The Thermal Decomposition of the Benzyl Radical in a Heated Micro-Reactor. II. Pyrolysis of the Tropyl Radical

David Robichaud, Grant Buckingham, Mark Nimlos, Jessica Porterfield, Oleg Kostko, Tyler Troy, Musahid Ahmed, John Daily, G. Ellison

Research output: Contribution to journalArticlepeer-review

28 Scopus Citations


Cycloheptatrienyl (tropyl) radical, C7H7, was cleanly produced in the gas-phase, entrained in He or Ne carrier gas, and subjected to a set of flash-pyrolysis micro-reactors. The pyrolysis products resulting from C7H7 were detected and identified by vacuum ultraviolet photoionization mass spectrometry. Complementary product identification was provided by infrared absorption spectroscopy. Pyrolysis pressures in the micro-reactor were roughly 200 Torr and residence times were approximately 100 μs. Thermal cracking of tropyl radical begins at 1100 K and the products from pyrolysis of C7H7 are only acetylene and cyclopentadienyl radicals. Tropyl radicals do not isomerize to benzyl radicals at reactor temperatures up to 1600 K. Heating samples of either cycloheptatriene or norbornadiene never produced tropyl (C7H7) radicals but rather only benzyl (C6H5CH2). The thermal decomposition of benzyl radicals has been reconsidered without participation of tropyl radicals. There are at least three distinct pathways for pyrolysis of benzyl radical: the Benson fragmentation, the methyl-phenyl radical, and the bridgehead norbornadienyl radical. These three pathways account for the majority of the products detected following pyrolysis of all of the isotopomers: C6H5CH2, C6H5CD2, C6D5CH2, and C6H513CH2. Analysis of the temperature dependence for the pyrolysis of the isotopic species (C6H5CD2, C6D5CH2, and C6H513CH2) suggests the Benson fragmentation and the norbornadienyl pathways open at reactor temperatures of 1300 K while the methyl-phenyl radical channel becomes active at slightly higher temperatures (1500 K).

Original languageAmerican English
Article numberArticle No. 014305
Number of pages14
JournalThe Journal of Chemical Physics
Issue number1
StatePublished - 7 Jul 2016

Bibliographical note

Publisher Copyright:
© 2016 Author(s).

NREL Publication Number

  • NREL/JA-5100-66666


  • benzyl radical
  • C7H7
  • pyrolysis


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