Gas phase formation of cyclopentanaphthalene (benzindene) isomers via reactions of 5- and 6-indenyl radicals with vinylacetylene. Issue 39 (30th September 2020)

• Record Type: Journal Article
• Authors: Zhao, Long; Kaiser, Ralf I.; Lu, Wenchao; Kostko, Oleg; Ahmed, Musahid; Evseev, Mikhail M.; Bashkirov, Eugene K.; Oleinikov, Artem D.; Azyazov, Valeriy N.; Mebel, Alexander M.; Howlader, A. Hasan; Wnuk, Stanislaw F.
• Is Part Of: Physical chemistry chemical physics. Volume 22:Issue 39(2020)
• Page Start: 22493
• Page End: 22500
• Publication Date: 2020-09-30
• Subjects: Chemistry, Physical and theoretical -- Periodicals; 541.3
• DOI: 10.1039/d0cp03846f
• Languages: English
• ISSNs: 1463-9076

Abstract

Abstract : The reaction of indenyl radicals with vinylacetylene leads to cyclopentanaphthalene at low temperature. Abstract : The tricyclic polycyclic aromatic hydrocarbons (PAHs) 3 H -cyclopenta[ a ]naphthalene (C13 H10 ), 1 H -cyclopenta[ b ]naphthalene (C13 H10 ) and 1 H -cyclopenta[ a ]naphthalene (C13 H10 ) along with their indene-based bicyclic isomers ( E )-5-(but-1-en-3-yn-1-yl)-1 H -indene, ( E )-6-(but-1-en-3-yn-1-yl)-1 H -indene, 5-(but-3-ene-1-yn-1-yl)-1 H -in-dene, and 6-(but-3-ene-1-yn-1-yl)-1 H -indene were formed via a "directed synthesis" in a high-temperature chemical micro reactor at the temperature of 1300 ± 10 K through the reactions of the 5- and 6-indenyl radicals (C9 H7 ˙) with vinylacetylene (C4 H4 ). The isomer distributions were probed utilizing tunable vacuum ultraviolet light by recording the photoionization efficiency curves at mass-to-charge of m / z = 166 (C13 H10 ) and 167 ( 13 CC12 H10 ) of the products in a supersonic molecular beam. The underlying reaction mechanisms involve the initial formation of van-der-Waals complexes followed by addition of the 5- and 6-indenyl radicals to vinylacetylene via submerged barriers, followed by isomerization (hydrogen shifts, ring closures), and termination via atomic hydrogen elimination accompanied by aromatization. All the barriers involved in the formation of 3 H -cyclopenta[ a ]naphthalene, 1 H -cyclopenta[ b ]naphthalene and 1 H -cyclopenta[ a ]naphthalene are submerged with respect to the reactants indicating that the mechanisms are in fact barrierless, potentially forming PAHs via the hydrogen abstraction – vinylacetylene addition (HAVA) pathway in the cold molecular clouds such as Taurus Molecular Cloud-1 (TMC-1) at temperatures as low as 10 K.