ATMOSPHERIC CHEMISTRY OF UNSATURATED CARBONYLS - BUTENEDIAL, 4-OXO-2-PENTENAL, 3-HEXENE-2,5-DIONE, MALEIC-ANHYDRIDE, 3H-FURAN-2-ONE, AND 5-METHYL-3H-FURAN-2-ONE

As part of a study on the oxidation mechanisms of aromatics some aspec ts of the atmospheric chemistry of several possible products, unsatura ted 1,4-dicarbonyl compounds and two furanones, have been investigated in a 1080-L reaction chamber by 296 +/- 2 K in 1000 mbar of synthetic air. Rate coefficients for the reaction of OH radicals with the follo wing compounds have been obtained using the relative method (in units of 10(-12) cm(3) molecule(-1) s(-1)): cis-butenedial (maleic dialdehyd e), 52.1 +/- 1.0; trans-butenedial (fumaric dialdehyde), greater than or equal to 24.1 +/- 7.9; cis/trans-4-oxo-2-pentenal (acetylacrolein), 55.8 +/- 2.1; cis-3-hexene-2,5-dione, 69.0 +/- 21.0; trans-3-hexene-2 ,5-dione, 40.0 +/- 4.0; maleic anhydride, 1.45 +/- 0.1; 3H-furan-2-one , 44.5 +/- 2.6; 5-methyl-3H-furan-2-one (alpha-angelica lactone), 69.0 +/- 4.6. The first gas-phase FTIR spectra of cis-butenedial, trans-bu tenedial, cis/trans-4-oxo-2-pentenal, and 3H-furan-2-one are presented . The photochemistry of the dicarbonyls is discussed, and preliminary results from product studies on the OH-initiated oxidation of the dica rbonyl compounds are reported. The results indicate that reaction with OH radicals will be an important atmospheric sink for all of the unsa turated carbonyls studied here. However, for butenedial, 4-oxo-2-pente nal, and hexene-2,5-dione the results suggest that photolysis will pro bably be an even stronger sink.