The effect of carbonyl group in the asymmetry of 3,4JCH coupling constants in norbornanones
Copyright (c) 2007 John Wiley & Sons, Ltd.
| Veröffentlicht in: | Magnetic resonance in chemistry : MRC. - 1985. - 46(2008), 2 vom: 14. Feb., Seite 107-9 |
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| 1. Verfasser: | |
| Weitere Verfasser: | , , , |
| Format: | Online-Aufsatz |
| Sprache: | English |
| Veröffentlicht: |
2008
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| Zugriff auf das übergeordnete Werk: | Magnetic resonance in chemistry : MRC |
| Schlagworte: | Journal Article |
| Zusammenfassung: | Copyright (c) 2007 John Wiley & Sons, Ltd. A rationalization of the known difference between the 3,4JC4H1 and 3,4JC1H4 couplings transmitted mainly through the 7-bridge in norbornanone is presented in terms of the effects of hyperconjugative interactions involving the carbonyl group. Theoretical and experimental studies of 3,4JCH couplings were carried out in 3-endo- and 3-exo-X-2-norbornanone derivatives (X = Cl, Br) and in exo- and endo-2-noborneol compounds. Hyperconjugative interactions were studied with the natural bond orbital (NBO) method. Hyperconjugative interactions involving the carbonyl pi*(C2=O) and sigma*(C2=O) antibonding orbitals produce a decrease of three-bond contribution to both 3,4JC4H1 and 3,4JC1H4 couplings. However, the latter antibonding orbital also undergoes a strong sigmaC3--C4 --> sigma*(C2=O) interaction, which defines an additional coupling pathway for 3,4JC4H1 but not for 3,4JC1H4. This pathway is similar to that known for homoallylic couplings, the only difference being the nature of the intermediate antibonding orbital; i.e. for 3,4JC4H1 it is of sigma*-type, while in homoallylic couplings it is of pi*-type |
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| Beschreibung: | Date Completed 08.04.2008 Date Revised 20.07.2009 published: Print Citation Status PubMed-not-MEDLINE |
| ISSN: | 1097-458X |