Relation between the substituent effect and aromaticity

Tadeusz M Krygowski; Krzysztof Ejsmont; Beata T Stepień; Michał K Cyrański; Jordi Poater; Miquel Solà

doi:10.1021/jo0492113

Relation between the substituent effect and aromaticity

J Org Chem. 2004 Oct 1;69(20):6634-40. doi: 10.1021/jo0492113.

Authors

Tadeusz M Krygowski¹, Krzysztof Ejsmont, Beata T Stepień, Michał K Cyrański, Jordi Poater, Miquel Solà

Affiliation

¹ Department of Chemistry, University of Warsaw, L. Pasteura 1, 02-093 Warsaw, Poland. tmkryg@chem.uw.edu.pl

PMID: 15387585
DOI: 10.1021/jo0492113

Abstract

Molecular geometries of benzene and its 18 monosubstituted derivatives were optimized at B3LYP/6-311+G** level of theory. The changes of pi-electron delocalization of the benzene fragment were estimated by use of aromatic stabilization energies (ASE) based on different homodesmotic reaction schemes, geometry-based HOMA model, magnetism-based NICS, NICS(1), NICS(1)zz, and an electronic delocalization index, PDI, derived from the AIM theory. Apart from aromatic stabilization energies the other descriptors of aromaticity vary to a very small extent, indicating high resistance of the pi-electron structure to the substituent effect. This is somewhat analogous to a tendency of benzene systems to retain their initial pi-electron structure during the reaction course that leads to aromatic substitution.