Ionizing Radiation-Induced Destruction of Benzene and Dienes in Aqueous Media

Pulse radiolysis with spectrophotometric and conductometric detection was utilized to study the formation and reactions of radicals from benzene and dienes in aqueous solutions. The benzene OH adduct, •C6H6OH, reacts with O2 (k = 3 × 108 L mol-1 s-1) in a reversible reaction. The peroxyl radical, HOC6H6O2 •, undergoes O2 •- elimination, bimolecular decay, and reaction with benzene to initiate a chain reaction, depending on the dose rate, benzene concentration, and pH. The occurrence of the chain reaction is demonstrated in low-dose-rate gamma radiolysis experiments where the consumption of O2 was monitored. 1,4-Cyclohexadiene, 1,4-hexadiene, and 1,4-pentadiene form OH-adducts and undergo H-abstraction by O•- radicals. The OH-adducts react with O2 to form peroxyl radicals. These peroxyl radicals, however, do not undergo unimolecular O2 •- elimination but rather decay by second-order processes, which lead to subsequent steps of O2 •- elimination.