Oxidation of Substituted Alkyl Radicals by IrCl62-, Fe(CN)63-, and MnO4- in Aqueous Solution. Electron Transfer versus Chlorine Transfer from IrCl62-

Article abstract of DOI:10.1021/ja00369a017

Alkyl radicals substituted at C_α by alkyl, carboxyl, hydroxyl, alkoxyl, and chlorine react in aqueous solutions with Ir^IVCl6^2- to yield Ir(III) species.In the case of substitution by hydroxyl and alkoxyl, the rate constants are in the diffusion-controlled range ((4-6)x10⁹ M^-1 s^-1) and the reaction proceeds by electron transfer.In the case of ethyl, methyl, carboxymethyl, and chloromethyl radicals the rate constants range from 3.1x10⁹ for ethyl to 2.8x10⁷ M^-1 s^-1 for trichloromethyl and the reaction proseeds by chlorine transfer from IrCl6^2- to the alkyl radical.With isopropyl and tert-butyl radicals the reaction proceeds by both electron and chlorine transfer.Alkyl radicals also react with Fe(CN)6^3-.The rate constants increase strongly with increasing alkylation at C_α from 5x10⁶ for methyl to 3.6x10⁹ M^-1 s^-1 for tert-butyl, indicating that the transition state for the reaction is highly polar.Rate constants for reaction of MnO4^- with alkyl radical are of the order 10⁹ M^-1 s^-1.