STUDIES ON KINETICS AND MECHANISM OF OXIDATION OF PYRIDOXAL BY DICHROMATES IN AQUEOUS HCLO4 SOLUTIONS

Oxidation of pyridoxal (PL) by Cr2O72- ion has been studied using an e xcess of the aldehyde under air or argon atmospheres. The reaction lea ds mainly to two Cr(III) complexes: [CT(PA)(H2O)(4)](2+) and [Cr(H2O)( 6)](3+) and to uncoordinated pyridoxic acid (PA). The rate of PL oxida tion follows a mixed third order rate law: first order in concentratio ns of Cr(VI), PL and H3O+. The reduction of Cr(VI) to Cr(III) proceeds through chromium(V) intermediate complex, which has been detected by the EPR method. Mechanism of the reaction has been discussed.