Absolute Aromaticity of Non-Congeneric Hydrocarbons

Although aromaticity has neither reached a definitive formulation nor a physical-chemical criterion of orderability, the important historical contributions have established so far the main directions a suitable scale has to be tested, namely the eneigetic, geometric (including topological), magnetic, and reactivity criteria the present discussion follows (Putz, 2010b). 

The reactivity criteria were previously formulated when minimum electronegativity and maximum chemical hardness features for molecular stabilization against electrophilicity were considered in assessing the maximiun and minimum hierarchical tendencies for the associated absolute aromaticities, Eqs. (4.19) and (4.20), respectively. In fact, it is this criterion that needs to be validated in comparison with the consecrated ones, described below. 

The HOMA, TOPAZ, TIR, REPE, and A indices and their aromatic scales for a series of representative benzenoid hydrocarbons are presented in Table 4.10. In order to compare them with the actual electronegativity and chemical hardness-based absolute aromaticities the AIM electronegativity and chemical hardness values are first computed and reported in Table 4.10 based on Eqs. (3.252) and (3.248), respectively then, they were combined with the CFD counterparts for all schemes from Table 3.8 applied on Eqs. (3.375) and (3.376) through employing the semi-empirical AMI quantum mechanically calculation of the involved frontier orbitals and energies the resulted absolute aromaticities are presented in Tables 4.11 and 4.12, respectively. 

It is obvious that electronegativity-based aromaticity A poorly correlates with almost all traditional aromaticity scales and criteria, except with the magnetic susceptibility exaltation based aromaticity the fascinating point here is that the best correlation of A with electronegativity absolute aromaticity parallels its poorest eorrelation with ehemieal hardness 

Molecule Name AIM OMA OPAZ Arn, ArePE A. Attf Iaim 

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