Initial Steps in the Reaction of H₂O₂ with Fe²⁺ and Fe³⁺ Ions: Inconsistency in the Free Radical Theory

Abstract

Consideration of the changes in free energy shows that the assumed initial steps in reactions of H2O2 with Fe2+ and Fe3+ in the free radical theory are not consistent. The free radical theory is unable to account for the Fe3+-initiated decomposition of H2O2 or for oxidations by it. In reactions with Fe2+ ions at high [H2O2], where O2 evolution reaches a limit, such limit is not foreseen by the free radical model. At lower [H2O2], because of a disallowed substitution in the equation used, the interpretation is not valid. It appears, therefore, that free radicals derived from H2O2 do not provide a suitable basis for constructing models for these reactions. Non-radical models are more successful in interpreting experimental results.

Keywords

• Fenton reaction
• free radicals
• free energy
• Fe²⁺
• Fe³⁺
• H₂O₂