Criteria for characterization of aromaticity

Abstract

Because of the importance of aromaticity in chemistry, there have been many attempts to rationalize and quantify this property, and to derive a universal quantitative measure of it. However, because of its multiple manifestations, there is not yet any generally accepted single quantitative definition of aromaticity. The evaluation of aromaticity is usually based on the classical aromaticity criteria, which can roughly be divided into six categories: electronic, energetic, structural or geometrical, magnetic, reactivity-based measures and spectroscopic criteria. Which criteria one chooses the best and the relationship between these different criteria (i.e., their orthogonality or nonorthogonality) is still a matter of debate.