On the electroreduction of 4-chloro-2,6-diisopropylamino-s-triazine (propazine) on mercury electrodes

This paper presents a polarographic (dc and differential pulse (DP)) study of the reduction of the s-triazine derivative propazine (4-chloro-2, 6-diisopropylamino-s-triazine). The study is performed in acidic media (from solutions 2.25 M in H2SO4 to pH 5) because no signals were obtained above pH 5 (even at pH values of 11-12). In the pH range 2-4 the polarograms decreased until they vanished. In DP polarography, two main reduction peaks were observed, accompanied by a pre-peak at less negative potentials, and a post-peak at more negative potentials, due to the adsorption of propazine on the electrode. The main peaks corresponded to two-electron reduction processes. At pH below the protonation pK of the triazine ring (about 1.7), the results showed that, in a first stage, propazine suffers a cleavage of the Cl atom via a CEC process (electron transfer placed between two chemical reactions) to yield a dechlorinated intermediate, which is reduced through an irreversible two-electron process, the rate-determining step (r.d.s.) being the second electron transfer. At pH above the pK, a protonation of the triazine ring precedes the reduction process, this reaction being also responsible for the observed decrease in limiting current. (C) 1999 Elsevier Science S.A. All rights reserved.