| Full text | |
| Author(s): |
Total Authors: 4
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| Affiliation: | [1] Univ Fed Lavras, Dept Quim, BR-37200000 Lavras, MG - Brazil
[2] Univ Estadual Campinas, Inst Chem, Dept Organ Chem, BR-13084971 Campinas, SP - Brazil
Total Affiliations: 2
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| Document type: | Journal article |
| Source: | Magnetic Resonance in Chemistry; v. 47, n. 4, p. 348-351, APR 2009. |
| Web of Science Citations: | 8 |
| Abstract | |
2-Bromocyclohexanone is a model compound in which a (4)J(H2,H6) coupling constant is observed, whereas the corresponding (4)J(H2,H4) is absent. The observed long-range coupling is not only a result of the known W-type coupling, in the axial conformation, but also because of the less usual diaxial spin-spin coupling in the equatorial conformer. The carbonyl group plays a determining role in describing the coupling pathway, as concluded by natural bond orbital (NBO) analysis; although the sigma(C2-H2) -> sigma({*}) (C1(O)-C6) and sigma(C6-H6) -> sigma({*}) (C1(O)-C2) interactions in the axial conformer contribute for transmitting the spin information associated with the W-type coupling, the strong sigma(C2-H2) -> pi({*}) (C=0) and sigma(C6-H6) -> pi({*}) (C=0) hyperconjugations in the equatorial conformer define an enhanced coupling pathway for (4)J(H2,H6), despite the inhibition of this coupling because of n(o) -> sigma({*}) (C(O)-C) interaction and the large carbonyl angle. These findings provide the experimental evidence that orbital interactions contribute for the conformational isomerism of 2-bromocyclohexanone. Copyright (c) 2008 John Wiley \& Sons, Ltd. (AU) | |
| FAPESP's process: | 05/59649-0 - Conformational equilibria studies by nuclear magnetic resonance spectroscopy, infrared spectroscopy and theoretical calculations |
| Grantee: | Roberto Rittner Neto |
| Support Opportunities: | Research Projects - Thematic Grants |