Direct Conversion of Benzene to Hydroquinone. Cooperative Action of Cu(I) Ion and Dioxygen

Article abstract of DOI:10.1021/jo00237a013

Hydroquinone (or benzoquinone) and phenol are obtained from the aqueous-phase reaction of benzene with hydroxyl radical generated in the combined system of Cu(I) ion and dioxygen.The relative yield of hydroquinone to phenol (n = HQ/PhOH) varies substantially with the change in the solution pH (n = 0.4 at pH 1.3 and n = 6 at pH 3.5).Factors affecting the n value have been studied extensively by comparing reactivites of OH radical generated in several different means such as γ-ray radiolysis or Fenton's reaction.Extraneously high n values were only obtained when bothoxygen and Cu(I) ion were present simultaneously in the reaction media.All of the experimental findings are consistent with the mechanism that involves several successive intermediates, hydroxycyclohexadienyl radical, its oxygen adduct (peroxy radical), and the reducton product of the peroxy radical (hydroperoxide).Oxygen is necessary to produce peroxy radical and Cu(I) ion to produce hydroperoxide.A somewhat complex behavior of pH effect has also been dicsussed.