Pulse‐Constructed Cu ^δ+ /CuO _x Reduces the C─Cl Dipole Moment to Enable Complete Deuterodechlorination of Trichloroacetic Acid

Abstract Electrocatalytic deuterodechlorination of trichloroacetic acid with D 2 O provides a high single‐pass deuterium ratio avenue for the synthesis of acetic‐ d 3 acid at room temperature. However, increasing C─Cl dipole moments via stepwise dechlorination, and gradual active site deactivation make active and stable complete dechlorination highly challenging. Here, metastable Cu δ+ /CuO x dual sites are constructed in situ and maintained under pulsed electrolysis, enabling 70 h of stable electrosynthesis of acetic‐ d 3 acid with a 97% deuterium ratio. Surface copper oxides are formed in situ and then convert to Cu δ+ /CuO x when the oxidation and reduction potentials are intermittently applied, which enhances C─Cl adsorption to promote electron transfer to Cl atoms and attracts ─COOH to increase the electronegativity of the C atom of C─Cl, remarkably reducing the C─Cl dipole moment and promoting complete dechlorination. The fast electrosynthesis of 20 g of CD 3 COOH with applications in the deuterium labeling of drugs and DNA bases and markedly increased yields in the hydrogenation/deuteration of other chlorides and bromides demonstrate the methodology's potential.