The Effect of Triethanolamine on the Iron(III)-Catalysed Decomposition of Hydrogen Peroxide

The influence of triethanolamine on the iron(III)-catalyscd decomposition of hydrogen peroxide was studied by manometric and spectrophotometric techniques. This ligand caused increasing inhibition with increasing concentration, attributed to the saturation of the coordination sphere of the metal, and also to its properties as a radical scavenger. Kinetic measurements indicated the formation and the subsequent breakdown of a peroxo-intermediate in the rate-determining step, for which a rate constant of 2.9 × 10 −2 s −1 was determined at 308 K. Evidence for the participation of oxygen radicals, as well as carbon-centred radicals, was obtained from ESR spectra of the radical adducts detected using the spin-trap method. Based on the pH profile for the reaction, a mechanism was proposed, suggesting the formation of different complexes with different catalytic activities, at higher pH.