Reactivity of hydroxyl radicals with ferrocenyl-substituted carboxylic acids. A radiation chemical study

Abstract

Radiation chemical studies demonstrate that the hydroxyl radical reacts readily with ferrocenyl-substituted carboxylic acids and that, when the ferrocenyl group and the carboxylate are separated by one or more methylene units, the reaction is principally an oxidation process. The nature of the reaction is less clear cut when the intervening group contains a double bond, a benzene ring, or is non-existent. Pulseradiolysis studies indicate that the rate constants for the reaction of OH with 2-ferrocenylethanoate and 3-ferrocenylpropanoate are, respectively, (2.2 ± 0.2)× 10¹⁰ and (2.9 ± 0.4)× 10¹⁰ dm³ mol^–1 s^–1, while those of (SCN)₂^– and of Br₂^– with the same anions are all less than 2 × 10⁹ dm³ mol^–1 s^–1. It is deduced that the diffusion coefficient of the hydroxyl radical may be appreciably greater than that of the self-diffusion of water.