin [46] in 1995. De Souza et al. investigated the Rh-catalyzed hydrogenation of cyclohexene in l-n-butyl-3-methylimidazolium ([BMIM]) tetrafluoroborate. Chauvin et al. dissolved the cationic Osborn complex [Rh(nbd)(PPh3)2][PFg] (nbd = norbornadiene) in ionic liquids with weakly coordinating anions (e.g., [PFg] , [BFJ , and [SbF ] ) and used the obtained ionic catalyst solutions for the biphasic hydrogenation of 1-pentene as seen in Scheme 5.2-7. 

The chloroaluminate(III) ionic liquids - [EMIM][C1-A1C13], for example (where EMIM is l-ethyl-3-methylimidazolium) - are liquid over a wide range of AICI3 concentrations [24]. The quantity of AICI3 present in the ionic liquid determines the physical and chemical properties of the liquid. When the mole fraction, X(A1C13), is below 0.5, the liquids are referred to as basic. When X(A1C13) is above 0.5, the liquids are referred to as acidic, and at an X(A1C13) of exactly 0.5 they are referred to as neutral. 

Room temperature ionic liquids arc currently receiving considerable attention as environmentally friendly alternatives to conventional organic solvents in a variety of contexts.144 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.145 Commonly used ionic liquids are tetra-alkylammonium, tetra-alkylphosphonium, 3-alkyl-l-methylimidazolium (16) or alkyl pyridinium salts (17). Counter-ions are typically PF6 and BF4 though many others are known. 

Anionic surfactants like alkanesulfonates can also be determined by poten-tiometric titration with ion-selective electrodes. Recently, a special PVC electrode was offered as a high-sense surfactant electrode in combination with the new titrant l,3-didecyl-2-methylimidazolium chloride [20]. This one-phase... 

A new class of solvents called ionic liquids has been developed to meet this need. A typical ionic liquid has a relatively small anion, such as BF4, and a relatively large, organic cation, such as l-butyl-3-methylimidazolium (16). Because the cation has a large nonpolar region and is often asymmetrical, the compound does not crystallize easily and so is liquid at room temperature. However, the attractions between the ions reduces the vapor pressure to about the same as that of an ionic solid, thereby reducing air pollution. Because different cations and anions can be used, solvents can be designed for specific uses. For example, one formulation can dissolve the rubber in old tires so that it can be recycled. Other solvents can be used to extract radioactive waste from groundwater. 

ENIM]C1 AICI31 [BP] Cl AICI3 J [BMIM] = 1-butyl-3-methylimidazolium cation [EMIM] = l-ethyl-3-methylimidazolium cation [BP] = N-l-butylpyridinium cation... 

Based on the properties of ionic hquids in high-temperature microwave-enhanced reactions, the authors chose l-butyl-3-methylimidazolium tetraflu-orophosphate ([bmimjPFe) as the suitable ionic liquid (Scheme 23). The addition of 0.15 mmol of [bmimjPFe to a reaction in 2.0 mL of DCF was found to increase the reaction rate dramatically and a set-temperature of 190 °C was reached in a mere 1 min, while the reactions programmed at 190 °C, in the absence of the ionic liquid, reached only 170 °C in 10 min. The reactions were finished in a mere 18-25 min of irradiation time, including the hydrolysis of the sensitive imidoyl chloride moiety with water. The formed bis-lactams were isolated in good yield and purity. 

Lipases from C. antarctica and P. cepacia showed higher enantioselectivity in the two ionic liquids l-ethyl-3-methylimidazolium tetrafluoroborate and l-butyl-3-methylimidazolium hexafluoroborate than in THE and toluene, in the kinetic resolution of several secondary alcohols [49]. Similarly, with lipases from Pseudomonas species and Alcaligenes species, increased enantioselectivity was observed in the resolution of 1 -phenylethanol in several ionic liquids as compared to methyl tert-butyl ether [50]. Another study has demonstrated that lipase from Candida rugosa is at least 100% more selective in l-butyl-3-methylimidazolium hexafluoroborate and l-octyl-3-nonylimidazolium hexafluorophosphate than in n-hexane, in the resolution of racemic 2-chloro-propanoic acid [51]. 

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... 

Cull and co-authors reported a microbe-mediated transformation of benza-mide from benzonitrile in a mixed solvent of IL, l-butyl-3-methylimidazolium... 

We recently prepared various types of differently fiuorinated alkyl sulfate ILs and discovered that the hydrophobicity was dependent on the content ratio of the fluorine on the alkyl sulfate anion and 2,2,3,3,4,4,5,5-octafiuoropentyl sulfate salts showed hydrophobic properties. Melting point and viscosity were also dependent on the fluorine contents of the anionic part, while conductivity was determined by the cationic part and not influenced by the fluorine contents. Efficient lipase-catalyzed transesterificafion was demonstrated using hydrophobic 1-butyl-3-methylimidazolium 2,2,3,3,4,4,5,5-octafiuoropentyl sulfate ([bmim][C5E8]) as solvent (Eig. 6). ... 

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