The Photoelectron Spectra the Chloro Toluenes

Abstract

The He_I and He_II photoelectron spectra of the chloro toluenes have been measured. The spectra are assigned using He_I/He_II cross-section ratios and a composite-molecule model within an ab initio valence-electron-only model potential (VEOMP) framework. The order of the first two ionization potentials for the chloro toluenes is assigned as πS < πA which is contrary to the VEOMP assignment for benzal chloride and benzotrichloride , but is consistent with linear correlations using group electronegativities and σ_I scales. Furthermore, linear correlations using the first two ionization potentials of fluoro and chloro toluenes with group electronegativities are shown to be a useful aid in spectral assignment and, moreover, suggest that for benzyl fluoride and benzal chloride the most appropriate σ_I values are 0.20 and 0.31 respectively.