‘Lone Pair’ and ‘CI Bond’ Ionization Energies of exo ‐ and endo ‐2‐Norbornyl Iodides

A PE‐spectroscopic study of exo ‐ and endo ‐2‐norbornyl iodides suggests that the relative ability of the 2‐norbornyl group to stabilize an electron deficiency on a substituent X (e.g. I) in exo ‐ or endo ‐position depends on the location of the positive charge. There is no difference if the positive hole is strongly localized on on the substituent X ( e.g. the 5p −1 state of the title compounds). On the other hand, our results indicate that teh positive hole semi‐localized in an exo ‐CX bond is better stabilized by the 2‐norbornyl group than a semi‐localized, positive hole in an endo ‐CX bond.