Exo-exo and endo-endo vicinal proton spin-spin coupling constants in norbornane and norbornene. An IPPP-CLOPPA analysis

✍ Scribed by C. N. Cavasotto; C. G. Giribet; M. C. Ruiz de Azúa; R. H. Contreras

• Book ID: 102879501
• Publisher: John Wiley and Sons
• Year: 1991
• Tongue: English
• Weight: 546 KB
• Volume: 12
• Category: Article
• ISSN: 0192-8651
• DOI: 10.1002/jcc.540120202

✦ Synopsis

The IPPP-CLOPPA method is used to study the origin of the difference between exo-exo and endoendo vicinal interproton couplings in norbornane and norbornene. The main pathway defining such Couplings is found to be determined by the corresponding C-H bonds and antibonds. For this reason they can be considered to be transmitted through space. Contributions from excitations involving MOs of bridge 7 and the C H endo and exo bonds and antibonds are found to be negligible in both compounds. Even though bridges 5-6 and 7 are not included in the coupling pathway, they influence the structure of endo and ex0 C H bonds, and thus cause the nonequivalence of endo-endo and exo-exo couplings. Results obtained with the NNBI method are compared to those of IPPP-CLOPPA.