The gaseous oxidation of acetone - II. The low-temperature reaction

The kinetics of the oxidation of acetone in the 'low-temperature’ region (i. e. below 320°C) have been carefully investigated. In contrast to the high-temperature region, the products include no methane, but appreciable quantities of methyl hydroperoxide as well as water, carbon monoxide and dioxide. A reaction scheme is suggested which involves degenerate chain branching by the homo­geneous decomposition of methyl hydroperoxide. The transition from the low-temperature mechanism to that prevailing at high tempera­tures is due to the changing importance of the alternative reactions of the methyl radical. At low temperatures, the formation of methyl hydroperoxide is favoured CH3 + O2 + M = CH3O2 + M, CH3O2+ RH = CH3O2H + R, whereas at high temperatures the methyl peroxy radical is too unstable to abstract hydro­gen and instead the reaction yields formaldehyde CH3 + O2 = HCHO + OH.