The oxygen Kα x-ray emission spectra of fluorinated anisoles and pentafluorophenol

Oxygen and fluorine K_α X-ray emission spectra have been obtained for a number of oxygen-containing compounds: H₂O, CH₃OH, C₆H₅OH, C₆H₅OCH₃, C₆F₅OH and 4-XC₆F₄OCH₃ (X = F, OCH₃, CF₃) in the solid or gaseous states and interpreted on the basis of the UV photoelectron and ESCA data and the results of MINDO/3 calculations. The mixing of the oxygen 2pAO with the highest occupied π-orbitals of the benzene ring is concluded to be small. The main contribution of the 2p(O)AO is shown to be to the system of σ-levels and lower-lying π-levels. CH₃OH is assumed to have hyperconjugation. Comparison of the electronic structures of oxygen in phenol and anisole with those in their polyfluorinated analogues shows the reduced effectiveness of oxygen 2pAO conjugation with the π-system of the benzene ring in the latter cases.