Electrochemical Properties of Herbicide (Paraquat) (1,1-Dimethyl-4,4- Bipyridilium Oichloride)

摘要

Electrochemical properties of herbicide 1,1-dimethyl-4,4'-bipyridilium dichloride (paraquat) were investigated using triangular wave cyclic voltammetry. The studies were carried out in various solvents of varying polarity with two different supporting electrolytes. The first and second reduction processes PQ+2+e () PQ.+ and PQ.++ e () PQ: were found to be reversible and each step involved one electron transfer. A third irreversible reduction was also observed in acetonitrile and dimethyl formamide. The disproportionation constant K for the equilibrium 2PQ.+ () PQ+2 + PQ: was evaluated and the effect of solvent on this equilibrium was studied. It was found that with the increase in the Z-value, solvent polarity parameter, the value of K decreased. The reactivities of the two reduction products PQ.+ and PQ: toward oxygen were also investigated. The rate constants for the reaction of PQ.+ and PQ: with oxygen in adsorbed phase (aqueous systems were determined to be 20 and 1 x 10 to the third power M(-1) sec(-1) respectively.