Ferryl for real. The Fenton reaction near neutral pH

According to the literature, the Fenton reaction yields HO˙ and proceeds with 53 M^-1 s^-1 at 25 °C and low pH. Above pH 5, the reaction becomes first-order in HO^-, and oxygen atom transfer has been detected, which indicates formation of oxidoiron(2+), FeO²⁺. These observations, and the assumption that the intermediate [FeHOO]⁺ decays approximately iso-energetically to FeO²⁺, allow one to estimate an Gibbs energy of formation FeO²⁺ of +15 ± 10 kJ mol^-1, from which follows the one-electron E°'(FeO²⁺, H₂O/[Fe(HO)₂]⁺) = +2.5 ± 0.1 V and the two-electron E°'(FeO²⁺, 2H⁺/Fe²⁺, H₂O) = +1.36 ± 0.05 V, both at pH 7. In the presence of HCO₃^-, formation of FeCO₃(aq) occurs which may facilitate formation of the [FeHOO]⁺ intermediate, and leads to CO₃˙^-. At pH 7, the product of the Fenton reaction is thus FeO²⁺, or CO₃˙^- if HCO₃^- is present.