A quantum-chemical study on the electrophilic addition of bromine to homobenzonorbornadiene

SCF-MO-LCAO AM I calculations have been performed for 1:1 molecular system of bromine with homobenzonorbornadiene (HBNB) and their stable configuratio ns have been determined. The stable configurations of the HBNB-Br-2 system correspond to HBNB-Br-2 (exo) and HBNB-Br-2 (endo) molecular complexes whic h are formed by the exo and endo orientations of Br-2 molecule to the doubl e bond of HBNB in axial position, respectively. Exo-molecular complex has b een found to be relatively more stable than the endo-complex. The cationic intermediates of the reaction have been studied by ab initio SCF method in STO-3G and STO-3G* basis and also by MNDO semiempirical route. Exo-bromoniu m cation is found to be more stable than endo-bromonium cation according to both the methods. The nonclassical delocalized bromocarbonium cation is th e most stable among these cations according to both methods, and the ionic addition reactions occur via this cation.