One-Electron Oxidation of Alkylbenzenes in Acetonitrile by Photochemically Produced NO3.: Evidence for an Inner-Sphere Mechanism

Article abstract of DOI:10.1021/j100123a003

The reaction between NO3^. and polyalkylbenzenes was studied using 308-nm laser flash photolysis of cerium(IV) ammonium nitrate in the presence of the alkylbenzenes in acetonitrile solution.For all benzenes, with the exception of monoalkylbenzenes and o- and m-xylene, the reaction with NO3^. was found to yield the corresponding radical cations and to proceed in an apparently straightforward bimolecular manner.For monoalkylbenzenes and o- and m-xylene, radicals were seen which are derived from the parents by formal loss of H^. from the side chain of the aromatic.This reaction proceeds via a complex between the aromatic and NO3^. with the decomposition of the complex being rate determining at higher concentrations of aromatic (rate constants for decomposition between 6 * 10⁵ and 4 * 10⁷ s^-1).In the complex, electron transfer from the aromatic to NO3^. is suggested to be concerted with deprotonation of the incipient radical cation.Formation of a complex between NO3^. and aromatics is likely even in those cases where radical cations are observed, with the assumption that in these cases the complex decomposition rate is greater than 6 * 10⁷ s^-1.