Pitfalls in the Photoelectron Spectroscopic Investigations of Benzyne. Photoelectron Spectrum of Cyclopentadienylideneketene

Abstract

The 9.24 eV ionization energy often quoted in photoelectron spectroscopic investigations of benzyne is not due to benzyne 1 but to benzene, C6H6. The 8.9 eV ionization is not due to benzyne either but to cyclopentadienylideneketene 12 when a 10.2 eV band is also present, or to biphenylene 5 when a 7.6 eV band is simultaneously present. Cyclopentadienylideneketene 12 has been generated by flash vacuum thermolysis of four different precursors, which permit a linking of infrared, mass, and photoelectron spectroscopic observations.