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p-se ヘテロサイクルの異常な分子間"空間を通る" j カップリング

Paula Sanz Camacho1, Kasun S Athukorala Arachchige1, Alexandra M Z Slawin1

  • 1†School of Chemistry, EaStCHEM and Centre of Magnetic Resonance, University of St. Andrews, Fife, KY16 9ST, U.K.

Journal of the American Chemical Society
|May 1, 2015
PubMed
まとめ

新しいP-Seヘテロサイクルは,隣接する分子間の異常な"空間を通る"J結合を示します. 相対論的DFT計算は,これらの非結合相互作用を確認し,結晶パッキングとJ結合機構の洞察を提供します.

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Vicinal or three-bond coupling is commonly observed between protons attached to adjacent carbons. Here, nuclear spin information is primarily transferred via electron spin interactions between adjacent C‑H bond orbitals. This generally favors the antiparallel arrangement of spins, so 3J values are usually positive.
The extent of coupling depends on the C‑C bond length, the two H‑C‑C angles, any electron-withdrawing substituents, and the dihedral angle between the involved orbitals. The...
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¹H NMR: Long-Range Coupling

The coupling interactions of nuclei across four or more bonds are usually weak, with J values less than 1 Hz. While these are usually not observed in spectra, the presence of multiple bonds along the coupling pathway can result in observable long-range coupling.
In alkenes, spin information is communicated via σ–π overlap, as seen in allylic (four-bond) and homoallylic (five-bond) couplings. These coupling interactions are stronger when the σ bond is parallel to the alkene...
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Two NMR-active nuclei bonded to a central atom can be involved in geminal or two-bond coupling. Geminal coupling is commonly seen between diastereotopic protons in chiral molecules and unsymmetrical alkenes, among others.
The central atom need not be NMR-active because its electrons are affected by the electron polarization of the spin-active atoms. However, spin information is transmitted less effectively than in one-bond coupling, and 2J values are usually weaker than 1J values. The energy of...
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