Perturbing the structure of the 2-norbornyl cation through C-H...N and C-H...pi interactions

Quantum chemical studies on complexes of the 2-norbornyl cation with ammonia and benzene are described. These calculations demonstrate that the delocalized, bridged, nonclassical geometry that is usually favored for this carbocation can be perturbed significantly toward the normally less favorable classical geometry through appropriately oriented noncovalent interactions. Since such cations have been proposed as intermediates in enzyme and antibody catalyzed reactions, these results have implications for the nature of the cationic species that may be generated in the presence of electron-rich amino acid side chains of the sort that may be present in the active sites of biocatalysts.