Accepted theories predict that substitution reactions are controlled by the electronic nature of the attacked site for electrophilic aromatic substitution.Here it is shown that in addition the bond strength of the broken bond may also influence the regioselectivity of the substitution reaction,and that the D_(pb) is a good indicator of the strength of a chemical bond.The D_(pb),denotes the depth of the potential acting on one election in a molecule at the bond center(bc).In this letter,the values of D_(pb) along the C-H and N-H bonds have been investigated,and it is demonstrated that for aromatic compounds,the regioselectivity of the electrophilic substitution can well be rationalized in terms of D_(pb) values.
