title: On the formation of cyclopentadiene in the C3H5˙ + C2H2 reaction.
abstract: The reaction between the allyl radical (C3H5˙) and acetylene (C2H2) in a heated microtubular reactor has been studied at the VUV beamline of the Swiss Light Source. The reaction products are sampled from the reactor and identified by their photoion mass-selected threshold photoelectron spectra (ms-TPES) by means of imaging photoelectron photoion coincidence spectroscopy. Cyclopentadiene is identified as the sole reaction product by comparison of the measured photoelectron spectrum with that of cyclopentadiene. With the help of quantum-chemical computations of the C5H7 potential energy surface, the C2H2 + C3H5˙ association reaction is confirmed to be the rate determining step, after which H-elimination to form C5H6 is prompt in the absence of re-thermalization at low pressures. The formation of cyclopentadiene as the sole product from the allyl + acetylene reaction offers a direct path to the formation of cyclic hydrocarbons under combustion relevant conditions. Subsequent reactions of cyclopentadiene may lead to the formation of the smallest polycyclic aromatic molecule, naphthalene.
authors.affiliation: Radboud University, Institute for Molecules and Materials, FELIX Laboratory, Toernooiveld 7c, NL-6525 ED Nijmegen, The Netherlands. j.bouwman@science.ru.nl.
authors.forename: Jordy
authors.initials: J
authors.lastname: Bouwman
authors.forename: Andras
authors.initials: A
authors.lastname: Bodi
authors.forename: Jos
authors.initials: J
authors.lastname: Oomens
authors.forename: Patrick
authors.initials: P
authors.lastname: Hemberger
mesh_terms: D000114:Acetylene / Q000737:chemistry*; D000498:Allyl Compounds / Q000737:chemistry*; D003517:Cyclopentanes / Q000138:chemical synthesis* / Q000737:chemistry; D005609:Free Radicals / Q000737:chemistry; D011789:Quantum Theory
chemical_list: D000498:Allyl Compounds; D003517:Cyclopentanes; D005609:Free Radicals; D000114:Acetylene