Kinetic Effect of Novel Osmium(VIII) for the Oxidation of Pyrazinamide by a Copper(III) Complex and Their Mechanistic Aspects

Abstract

The oxidation of an anti-tuberculosis drug, Pyrazinamide (PYZ) by Cu(III) complex has been investigated with and without Osmium(VIII) catalyst in aqueous alkaline media at constant ionic strength using spectrophotometer. The stoichiometric ratio was found to be 1:2 in both the cases. The reaction was unit order with respect to DPC and Os(VIII), whereas less than unity with respect to PYZ. The rate increased with increase in concentration of alkali and retarding effect was observed with increase in periodate concentration in both the cases. The oxidation product was identified and characterized by spectral analysis. A plausible mechanism was proposed and physical quantities such as activation parameters and thermodynamic quantities were determined with respect to slow step. Active species for Cu(III) and Os(VIII) were [Cu(H2IO6)(H20)2] and [OsO4(OH)2]−2 respectively. The reaction constants involved in different steps were calculated for both the cases. The catalytic constant (KC) for catalyzed reaction was calculated at different temperatures.