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 degrees 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 degrees '(FeO2+, H2O/[Fe(HO)(2)](+)) = +2.5 +/- 0.1 V and the two-electron E degrees '(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.

Automated summary

According to the literature, the Fenton reaction produces hydroxyl radicals at low pH and 25 degrees C. The formation of oxidoiron(2+), FeO2+, and its corresponding Gibbs energy of formation can be estimated based on observed reactions and assumptions. The presence of HCO3- leads to the formation of FeCO3(aq) and may facilitate the formation of the intermediate [FeHOO](+).