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¹³C NMR: ¹H–¹³C Decoupling01:04

¹³C NMR: ¹H–¹³C Decoupling

The probability of having two carbon-13 atoms next to each other is negligible because of the low natural abundance of carbon-13. Consequently, peak splitting due to carbon-carbon spin-spin coupling is not observed in spectra. However, protons up to three sigma bonds away split the carbon signal according to the n+1 rule, resulting in complicated spectra.
A broadband decoupling technique is used to simplify these complex, sometimes overlapping, signals. Broadband decoupling relies on a...
NMR Spectroscopy: Spin–Spin Coupling01:08

NMR Spectroscopy: Spin–Spin Coupling

The spin state of an NMR-active nucleus can have a slight effect on its immediate electronic environment. This effect propagates through the intervening bonds and affects the electronic environments of NMR-active nuclei up to three bonds away; occasionally, even farther. This phenomenon is called spin–spin coupling or J-coupling. Coupling interactions are mutual and result in small changes in the absorption frequencies of both nuclei involved. While nuclei of the same element are involved in...
¹H NMR: Long-Range Coupling01:27

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 π orbitals.
Spin–Spin Coupling: Three-Bond Coupling (Vicinal Coupling)01:22

Spin–Spin Coupling: Three-Bond Coupling (Vicinal Coupling)

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...
Spin–Spin Coupling Constant: Overview01:08

Spin–Spin Coupling Constant: Overview

In bromoethane, the three methyl protons are coupled to the two methylene protons that are three bonds away. In accordance with the n+1 rule, the signal from the methyl protons is split into three peaks with 1:2:1 relative intensities. The methylene protons appear as a quartet, with the relative intensities of 1:3:3:1.
Qualitatively, any spin plus-half nucleus polarizes the spins of its electrons to the minus-half state. Consequently, the paired electron in the hydrogen–carbon bond must have a...
Chemical Shift: Internal References and Solvent Effects01:17

Chemical Shift: Internal References and Solvent Effects

In an NMR sample, precise measurement of the absolute absorption frequencies of nuclei is difficult. A standard internal reference compound is added, and the frequency difference between the reference signal and sample signals is measured.
The internal reference compound generally used in NMR spectroscopy is tetramethylsilane (TMS). TMS is preferred because it is chemically inert, soluble in NMR solvents, and easily removable. Also, the highly shielded methyl protons in TMS yield an intense...

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関連する実験動画

Updated: Jun 29, 2026

Atomic Scale Structural Studies of Macromolecular Assemblies by Solid-state Nuclear Magnetic Resonance Spectroscopy
14:55

Atomic Scale Structural Studies of Macromolecular Assemblies by Solid-state Nuclear Magnetic Resonance Spectroscopy

Published on: September 17, 2017

マイクロソルベーションと13C-Li NMR カップリング

Rudolf Knorr1, Thomas Menke, Kathrin Ferchland

  • 1Department of Chemistry and Biochemistry, Ludwig-Maximilians-Universität, Butenandtstrasse 5-13, 81377 München, Germany. rhk@cup.uni-muenchen.de

Journal of the American Chemical Society
|October 3, 2008
PubMed
まとめ

新しい経験的表現は,炭素-リチウム化合物のNMR結合定数 ((1) J(CLi)) をリチウム核と協調ドナーリガンドの数と関連付けています. この発見は,オーガノリチウム積層の未知の微溶解数値を決定するのに役立ちます.

科学分野:

  • 有機金属化学 有機金属化学
  • 核磁共振スペクトロスコーピー 核磁共振スペクトロスコーピー

背景:

  • 核磁共振 (NMR) スペクトロスコピーは,オルガノリチウム化合物の特徴づけに不可欠です.
  • リチウム核の周囲の調整環境を理解することは,反応性と構造を予測するために不可欠です.

研究 の 目的:

  • (1) J ((CLi)) のNMR結合定数と構造パラメータを相関させる経験表現を提案し,検証する.
  • 様々な炭素-リチウム (C-Li) 化合物における (1) J (CLi) への溶解と集積の影響を調査する.

主な方法:

  • コーディネートドナーリガンドとフリードナーリガンド (t-BuOMe,Et2O,THF) のNMR共鳴の統合.
  • 核オーバーハウザー相関の分析と固体構造の決定.
  • 派生された経験的表現を様々なC-Li化合物 (単体,二重体,四重体,および集積物) に適用する.

主要な成果:

  • (1) J(CLi) = L[n(a + d) ](-1という経験表現が確立され,リチウム核数 (n) とリガンド協調和 (a + d) における相互依存を示した.
  • マイクロ溶解数 (d) は,カルバニオン (13) C ((alpha),C ((para) とp-Hに対するNMR化学シフトの観測された変化と相関する.
  • この式は,溶解されたおよび溶解されていない集積物を含む様々なC-Li化合物の適用性を示しています.

さらに関連する動画

Using Solution NMR to Characterize Biomolecular Condensates Under Biphasic Conditions
09:01

Using Solution NMR to Characterize Biomolecular Condensates Under Biphasic Conditions

Published on: April 17, 2026

15N CPMG Relaxation Dispersion for the Investigation of Protein Conformational Dynamics on the &#181;s-ms Timescale
08:09

15N CPMG Relaxation Dispersion for the Investigation of Protein Conformational Dynamics on the µs-ms Timescale

Published on: April 19, 2021

関連する実験動画

Last Updated: Jun 29, 2026

Atomic Scale Structural Studies of Macromolecular Assemblies by Solid-state Nuclear Magnetic Resonance Spectroscopy
14:55

Atomic Scale Structural Studies of Macromolecular Assemblies by Solid-state Nuclear Magnetic Resonance Spectroscopy

Published on: September 17, 2017

Using Solution NMR to Characterize Biomolecular Condensates Under Biphasic Conditions
09:01

Using Solution NMR to Characterize Biomolecular Condensates Under Biphasic Conditions

Published on: April 17, 2026

15N CPMG Relaxation Dispersion for the Investigation of Protein Conformational Dynamics on the &#181;s-ms Timescale
08:09

15N CPMG Relaxation Dispersion for the Investigation of Protein Conformational Dynamics on the µs-ms Timescale

Published on: April 19, 2021

結論:

  • (1) J(CLi) カップリング定数は,オーガノリチウム種における未知の微溶解数値を評価するための貴重なツールとして役立つ.
  • この研究は, (13) C NMR C-Li マルチプレート分割を,流動的および非流動的集合体の両方に分析することの重要性を強調しています.