Miscellaneous Reactions in Ionic Liquids

A novel use ofthe salt [BMIM][PF6] is to enhance microwave absorption and hence accelerate the rate of a reaction. Ley found that [BMIM][PF6] enhanced the rate of the microwave promoted thionation of amides using a polymer supported thionating agent [304]. Hardacre et al. have developed a protocol for the synthesis of deuterated imidazoles and imidazolium salts [305]. The procedure involves the platinum- or palladium- catalyzed deuterium exchange of 1-methyl-d -imidazole with D2O to give 1-methylimidazole-d , followed by reaction with a deuterated alkyl halide. 

Finally, a word of caution when using [BF4] and [PF ] ionic liquids - they are not stable and give off HF, particularly when heated in the presence of a proton source or a metal salt [21]. There are many examples of this in this chapter. An example of a HF-catalyzed reaction is ether formation from alcohols is a classic acid-catalyzed reaction. An ether formation reaction was found to occur in a range of [BF4] ionic liquids, with an example being the addition of methanol to ten-butanol to form methyl-tert-butyl ether (MTBE) [306]. The author is of the opinion that [Bp4] ionic liquids (even hydrophobic ones) can dehydrate alcohols to ether and refers to these ionic liquids as dehydrators. All that is happening here is a simple HF-catalyzed reaction. With many authors not aware of this phenomenon, they resort to all kinds of inappropriate explanations for what is occurring. 

Rogers, K. R. Seddon, S. Volkov, in NATO Science Series II Mathematics, Physics and Chemistry, Voi. 92. Kluwer, Dordrecht, 2002. 

Advanced Organic Chemistry, 4th edn., Wiley, Chichester, 1992. 

New Products, in Ionic liquids as Green Solvents, Prq ess and Prospects, R. D. 

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