A contribution to the study of the electroreduction of 2-chloro-4,6-di(ethylamino)-1,3,5-triazine (simazine) on mercury electrodes

This paper presents polarographic (dc and DP) and voltammetric studies of t he electroreduction of the s-triazine derivative simazine (2-chloro-4,6-di( ethylamino)- 1,3,5-triazine) on mercury electrodes. The study is performed in the acidity range 2.25 M H2SO4 to pH 5. Above this last pH value no sign als were obtained. In DP polarography, two main reduction peaks were observ ed, accompanied by a pre-peak, at less negative potentials, and a post-peak , at more negative potentials, due to the adsorption of simazine on the ele ctrode. The main peaks corresponded to two-electron reduction processes. At pH below the protonation pK of the triazine ring (ca. 1.7), the results sh owed that in the first stage, simazine suffers a cleavage of the Cl atom vi a a CEC process to yield a dechlorinated intermediate. which is reduced thr ough an irreversible two-electron process, the rate-determining step being the second electron transfer. At pH > pK, a protonation of the triazine rin g precedes the reduction process, this reaction being also responsible for the observed decrease in limiting current. Linear-sweep voltammetry showed that simazine is adsorbed on the electrode with the triazine ring parallel to the electrode surface, as can be inferred from the value of the calculat ed area covered by one molecule. At pH values where both the protonated and unprotonated forms of simazine coexist, both forms are co-adsorbed on the electrode. (C) 1999 Elsevier Science S.A. All rights reserved.