The Use of D’ Index in the Determination of the Aromatic Character of Organic Compounds. Comparison with HOMHED and NICS.

Abstract

AbstractThe comparison of D index with HOMHED gave a good correlation (R2= 0.8221). However, a modification of D index, namely D’, where the number of cycles involved in the tested molecule is substituted by the ratio between the number of atoms involved in π orbitals in the tested molecule and in reference molecule, gave a better correlation with a larger number of compounds (R2=0.8819), The correlation of D’ with calculated HOMHED for pentatomic heterocyclic compounds did not give a unique correlation but a series of possible correlations. This behavior depends on the parameters used for the calculation of HOMHED that allow some negative values. In fact, the comparison of D’ with NICS for selected pentatomic heterocycles gave good correlation. Good correlations were observed also in the comparison of D’ with HOMHED and NICS for antiaromatic compounds.