GAS-PHASE REACTION OF OZONE WITH TRANS-2-HEXENAL, TRANS-2-HEXENYL ACETATE, ETHYLVINYL KETONE, AND 6-METHYL-5-HEPTEN-2-ONE

The gas-phase reaction of ozone with the unsaturated oxygenates trans- 2-hexenal, trans-2-hexenyl acetate, ethylvinyl ketone, and 6-methyl-5- hepten-2-one. which are components of biogenic emissions and/or close structural homologues thereof, has been investigated at atmospheric pr essure and ambient temperature (286-291 K) and humidity (RH = 55 +/- 1 0%). Reaction rate constants, in units of 10(-18) cm(3) molecule(-1) s (-1), are 1.28 +/- 0.28 for trans-2-hexenal, 21.8 +/- 2.8 for trans-2- hexenyl acetate, and 394 +/- 40 for 6-methyl-5-hepten-2-one. Carbonyl product formation yields, measured with sufficient cyclohexane added t o scavenge the hydroxyl radical, are 0.53 +/- 0.06 for n-butanal and 0 .56 +/- 0.04 for glyoxal from trans-2-hexenal, 0.47 +/- 0.02 for n-but anal and 0.58 +/- 0.14 for 1-oxoethyl acetate from trans-2-hexenyl ace tate, 0.55 +/- 0.07 for formaldehyde and 0.44 +/- 0.03 for 2-oxobutana l from ethylvinyl ketone, and 0.28 +/- 0.02 for acetone from 6-methyl- 5-hepten-2-one. Reaction mechanisms are outlined and the atmospheric p ersistence of the compounds studied is briefly discussed. (C) 1996 Joh n Wiley & Sons, Inc.