Selective Synthesis of p-Hydroxybenzaldehyde by Liquid-Phase Catalytic Oxidation of p-Cresol

Liquid-phase oxidation of p -cresol over insoluble cobalt oxide (Co 3 O 4 ) catalyst under elevated pressure of air gave 95% selectivity to p -hydroxybenzaldehyde, an important flavoring intermediate. The selectivity to p -hydroxybenzaldehyde could be enhanced by manipulating the concentrations of p -cresol, sodium hydroxide, and catalyst and the partial pressure of oxygen in such a way that the byproducts normally encountered in this oxidation process were eliminated or minimized significantly.