On the (4)J(HH) long-range coupling in 2-bromocyclohexanone: conformational insights

Autor(es)

Coelho, Jakelyne V. ^[1] ; Freitas, Matheus P. ^[1] ; Tormena, Claudio F. ^[2] ; Rittner, Roberto ^[2]

Afiliação do(s) autor(es)

^[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

• Tipo de documento: Artigo Científico
• Fonte: Magnetic Resonance in Chemistry; v. 47, n. 4, p. 348-351, APR 2009.
• Citações Web of Science: 8

Resumo

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)

• Processo FAPESP: 05/59571-0 - Estudo de biomoléculas através de técnicas avançadas de RMN no estado líquido
• Beneficiário: Alviclér Magalhães
• Modalidade de apoio: Auxílio à Pesquisa - Jovens Pesquisadores
• Processo FAPESP: 06/03980-2 - Interacoes de orbitais e seus efeitos nas constantes de acoplamento escalar em rmn: estudo experimental e teorico.
• Beneficiário: Claudio Francisco Tormena
• Modalidade de apoio: Auxílio à Pesquisa - Regular
• Processo FAPESP: 05/59649-0 - Estudos de estrutura eletrônica e molecular através de métodos espectroscópicos e cálculos teóricos
• Beneficiário: Roberto Rittner Neto
• Modalidade de apoio: Auxílio à Pesquisa - Temático