A Free-Radical Prompted Barrierless Gas-Phase Synthesis of Pentacene |
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Authors: | Long Zhao Ralf I Kaiser Wenchao Lu Musahid Ahmed Mikhail M Evseev Eugene K Bashkirov Valeriy N Azyazov Christina Tönshoff Florian Reicherter Holger F Bettinger Alexander M Mebel |
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Institution: | 1. Department of Chemistry, University of Hawaii at Manoa, Honolulu, HI, 96822 USA;2. Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720 USA;3. Samara National Research University, Samara, 443086 Russian Federation;4. Lebedev Physical Institute, Samara, 443011 Russian Federation;5. Institute of Organic Chemistry, University of Tübingen, Auf der Morgenstelle 18, 72076 Tübingen, Germany;6. Department of Chemistry and Biochemistry, Florida International University, Miami, FL, 33199 USA |
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Abstract: | A representative, low-temperature gas-phase reaction mechanism synthesizing polyacenes via ring annulation exemplified by the formation of pentacene (C22H14) along with its benzoa]tetracene isomer (C22H14) is unraveled by probing the elementary reaction of the 2-tetracenyl radical (C18H11.) with vinylacetylene (C4H4). The pathway to pentacene—a prototype polyacene and a fundamental molecular building block in graphenes, fullerenes, and carbon nanotubes—is facilitated by a barrierless, vinylacetylene mediated gas-phase process thus disputing conventional hypotheses that synthesis of polycyclic aromatic hydrocarbons (PAHs) solely proceeds at elevated temperatures. This low-temperature pathway can launch isomer-selective routes to aromatic structures through submerged reaction barriers, resonantly stabilized free-radical intermediates, and methodical ring annulation in deep space eventually changing our perception about the chemistry of carbon in our universe. |
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Keywords: | gas-phase chemistry hydrogen abstraction/vinylacetylene addition (HAVA) interstellar medium mass spectrometry polycyclic aromatic hydrocarbons (PAHs) |
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