Kinetics of oxidation of 3-hydroxy-6-methyl-2-pyridinemethanol (hmpol) by CrVI at HClO4 was studied under the pseudo-first-order conditions. The hmpol oxidation products were the appropriate aldehyde (hmpal) and acid (hmpac) coordinated to the chromium( III). The linear dependence of the pseudo-first-order rate constant (kobs) on [hmpol] at 1.0 and 2.0 M HClO4 and a parabolic dependence of kobs on [H+] were established. The apparent activation parameters were determined from the second-order rate constants at 1.0MHClO4. The presence of the CrII and CrIV intermediates was deduced, based on rate retardation effect caused by O2 and MnII respectively, whereas the presence of CrV was established by EPR. Some correlations between the structure and stability of intermediate chromium(V) complexes have been discussed from EPR spectra, recorded during the redox process.
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