A Photoionization study of some benzoyl compounds—Thermochemistry of [C7H5O]+ formation

Appearance energies for C₇H₅O]⁺ fragment ions, formed from a variety of benzoyl compounds, have been measured by photon impact. The mean heat of formation calculated for C₇H₅O]⁺ is 705 ± 6 kJ mol^?1, which can be correlated with either a single threshold structure or a mixture of structures with similar heats of formation. Previously observed variations of ΔH_f(C₇H₅O]⁺) with precursor molecule are shown to be consistent with a structure dependent kinetic shift, rather than the presence of isolated electronic states.