Bipyridylium quaternary salts and related compounds. Part 6.—Pulse radiolysis studies of the reaction of paraquat radical analogues with oxygen

Abstract

Decay curves have been measured for reaction with oxygen of radicals derived by pulse radiolysis from a series of bipyridylium salts. The shapes of the curves were consistent with decay due to reaction of the bipyridyl radicals with both oxygen and superoxide ion, and rate constants k₁ and k₂ for these reactions were estimated. For compounds with redox potentials above –0.2 V, the reverse reaction, between superoxide ion and bipyridylium salt, was included in the kinetic scheme. k₁ values were mostly between 4 and 9 × 10⁸ dm³ mol^–1 s^–1 and k₂ values were all higher.

The correlation of rate constants with difference between redox potentials of donor and acceptor is discussed.