Pulse radiolysis of aqueous solutions of aniline and substituted anilines

Abstract

The primary reactions of hydrated electrons, hydrogen atoms and hydroxyl radicals with aniline and the aniline cation in aqueous solutions have been studied by the technique of pulse radiolysis and by determination of end products after γ-radiolysis. Hydrogen atoms and hydrated electrons react with aniline to form the cycloehxadienyl type radical with absorption maximum at 355 nm and an extinction coefficient of 410 m 2/mol. A similar radical formed by reaction of hydrogen atoms with the aniline cation has its absorption maximum at 310 nm and an extinction coefficient of 320 m 2/mol. Hydrogen atoms react with the acid and neutral forms of aniline with rate constant of (1.3 ±0.2)×10 9 dm 3 mol −1 s −1 and (2.9±0.7)×10 9 dm 3 mol −1 s −1, respectively. OH radicals react with aniline with rate constant of (1.4±0.3) x 10 10 dm 3mol −1s −1 to form the cyclohexadienyl radical HOC 6H 5NH 2 with absorption maximum at 355 nm and the anilino radical with absorption maxima at 300 and 400 nm. The cyclohexadienyl radical decayed in a radical dissappeared in a second-order reaction to form hydrazobenzene. O- radicals react with aniline at pH 13.3 with a rate constant of (3.1±0.6)×10 9 dm 3 mol −1S −1 to form anilino radicals. The reaction of OH radicals with the aniline cation produced the anilino radical cation with a rate constant of (4.8±0.8)×10 9dm 3mol −1s −1. The absorption maximum was placed at 415 nm. The cyclohexadienyl-type radical with absorption maximum at 350 nm was also found in aqueous solutions of 2-amino-1, 3-dimethylbenzene but was not formed in solutions of N, N '- dimethylaniline.