Mechanistic aspects of Os(VIII) catalysed oxidation of loop diuretic drug furosemide by Ag(III) periodate complex in aqueous alkaline medium

Abstract

The kinetics of oxidation of a loop diuretic drug furosemide (Fur) by diperiodatoargentate(III) (DPA) has been investigated in the presence of osmium(VIII) (Os(VIII)) used as homogeneous catalyst in alkaline medium at a constant ionic strength of 0.20 mol dm-3 spectrophotometrically attached with HI-TECH SFA-12 stopped flow accessory. The stoichiometry was 1:2 (Fur:DPA). The order of the reaction with respect to [DPA] was unity while the order with respect to [Fur] was less than unity over the concentration range studied. The rate increased with an increase in [OH-] and decreased with an increase in [IO-]. The order with respect to [Os(VIII)] was unity. The oxidation products were identified as 2-(4-carboxy-2-oxo-but-3- enylamino)-4-chloro-5-sulfamoyl-benzoic acid and Ag(I). A suitable mechanism was proposed. The reaction constants involved in the different steps of the reaction mechanism were calculated. Kinetic experiments suggest that [Ag(H 2IO6)(H2O)2] is the reactive silver(III) species and [OsO4(OH)2]2- is the reactive Os(VIII) species. [Figure not available: see fulltext.] © 2011 Indian Academy of Sciences.