Oxidation of Mandelic Acid by Fenton's Reagent

Article abstract of DOI:10.1021/ja00369a005

Mandelic acid forms a stable 1:1 complex with Fe²⁺ at pH 1-3.Its oxidation by H2O2 and S2O8^2- has been investigated in the hope of detecting intramolecular oxidation-reduction of any intermediate Fe^IV species, rather than the usual hydroxyl radical process.Products are benzaldehyde and hydroxymandelic acids, consistent with either, but added hydroxyl radical traps - acetone or crotonic acid - are able to intercept only about half of the reaction.However, they reduce yields of benzaldehyde but not hydroxymandelic acids, and it is concluded that the balance of the reaction involves cage reactions of newly formed hydroxyl radicals rather than a high-valence iron species.