FORMATION AND REDOX PROPERTIES OF RADICAL IONS OF IODOPENTAFLUOROBENZENE IN AQUEOUS-SOLUTION - A PULSE-RADIOLYSIS STUDY

The transient optical absorption bands (lambda(max) = 290 and 400 nm) formed on reaction of (OH)-O-. radicals in neutral aqueous solution of iodopentafluorobenzene are assigned to the phenoxyl radical. The radi cal decays by second-order kinetics with 2k/epsilon l = 4.2 x 10(6) s( -1) and results in the formation of F- and I- [G(F-) = 5.3, G(I-) = 0. 2]. The rate constant for the reaction of (OH)-O-. radical with iodope ntafluorobenzene is 1.1 x 10(9) dm(3) mol-l s(-1). In acidic solution ([HClO4] < 1 mol dm(-3)), the nature of the transient optical absorpti on spectrum remained the same whereas when [HClO4] > 1 mol dm(-3), the transient optical absorption bands formed at 310 and 660 nm are assig ned to the solute radical cation. Cl(2)radical anion is unable to unde rgo electron transfer reaction with C6F5I whereas SO(4)radical anion i s able to react with a bimolecular rate constant of 3.3 x 10(8) dm(3) mol(-1) s(-1), and transient bands observed at 290 and 390 nm are assi gned to the phenoxyl radical. The solute radical cation is a powerful one-electron oxidant and is able to oxidize a number of organic compou nds with high rate constant values. The hydrated electron reacts with C6F5I by a nondissociative electron capture process, and the resulting radical anion undergoes fast protonation to form the cyclohexadienyl radical (lambda(max) = 290 mm). The bimolecular rate constant for the reaction of e (-) with C6F5I was 8 x 10(9) dm(3) mol(-1) s(-1). Simila r transient species is also observed on reaction of CO(2)radical anion with C6F5I. The spectrum of the radical anion is not observed even at pH 14.