Stereoelectronic interactions: A booster for (4)J(HF) transmission

Autor(es)

Soares, Joao Vitor ; Dal Poggetto, Guilherme ; Viesser, Renan V. ; Couto, Uenifer R. ; Tormena, Claudio F.

• Tipo de documento: Artigo Científico
• Fonte: Magnetic Resonance in Chemistry; v. 60, n. 5, p. 8-pg., 2022-01-22.

Resumo

Long-range proton-fluorine coupling constants ((n)J(HF)) are helpful for the structure elucidation of fluorinated molecules. However, their magnitude and sign can change with the relative position of coupled nuclei and the presence of substituents. Here, trans-4-tert-butyl-2-fluorocyclohexanone was used as a model compound for the study of the transmission of (4)J(HF). In this compound, the (4)J(H6axF) was measured to be +5.1 Hz, which is five times larger than the remaining (4)J(HF) in the same molecule ((4)J(H4F) = +1.0 Hz and (4)J(H6eqF) = +1.0 Hz). Through a combination of experimental data, natural bond orbital (NBO) and natural J-coupling (NJC) analyses, we observed that stereoelectronic interactions involving the pi system of the carbonyl group are involved in the transmission pathway for the (4)J(H6axF). Interactions containing the pi system as an electron acceptor (e.g., sigma(C6-H6ax) -> pi*(CO) and sigma(C-F) -> pi*(CO)) increase the value of the (4)J(H6axF), while the interaction of the pi system as an electron donor (e.g., pi(CO) -> sigma*(C-F)) decreases it. Additionally, the carbonyl group was shown not to be part of the transmission pathway of the diequatorial (4)J(H6eqF) coupling in cis-4-tert-butyl-2-fluorocyclohexanone, revealing that there is a crucial symmetry requirement that must be fulfilled for the pi system to influence the value of the (4)J(HF) in these systems. (AU)

• Processo FAPESP: 15/08541-6 - Ressonância magnética nuclear: além da determinação estrutural
• Beneficiário: Claudio Francisco Tormena
• Modalidade de apoio: Auxílio à Pesquisa - Temático
• Processo FAPESP: 17/20890-1 - Avaliação dos mecanismos de blindagem e de transmissão dos acoplamentos em RMN de 1H, 13C e 19F
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• Modalidade de apoio: Bolsas no Brasil - Pós-Doutorado
• Processo FAPESP: 20/10246-0 - Ressonância magnética nuclear: das sequências de pulso a determinação estrutural
• Beneficiário: Claudio Francisco Tormena
• Modalidade de apoio: Auxílio à Pesquisa - Temático
• Processo FAPESP: 16/24331-4 - Espectroscopia de Ressonância Magnética Nuclear e cálculos teóricos aplicados ao estudo de mecanismos de reação
• Beneficiário: Uenifer Rodrigues Couto
• Modalidade de apoio: Bolsas no Brasil - Doutorado
• Processo FAPESP: 18/19253-0 - Novas sequências de pulso e ferramentas de processamento para experimentos multidimensionais em RMN: Aplicação em análises de misturas de produtos naturais
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• Modalidade de apoio: Bolsas no Brasil - Pós-Doutorado