Arylation of Nitrobenzene Induced by γ-Radiation

Phenylation and nitrophenylation take place during γ-radiolysis of nitrobenzene to produce the three isomeric nitrobiphenyls and the six isomeric dinitrobiphenyls (one nitro group per phenyl ring), respectively. For the radiolytic phenylation and nitrophenylation, all positions of nitrobenzene are attacked and ortho-para substitution is favored over meta substitution. This is in general agreement with the free radical arylation of aromatic compounds. Relative reactivities for the radiolytic phenylation of nitrobenzene were obtained, and the radiolytic phenylating intermediates show less ortho-para selectivity than the phenyl radical. The relative reactivities for the radiolytic phenylation are not in quantitative agreement with the relative reactivities reported for the free radical phenylation of nitrobenzene. The results of irradiations of nitrobenzene with DPPH scavenger show that both the scavenged and non-scavenged precursors for the formation of the nitrobiphenyls exhibit about the same relative reactivities.