Tailoring the Oxidizing Intermediate in the Fenton Reaction, OH⋅ or Fe^IV=O_aq, by Modifying the pK_a of the (H₂O)₅Fe^II(H₂O₂) Complex, and the Case of PDS – a DFT Study

A DFT analysis of the Fenton and Fenton-like reactions points out that the pH effect on the nature of the oxidizing intermediate formed is due to a pK_a of the peroxide when hydroperoxides are used. When S₂O₈²⁻ is used, the pH effect is due to the pK_a of one of the water ligands of the central iron cation. The results suggest that the choice of the hydroperoxide and the ligands present affects the pH at which the transition from the formation of hydroxyl radicals to the formation of Fe^IV=O_aq occurs.