Gas-phase ozonolysis of alkenes: formation of OH from anti carbonyl oxides.
Gas-phase ozone-alkene reactions are known to produce the hydroxyl radical (OH) in high yields. Most mechanistic studies to date have focused on the role of syn carbonyl oxides; however, OH production from ethene ozonolysis indicates a second, poorly understood OH-forming channel, which may contribute to OH production in the ozonolysis of substituted alkenes as well. Using laser-induced fluorescence, we have measured OH and OD yields from the ozonolysis of two partially deuterated alkenes, cis- and trans-3-hexene-3,4-d2. OD is formed from both alkenes, indicating a pathway of hydroxyl-radical formation involving vinylic hydrogens, accounting for one-third of total OH formation from cis-3-hexene. The lack of a significant kinetic isotope effect suggests this pathway is the "hot acid" channel, arising from rearrangement of anti carbonyl oxides. Measured yields also allow for the estimation of syn:anti carbonyl oxide ratios, approximately 50:50 for trans-3-hexene and approximately 20:80 for cis-3-hexene, qualitatively consistent with our understanding of ozonide decomposition pathways.
Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, USA. kroll@huarp.harvard.edu
Jesse H
JH
Kroll
Neil M
NM
Donahue
Victor J
VJ
Cee
Kenneth L
KL
Demerjian
James G
JG
Anderson