Affiliation:
1. Christian-Albrechts-Universität, Institut für Physikalische Chemie, Kiel, Deutschland
Abstract
Abstract
The primary products of the bimolecular reactions of ortho-benzyne, o-C6H4 (1,2-dehydrobenzene), with ethene, propene, and acetylene have been detected by molecular beam mass spectrometry at a combustion relevant temperature of T = 1475 K. o-Benzyne was produced by flash pyrolysis of phthalic anhydride in the absence and presence of the respective reactant. Potential reaction pathways of the addition reactions were investigated by quantum chemical calculations. Channels with biradical intermediates were found to be energetically more favorable than alternative quasi-concerted [2+1] cycloaddition and concerted H-transfer pathways. Bicyclic benzocyclobutene and benzocyclobutadiene were identified as the main products of the reactions with C2H4 and C2H2, respectively. At combustion temperatures, however, these cyclic products are likely to undergo sequential ring opening. In the case of propene, the presence of an allylic H atom initiates a favorable ene-type reaction sequence yielding the open-chain product allylbenzene. Overall, hydrocarbon reactivity was found to increase in the order C2H2, C2H4 to 3H8. The range of the estimated bimolecular rate constants is comparable to the rate constants of the corresponding phenyl radical reactions and hence point out a potentially important role of o-C6H4 reactions in flame and soot formation chemistry.
Subject
Physical and Theoretical Chemistry
Cited by
22 articles.
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