Tetraalkylammonium chlorides, their melting

Tetraalkylammonium chlorides, their melting True electrolytes... 

The first example of biphasic catalysis was actually described for an ionic liquid system. In 1972, one year before Manassen proposed aqueous-organic biphasic catalysis [1], Par shall reported that the hydrogenation and alkoxycarbonylation of alkenes could be catalysed by PtCh when dissolved in tetraalkylammonium chloride/tin dichloride at temperatures of less than 100 °C [2], It was even noted that the product could be separated by decantation or distillation. Since this nascent study, synthetic chemistry in ionic liquids has developed at an incredible rate. In this chapter, we explore the different types of ionic liquids available and assess the factors that give rise to their low melting points. This is followed by an evaluation of synthetic methods used to prepare ionic liquids and the problems associated with these methods. The physical properties of ionic liquids are then described and a summary of the properties of ionic liquids that are attractive to clean synthesis is then given. The techniques that have been developed to improve catalyst solubility in ionic liquids to prevent leaching into the organic phase are also covered. 

As a matter of fact, various tetraalkylammonium salts, the most famous one being the commercial Aliquat 336 (a 2 1 mixture of methyl trioctyl and methyl tridecylammonium chloride), are used as synergistic agents for Ln (III) extraction in traditional solvents (Atanassova, 2009 Atanassova and Dukov, 2010), and we would like to recall that many tetraalkylammonium salts are, in fact, ILs for example, tetraoctylammonium bromide melts at ca. 95 °C. On the other hand, new routes for the synthesis of ammonium-type ILs have been proposed (Mikkola et al., 2006 Sun et al., 1998). However, it is out of the scope of this work to review all literature involving Aliquat salts, especially because, being commercial mixtures, their chemical and physical properties are difficult to determine. Therefore, we will restrict ourselves to systems in which the additive was clearly considered by the authors as an IL. 

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