Collection of Czechoslovak Chemical Communications - digital archive 

Abstract

The He(Iα) PE spectra of cyclopropabenzene, cyclopropa[b]naphthalene, cyclopropa[b]anthracene, their 1,1-difluoro derivatives and of some of their substituted derivatives have been recorded, analyzed and assigned by correlation with the PE spectra of the parent molecules benzene, naphthalene and anthracene. It is shown that the PE spectroscopic data yield no information about the presence or absence of a Mills-Nixon effect in the molecules investigated. The inductive effect of the bridging CH₂ group of the cyclopropeno ring is close to zero, whereas that of the CF₂ group leads to positive ionization energy shifts in good agreement with previous experience. The hyperconjugative interaction of the local pseudo-π orbital of the CH₂ group yields a significant destabilization of the π-orbitals of B₁ symmetry.