Pyrazine Antiviral Drugs and O2 The reactivity between T-705 and electro-generated O2 •-was confirmed, through in situ electrolytic UV-Vis spectral measurements using the optically transparent thin layer electrochemical (OTTLE) cell (Supporting Information, Figure ). First, the electrochemical oxidation of T-705 at a GC electrode in a DMF solution under purging N2 was conducted using cyclic voltammetry (Figure ). Over the accessible potential range (1.5 to 0 V vs. Measured in the OTTLE cell having a 1.0-mm thin layer, the spectra immediately disappeared when the potential was applied. Thus, the following reactions will proceed in a superior kinetics via the intermediates; T-705 -and T-705 • , otherwise concertedly with the initial PT. Since the radical product was undetectable using in situ electrolytic electron spin resonance (ESR) system (Supporting Information, Figure ), T-705 • would be decomposed at the subsequent reaction (no data is shown). These series of reactions, the initial PT (Equation ( )) followed by the subsequent oxidation and others, are referred to as the base-catalyzed oxidation process or the SFO. The SFO is the oxidation of the substrate anion (generated by alkali O2 •-) by O2. When considering the superior kinetic expected from the CV and in situ spectral results, the mechanism will involve the sequential ET from T-705 -to HO2 • coupled to the initial PT; i.e., PCET, rather than SFO. Thus, the electron acceptor will be HO2 • , not O2 •-. Considering the CV results in Figure that the generated HO2 • is not detected at the electrode reaction with the energy scanning shown in Figure , the electron donor will be H b formed after the initial PT with dihedral rotation, for which the bold red line indicates the downhill energy relationship in Figure . Thus, this change in HOMO-LUMO energies upon PT between the T-705 and O2 •-forming H b and HO2 • and the subsequent ET is reasonable for the fact that HO2 • was eliminated in the CV.