Mechanistic investigation on the oxidation of ampicillin drug by diperiodatoargentate (III) in aqueous alkaline medium

The kinetics of oxidation of antibiotic drug, ampicillin (AMP) by diperiodatoargentate (III) (DPA) in alkaline medium at a constant ionic strength of 0.25‐mol dm^?3 was studied spectrophotometrically. The reaction between DPA and AMP in alkaline medium exhibits 1:2 stoichiometry (AMP:DPA). The reaction is of first order in DPA] and has less than unit order in both AMP] and alkali]. Added periodate retarded the rate of reaction and intervention of free radicals was observed in the reaction. The oxidation reaction in alkaline medium has been shown to proceed via a DPA–AMP complex, which decomposes slowly in a rate‐determining step followed by other fast steps to give the products. The main products were identified by spot test, IR and NMR studies. The reaction constants involved in the different steps of the mechanism are calculated. The activation parameters with respect to slow step of the mechanism were computed and discussed and thermodynamic quantities were also determined. Copyright © 2008 John Wiley & Sons, Ltd.