Studies on the mechanism of electroreduction of isonicotinic acid and its carboxylic isomers on mercury cathode

Abstract

A mercury pool of about 10 cm 2 was used as a cathode and linear potential sweep were used for voltammetric studies of isonicotinic acid and its carboxylic isomers in aqueous solutions. The authors discovered that at every second scanning in isonicotinic acid solution there began to appear a new wave at a half-wave potential more positive than the original one. These new waves seem to be due to a new these intermediates bear a linear relationship with pH, slopes of these straight lines being 55–60 mV pH −1. These active species decayed according to the second order reaction law and the 2 k rate constants have been determined. Also, a coloured substance was observed during the electroreduction of isonicotinic acid. The relationship of the formation of the coloured substance and the simultaneous decay of the active intermediates has been demonstrated. A scheme of the electroreduction is suggested: the first step of the reaction is: ▪ and the succeeding steps are going through the following courses: ▪ Interesting comparisons have been made between the electrochemical reduction processes and the radiation processes of the three pyridine monocarboxylic acids. Similarity and parallelism between these two processes are prevailing.