Unexpected behavior of the (3)J(CH) coupling constant in unsaturated compounds

Autor(es)

Couto, Uenifer Rodrigues ^[1] ; Navarro-Vazquez, Armando ^[2] ; Tormena, Claudio Francisco ^[1]

Afiliação do(s) autor(es)

^[1] Univ Estadual Campinas, Inst Chem, BR-13083970 Campinas, SP - Brazil

^[2] Univ Fed Pernambuco, CCEN, Dept Quim Fundamental, Recife, PE - Brazil

• Tipo de documento: Artigo Científico
• Fonte: Magnetic Resonance in Chemistry; v. 57, n. 11, p. 939-945, NOV 2019.
• Citações Web of Science: 0

Resumo

The experimental and theoretical behavior of the (O(sic)C)-C(sic)C-H (3)J(CH) coupling constant is investigated for a series of alpha,beta-unsaturated compounds (1 to 8), and for some of them, the well-known relationship ((3)J(CHcis) J(CHtrans)) was observed. However, for some compounds, close values for (3)J(CHcis) and (3)J(CHtrans) couplings were observed, and for aldehydes group containing compounds (7 and 8E), an inversion order is observed ((3)J(CHcis) > (3)J(CHtrans)). In all cases where the (3)J(CHcis) J(CHtrans) relationship it is not followed, a polar group or electronegative atom oriented in opposite direction (s-trans) to the H-C(sic)C hydrogen is present, suggesting that conformational preference of such polar group or atoms are important factor on the behavior of (3)J(CH) couplings. Taking all of these in consideration, a new Karplus-type equation was proposed for (3)J(CH) couplings in alpha,beta-unsaturated compounds, which can be used for configurational and conformational assignment on trisubstituted double bond derivatives. (AU)

• 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: 15/08541-6 - Ressonância magnética nuclear: além da determinação estrutural
• Beneficiário: Claudio Francisco Tormena
• Modalidade de apoio: Auxílio à Pesquisa - Temático