Wei-Dong Wang

Hydrogen Atom Abstraction by Methyl Radicals from tert-Butyl Hydroperoxide in a Modified Fenton Reaction

Abstract Feaq2+ reacts with tert-butyl hydroperoxide, (CH3)3- COOH, in air-free acidic aqueous solutions at 25° C with a rate constant kFe = 18.7 M-1 s-1 in H2O and 11.7 M -1 s -1 in D2O. The reaction produces methyl radicals which abstract hydrogen atoms from excess (CH3)3COOH to yield CH, and (CH3)3COO*, kMe = 1.9(±0.6) x 104 M-1 s-1 in H2O and 2.7(±0.8) x in D2O. The formation of alkylperoxyl radicals under air-free conditions causes the followup chemistry to approach that normally seen in the presence of air. There is no evidence for the attack of methyl radicals at the peroxo oxygen to give methanol and alkoxyl radicals (k < 2 x 103M -1 s -1), even though this reaction is thermodynamically favored over the observed hydrogen abstraction by over 130 kJ/mol. The reaction between Feaq2+ and tert-butylperoxyl radicals is unusually slow, 2 x 102 ≤ k ≤ 5x 104 M-1s-1 .