Selective hydrodechlorination of 3,5,6-trichloropicolinic acid at an activated silver cathode: Synthesis of 3,5-dichloropicolinic acid

Electrochemical reduction of 3,5,6-trichloropicolinic acid (3,5,6-T) at glassy carbon, Ni, Cu, and Ag cathodes in aqueous solutions at different pH values was investigated. Experiments suggest that the selectivity of the reduction strongly depends on the cathode materials used and the pH of the aqueous solutions. A high selectivity for the hydrodechlorination of 3,5,6-T to 3,5-dichloropicolinic acid (3,5-D) has been achieved exclusively at an activated Ag cathode and at pH 3: a selectivity of 95% at 42% conversion under potentiostatic mode and a selectivity of 89% at 88% conversion under intentiostatic mode. An explanation is proposed for this high selectivity.