Substituent effects and electron delocalization in five-membered N-heterocycles
Paweł A. Wieczorkiewicz, Tadeusz M. Krygowski, Halina Szatyłowicz
Abstract
) N atoms. While substituent constants correctly describe the changes of their properties (including those attached to the heterocycles), a testimony to Hammett's genius, quantum chemical models must be used to quantify the exact properties. In most heterocycles, electron-donating substituents hinder the cyclic delocalization, except 4-pyrazole. The applied recent EDDB method allows to study this phenomenon in detail. It follows that changes in aromaticity originate from the π-electronic effects of substituents on the ring bonds, changing the localization and delocalization of particular bonds in a correlated manner.
Topics & Concepts
SubstituentMoietyElectron delocalizationChemistryImidazolePyrazolePyrroleDelocalized electronQuantum chemicalComputational chemistryCombinatorial chemistryStereochemistryOrganic chemistryMoleculeSynthesis and Properties of Aromatic CompoundsOrganic Chemistry Cycloaddition ReactionsSynthesis of Indole Derivatives