Substituent effects on the photoelectron spectra of benzene derivatives

Systematics in the ionization energies corresponding to the different π orbitals of para, meta and ortho-disubstituted benzenes obtained from PES have been investigated. The data have been discussed in terms of correlations with substituents constants and such correlations are shown to provide the basis to differentiate steric from electronic effects in the case of ortho derivatives. Ionization energies from PES corresponding to the lone pair orbitals of substituents in related series of p-disubstituted benzenes are shown to vary systematically with the substituent constants.