A Homogeneous Mixture Composed of Vanadate, Acid, and TEMPO Functionalized Ionic Liquids for Alcohol Oxidation by H₂O₂

The functionalized ionic liquids (ILs) of N-n-dodecyl pyridinium vanadate (1), N-(propyl-1-sulfonic acid) pyridinium tetrafluoroborate (2), and 4-(propanoate-2,2,6,6,-tetramethylpiperidine-1-oxyl) pyridinium tetrafluoroborate (5) were synthesized. The mixture of 1, 2, and 5 in [Bpy]BF₄ yielded the compatible IL compositions (ILCs) as a homogenous mixture, which proved to be an efficient catalytic system for oxidation of a wide range of alcohols using H₂O₂. With the aid of 2 and 5, 1 in [Bpy]BF₄ could easily be recovered and reused for at least six runs without a loss in activity. UV/Vis spectroscopic analysis indicated that the role of 2 was to promote the formation of the active peroxo V^V species, which is responsible for substrate activation, and the role of 5 was to oxidize the low-valent vanadium(II-IV) species to regenerate 1.