Electrochemical behaviour of 3,5,6-trichloro-4-methyl-pyridine-2-carboxylic acid on mercury and carbon electrodes

This paper presents voltammetric (linear-sweep cyclic voltammetry) and chronoamperometric studies on the electroreduction of 3,5,6-trichloro-4-methylpyridine-2-carboxylic acid (3CMPA) on mercury and carbon electrodes. The dissociation constants of 3CMPA were obtained from UV–vis spectra. The pK values were 1.7 ± 0.1 (COOH group) and 4.1 ± 0.1 (pyridinic nitrogen). The electrochemical studies were performed in the acidity range 6 M H2SO4 to pH 7. Above the last pH value no signals were obtained. 3CMPA is adsorbed on the mercury electrode via a nucleation and growth process but no monolayer is formed in the accessible experimental conditions. From the voltammetric results in the carbon electrode, reaction pathways are proposed.