Separation of the energetic and geometric contributions to the aromaticity of π-electron carbocyclics. Part V. Analysis of the aromatic character of aza-analogues of benzenoid hydrocarbons

Abstract

Analysis of the aromatic character based on the experimental geometry of 24 aza analogues of 7 benzenoid hydrocarbons led to the conclusion that presence of the nitrogen atom in the ring increases usually it's aromaticity and often increases also aromatic character of the neighbouring rings. Depending on the topological environment the increase of the aromatic character is due either to the decrease of bond length alternation or to to the increase of the mean bond length, or both. Quantitative comparison based on using of HOMA, EN and GEO indices has been carried out. Analysis of the aromatic character of 24 aza-analogues of benzenoid hydrocarbons has been carried out. The presence of the nitrogen atom in the ring usually increases it's aromaticity and often increases also the aromatic character of the neighbouring rings. Quantitative measure of the aromatic character is done using HOMA, EN and GEO indices of aromaticity.