ATMOSPHERIC CHEMISTRY OF OLEFINS - A PRODUCT STUDY OF THE OZONE ALKENE REACTION WITH CYCLOHEXANE ADDED TO SCAVENGE OH

Carbonyl and carboxylic acid products of the ozone-olefin reaction, in which the hydroxyl radical is produced, have been identified and meas ured for eight alkenes in the presence of excess cyclohexane, i.e., un der conditions that minimize subsequent reactions of OH with the alken es and with their carbonyl products. The carbonyls expected to form di rectly, i.e., alkene + ozone --> 1,2,3-trioxolane adduct --> two carbo nyls + two Criegee biradicals, were observed as major products (e.g., formaldehyde and 2-butanone from 2-methyl-1-butene). Their yields rang ed from 9 +/- 2% for 1,3-butadiene to 88 +/- 4% for 2,3-dimethyl-2-but ene. For alkenes that lead to two Criegee biradicals, carbonyl yields were consistent with preferential formation of the more substituted bi radical. Criegee biradical decomposition to hydroxycarbonyl and/or dic arbonyl products (yields 20-52%) was observed in all cases. Unimolecul ar decomposition of Criegee biradicals was also observed, yielding for maldehyde (5-12%) from methyl-substituted biradicals and acetaldehyde (15-39%) from ethyl-substituted biradicals. Carboxylic acid yields wer e 8-10% for acetic acid (from trans-2-butene and 2-methyl-2-butene) an d 13-17% for formic acid (from isobutene, 1-butene, 2-methyl-1-butene, and 1,3-butadiene).