Zero Steric Potential and bond order

Highlights: • Bond multiplicities can be well discriminated by this index. • Could be applied to both aliphatic and aromatic hydrocarbons. • The first reported bond order index within the DFT framework. • In many cases this method is more reliable than NBO and Laplacian methods. The variation of Zero Steric Potential (ZSP) through a C–C bond shows two maximums, which their values depend on the bond order (BO). A good relationship (R² = 1) is observed between the mean values of maximum ZSPs and the bond orders of C–C bonds in ethane, ethylene and acetylene, as reference molecules ($\text{Ln BO}=1.956{\overline{\text{ZSP}}}_{\text{max}}-0.898$). The obtained equation is used to predict the C–C bond orders of more than twenty aromatic and aliphatic hydrocarbons. The results show that the obtained bond orders from ${\overline{\text{ZSP}}}_{\text{max}}$ are more reliable than those which are evaluated using NBO and Laplacian methods.