Radiation chemical oxidation of benzaldehyde, acetophenone, and benzophenone

Radiation chemical reactions of •OH, O•-, and SO4•- with benzaldehyde, acetophenone, and benzophenone have been studied using both pulse and steady-state radiolysis techniques. The observed rates for the •OH addition (k = (2.6-8.8) × 109 M-1 s-1) are higher than those found for the SO4•- reaction (k = (0.7-4.0) × 109 M-1 s-1). The rate for the reaction of O•- with benzaldehyde is higher than that found for •OH, while a reverse trend is observed in the case of the two ketones. Optical absorption spectra of the intermediate transients formed in the reactions of •OH and SO4•- with all three compounds are similar with a peak around 370-380 nm. The absorption spectra from the O•- reaction have shown a major peak at 310 nm and are somewhat different from those obtained in the reaction of •OH. The yields of the phenolic products formed in the reaction of •OH with benzaldehyde and acetophenone in the presence of 0.1 mM ferricyanide corresponded to only 30% and 50% •OH yields, respectively. Benzoic acid is a major product formed with benzaldehyde in the reaction of •OH as well as SO4•- with G values of 2.1 and 1.3 per 100 eV, respectively. The formation of the exocyclic OH adduct is a major pathway in the reactions of •OH (by addition) and of SO4•- from hydrolysis of the initially formed radical cation (k = 2.4 × 104 s-1) with benzaldehyde. The exocyclic OH adduct undergoes disproportionation to give benzoic acid. The formation of the exocyclic OH adduct of acetophenone is possibly hindered owing to the bulky -COCH3 group