Electrochemically Driven C−H Hydrogen Abstraction Processes with the Tetrachloro‐Phthalimido‐N‐Oxyl (Cl 4 PINO) Catalyst

The radical redox mediator tetrachloro‐phthalimido‐N‐oxyl (Cl 4 PINO) is generated at a glassy carbon electrode and investigated for the model oxidation of primary and secondary alcohols with particular attention to reaction rates and mechanism. The two‐electron oxidation reactions of a range of primary, secondary, and cyclic alcohols are dissected into an initial step based on C−H hydrogen abstraction (rate constant k 1 , confirmed by kinetic isotope effect) and a fast radical‐radical coupling of the resulting alcohol radical with Cl 4 PINO to give a ketal that only slowly releases the aldehyde/ketone and redox mediator precursor back into solution (rate constant k 2 ). In situ electrochemical EPR reveals Cl 4 PINO sensitivity towards moisture. DFT methods are applied to confirm and predict C−H hydrogen abstraction reactivity.