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

Author(s)

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

Affiliation

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

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

• Document type: Journal article
• Source: Magnetic Resonance in Chemistry; v. 57, n. 11, p. 939-945, NOV 2019.
• Web of Science Citations: 0

Abstract

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)

• FAPESP's process: 16/24331-4 - Nuclear Magnetic Resonance spectroscopy and theoretical calculation for real-time reaction monitoring and mechanistic investigation
• Grantee: Uenifer Rodrigues Couto
• Support Opportunities: Scholarships in Brazil - Doctorate
• FAPESP's process: 15/08541-6 - Nuclear magnetic resonance spectroscopy: beyond molecular structure assignment
• Grantee: Claudio Francisco Tormena
• Support Opportunities: Research Projects - Thematic Grants