Silver Cathodes as Electrocatalysts in the Carboxylation of Benzyl Chlorides

Very recently, a series of papers dealing with the reduction of organic halides at silver cathodes have appeared. The most important result emerging from such studies is that silver exhibits extraordinary electrocatalytic activities towards the reduction process, especially in the case of bromides and iodides. The possibility of exploiting the electrocatalytic nature of silver in electrocarboxylations has not been explored yet. Here we report the results of an investigation on the potentialities of silver as an electrocatalyst in the carboxylation of benzyl chlorides. The process was studied in CH3CN + 0.1 M Et4NClO4 at Ag, Hg and carbon cathodes at 25 °C. Two types of silver electrode were used: one made from the bulk metal and the other (denoted Ag/Pt) prepared by electrodeposition of Ag on Pt. On all three electrodes, a single irreversible peak is observed in cyclic voltammetry. The position of the peak, however, depends strongly on the electrode material. The data obtained at Ag, Hg and glassy carbon (GC) electrodes are collected in Table 1. The data obtained on Ag/Pt (not shown in the Table) were the same, within experimental error, as those reported for Ag. Whereas the presence of CO2 had no effect on the peak potential (Ep) of RCl at GC or Hg, significant positive shifts were observed at the silver electrodes. The last column shows Ep values obtained at Ag in CO2-saturated CH3CN.