Oxidation of 2,4-di-t-butylphenol with t-butyl hydroperoxide catalysed by copper(II)–ethylenediamine complexes

Abstract

In the oxidation of 2,4-di-t-butylphenol (1) with Bu^tO₂H in alcohols in the presence of Cu^II–ethylenediamine (including N,N′-dialkylethylenediamines)(abbreviated to EDA)(1:2) complexes, the solvents are partly oxidized to the corresponding aldehydes or ketones in a competitive manner with phenol (1), while Bu^tO₂H is quantitatively reduced to Bu^tOH. Suitable solvents, e.g., chlorobenzene, used in the oxidation of (1) are found to be inert. Activity of the copper(II) complexes in the oxidation of phenol (1) is strongly dependent on the structure of the EDA ligands, as in the case of the oxidation of the phenol (1) by O₂ or H₂O₂. In the Bu^tO₂H oxidation of (1), the greatest degree of efficiency is brought about by the combination of copper(II) and N,N′-di-t-butyl–EDA. The initial stage of the oxidation of the phenol (1) has been kinetically investigated. The reaction velocity can be summarized by the equation: v=k[Bu^tO₂H][phenol (1)][Cu^II–EDA] Taking into account the results of the product analyses and kinetics, a mechanism for the oxidation of the phenol (1) with Bu^tO₂H catalysed by Cu^II–EDA complexes is proposed.