N. Farzinnegad, M. M. Heravi, and Sh. KhaleghiDepartment of Chemistry, Faculty of Science, Al-Zahra University, P.O. Box 1993891176, Tehran, IranReceived January 6, 2003An electrochemical study related to the electroreduction of 4-amino-6-methyl-3-thio-1,2,4-triazin-5-one(I), 6-methyl-3-thio-1,2,4-triazin-5-one(II), and 2,4-dimetoxy-6-methyl-1,3,5-triazine(III) in dimethylformamide atglassy carbon electrode has been performed. A variety of electrochemical techniques, such as differential pulsevoltammetry (DPV), cyclic voltammetry (CV), chronoamp erometry, and coulometry were employed to clarifythe mechanism of the electrode process. The compounds I and II with thiol group exhibited similar redoxbehavior. Both displayed two cathodic peaks, whereas the third compound, III, without thiol group showedonly one cathodic peak in the same potential range of the second peak of I and II. The results of this studysuggest that in the first step the one electron reduction of thiol produced a disulfide derivative and in the secondreduction step the azomethane in the triazine ring was reduced in two electron processes. A reductionmechanism for all three compounds is proposed on this basis. In addition, some numerical constants, such asdiffusion constant, transfer coefficient, and rate constant of coupled chemical reaction in the first reductionpeak were also reported.Key Words : Electrochemistry, Triazine, Disulfide, Coupled chemical reactionIntroductionS-triazine compounds containing both -C=N- moiety andthiol group are of interest in agriculture and biologicalprocesses. From the agricultural point of view thesecompounds have proved to be useful as herbicides andpesticides. Owing to the NH-C=N- moiety they are able tocompete with a molecule of the natural electronic acceptor atthe same binding site in the protein of the photosyntheticreaction center.