On the Dimensionality of Aromaticity Criteria

A plausible explanation for the contradictory results published by several groups on the dimensionality of the concept of aromaticity is found. We demonstrate that the good linear relationships between the molar diamagnetic exaltation (Λ) and the resonance energy (RE) of heteroaromatic compounds is not fundamental, but only a consequence of the strong correlation of both properties with the molecular weight. Our findings are based on the fact that molecular weight appears as a “hidden variable” in the resonance energy and as an explicit parameter in the diamagnetic exaltation. Consequently, depending on the data set of compounds selected linear correlations or orthogonality between both properties can be found. New results are obtained mainly when the data set contains great molecular weight variability. This linearity can decrease or even disappear when a data set with smaller molecular weight variability is used.