Electrochemical reduction of propazine: NMR evidence for dechlorination and reduction of the triazine ring

Abstract

Propazine (2-chloro-4,6-diisopropylamino-1,3,5-triazine) is a triazine herbicide used to control broadleaf weeds and annual grasses during the production of milo grain sorghum. This compound provides post-emergent protection by interfering with photosynthetic electron transport of target weeds. Tolerant crops are able to degrade the applied herbicide to nontoxic metabolites. Propazine is electrochemically active under acidic conditions. Electrochemical reduction pathways for this herbicide have been proposed based on differential pulse polarography (DPP) studies. Theoretical deconvolutions of the experimental polarograms were consistent with a 2-electron cleavage of the C–Cl bond via a mechanism involving a protonation step in between the two electron transfers. The resulting intermediate was then reduced by an irreversible 2-electron reduction of the ring to produce the final product. We report supporting nuclear magnetic resonance (NMR) evidence for the electrochemical dechlorination of propazine and reduction of the triazine ring using controlled potential electrolysis (CPE) and a mercury pool electrode under acidic conditions.