To understand the AC frequency-dependent product selectivity, we conducted the following experiments to examine the time-resolved amine oxidation behavior. The CVs of 1 were acquired in the presence (black) and absence (red) of NaOAc at different scan rates from 0.02 to 20 V/s (Figure ). As previously discussed, 1 undergoes a reversible oneelectron redox cycle in the absence of NaOAc, so its anodic peak current (i0) is an ideal reference of a one-electron oxidation process. After introducing NaOAc to the reaction, two-electron oxidation of 1 becomes possible at low potentials (<0.6 V). If two-electron oxidation does happen, the anodic peak current (i1) would be larger than io; otherwise, i1 = io. By varying the scan rate, we can control the oxidation time (tox): the higher scan rate, the shorter tox. In this study, tox is defined as the time to scan the electrode potential from the onset potential where the oxidation of 1 starts to the anodic peak potential. For example, at a scan rate of 0.02 V/s, tox is ~8 s and i1 is approximately twice of io (Figure ), suggesting that two-electron oxidation of 1 is dominant for tox =8 s. Interestingly, the difference between i1 and io decreases with increasing scan rate, suggesting that two-electron oxidation of 1 is suppressed as tox is shortened. At 5 V/s or tox = ~45 ms, i1 became equal to io and part of the CV curve overlapped with the reference CV (red curve), meaning that only one-electron transfer occurred during the 45-ms-long anodic potential scan. Recall that the second-electron oxidation of 1 at low potentials is achievable only after deprotonation of 3 to 4. Therefore, when tox is short, the secondelectron oxidation is hindered possibly due to the slow deprotonation of 3, resulting in such tox-dependent oxidation behavior.