THE EFFECT OF CATHODE COMPOSITION ON THE EFFICIENCY OF ELECTROCARBOXYLATION OF AROMATIC HALIDES

The composition of the cathode has a significant effect on the efficie ncy of electrocarboxylation of aromatic halides which are relatively d ifficult to reduce in N,N-dimethylformamide. At low temperatures (< O degrees C) and controlled current conditions, aromatic bromides and io dides are carboxylated with much greater efficiency than aromatic chlo rides at a silver electrode, while at stainless steel the chlorides ar e carboxylated more efficiently. At silver the efficiency depends on t he ease of reduction of the halides relative to CO2, while at stainles s steel passivation effects, which are more serious for the bromides a nd iodides, primarily influence the efficiency. Experiments with added D2O provide no evidence for production of aromatic radical intermedia tes via CO2-mediated one-electron reduction of the halides.