The kinetics of the oxidation reactions of APAP and Cafn by a Mn(IV)-oxidant, [MnIV3(µ-O)4(phen)4(H2O)2]4+ (1) has been studied at room temperature. Under the acidic reaction condition ([H+] = 0.2–1.0 M), both APAP and Cafn exist in equilibrium with their conjugate acids APAPH+ and CafnH+ and each of the species acts as the potential reductants. Kinetic observations reveal that the observed rate constant, ko, values increase with the increase in media acidity and the ionic strength, I. The second-order rate-constant values for oxidizing the protonated forms of the two reductants (APAPH+ and CafnH+) were evaluated to be 6.04 ± 0.29 and 0.18 ± 0.01 M−1 s−1, respectively. Overall, under acid media, Mn(IV)-complex efficiently oxidizes APAP to a mixture of benzoquinone and acetamide (or, to quinone oxime and acetic acid) and Cafn to 1,3,7-trimethyluric acid. [ABSTRACT FROM AUTHOR]