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

Data on 13 C chemical shifts and 13 C 1 H spin coupling constants of norbornane ( 1 ), norbornene ( 2 ), norbornadiene ( 3 ), benzonorbornene ( 4 ) and benzonorbornadiene ( 6 ) are reported. The non‐equivalence in J ( 13 CH) 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.