REACTIONS OF C2 AND C-4 ALPHA-HYDROXY RADICALS WITH OXYGEN

To determine the relative importance of addition vs. H-atom abstraction in the reaction of oxygen with α-hydroxy radicals, we irradiated ethanol or 2-butanol in NOx-air or Cl2-NOx-air mixtures under simulated atmospheric conditions in a 5800-L evacuable environmental chamber. Products from the reactions of α-hydroxy radicals, formed via initial OH or Cl-atom abstraction of hydrogen from the alcohols, were identified and measured. The major primary products were acetaldehyde (80 ± 15%) in the ethanol experiments and methyl ethyl ketone (75-80%) and acetaldehyde (12-16%) in the 2-butanol experiments. Other products measured were formaldehyde, propionaldehyde, PAN, formic acid, and acetic acid as well as methyl, ethyl, and 2-butyl nitrates. The total organic acid yields were <3 and <7% in the ethanol and 2-butanol experiments, respectively. The α-hydroxy radicals react with O2 almost exclusively by hydrogen atom abstraction from the hydroxyl group to give acetaldehyde and methyl ethyl ketone. Addition of O2 to α-hydroxy radicals to form α-hydroxyperoxy radicals occurred less than 5% of the time in both systems. These results have implications for mechanisms of alkane, alkene, and alcohol oxidations in photochemical smog as well as other photooxidation processes. © 1979 American Chemical Society.