Substituent Effect on the Structure of the Phenonium Ion

Abstract

An ab initio MO calculation is made for the substituent (X) effect on the phenonium ion, X-C₆H₄C₂H₄⁺ and C₆H₅C₂H_4-n(-Me)_n⁺ The electron-donating group X on para posit ion strengthens the bridge bond, while the electron-withdrawing group weakens it. The trend is interpretable in terms of the C₆H₄X⁺→C₂H₄ back charge transfer. The methyl groups attached to the C₂H₄ site deform considerably the structure. They give the intermediate geometries in the “symmetric bridge-asymmetric open” spectrum.