Carbonyl products of the ozone‐unsaturated alcohol reaction

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Abstract
Carbonyl products of the gas phase reaction of ozone with four monosubstituted and three 1,2‐disubstituted unsaturated alcohols that are relevant to biogenic emissions have been identified in laboratory experiments involving unsaturated alcohol‐ozone mixtures in the dark. Cyclohexane was added to scavenge the hydroxyl radical, which forms as a product of the ozone‐unsaturated alcohol reaction. Major carbonyl products included formaldehyde and hydroxyacetaldehyde from allyl alcohol, acetaldehyde, and hydroxyacetaldehyde from 2‐buten‐1‐ol, propanal, and hydroxyacetaldehyde 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 + unsaturated alcohol → 2 primary carbonyls + 2 biradicals) averaged 0.91±0.29, which compares to a theoretical value of 1.0. Yields of carbonyls that are not hydroxy substituted averaged 0.48±0.13, which compares to a theoretical value of 0.50 if one assumes that the alkyl‐substituted and the hydroxyalkyl‐substituted biradicals are formed in equal yields. The corresponding reaction mechanisms are outlined with focus on similarities between unsaturated alcohols and alkene structural homologues. Possible decomposition pathways for hydroxyalkyl‐substituted biradicals are examined. The atmospheric persistence and the fate of unsaturated alcohols from biogenic emissions and of their carbonyl products are briefly discussed.