A new type of polarographic catalytic wave of organic compound

Abstract

The polamgraphic behavior and catalytic wave mechanism of medroprogestemne acetate (MPA) were studied in both aqueous and DMF media. In 0.2 mol/L acetic acid-sodium acetate (pH 5.0) buffer solution, the bond of MPA first undergoes le, lH+ reduction to form protonated free radical HMPA, the further reduction of HMPA in le,1H+ process is simultaneous with the dimerization reaction between HMPA and neutral molecular MPA. In DMF media containing 0.1 mol/L tetrabutylammonium tetrafluoborate (TBA.BF4), the bond of MPA shows two le, 1H+reduction waves, which are ascribed to the reduction of MPA and free radical MPA.-, respectively. Here, no dimerization reaction occurs. These processes produce the reduction wave of MPA. In the presence of oxidant KIO3,a polamgraphic catalytic wave of MPA is observable due to a chemical reaction between HMPA. or MPA.- and KIO3 as well as its intermediate species to regenerate MPA. The catalytic wave, which is caused by the reduction of organic compound itself and the chemical reaction between oxidant and organic intermediate free radical to regenerate original organic compound, is a new-type wave of organic compound. Under optimum experimental conditions, the sensitivity of MPA catalytic wave in the presence of KIO3 is an order of magnitude higher than that of its reduction wave. The catalytic wave can be used for analytical purpose. The calculated rate constant of catalytic reaction is 1.7 × 103 mol·L-1·s-1.