Dedicated to the honorable Prof. Brindaban C. Ranu
Abstract
Here, we report the NiCo2 O4 -nanoparticle-catalyzed dehydrogenative direct oxidation of primary alcohols to carboxylic
acid in the presence of KOH under microwave irradiation in the absence of any oxidant
in good to excellent yields (75–99%) within a short reaction time (5–10 min). The
polycrystalline cubic spinel phase of NiCo2 O4 nanoparticles (NPs) with an average size of 25 nm were synthesized by the co-precipitation
method and analyzed properly by using powder X-ray diffraction, field emission scanning
electron microscopy, energy-dispersive X-ray spectroscopy, and transmission electron
microscopy measurements. The NiCo2 O4 NPs were stable under the reaction conditions and reused for up to eight cycles without
appreciable loss in the yield of benzoic acid. According to mechanistic insight, the
KOH acts as a second oxygen source and is essential for the synthesis of carboxylic
acid from alcohols. The hydrogen gas was found to be the only byproduct of this method
detected by chemical reactions.
Keywords nano-NiCo
2 O
4
- dehydrogenative oxidation - direct oxidation of primary alcohols - carboxylic acids
- green synthesis - recyclability