International Journal of Molecular Sciences, Vol.6, No.1-2, 45-51, 2005
How the substituent effect influences pi-electron delocalisation in the ring of reactants in the reaction defining the Hammett substituent constants sigma(m) and sigma(p).
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 pi-electron delocalisation. This resembles ( qualitatively) the resistance of benzene ( and typical aromatic systems) against reactions leading to the change of pi-electron delocalisation.
Keywords:substituent effect;pi-electron delocalisation;Hammett substituent constants;ab initio calculations