Abstract
Vicinal 1H, 13C coupling constants were measured for rigid unsaturated 1H-C-C=13C molecular frameworks at natural abundance. As a general trend, an empirical range of 4.5-6.5 Hz is observed independent of the value of the dihedral angle between the CH bond and the plane of the double bond. Furthermore, through-bond and through-space substituent effects also influence the magnitude of the coupling constants in a similar way to that known for saturated systems. In summary, two different additive transmission mechanisms take part in these coupling paths depending on the orientation of the π-system with respect to the allylic bond. The experimental evidence presented demonstrates the breakdown of the Karplus rule in this particular structural fragment.
Original language | English |
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Pages (from-to) | 30-34 |
Journal | Magnetic Resonance in Chemistry |
Volume | 35 |
Issue number | 1 |
DOIs | |
Publication status | Published - 1 Jan 1997 |
Keywords
- 1 H NMR
- Allylic systems
- Long-range proton-carbon coupling constants
- NMR