1-butyl-3-methylimidazolium BMIM

Table 4.2 Effect of the anion on the melting point of the 1 -butyl-3-methylimidazolium, [bmim]+, cation...

In 1992, Wilkes and Zaworotko described the synthesis of the first imidazolium tetra-fluoroborate ionic liquids [6], These systems together with the slightly later published [7] hexafluorophosphate analogues are the working horses of the actual research with ionic liquid. However, their use in many technical applications is still limited by their relatively high sensitivity versus hydrolysis. The tendency of anion hydrolysis is of course much less pronounced than for the chloroaluminate melts but still existent. The [PFe] anion of 1-butyl-3-methylimidazolium ([BMIM]) hexafluorophosphate - for example - has been found in our laboratories to completely hydrolyse after addition of excess water when the sample... 

Li and collaborators devised a facile, clean, one-pot approach to the synthesis of 2,7-diamino-5-aryl-3,4,5-8-tetrahydro-4-oxopyrido[2,3-with aromatic aldehydes and malononitrile in an ionic liquid, specifically, 1-butyl-3-methylimidazolium (bmim) boron tetrafluoride (Scheme 46) (13JHC534). 

Ionic liquids 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 imidazoHum cations like 1-butyl-3-methylimidazolium [bmim] with an appropriate counter anion like hexafluorophosphate [PFs]. 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. 

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. 

In the process of developing the Stetter reaction in ionic liquids, Gree and coworkers applied their methodology to the synthesis of haloperidol (Scheme 25) [101], A variety of aromatic aldehydes react with methyl acrylate 160 when butyl-methylimidazolium tetrafluoroborate [bmim][BF ] is used as solvent. In the synthesis of haloperidol, electron-deficient aldehyde 153 was subjected to standard reaction conditions with 160 to provide 161 in good yield. 

Certain quaternary salts of imidazoles have become important as ionic liquids, in particular salts of l-butyl-3-methylimidazolium (bmim). Preparation of imidazolium-containing ionic liquids, in the desired product ionic liquid as a solvent, is a virtually solvent-free, one-pot process proceeding in good to excellent yields <2003S2626>. There are also microwave-assisted, solvent-free processes for the preparation of imidazolium-based ionic liquids <2001CC643, 2003GC181>. 

Figure 2.17 Quantitative synthesis of l-butyl-3-methylimidazolium [Bmim] ionic liquids via solvent free anion metathesis.

Emim= l-ethyl-3-methylimidazolium, Bmim= l-butyl-3-methylimidazolium, Hmim= l-hexyl-3-methylimidazolium... 

Hunt et al. have used ab initio methods to study ion pairs in l-butyl-3-methylimidazolium (Bmim) ILs. The anions were Cl, BF4 , and NTf2". The authors established relationships between ion-pair association energy and a derived parameter called the connectivity index . Overall, the results suggest that Bmim-Cl forms a strongly connected and quite highly structured network, which leads to the rather high viscosity observed experimentally. In contrast, Bmim-NTf2 only forms a rather weak network, where the connectivity and the viscosity are much lower [106],... 

Wasserscheid P, van Hal R, Bosmann A (2002) l-n-Butyl-3-methylimidazolium ([bmim]) octylsulfate-an even greener ionic liquid. Green Chem 4 400-404... 

The catalytic efficiency of the RTILs derived from l-butyl-3-methylimidazolium (bmim) cation is influenced by the structure of the imidazolium moiety and the counteranion following the order [bmim][MeSO ]>[bmim][HSO ] [bmim]... 

Chapter 13 discusses the design and analysis of the microscopic features of binary solvent systems formed by room temperature ionic liquids (RTILs) with molecular solvents. For this purpose, protic ionic hquids (PILs), ethylammoiuum nitrate (FAN), and l-n-butyl-3-methylimidazolium (bmim)-based ILs and the molecular solvents such as acetonitrile, dimethyl sulfoxide, A,A-dimethylfonnamide, and protic (different alcohols) are selected. The study focuses on the identification of solvent mixtures of relevant solvating properties to propose them as new solvents. ... 

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. 

Figure 4.2-6 shows RDFs for the center of mass of [PFe] with the l-n-butyl-3-methylimidazolium [BMIM]" and [BMMIM]+ cations. The first sharp peak in g(r) for the [BMIM][Pp6] system is due to the anion localizing near the C2 carbon of the ring (the carbon between the two nitrogens). This behavior has been observed in nearly all simulations involving l-alkyl-3-meth)dimidazolium cations [11,12,14,15,... 

Scheme 1 Proposed metabolic pathways of the l-butyl-3-methylimidazolium ([BMIM]) cation.

Table 11.4 Melting Point and Decomposition Temperature of Four l-Butyl-3-Methylimidazolium (bmim" ) Salts ...

Wasserscheid, R, R. van Hal, and A. Bosmann. 2002. l-N-Butyl-3-Methylimidazolium ([Bmim]) Octylsulfate-an Even Greener Ionic Liquid. Green Chemistry 4 (4) 400-404. 

Fig. 3. IRNMR shift of l-butyl-3-methylimidazolium (bmim) cation with various halide anions.

Fig. 1. Optimized structures of trans-trans (tt) and gauche-trans (gt) conformers of l-butyl-3-methylimidazolium ([bmim]) cation by B3LYP/6-311G+(d) level.

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