Pulse Radiolysis Investigations on Acidic Aqueous Solutions of Benzene: Formation of Radical Cations

The transient optical absorption bands (λmax = 310, 350−500 nm, k = 5.6 × 109 dm3 mol-1 s-1) formed on pulse radiolysis of an acidic (HClO4 = 7.8 mol dm-3) aqueous solution of benzene are assigned to the solute radical cation formed on acid-catalyzed dehydration of the OH adduct. The solute radical cation is able to undergo an electron transfer reaction with Br- with a bimolecular rate constant of 8 × 109 dm3 mol-1 s-1. On the other hand, the OH adduct (λmax = 310 nm) was oxidized by Fe(CN)63- with a bimolecular rate constant of 6.6 × 107 dm3 mol-1 s-1. The radical cation of benzene is a strong one-electron oxidant with oxidation potential in the range 2.1−2.4 V vs NHE.