1.3- dimethylimidazolium chloride

Bowron et al. [11] have performed neutron diffraction experiments on 1,3-dimethylimidazolium chloride ([MMIM]C1) in order to model the imidazolium room-temperature ionic liquids. The total structure factors, E(Q), for five 1,3-dimethylimidazolium chloride melts - fully probated, fully deuterated, a 1 1 fully deuterated/fully probated mixture, ring deuterated only, and side chain deuterated only - were measured. Figure 4.1-4 shows the probability distribution of chloride around a central imidazolium cation as determined by modeling of the neutron data. 

Dynamic information such as reorientational correlation functions and diffusion constants for the ions can readily be obtained. Collective properties such as viscosity can also be calculated in principle, but it is difficult to obtain accurate results in reasonable simulation times. Single-particle properties such as diffusion constants can be determined more easily from simulations. Figure 4.3-4 shows the mean square displacements of cations and anions in dimethylimidazolium chloride at 400 K. The rapid rise at short times is due to rattling of the ions in the cages of neighbors. The amplitude of this motion is about 0.5 A. After a few picoseconds the mean square displacement in all three directions is a linear function of time and the slope of this portion of the curve gives the diffusion constant. These diffusion constants are about a factor of 10 lower than those in normal molecular liquids at room temperature. 

Thermodynamic information can also be obtained from simulations. Currently we are measuring the differences in chemical potential of various small molecules in dimethylimidazolium chloride. This involves gradually transforming one molecule into another and is a computationally intensive process. One preliminary result is that the difference in chemical potential of propane and dimethyl ether is about 17.5 kj/mol. These molecules are similar in size, but differ in their polarity. Not surprisingly, the polar ether is stabilized relative to the non-polar propane in the presence of the ionic liquid. One can also investigate the local arrangement of the ions around the solute and the contribution of different parts of the interaction to the energy. Thus, while both molecules have a favorable Lennard-Jones interaction with the cation, the main electrostatic interaction is that between the chloride ion and the ether molecule. 

D.1.1. Chloride-Containing Ionic Liquids. The melting points of some typical [AMIMJCl compounds are shown in Table I. Except for dimethylimidazolium chloride, which has a melting point above 120°C, the higher-alkyl [AMIM]C1 ionic liquids melt at temperatures below 100°C. 

The standard route to sydnones is the cyclodehydration of iV-nitroso-P-amino acids. 2-Chloro-4,5-dihydro-13-dimethylimidazolium chloride 97 has been shown to be an excellent reagent for this conversion, as, for example, in the synthesis of 3-phenylsydnone 98 <99JOC6989>. Functional group manipulations of fused sydnones have led to the isolation of several new compounds including 99 and 100 <99H(51)1433>. 4-Acetylsydnones react with hydrazine at room temperature to give 2,4-dihydropyrazol-3-ones 101 <99H(51)95>. ... 

The simplest alkylimidazolium ionic liquid 1,3-dimethylimidazolium chloride ([CiCiIm]Cl, numbering of the cation atoms is shown in Figure 2.2) and... 

Biihl, M., Chaumont, A., Schurhammer, R., and Wipff, G., Ab Initio Molecular dynamics of liquid 1,3-dimethylimidazolium chloride, /. Phys. Chem. B, 109, 18591-18599,2005. 

Bhargava, B.L., and Balasubramanian, S., Intermolecular structure and dynamics in an ionic liquid A Car-Parrinello molecular dynamics simulation study of 1,3-dimethylimidazolium chloride, Chem. Phys. Lett., 417, 486-491, 2006. 

Youngs, T.G.A., Holbrey, J.D., Deetlefs, M., Nieuwenhuyzen, M., Gomes, M.F.G., and Hardacre, C., A molecular dynamics study of glucose solvation in the ionic liquid 1,3-dimethylimidazolium chloride, Chem. Phys. Chem., 7, 2279-2281,... 

Lecocq et al. [108] studied ionic liquids formed between zinc chloride and TbutyT2,3-dimethylimidazolium chloride [BMMIMJC1 with the amount of Zn(H2 between 0 and 0.75 mol%. Analysis using NMR, and mass spectrometry showed Cl and [ZnCl j] in Lewis basic liquids and [ZnCh] and [Zn>,Cl7] in Lewis acidic liquids. Infrared spectra with pyridine were used to quantify the Lewis acidity and high temperature (110 °C) NMR experiments showed that the structure varies with time from [BMMIM][ZnCl3] to [BMMIM... Cl... ZnCy. 

The 2,3,5,6-tetrahydro-imidazo[l,2- ]imidazole system 40, a bicyclic guanidine, has been prepared by treatment of the 2-(2-hydroxyethylimino)imidazolidine 39 with 2-chloro-l,3-dimethylimidazolium chloride (CDIC) (Scheme 27) C2000JOC7779, CHEC-III(11.04.9.1.4)159>. 

Reports from Kuhn and co-workers identified the reaction of stable car-benes with 1,2-dichloroethane to yield 2-chloro-l,3-disubstituted imidazo-lium chloride salts.58 The versatility of these salts has been demonstrated by Ishikawa and co-workers.59 Due to its strong electrophilicity, 2-chloro-l, 3-dimethylimidazolium chloride can be used in chlorination, oxidation, reduction and rearrangement reactions, in addition to being used as a dehydrating agent. 

Reactions proceed faster and more smoothly when the reactants are dissolved, because of diffusion. Although reactions in the solid state are known [1] they are often condensations in which a molecule of water is formed and reaction takes place in a thin film of water at the boundary of the two solid surfaces. Other examples include the formation of a liquid product from two solids, e.g. dimethylimidazolium chloride reacts with aluminum chloride to produce the ionic liquid, dimethylimidazolium tetrachloroaluminate [2]. It is worth noting, however, that not all of the reactant(s) have to be dissolved and reactions can often be readily performed with suspensions. Indeed, so-called sol-id-to-solid conversions, whereby a reactant is suspended in a solvent and the product precipitates, replacing the reactant, have become popular in enzymatic transformations [3]. In some cases, the solvent may be an excess of one of the reactants. In this case the reaction is often referred to as a solvolysis, or, when the reactant is water, hydrolysis. 

A broader exploitation of cellulose solubility in ionic liquids lies in modification of cellulose into more useful forms. Cellulose acetate is currently the most useful derivative of cellulose, with uses in photographic film, as a synthetic fibre and as a component of adhesives. Acetylation of cellulose has been carried out effectively in l-allyl-3-methylimidazolium chloride [Amim][Cl], [C4mim CI], [C2mim][Cl], l-butyl-2,3-dimethylimidazolium chloride [C4dmim][Cl] and l-allyl-2,3-dimethyl-imidazolium bromide [Admim][Br] [136, 159-162], The first report of cellulose acetylation in an ionic liquid involved a one-step reaction in [Amim][Cl] without catalyst, yielding cellulose acetate with a controllable degree of substitution [136], Yields of cellulose acetate of up to 86% have been obtained via reaction in [C4mim] [Cl] at 80 °C for 2 h [160],... 

Fig. 1 Diagrams depicting a a layer of a cubic sodium chloride crystal b a monoclinic 1,3-dimethylimidazolium chloride ionic-liquid crystal c two radial distribution functions (RDFs) in liquid l-dodecyl-3-methylimidazolium hexafluorophosphate. Anions and cations are depicted in red and blue. In the cases of b and c the blue circles represent the centroid of the imidazolium rings of the cations. The alternating sequences of red and blue circles in a and b as well as the two curves in phase opposition in c clearly indicate the existence and nature of the polar networks in ionic condensed phases...

Chloro-l,3-dimethylimidazolium chloride (DMC) [26] (R =R = Me, L = H in 11, Scheme 4.8a) not only acts as a powerful dehydration agent but also has unique and versatile abilities to chlorinate primary alcohols, to oxidize primary and secondary alcohols and to reduce sulfoxides and so on. In addition, DMC easily reacts with amines to yield the corresponding guanidines. Thus, methods of preparing monocyclic and bicyclic systems by application of DMC chemistry in the key steps have been developed [27] the reaction of DMC-type chloroamidine compounds with amines for trisubstituted mono-cyclic guanidines [27a] (Scheme 4.8a), the intramolecular cyclization of thiourea derivatives after activation with DMC for monosubstituted or disubstituted monocyclic and bicyclic guanidines [27b] (Scheme 4.8b), and the DMC mediated cyclization of... 

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