1- Butyl-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... 

The enthalpy difference befween the AA and the GA conformers in the [C4CiIm][BFJ is much smaller than the corresponding enthalpy difference befween the conformers of a free butane chain. This indicates that the 1-butyl-3-methylimidazolium cations most likely form local liquid structures specific fo each rofafional isomers [50]. Coexistence of these local structures, incorporating different rotational isomers, seems to hinder crystallization. This is probably the reason for fhe low melting points of such ILs. 

Figure 7.2a and b depicts the numbering scheme and the model for the molecular orientation of the 1-butyl-3-methylimidazolium cation, [C4mim] in ionic liquids at the air-liquid interface, respectively. SFG results show that the butyl chain of the cation extends towards the gas phase witii the imidazolium ring lying parallel to the surface plane. This configuration has been found to be consistent, regardless of the anion [32], for 1-butyl-3-methylimidazolium room-temperature ionic liquids, particularly where the anions are composed of Br , r, [PFg] ,... 

The l-butyl-3-methylimidazolium cation, bmim (Fig. 1), makes a number of ILs with varying properties, when combined with different anions [4]. BmimCl and bmimBr are crystals at room temperature, while bmimi is a RIL. By cooling down molten bmimCl and bmimBr below the melting points, their... 

Ozawa, R., Hayashi, S., Saha, S., Kobayashi, A., and Hamaguchi, H., Rotational isomerism and structure of the l-butyl-3-methylimidazolium cation in the ionic liquid state, Chem. Lett., 32, 948-949, 2003. 

The use of two-phase catalysis in water or high-polar organic solvents is one of best approaches to clean catalytic hydrogenation (Hermann and Kohlpainter, 1993). Ionic solvents with a wide range of liquid phase (down to -81°C) based on l- -butyl-3-methylimidazolium cations can be used in these reactions. 

EMIM]+, l-ethyl-3-methylimidazolium cation [BMIM]+, l-butyl-3-methylirniadzoliurn cation. Reference numbers are shown as superscripts to the data. 

In the case of the l-butyl-3-methylimidazolium cation a stable radical is obtained... 

The ionic liquid based on the l- -butyl-3-methylimidazolium cation was also used as an efficient catalytic medium for the chemoselective dithioacetalization of carbonyl compounds. This reaction proceeded with both activated and weakly activated aromatic aldehydes in almost quantitative yields in short reaction times. In addition, an acid-sensitive substrate such as furfural also gave the corresponding 1,3-dithiolane without a formation of any side products (Table 8). Moreover, aromatic ketones did not produce dithioketals under the same reaction conditions (room temperature, 10-20 min) or even after a prolonged reaction time <2004ASC579>. 

Broeke J V D, Stam M, Lutz M, et al. Designing ionic hquids l-butyl-3-methylimidazolium cations with substimted tetraphenylbo-rate counterions. Eur. J. Inorg. Chem. 2003. 2003, 2798-2811. 

Figure 6 Viscosity of [bmim][BF4] versus molal concentration of chloride added as [bmim]Cl at 20 °C (where [bmim] is the l-butyl-3-methylimidazolium cation).

To prove our hypothesis on the organocatalytic effects of anions, we chose a series of relatively basic anions, combined with l-butyl-3-methylimidazolium cations. Surprising results were obtained in the esterification of benzyl alcohol and acetic acid, which not only showed that the yields with any of the ionic liquids investigated are much lower than in the absence of ionic liquid (27% after 5 h 75-80% after 100 h in equilibrium), but also that in none of the cases equilibrium was reached after 5 h at 100 °C (ROH R COOH ionic liquid = 1 1.5 1). However, slight effects of the nature of the anion were observed, giving decreasing reaction... 

Since the nature of anion has a great effect on the properties of IL, there are major differences between ILs with different anions. The introduction of different anions results in an increasing number of alternative ILs with various properties [153], The physical and chemical properties of the ILs can be determined by different ion pairs. IL with l-n-butyl-3-methylimidazolium cation and PF " anion is immiscible with water, whereas IL with same cation and BF anion is water soluble. This example represents the designer solvent property of ILs. By changing the anion, the hydrophobicity, viscosity, density, and solvation of the IL system may be changed [67]. 

Besides, Shen et al. [26] have performed comparative studies on alkylation of phenol with ferf-butyl alcohol (TBA) with liquid acids such as H PO or solid acids, for example, HZSM-5, H-(), dodecatungstophosphoric acid (HPW), and HPW/ MCM-41, in the ionic liquids [BMIM]PFg, [OMIM]BF ([OMIM] = 7-octyl-5-methylimidazolium cation), and [HMIM]BF ([HMIM] = 7-hexyl-5-methylimidazo-lium cation). The results suggested that ionic liquids improve the catalytic activity of HjPO, with the conversion of phenol increasing from 44.5% to the maximum value of 77.3% in the alkylation of phenol with TBA by H PO in different ionic liquids. This improvement effect in conversion may be attributed to the higher solubility of... 

Fig. 6.2 A three-dimensional simplified schematic view of the arrangements of l-sec-butyl-3-methylimidazolium cation associated with SbFs" (a) and (b) showing the channels formed [56].

This result is in sharp contrast with earlier assumptions that due to the inherently weak interactions between the chloride anion and the l-butyl-3-methylimidazolium cation (ca. ISkJmoP ), chloride dissociation from a transition metal complex can be thermodynamically disfavored in ILs. ... 

Use of IL in other reaction 1-Alkyl-3-methylimidazolium cation-based ILs were used for A-teri-butyloxycarbonylation of amines with excellent chemose-lectivity [32]. 1,3-dialkylimidazolitrm ILs such as [bmim][PFg]. [bmTr][PFg] and [bmTr][NTf2] were reported for reaction media for the Baylis-Hillman reaction [33]. 1-butyl-3-methylimidazohrrm-based IL [bmim][NTf2] is used as solvent for a-methylenations of carbonyl compotmds [34]. M. L. Kantam et al. described copper-catalyzed cross-coupling reaction of arylboronic acids with sulfonic acid for alkylaryl and diaryl sulfones using IL [35]. 

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