CARBONYL PRODUCTS OF THE OZONE-UNSATURATED ALCOHOL REACTION

Carbonyl products of the gas phase reaction of ozone with four monosub stituted and three 1,2-disubstituted unsaturated alcohols that are rel evant to biogenic emissions have been identified in laboratory experim ents involving unsaturated alcohol-ozone mixtures in the dark. Cyclohe xane was added to scavenge the hydroxyl radical, which forms as a prod uct of the ozone-unsaturated alcohol reaction. Major carbonyl products included formaldehyde and hydroxyacetaldehyde from allyl alcohol, ace taldehyde, and hydroxyacetaldehyde from 2-buten-1-ol, propanal, and hy droxyacetaldehyde from cis-2-penten-1-ol, formaldehyde from 3-buten-2- ol, 1-penten-3-ol, and 2-methyl-3-buten-2-ol, and hydroxyacetaldehyde from 2-buten-1,4 diol. Yields of the primary carbonyls (ozone + unsatu rated alcohol --> 2 primary carbonyls + 2 biradicals) averaged 0.91 +/ - 0.29, which compares to a theoretical value of 1.0. Yields of carbon yls that are not hydroxy substituted averaged 0.38 +/- 0.13, which com pares to a theoretical value of 0.50 if one assumes that the alkyl-sub stituted and the hydroxyalkyl-substituted biradicals are formed in equ al yields. The corresponding reaction mechanisms are outlined with foc us on similarities between unsaturated alcohols and alkene structural homologues. Possible decomposition pathways for hydroxyalkyl-substitut ed biradicals are examined. The atmospheric persistence and the fate o f unsaturated alcohols from biogenic emissions and of their carbonyl p roducts are briefly discussed.