PURPOSE: To oxidize efficiently a variety of hydroxy-containing aromatic compounds by contact with oxygen in a specific alcohol in the presence of a cobalt (II) compound such as cobalt (II) naphthate and a specific primary aliphatic amine.

CONSTITUTION: Various hydroxy-containing aromatic compounds of formula I (X is OH or formula II; R is H, alkyl, phenyl or aralkyl) such as p- hydroxydiphenylamine or 2,5-di-tert.-amylhydroquinone are catalytically oxidized by bringing into contact with an oxygen-containing gas in an alcoholic solvent such as methyl alcohol, ethyl alcohol, isopropyl alcohol or butyl alcohol in the presence of a cobalt (II) compound such as cobalt (II) naphthate, cobalt (II) octate or cobalt (II) chloride, and a primary aliphatic amine having the nitrogen atom attached to a tertiary carbon atom such as t-butylamine, thereby to give corresponding quinone compounds such as 2,5-di-tert.-amylbenzoquinone.