ATMOSPHERIC CHEMISTRY OF UNSATURATED ALCOHOLS

The atmospheric oxidation of the unsaturated alcohols [allyl alcohol (CH2=CHCH2OH), 3-buten-1-ol (CH2=CHCH2CH2OH), and cis-3-hexen-1-ol (CH3CH2CH=CHCH2CH2OH)] has been studied in experiments involving unsaturated alcohol-ozone-cyclohexane mixtures in the dark and involving unsaturated alcohol-nitric oxide mixtures in the sunlight. Major carbonyl products of the ozone-unsaturated alcohol reaction, with cyclohexane added to scavenge OH, included formaldehyde and hydroxyacetaldehyde from allyl alcohol (yields 0.50 +/- 0.03 and 0.30 +/- 0.03, respectively); formaldehyde from 3-buten-1-ol (yield 0.37 +/- 0.09); and propanal, methylglyoxal, and acetaldehyde from cis-3-hexen-1-ol (yields 0.59 +/- 0.12, 0.17 +/- 0.05 and 0.13 +/- 0.02, respectively). The corresponding reaction mechanisms are outlined with focus on formation and decomposition pathways for hydroxyalkyl-substituted Criegee biradicals. Carbonyl and peroxyacyl nitrate products of the alcohol-NO reaction in sunlight have been identified and their concentrations measured. Their formation is discussed in terms of pathways initiated by reaction with the hydroxyl radical. Peroxypropionyl nitrate [PPN, CH3CH2C(O)OONO2] was a major product of cis-3-hexen-1-ol and accounted for 14-20% of the initial NO. Atmospheric persistence of unsaturated alcohols and implications for the formation of propanal and PPN from biogenic emissions of cis-3-hexen-1-ol are briefly discussed.