Reactivity of the Indenyl Radical (C 9 H 7 ) with Acetylene (C 2 H 2 ) and Vinylacetylene (C 4 H 4 ).

Autor: Zhao L; Department of Chemistry, University of Hawaii at Manoa, Honolulu, Hawaii, 96822, USA., Prendergast MB; Department of Chemistry, University of Hawaii at Manoa, Honolulu, Hawaii, 96822, USA., Kaiser RI; Department of Chemistry, University of Hawaii at Manoa, Honolulu, Hawaii, 96822, USA., Xu B; Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA., Lu W; Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA., Ablikim U; Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA., Ahmed M; Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA., Oleinikov AD; Samara National Research University, Samara, 443086, Russia., Azyazov VN; Samara National Research University, Samara, 443086, Russia., Mebel AM; Samara National Research University, Samara, 443086, Russia.; Department of Chemistry and Biochemistry, Florida International University, Miami, FL 33199, USA., Howlader AH; Department of Chemistry and Biochemistry, Florida International University, Miami, FL 33199, USA., Wnuk SF; Department of Chemistry and Biochemistry, Florida International University, Miami, FL 33199, USA.
Jazyk: angličtina
Zdroj: Chemphyschem : a European journal of chemical physics and physical chemistry [Chemphyschem] 2019 Jun 04; Vol. 20 (11), pp. 1437-1447. Date of Electronic Publication: 2019 Apr 18.
DOI: 10.1002/cphc.201900052
Abstrakt: The reactions of the indenyl radicals with acetylene (C 2 H 2 ) and vinylacetylene (C 4 H 4 ) is studied in a hot chemical reactor coupled to synchrotron based vacuum ultraviolet ionization mass spectrometry. These experimental results are combined with theory to reveal that the resonantly stabilized and thermodynamically most stable 1-indenyl radical (C 9 H 7 . ) is always formed in the pyrolysis of 1-, 2-, 6-, and 7-bromoindenes at 1500 K. The 1-indenyl radical reacts with acetylene yielding 1-ethynylindene plus atomic hydrogen, rather than adding a second acetylene molecule and leading to ring closure and formation of fluorene as observed in other reaction mechanisms such as the hydrogen abstraction acetylene addition or hydrogen abstraction vinylacetylene addition pathways. While this reaction mechanism is analogous to the bimolecular reaction between the phenyl radical (C 6 H 5 . ) and acetylene forming phenylacetylene (C 6 H 5 CCH), the 1-indenyl+acetylene→1-ethynylindene+hydrogen reaction is highly endoergic (114 kJ mol -1 ) and slow, contrary to the exoergic (-38 kJ mol -1 ) and faster phenyl+acetylene→phenylacetylene+hydrogen reaction. In a similar manner, no ring closure leading to fluorene formation was observed in the reaction of 1-indenyl radical with vinylacetylene. These experimental results are explained through rate constant calculations based on theoretically derived potential energy surfaces.
(© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)
Databáze: MEDLINE
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