Radical-cations as reference chromogens in kinetic studies of ono-electron transfer reactions: pulse radiolysis studies of 2,2′-azinobis-(3-ethylbenzthiazoline-6-sulphonate)

Abstract

Electrophilic free radicals such as OH˙, RS˙, CCl₃O₂˙, Br₂˙^–, and (SCN)₂·^– react rapidly with 2,2′-azinobis-(3-ethylbenzthiazoline-6-sulphonate)(ABTS) to form the radical-cation ABTS˙⁺, λ_max. 415 nm (ε 3.6 × 10⁴ l mol^–1 cm^–1). Absolute rate constants for these electron-transfer reactions have been determined by pulse radiolysis. Results suggest that ABTS˙⁺ is likely to prove a useful reference free radical, not only for the study of reactions in which a free radical is the electron acceptor, but also in studies of reactions of organic radicals with sulphydryl compounds.