NMR studies of bridged ring systems: XIX—13C1H spin coupling and 13C chemical shift of the bridge methylene in benzonorbornene and benzonorbornadiene

Data on 13C chemical shifts and 13C1H spin coupling constants of norbornane (1), norbornene (2), norbornadiene (3), benzonorbornene (4) and benzonorbornadiene (6) are reported. The non-equivalence in J(13CH) values determined from the two bridge methylene proton signals in 2,2,3,3-tetradeuteriobenzonorbornene (5) and 6 is briefly discussed. The extraordinary deshielding of the bridge methylene carbon in 6 has been noted.