Reductive cleavage of chlorine from 6-chloronicotinic acid on mercury electrodes |
| |
Authors: | M Ruiz Montoya S Pintado JM Rodríguez Mellado |
| |
Affiliation: | aDepartamento de Ingeniería Química, Química Física y Química Orgánica, Universidad de Huelva, Campus El Carmen, Facultad de Ciencias Experimentales, E-21071 Huelva, Spain;bDepartamento de Química Física y Termodinámica Aplicada, Universidad de Córdoba, Campus Universitario de Rabanales, edificio “Marie Curie”., E-14014 Córdoba, Spain |
| |
Abstract: | This paper presents polarographic (direct current, dc, and differential pulse, DP) and voltammetric (linear-sweep cyclic voltammetry) studies on the electroreduction of 6-chloronicotinic acid (6CNA) on mercury electrodes. In order to obtain the dissociation constants of 6CNA, UV–vis spectra were recorded as a function of pH. pK values of −0.80 ± 0.05 (–COOH group) and 3.2 ± 0.1 (pyridinic nitrogen) were obtained. The electrochemical studies were performed in the acidity range 6 M H2SO4 to pH 8. Above the last pH value no signals were obtained. Electrolysis made at potentials corresponding to the limiting current of the first wave indicates that there is a reductive cleavage of chlorine from the molecule. This was confirmed by dc and DP polarografic results and also by voltammetric results. Kinetic parameters such as Tafel slopes and electrochemical reaction orders have been determined at potentials corresponding to the foot of the waves. From these results, together with those obtained by cyclic voltammetry, a reaction pathway is proposed, in which the rate-determining step of the process is the release of a chloride ion from the radical formed after the uptake of a H+ ion and an electron. |
| |
Keywords: | Reduction mechanisms Pyridine herbicides Electrode kinetics Chlorine cleavage |
本文献已被 ScienceDirect 等数据库收录! |
|