Epoxidation of unsaturated fatty acid ester promoted by imidazolium acidic ionic liquids: An unexpected selectivity phenomena

Epoxidation of linseed oil fatty acid ethyl esters promoted by a series of functionalized imidazolium ionic liquids was studied. In this reaction acidic imidazolium ILs behave not only as an acid catalysts but also play an additional role as a specific activator for the reaction of epoxidation of unsaturated fatty derivatives in H2O2/formic acid oxidation system. The obtained results indicate that the hydrogen-bonding interaction of imidazolium cation with epoxide group influences the selectivity of the epoxidation reaction. In particular, the presence of unprotected weak "acid" C2-H proton significantly lowers the selectivity to hydroxyl derivatives. The obtained results also point to another example of specific polyfunctionality of ILs, especially imidazolium one, used as surfactants and process activators.