Relation between the substituent effect and aromaticity.
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.
Krygowski
Tadeusz M
TM
Department of Chemistry, University of Warsaw, L. Pasteura 1, 02-093 Warsaw, Poland. tmkryg@chem.uw.edu.pl
Ejsmont
Krzysztof
K
Stepień
Beata T
BT
Cyrański
Michał K
MK
Poater
Jordi
J
Solà
Miquel
M