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Formation of phenylacetylene and benzocyclobutadiene in the -benzyne + acetylene reaction
Ortho -benzyne is a potentially important precursor for polycyclic aromatic hydrocarbon formation, but much is still unknown about its chemistry. In this work, we report on a combined experimental and theoretical study of the o -benzyne + acetylene reaction and employ double imaging threshold photoe...
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| Published in: | Physical chemistry chemical physics : PCCP 2022-01, Vol.24 (3), p.1869-1876 |
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| Main Authors: | , , , , , , |
| Format: | Article |
| Language: | |
| Online Access: | Get full text |
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| Summary: | Ortho
-benzyne is a potentially important precursor for polycyclic aromatic hydrocarbon formation, but much is still unknown about its chemistry. In this work, we report on a combined experimental and theoretical study of the
o
-benzyne + acetylene reaction and employ double imaging threshold photoelectron photoion coincidence spectroscopy to investigate the reaction products with isomer specificity. Based on photoion mass-selected threshold photoelectron spectra, Franck-Condon simulations, and ionization cross section calculations, we conclude that phenylacetylene and benzocyclobutadiene (
PA
:
BCBdiene
) are formed at a non-equilibrium ratio of 2 : 1, respectively, in a pyrolysis microreactor at a temperature of 1050 K and a pressure of ∼20 mbar. The C
8
H
6
potential energy surface (PES) is explored to rationalize the formation of the reaction products. Previously unidentified pathways have been found by considering the open-shell singlet (OSS) character of various C
8
H
6
reactive intermediates. Based on the PES data, a kinetic model is constructed to estimate equilibrium abundances of the two products. New insights into the reaction mechanism - with a focus on the OSS intermediates - and the products formed in the
o
-benzyne + acetylene reaction provide a greater level of understanding of the
o
-benzyne reactivity during the formation of aromatic hydrocarbons in combustion environments as well as in outflows of carbon-rich stars.
A combined experimental and theoretical study of the
ortho
-benzyne + acetylene reaction using iPEPICO spectroscopy concludes that phenylacetylene and benzocyclobutadiene are formed in a 2 : 1 ratio under nonequilibrium conditions. |
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| ISSN: | 1463-9076 1463-9084 |
| DOI: | 10.1039/d1cp05183k |