Thermodynamic quantities for the oxidation of ranitidine by diperiodatocuprate(III) in aqueous alkaline medium

The kinetics of oxidation of the anti-ulcer drug, ranitidine hydrochloride (RNH) by diperiodatocuprate(III) (DPC) in alkaline medium was studied spectrophotometrically. The reaction exhibits 1:2 stoichiometry (ranitidine:DPC). The reaction is of first order in [DPC] and has less than unit order in [RNH] and negative fractional order in [alkali]. The involvement of free radicals was observed in the reaction. The oxidation has been found to proceed via a DPC-ranitidine complex, which decomposes slowly in a rate-determining step followed by other fast steps to give the products, which were identified as ranitidine sulfoxide by spot test and spectroscopic studies.