Cold-applied liquid compounds

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The bromine test is applied first. The organic compound, if a liquid, is treated with 2-3 drops of liquid bromine or (preferably) a solution of bromine in carbon tetrachloride if the organic compound is a solid, it should first be dissolved in cold carbon tetrachloride or chloroform. The rapid absorption of the bromine (and consequent disappearance of the red colour) is a strong indication that the compound is unsaturated, and is therefore undergoing direct addition of the bromine. 

Salts are purified by recrystallization and this procedure can be applied for ILs also. The recrystallization is performed by solving the compound in a small amount of acetonitrile and by adding a small amount of toluene to the solution. The solution was cooled in a freezer (-18°C). White crystals of the IL were formed. After filtration, the crystals were washed with an ice-cold toluene and the remaining solvent was removed by evaporation on a rotavap under reduced pressure [39]. This method is not universal as many ILs are oily liquids at room temperature or even at temperatures well below room temperature and are quite difficult to crystallize. There is of course always a loss of IL due fo the washing of the samples. It is always necessary to avoid using environmentally unfriendly solvents, especially halogen-containing ones that are not suitable for industrial applications. 

The reactor is now cooled with liquid nitrogen and the entire system evacuated to about 0.1 mm. The cold bath is removed and the second flask (at the manifold) is cooled within a few minutes, CI3 and CIO3 distill with foaming. To remove these gases completely, the vessel is immersed in a bath at + 20°C for one half hour and vacuum is applied. As soon as no further volatiles distill, the bath temperature is raised to about 35-36°C. The Cr03(Cl04)3 now distills into the manifold and flows into the first ampoule (transparent red liquid). The manifold with the ampoules should be somewhat inclined. When sufficient compound has collected in the first ampoule, the latter is sealed off. Additional distilled product collects in the stub left from the first ampoule, and is driven into the next ampoule by heating with a hot-air blower. 

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