Chemical model of the enzyme system for hydroxylating cyclohexane

The kinetics of co-oxidation of cyclohexane and ferrous chloride by molecular oxygen in methanol in the temperature range 25–50°C has been studied. The total yield of the reaction products, cyclohexanol and cyclohexanone, equals about 25% of the reacted ferrous ion. A redox-active ligand, cysteine, added to the system FeCl₂-C₆H₁₂-O₂ increases product yield. The reaction involving FeCl₂ oxidation by oxygen in the presence of HCl is bimolecular. The effective value of the activation energy of reaction is 9.0 kcal/mol. In the absence of HCl the hydroxylating species is a complex Fe³⁺O₂⁻], and in the presence of HCl this complex comes together with HO₂^• radicals. A scheme for co-oxidation of FeCl₂ and cyclohexane is proposed. Similarities and contrasts between various hydroxylating species in enzymatic and nonenzymatic hydroxylations are discussed.