Ionic Liquids: An Introduction To Ionic Liquids

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2.1 Introduction to Ionic Liquids Ionic liquids (ILs) are liquids composed entirely of ions. Molten salt is the term normally reserved for those systems that are liquid at high temperatures, for example NaCl (table salt is a liquid at ≈ 800 0C). Room-temperature ILs are liquid below 100˚C, have received considerable attention as substitutes for volatile organic solvents. Due to their remarkable properties, such as negligible vapour pressure, large liquidous range, high thermal stability, good ionic conductivity, high electrochemical stability, they are considered favourable medium candidates for chemical syntheses. ILs are usually categorized into four types based on their cation segment: 1) alkylammonium-, 2) dialkylimidazolium-, 3) phosphonium- and 4) N-alkylpyridiniumbased ILs (Figure 1). Ionic liquids are generally composed of a bulky organic cation, such 1-butyl-3 methylimidazolium and typically an inorganic anion such as a halide. Below are the chemical structures of some common cations and anions used to make ILs. Figure 1. Some common cations and anions used for ionic liquids ILs are designer solvents. One or both of the constituent ions can be changed in order to control physical properties. …show more content…

This means there is no "vapour" or gas sitting above the liquid. Think of the fumes that come off petrol, or the smell of coming out of an open bottle of vinegar. Petrol and vinegar have a positive vapour pressure, and you can smell the vapour that is sitting above the liquid. Well, it means there is no toxic or potentially explosive gas sitting above the solvent, unlike for example, petrol! If industrial processes can be changed to use ionic liquids, instead of the dangerous and environmentally damaging organic solvents they use now, processes will be much safer for workers, greener for the environment and easier to handle for the industrialist. Ionic liquids are also known as green

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