The influence of fluoro substituents on cyclopropa-benzene, -naphthalene, and -anthracene

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.