Pulse radiolysis investigations on acidic aqueous solutions of benzene: Formation of radical cations

The transient optical absorption bands (lambda(max) = 310, 350-500 nm, k = 5.6 x 10(9) dm(3) mol(-1) s(-1)) formed on pulse radiolysis of an acidic (H ClO4 = 7.8 mol dm(-3)) aqueous solution of benzene are assigned to the solu te radical cation formed on acid-catalyzed dehydration of the OH adduct. Th e solute radical cation is able to undergo an electron transfer reaction wi th Br- with a bimolecular rate constant of 8 x 10(9) dm(3) mol(-1) s(-1). O n the other hand, the OH adduct (lambda(max) = 310 nm) was oxidized by Fe(C N)(6)(3-) with a bimolecular rate constant of 6.6 x 10(7) dm(3) mol(-1) s(- 1). The radical cation of benzene is a strong one-electron oxidant with oxi dation potential in the range 2.1-2.4 V vs NHE.