Photoionization of 1,3-Butadiene, 1,2-Butadiene, Allene, and Propyne

Publisher Website
Google Scholar
Abstract
Using a photoionization mass spectrometer, the ionization potentials of the parent molecules and the appearance potentials of the fragment ions, observed below 13 eV, have been determined for 1,3‐butadiene, 1,2‐butadine, allene, and propyne. The ionization potentials of 1,3‐butadiene are 9.07 ± 0.02 eV, 9.80 ± 0.04 eV, and 11.7 ± 0.04 eV. The adiabatic ionization potential of 1,2‐butadiene is 9.23 ± 0.02 eV. The adiabatic ionization potential of allene is 9.62 ± 0.04 eV. The ionization potentials of propyne are 10.38 ± 0.02 eV and 11.30 ± 0.02 eV. The heat of formation of C3H3+ and C4H5+ is calculated to be 11.18 ± 0.04 eV and 10.45 ± 0.04 eV, respectively. Derived bond energies for the ionic states are given. The data are shown to be consistent with rearrangement of 1,3‐butadiene via hydrogen migration in the excited molecular ion. At threshold for fragmentation, the C4H5+ and C3H3+ ions from 1,3‐butadiene and 1,2‐butadiene are identical.