An analysis of the photo-electron and U.V. spectra of the fluorobenzenes and its relevance to the position of the second ?-ionization potential of benzene

Abstract

The effect of fluorosubstitution on the π-electron energy levels of benzene has been explained in terms of a two-parameter inductive model. One parameter is associated with a long-range perturbation which depends on the electric field of the C-F dipole moment, the other is associated with a short-range perturbation which depends on this field together with an exchange energy arising from the fluorine lone-pair electrons. The two parameters are calculated from the first IP of the fluorobenzenes and are then used to predict the shift in the second π IP and the u.v. (2600 å) band of benzene on fluorosubstitution. There is good agreement between the calculated and observed results, and it is concluded that the second π IP of benzene is at 12·0 ev.