Reactions of nitrosodimethylaniline with free radicals

Abstract

The changes in absorption spectra of aqueous Ar-, N₂O- or O₂-saturated, solutions of p-nitro-sodimethylaniline(P) subjected to γ-rays under steady-state conditions or to 2.9 MeV electron pulses, and the effects on these of various OH radical scavengers S, (and some e^–_aq scavengers) have been measured. The optical density of the solutions at 440 nm, where P absorbs strongly, initially diminishes rapidly due to reactions of P with e^–_aq(k= 3.4 × 10¹⁰ M^–1 sec^–1), confirmed by measurement of the effect of P on G(₂) for γ-radiolysis, and OH(k= 1.8 ×10¹⁰ M^–1 sec^–1), and then undergoes partial or complete, rapid or slow, recovery, dependent on the nature of both S and the dissolved gas. Rate constants of reactions of P with the oxidized form of S have been measured. O^–₂ does not react with P but the complexities of the secondary reactions prevent the calculation of reliable values of k for OH + S from the effect of S on G(–P) for steady-state conditions. However, the effect of S on the maximum O.D. change at 440 nm following pulse radiolysis of O₂-saturated solutions can be used to obtain trustworthy values of k(OH + S) in specified cases.