Thermal Decomposition of 1-Pentyl Radicals at High Pressures and Temperatures
Andrea Comandini, Iftikhar A. Awan, Jeffrey A. Manion
Complementary shock-tube studies at the National Institute of Standards and Technology (NIST) and the University of Illinois at Chicago (UIC) have been used to examine the decomposition reactions of the 1-pentyl radical at temperatures of 833 K to 1130 K and pressures of 100 kPa to 5000 kPa. 1-Pentyl radicals were generated from the thermal decomposition of dilute concentrations (50 μL/L) of 1-iodopentane in an argon bath gas and the stable olefin products monitored by post-shock gas chromatographic analyses utilizing flame-ionization and mass-spectrometric detection. In accordance with a recent study carried out at NIST, ethene and propene are the main olefin products from the decomposition of the 1-pentyl radical and the product ratio is found to be temperature and pressure dependent. The current work extends the experimental pressure range and high pressure limiting values of the product branching ratios appear to be approached at the highest pressures studied. The olefin ratio reflects the competition between the five-center intramolecular H transfer reaction that interconverts the 1-pentyl and 2-pentyl radicals, and beta C-C bond scissions that lead to the stable alkene products. New results obtained at UIC at high pressures are in excellent agreement with the pressure dependence predicted by a "best-fit" model previously developed (Awan, I. A.; Burgess, D. R., Jr.; Manion, J. A. J. Phys. Chem. A 2012, 116, 2895−2910) on the basis of experiments at lower pressures, quantum chemical calculations, and a critical analysis of literature data. The present data continue to support a value of <ΔEdown> = (675 ± 100) cm-1 at 1000 K for the average energy transferred in deactivating collisions in an argon bath gas when an exponential-down model is employed.
, Awan, I.
and Manion, J.
Thermal Decomposition of 1-Pentyl Radicals at High Pressures and Temperatures, Chemical Physics Letters, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=911290
(Accessed December 1, 2023)