A preliminary investigation on the use of organic ionic liquids as green solvents for acylation and oxidation reactions

Different organic ionic liquids (OILs) have been used as green solvents in Friedel–Crafts acylation and alcohol oxidation reactions. Specifically, three OILs were employed, 1-ethyl-3-methylimidazolium chloride, tetraethylammonium bromide, and 1-butyl-3-methylimidazolium chloride, and four reactions studied, acylation of toluene by acetyl chloride, acylation of benzene by propionyl chloride, oxidation of benzyl alcohol by N-methylmorpholine N-oxide, and oxidation of salicylic alcohol by o-iodoxybenzoic acid. The reactions were carried out, at room temperature, in a well-stirred lab-scale glass batch reactor, under inert atmosphere and for reaction times ranging from 5 to 90 min. Gas chromatography was employed to characterize the reaction products. First of all, the desired products yield as a function of the reaction time was investigated. Moreover, simple kinetic models were built for the interpretation of the experimental results. Additional tests were carried out to assess the possibility of recycling the OILs employed. The results of this preliminary study were satisfactory as the OILs investigated proved to be good media in which to carry out the reactions studied in this work (desired products yield greater than 90% were achieved). Moreover, the reaction rate expressions of the kinetic models were able to satisfactorily predict the experimental results. Finally, the possibility of recycling the OIL (in one of the reactions) was proved to be feasible and this suggests the use of recycled OIL together with a fresh make-up, to match high yield values with economical/ecological advantages.