Acetonylperoxyl Radicals, CH3COCH2O2: A Study on the γ-Radiolysis and Pulse Radiolysis of Acetone in Oxygenated Aqueous Solutions

Abstract

Hydroxyl radicals from the radiolysis of N2O/O2 (4:l)-saturated aqueous solutions of acetone (10-3mol dm-3) react with the solute by H-abstraction thereby forming acetonyl radicals. As shown by pulse radiolysis, the acetonyl radicals rapidly add oxygen (k = 3 x 109 dm3mol-1 s-1) thereby forming acetonylperoxyl radicals which decay by second-order kinetics (2 k = 8 x 108 dm3mol-1s-1). Under steady-state radiolysis conditions (0.24 Gy s-1) the products (G values in parentheses) are methylglyoxal (2.5). hydroxyacetone (0.5), formaldehyde (1.6), acids (1.7), carbon dioxide (0.5), organic (hydro)peroxides (0.4), hydrogen peroxide (2.2), and G(oxygen uptake) has been determined at 5.2. In the decay of the acetonylperoxyl radicals the major process (slightly less than one half) leads in a concerted reaction to two molecules of methylglyoxal and one molecule of hydrogen peroxide. The Russell mechanism which yields one molecule of methylglyoxal. hydroxyacetone and oxygen contributes about one fifth as does the breakdown into two molecules of formaldehyde, one molecule of oxygen and two acetyl radicals. Carbon dioxide, formaldehyde and acetic acid are among the products which result from the acetylperoxyl radicals formed upon oxygen addition to the acetyl radicals. About one tenth of the organic peroxyl radicals is converted into hydroperoxides by O2produced as a byproduct in the water radiolysis. © 1986, Walter de Gruyter. All rights reserved.