The Mechanism of Catalytic Co-oxidation of Cyclohexane with Aldehyde

Abstract

Co-oxidation of cyclohexane with acetaldehyde in the presence of cobaltous acetylacetonate catalyst has been investigated in benzene at 40∼70°C. In the absence of the aldehyde, cyclohexane is not oxidized, but in its presence in high selectivity (95 %), forming cyclohexanol, cyclohexanone and e-caprolactone. The mechanism of this reaction is different from the reported mechanism of the oxidation of the neat cyclohexane. In co-oxidation, cyclohexane is oxidized consecutively (cyclohexane → cyclohexanol → cyclohexanone → ε-caprolactone). In the absence of the catalyst, (I) and (II) proceeded by the reactions of cyclohexane and cyclohexanol with acylperoxy radical which is formed in the autoxidation of aldehyde. The step (III) is the reaction of cyclohexanone with peracetic acid (Baeyer Villiger reaction). With cobalt catalyst, (I) and (II) seem to proceed also by the reaction with acyloxy radical or acylperoxy radical which is produced by the decomposition of peracetic acid.