Experimental Mechanistic Studies on Alternating Polarity Electrolysis for Carbon-Centered Radical Generation

Electrosynthesis offers a sustainable and tunable approach to organic transformations, enabling precise control over reaction thermodynamics and kinetics via the applied potential and current. A key recent advancement is alternating polarity (AP) electrolysis, where periodic electrode polarity reversal enhances selectivity and yield by mitigating electrode fouling, balancing redox processes, and stabilizing reactive intermediates. However, experimental mechanistic studies to understand the key factors controlling AP electrolysis, such as current magnitude, waveform frequency, and electrode material together with the type of radical intermediates generated, remain underexplored. In this study, we investigate the mechanistic basis of AP electrolysis using anodic oxidation for the generation of carbon-centered radicals as the model reactivity profile. Specifically, we utilize the well-documented anodic oxidation of organoboron or carboxylic acids in the generation of aryl, alkyl, and benzyl radicals under AP electrolysis. Experimental mechanistic studies using electroanalytical techniques reveal that the electrode potential depends on both current and frequency, serving as a reliable predictor of synthetic efficiency. Maps of electrode potential as a function of current and frequency were constructed for each radical type to enable identification of optimal AP electrolysis conditions aligned with key reaction potentials and substrate reactivity. Applying these insights to benzyl radical generation, a challenging case due to facile radical overoxidation, led to a 63% yield of the dimer product under the predicted optimal conditions. This work provides a predictive framework for AP electrolysis, empowering chemists to optimize conditions for efficient and selective radical-mediated electrosynthesis.