Proton affinities and photoelectron spectra of three-membered-ring heterocycles

Phospha‐Organic Chemistry: Panorama and Perspectives

“…[174] As can be seen, the gap between the lone pair and PÀC bond ionization energies is small (À0.46 eV) when compared to the corresponding data for aziridine (À1.96 eV). [174] In fact, the situation is rather similar to that found in phosphaalkenes. An electrophilic reagent will "hesitate" between the lone pair and the PÀC ring bonds.…”

“…The electronic structure of parent phosphirane is characterized by a lone-pair orbital lying at relatively low energy (À9.75 compared with À9.10 eV for the n P orbital of Me 2 PH). [174] The next ionization at 10.21 eV corresponds to the antisymmetric Walsh-type orbital essentially localized on the PÀC ring bonds. [174] As can be seen, the gap between the lone pair and PÀC bond ionization energies is small (À0.46 eV) when compared to the corresponding data for aziridine (À1.96 eV).…”

“…[174] The next ionization at 10.21 eV corresponds to the antisymmetric Walsh-type orbital essentially localized on the PÀC ring bonds. [174] As can be seen, the gap between the lone pair and PÀC bond ionization energies is small (À0.46 eV) when compared to the corresponding data for aziridine (À1.96 eV). [174] In fact, the situation is rather similar to that found in phosphaalkenes.…”

Photoelectron Spectroscopy of Heterocycles. Phenyloxiranes

“…A correlation diagram of the lowest ionization energies of benzene and ethylene with those of the phenylethenes as well as of benzene and oxirane with those of the measured phenyloxiranes is shown in Figure 4. It can be seen that in all PE spectra, like in the PE spectrum of oxirane [6][7][8][9]. there is a gap after 10 eV and again at about 13eV.…”

“…Molecular photoelectron (PE) spectroscopy as a method yield ing direct information about the electronic structure (Koopman's theorem) proved to be an important support in these studies. Thus, the ionization ener gies of ethylene oxide (oxirane) measured by PE spectroscopy were reported by Al Joboury and Tur ner [5] as early as in 1964, and several groups reported its PE spectrum and discussed its elec tronic structure in the following years [6][7][8][9]. Pre sently, we can take as confirmed the electronic structure of oxirane -at least as far as the two lowest energy levels (highest occupied orbitals) are concerned.…”