Osmium(viii)-catalyzed oxidative degradation of paracetamol by chloramine-T in an aqueous alkaline medium: computational screening and mechanistic pathways

Abstract

The kinetics between paracetamol and N-chloro-p-toluenesulfonamide (chloramine-T) in the presence of an osmium(VIII) catalyst in an alkaline medium was studied. The reaction followed second-order kinetics, and the effect of the catalyst indicated that an uncatalyzed reaction occurred simultaneously. The rate was slowed down by hydroxide ions. The oxidation product was spectrally confirmed to be quinone oxime in stoichiometry, where two moles of oxidant were required for each mole of the substrate. The thermodynamic quantities were also computed using the Eyring equation. A plausible reaction mechanism is suggested, accounting for all the experimental observations. To further support our proposed mechanism, density functional theory (DFT) computations at the M06-2X/6-31G* and b3lyp/lanl2dz/6-311*g (d,p) levels further confirmed the reaction mechanism that has been hypothesized based on the kinetic observations. The suggested mechanism is strongly supported by the computational results, which demonstrate a significant correlation between the activation energy barriers and the reactivity trends shown in the kinetic studies.