A new type of polarographic catalytic wave of organic compound - Studies on the polarographic catalytic wave of medroprogesterone acetate in the presence of KIO3

The polarographic behavior and catalytic wave mechanism of medroprogesteron e acetate (MPA) were studied in both aqueous and DMF media. In 0.2 mol/L ac etic acid-sodium acetate ( pH 5.0) buffer solution, the C=C bond of MPA fir st undergoes 1e,1H(+) reduction to form protonated free radical HMPA(.), th e further reduction of HMPA(.) in 1e,1H(+) process is simultaneous with the dimerization reaction between HMPA(.) and neutral molecular MPA. In DMF me dia containing 0.1 mol/L tetrabutylammonium tetrafluoborate (TBA . BF4), th e C=C bond of MPA shows two 1e, 1H(+) reduction waves, which are ascribed t o the reduction of MPA and free radical MPA(.-), respectively. Here, no dim erization reaction occurs. These processes produce the reduction wave of MP A. In the presence of oxidant KIO3, a polarographic catalytic wave of MPA i s 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 chemic al reaction between oxidant and organic intermediate free radical to regene rate original organic compound, is a new-type wave of organic compound. Und er optimum experimental conditions, the sensitivity of MPA catalytic wave i n the presence of KIO3 is an order of magnitude higher than that of its red uction wave. The catalytic wave can be used for analytical purpose. The cal culated rate constant of catalytic reaction is 1.7 x 10(3) mol.L-1.s(-1).