L-Ethyl-3-methylimidazolium cation

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

Hydrogenation of aromatics in the ionic liquid system [emim]Cl-AlCl3 ([emim]+ = l-ethyl-3-methylimidazolium cation) with electropositive metals (Li, Zn, Al) and a proton source can be performed with excellent yields and stereoselectivity 480... 

Ion radius is given in parentheses, a Decomposition temperature, [Nuu]+, tetramethylammonium cation [N2222]+, tetraethylammonium cation [EMIM]+, l-ethyl-3-methylimidazolium cation. 

Typical ionic hquids consist of a cation and an anion represented in Figure 17.2 [11, 12]. However, as described in the previous section, a fundamental electrochemical property such as high electrolytic conductivity is required for ionic liquids in their use as a hquid electrolyte. Many combinations of heterocyclic cations and various anions have been examined, and the ionic compounds containing the l-ethyl-3-methylimidazolium cation (EMl ) have generally showed the highest conductivity. No cation better than EMl has been found. 

K. Hayamizu, S. Tsuzuki, S. Seki, Y. Umebayashi, J. Chem. Phys. 2011, 135, 084505/ 1-084505/11. Nuclear magnetic resonance studies on the rotational and translational motions of ionic liquids composed of l-ethyl-3-methylimidazolium cation and bis (trifluoromethanesulfonyl)amide and bis(fluorosulfonyl)amide anions and their binary systems including lithium salts. 

Amino acids (AA), as one of the most abundant biomaterials in nature, are known to be nontoxic, biodegradable, and biocompatible. They are excellent feedstocks for the synthesis of ILs, because of their reasonable cost and environment-friendly characteristics. In 2005, a group of amino acid ionic liquids (AAILs) was first synthesized by Fukumoto s group from 20 natural AA [85]. They prepared AAILs based on l-ethyl-3-methylimidazolium cation, [emim], by neutralization method. In this method, [emim]OH was prepared by anion exchange resin, followed by addition of [emim]OH to a slight excess of an equimolar AA aqueous solution to prepare salts and water as a by-product [86]. Further, they synthesized tetrabutylphosphonium-based AAILs ([TBP][AA]) by mixing AA with aqueous solution of tetrabutylphosphonium hydroxide ([TBP][OH]) [87]. Tao et al. [88] synthesized [AAE]N03 ILs ([AAE] stands for AA ester as cation and NO3 stands... 

Ohno and Fukumoto [86] synthesized for the first time a new class of ILs by coupling of 20 different natural AA (e.g., glycine, leucine, proline, valine, alanine, etc.) as anions, with l-ethyl-3-methylimidazolium cation. Since the AA contains both an amino group and a carboxylic acid residue in a single molecule, with various side groups/chains and a chiral carbon atom, AA are good candidates to act as a platform for functional ILs [97-99]. Scheme 20.4 represents the use of AA both as cation or anion for synthesis of AA-based ILs. 

Kawanami and coworkers reported the PC synthesis from PO using various imidazoUum salts under supercritical carbon dioxide (SCCO2) that is highly miscible with ILs [10]. The experimental results showed that both the type of anion and the length of alkyl chain in the cation have decisive effects on the conversion and selectivity. The performance of different ILs of l-ethyl-3-methylimidazolium cation ([EMIm]+) with NOs", CFsSOs", BF4" and PFe" was investigated, and BF4 was again found to be the most effective. In addition, the... 

Highly conducting ionic liquids based on l-ethyl-3-methylimidazolium cation. S /nth. Met., 153,421-424... 

Alkylimidazolinm tetraflnoroborates are, for example, ionic liquids at room-temperature that can provide an anion to stabilize an intermediate cation-radical with no possibility of nucleophilic attack on it. Ionic liquids have a huge memory effect, and their total friction is greater than that of conventional polar solvents. Thus, the total friction of l-ethyl-3-methylimidazolium hexafluoro-phosphate is about 50 times greater than that of AN (Shim et al. 2007). The solvent effects of ionic liquids on ion-radical ring closures deserve a special investigation. The ring closure reactions can be, in principal, controlled by solvent effects. 

Another type of room temperature ionic liquids are typically the salts between cations like 1-butyl-3-methylimidazolium (BMI+), l-ethyl-3-methylimidazolium, and 1-butyl-pyridinium (see Scheme) and anions like BF7, PFq, CF3COO , CF3S03 and (CF3S02)2] T [29, 30]. By suitably selecting the cation and the anion, we can design ionic liquids that are nonvolatile, nonflammable, chemically stable, highly... 

The choice of anion will have a known effect on the physicochemical properties of the ionic liquid. To demonstrate the anion effect, selected data on properties of general interest to electrochemists (density, viscosity, conductivity and electrochemical window) have been gathered in Table 2.2. In each case, the anion is paired with the same cation l-ethyl-3-methylimidazolium. Certain trends from this data can be generalized, as well as in other collections of such data (for example, see Ref. [61] and references therein), that hold true regardless of the identity of the cation. For example, the effect of the anion on density follows the trend ... 

Symmetry is another factor to affect Tm. The salts with symmetric ions generally show higher Tm than those with asymmetric ones. For example, 1,3-dimethylimidazolium tetrafluoroborate showed higher Tm than 1-methylimi-dazolium or l-ethyl-3-methylimidazolium salts, as shown in Figure 3.1. In the case of tetraalkylammonium salts, their Tm also increased with increasing symmetry of the cation structure [18]. This tendency is understood to relate to the structural effect on crystallinity [19], i.e., highly symmetric ions are more efficiently packed into the crystalline structure than unsymmetric ones. Other kinds of chain structures such as polyether [20], perfluorocarbon [21], etc. [22] are obviously also effective in influencing thermal properties. 

The densities of ILs are also affected by the anion species. Similarly to the trends for cations, the density of ILs decreases with increasing alkyl chain length of the anion. The density of ILs is increased on the introduction of a heavy chain such as fluoroalkyl chains. For example, l-ethyl-3-methylimidazolium (EMIM) salts became heavier with the following anion species CH3SO3- < BF4 andCF COO < CF SOi < (CF3S02)2N- < (C2F5S02)2N-. It is easy to understand this order as an efFect of formula weight of the ions. However, these tendencies are still empirical, and a perfect correlation between ion structure and density is not yet available. 

To reveal ionic transport behavior through self-diffusion studies [22], we choose four different ionic liquids l-ethyl-3-methylimidazolium tetrafluoro-borate (EMIBF4), l-ethyl-3-methylimidazolium l ii(trifluoromethylsulfonyl)imide (EMITFSI), 1-butylpyridinium tetrafluoroborate (BPBF4), 1-butylpyridinium, and Z7w(trifluoromethylsulfonyl)imide (BPTFSI) (Scheme 5.1). The ionic liquids are comprised of two different cations and anions, and they allow us to visualize the dependence of ionic transport behavior on structural variety from the comparative self-diffusion behavior. 

In this chapter the neutral DA charge transfer complex that exhibits a rapid increase of conductivity during the melt, the cation radical salts of TTF derivatives with low melting point, the anion radical salts of TCNQ with imidazolium cations with low melting point, and l-ethyl-3-methylimidazolium (EMI) salts containing complexes with paramagnetic metals will be described. 

The IL polymers were prepared from polymerizable anions and free imidazolium cations. To investigate the effect of the anion structure on the properties, four kinds of IL monomers were synthesized by neutralizing A-ethylimidazole with acryhc acid, -styrenesulfonic acid, vinylsulfonic acid, and vinylphosphonic acid, respectively, as shown in Figure 29.6 [32]. Table 29.1 summarizes the properties of IL monomers composed of the polymerizable anion and an ethylimidazolium cation. They are liquid at room temperature and show quite low Tg s in the range of —100 to —60°C. EImVS showed the lowest Tg of 95°C among these four IL monomers. In addition it showed the highest ionic conductivity of about 10 S cm at 30°C, which is comparable to that of the best ILs such as the l-ethyl-3-methylimidazolium salts. 

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