EC(EE) processes in the reduction of some 2-methylthio-4,6-di(alkylamino)-1,3,5-triazines on mercury electrodes

Abstract Polarographic (direct current, dc, and differential pulse, DP) studies of the electroreduction of the s-triazine derivatives ametryn (2-methylthio-4-ethylamino-6-isopropylamino)-1,3,5-triazine), dimethametryn (2-methylthio-4-ethylamino-6-(1,2-dimethylpropyl) amino-1,3,5-triazine) and simetryn (2-methylthio-4,6-di(ethylamino)-1,3,5-triazine) were made in the acidity range from 2.25 M H 2 SO 4 to pH 6.5. Above this last pH value no signals were obtained. In DP polarography, two main reduction peaks were observed, accompanied by a pre-peak due to the adsorption of the herbicides on the electrode. The main peaks corresponded to two-electron irreversible reduction processes, at pH values higher than the protonation p K of the triazine ring (ca. 4). In this pH range, the protonation of the triazine ring preceding the reduction process is responsible for decrease in limiting current. At pH K the herbicides suffer a cleavage of the –SCH 3 group via two different intermediates related by a chemical reaction, whose extension depends on the herbicide.