Substituted naphthalenes: Stability, conformational flexibility and description of bonding based on ETS-NOCV method

Abstract

For all dimethylnaphthalenes (DMNs) the transition from a planar ring conformation to a nonplanar one results in energy increase in the range 1.7-2.4 kcal/mol. There is a linear relationship between averaged rigidity constant and relative energy of DMNs. The relative stability of DMNs does not follow the aromatic stabilization based on NICS values. The ETS-NOCV analysis shows that more efficient bonding in the pi-electron system is the origin of enhanced stability in laterally substituted (CH3, Cl and NO2) naphthalenes. The results for C-aryl-CH3 system indicate more steric repulsion in going from 2,7-DMN to 1,8-DMN following the increase of relative energies.