Quaternary ammonium-containing ionic liquids

Egashira M, Okada S, Yamaki J, et al. The preparation of quaternary ammonium-based ionic liquid containing a cyano group and its properties in a lithium battery electrolyte. J. Power Sources. 2004. 138, 240-244. 

Egashira M, Nakagawa M, Watanabe I et al (2005) Cyano-containing quaternary ammonium-based ionic liquid as a co-solvent for lithium battery electrolyte. J Power Sources 146 ... 

Heretofore, ionic liquids incorporating the 1,3-dialkylimidazolium cation have been preferred as they interact weakly with the anions and are more thermally stable than the quaternary ammonium cations. Recently, the physical properties of 1,2,3,4-tetraalkylimidazolium- and 1,3-dialkylimidazolium-containing ionic liquids in combination with various hydrophobic and hydrophilic anions have been systematically investigated (36,41). The melting point, thermal stability, density, viscosity, and other physical properties have been correlated with alkyl chain length of the imidazolium cation and the nature of the anion. The anion mainly determines water miscibility and has the most dramatic effect on the properties. An increase in the alkyl chain length of the cations from butyl to octyl, for example, increases the hydrophobicity and viscosity of the ionic liquid, whereas densities and surface tension values decrease, as expected. 

Abbott, A.P., G. Capper, D.L. Davies, R.K. Rasheed and V. Tambyrajah, Quaternary Ammonium Zinc- or Tin-Containing Ionic Liquids Water Insensitive, Recyclable Catalysts for Diels-Alder Reactions, Green Chemistry, 4,24—26 (2002). 

Abbott AP, Capper G, Davies DL, Rasheed RK, Tambyrajah V (2002) Quaternary ammonium zinc-or tin-containing ionic liquids water insensitive, recyclable catalysts for Diels-Alder reactions. Green Chem 4 24-26... 

However, ionic liquids containing other classes of organic cations are known. Room-temperature ionic liquids containing organic cations including quaternary ammonium, phosphonium, pyridinium, and - in particular - imidazolium salts are currently available in combination with a variety of anions (Figure 3.1-1 provides some common examples) and have been studied for applications in electrochemistry [7, 8] and in synthesis [9-11]. 

There are a number of industrially important reactions where two liquid phases are involved and the aqueous phase contains ionic species. Here the rate may be severely limited due to low solubiblity of the reactant, located in the organic phase, in water. We would benefit from using a pha.se-transfer (PT) catalyst, which ferries the ionic species into the organic phase thus overcoming a severe limitation. Such PT catalysts are typically quaternary ammonium compounds like tetrabutylammonium halides, trioctylmethylammonium chloride, etc. (see also Section 3.8). 

Ionic hquids are low melting organic salts that are liquids at ambient temperature. They typically contain quaternary ammonium cations such as l-butyl-3-methylimida-zolium- or N-butylpyridinium- with inorganic anions, such as tetrachloroaluminate or tetrafluoroborate (Chauvin and Helene, 1995 Freemantle, 1998). Melting points for these materials can be near -100°C, and the liquids are often thermally stable at temperatures approaching 200°C. 

Abbott A P, Capper G, Davies D L, et al. Preparation of novel, moisture-stable, Lewis-acidic ionic liquids containing quaternary ammonium salts with functional side chains. Chem. Commun. 2001. 1, 2010-2011. 

Quaternary ammonium surfactants (dodecyl-, tetradecyl-, and hex-adecyltrimethylammonium or didodecyldimethylammonium) with Tp anion were prepared and characterized also by measurement of their Kraft temperatures and critical aggregation concentrations. NMR spectroscopy suggested that the single-chain surfactants containing the dodecyl ammonium form small aggregates in water. The X-ray structure analysis of the dodecyl derivative was performed.192Azolium poly(l,2,4-triazolyl)borate salts melt at relatively low temperatures to give thermally stable ionic liquids. Some of them exhibit conductivities close to that of KC1 in MeCN/H20... 

To learn more about the stability of superoxide in the presence of quatemary-alkyl-ammonium cations, Evans et al. [20] performed a comprehensive study of the oxygen reduction reaction in several ILs containing highly fluorinated anions, including the quaternary ammonium ionic liquids [N2226l[N(Tf)2]. 

Quaternary ammonium salts containing 3-, 4-, 5-, 6- and 7-membered saturated rings have been structurally characterised, some of which are ionic liquids. 

Chitosan, a widely used natural biopolymer, has been studied for the adsorption of various metal ions from dilute solutions. Unfortunately, the inherent properties of chitosan, such as hydrophilicity and metal-binding capability, are often insufficient to meet the requirements of a number of applications. To improve these properties, both chemical and physical modifications of chitosan are required. Thus, Aliquat 336-functionalized chitosan as adsorbent was prepared. In fact, the new chitosan adsorbent can also be described as P-SIL containing quaternary ammonium ionic liquid [23]. Unlike the previous reported structure, the Aliquat 336-functionalized chitosan, which was prepared by acid/base neutralization reaction, consists largely of cations and anions (Fig. 5.12). The structure was so flexible that the adsorption ability could be controlled precisely. Moreover, incorporation of Aliquat 336 into the chitosan backbone could significantly enhance its metal ions extraction ability. It has been shown to have much improved affinity for Pb " than pure chitosan. This may be explained in that the new strategy doesn t reduce the original amino active sites besides, the synergistic effect between cation and anion also contributes to the enhancement of adsorption capabilities. On the other hand, the effort to increase selectivity of the adsorbent for one metal ion over others is to make the adsorbent sterically efficient with that metal ion only. The new chitosan-... 

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