The Role of Oxygen in the Hydroxylation Reaction of Benzene with Fenton's Reagent. 18O Tracer Study

Article abstract of DOI:10.1021/ja00279a057

The role of oxygen in the hydroxylation of benzene with Fenton's reagent was studied in a 0.05 M H2SO4 solution.The main products are phenol and benzoquinone in the molar ratio ca. 10:1.A precise determination of material balance with respect to benzene indicated that the selectivity of phenol is rather low, less than 50percent.On the other hand, the conversion of H2O2 into aromatic oxidation products including unidentified byproducts is unexpectedly high.Tracer study with (18O2)2 gas indicated that the isotope incorporation in phenol is ca. 20percent, while the incorporation in benzoquinone is perfect.It was also shown that both oxygen and benzene were consumed in excess of H2O2 during the reaction.To account for all of these results, regeneration of H2O2 resulting from Dorfman's mechanism has been proposed.By the aid of computer simulation, the amount of H2O2 regenerated was estimated to be around 20percent of H2O2 initially used.Factors affecting the isotope incorporation in phenol were also discussed.