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Title: Time- and isomer-resolved measurements of sequential addition of acetylene to the propargyl radical

Soot formation in combustion is a complex process in which polycyclic aromatic hydrocarbons (PAHs) are believed to play a critical role. Recent works concluded that three consecutive additions of acetylene (C 2H 2) to propargyl (C 3H 3) create a facile route to the PAH indene (C 9H 8). However, the isomeric forms of C 5H 5 and C 7H 7 intermediates in this reaction sequence are not known. We directly investigate these intermediates using time- and isomer-resolved experiments. Both the resonance stabilized vinylpropargyl ( vp-C 5H 5) and 2,4-cyclopentadienyl ( c-C 5H 5) radical isomers of C 5H 5 are produced, with substantially different intensities at 800 K vs 1000 K. In agreement with literature master equation calculations, we find that c-C 5H 5 + C 2H 2 produces only the tropyl isomer of C 7H 7 ( tp-C 7H 7) below 1000 K, and that tp-C 7H 7 + C 2H 2 terminates the reaction sequence yielding C 9H 8 (indene) + H. Lastly, this work demonstrates a pathway for PAH formation that does not proceed through benzene.
Authors:
 [1] ;  [1] ;  [1] ;  [1] ;  [1]
  1. Sandia National Lab. (SNL-CA), Livermore, CA (United States)
Publication Date:
Report Number(s):
SAND-2016-10081J
Journal ID: ISSN 1948-7185; 648116
Grant/Contract Number:
AC04-94AL85000
Type:
Accepted Manuscript
Journal Name:
Journal of Physical Chemistry Letters
Additional Journal Information:
Journal Volume: 6; Journal Issue: 20; Journal ID: ISSN 1948-7185
Publisher:
American Chemical Society
Research Org:
Sandia National Lab. (SNL-CA), Livermore, CA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; molecular weight growth; photoionization; resonance stabilized radicals; soot formation
OSTI Identifier:
1329623