Peroxydisulfate (S2O8 2-) is an oxidizing reagent widely used in industrial processes, such as in the etching of printed circuit boards 1 and water remediation, 2 due to its oxidizing properties, low cost, and ease of handling. Cleavage of the peroxo bond at elevated temperatures or using light, also referred to as S2O8 2-activation, results in the formation of the sulfate radical anion (SO4 •-), which has a standard reduction potential (E 0 ) of ~ 2.2 V vs. Ag/AgCl. The resulting SO4 •- is capable of abstracting an electron or a hydrogen atom from molecules to form SO4 2-or HSO4 -, respectively. The ability of SO4 •-to abstract a hydrogen atom is leveraged frequently in organic synthesis for C-H activation. For instance, McMillan and coworkers carried out α-arylation of ethers using photochemical reduction of S2O8 2-. Recently, we reported the selective oxidation of alcohols to the corresponding aldehydes/ketones (pH < 7) and carboxylic acids (pH > 7) via the electrocatalytic reduction of S2O8 2-to S2O8 3•-using electrogenerated Ru(NH3)6 2+ . Our prior studies suggested an eight-step mechanism for the overall alcohol oxidation, with the first five steps, shown below as eqs. 1-5, involving the generation of SO4 •-(eqs. 1-3) followed by its reaction either with Ru(NH3)6 2+ (eq. 4) or by direct reduction at the electrode (eq. 5). Eqs. 4 and 5 represent quenching reactions, preventing SO4 •-from participating in the intended oxidation of the alcohol substrate. Cyclic voltammetry (CV) studies performed using glassy carbon macroelectrodes, along with finitedifference simulations, were employed to estimate the rate constants of eq. 2 as ~ 2 × 10 5 M -1 s -1 and provided lower limits for eq. 3 (> 1 × 10 6 s -1 ), and eq. 4 (> 1 × 10 7 M -1 s -1 ). Density functional theory (DFT) and molecular dynamics computational analysis, however, suggest that S2O8 3•- fragmentation occurs on time scales of ~ 10 -12 s. Similarly, the free energy change for the homogeneous reduction of SO4 •-by Ru(NH3)6 2+ , based on E 0 values of eqs. 1 and 5, DG ~ -2.4 eV, would suggest that this single electron-transfer reaction should occur at a diffusion-controlled rate. Thus, the rate constants of eqs. 3 and 4 should be significantly higher than the lower limits previously reported based on CV analysis. Ru(NH3)6 3+ + e -⇌ Ru(NH3)6 E 0′ = -0.12 V vs. Ag/AgCl (1)