How the substituent effect influences π-electron delocalisation in the ring of reactants in the reaction defining the Hammett substituent constants σm and σp

Abstract

Application of the geometry (HOMA, EN, GEO) and magnetism based (NICS, NICS(1)) indices of aromaticity to optimised geometry of the ring in 12 meta - and 12 para - substituted benzoic acids and their anions by use of DFT computations at B3LYP/6-311+G(d,p) level has shown a very low substituent effect on the π-electron delocalisation. This resembles (qualitatively) the resistance of benzene (and typical aromatic systems) against reactions leading to the change of π-electron delocalisation. © 2005 by MDPI.