Competition between aromatic substitution and addition

Abstract

One of the criteria of aromatic character is the ability to undergo substitution reactions with certain reagents. Whether overall substitution or addition occurs depends on the reactions of the so-called σ-complex intermediate. With some simple assumptions about the relationship between charge/spin density and reactivity, it is possible, from simple MO theory, to predict whether substitution should occur to a significant extent and to calculate indices for the ‘aromaticity’ or ‘aromatic character’ of a molecule.