Jove
Visualize
联系我们
JoVE
x logofacebook logolinkedin logoyoutube logo
关于 JoVE
概览领导团队博客JoVE 帮助中心
作者
出版流程编辑委员会范围与政策同行评审常见问题投稿
图书馆员
用户评价订阅访问资源图书馆顾问委员会常见问题
研究
JoVE JournalMethods CollectionsJoVE Encyclopedia of Experiments存档
教育
JoVE CoreJoVE BusinessJoVE Science EducationJoVE Lab Manual教师资源中心教师网站
使用条款与条件
隐私政策
政策

相关概念视频

Carbon-13 (¹³C) NMR: Overview01:10

Carbon-13 (¹³C) NMR: Overview

Carbon-13 is a naturally occurring NMR-active isotope of carbon with a low natural abundance of 1.1%. In contrast, carbon-12 is the most abundant isotope of carbon with zero nuclear spin. Therefore, it is NMR inactive. The gyromagnetic ratio of carbon-13 is smaller than that of protons. As a result, carbon-13 resonance is about 6000 times weaker than proton resonance. For a given magnetic field strength, the resonance frequency of carbon-13 is about one-fourth of the resonance frequency for...
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...
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...
Spin–Spin Coupling: One-Bond Coupling01:17

Spin–Spin Coupling: One-Bond Coupling

Coupling interactions are strongest between NMR-active nuclei bonded to each other, where spin information can be transmitted directly through the pair of bonding electrons. While nuclei polarize their electrons to the opposite spins, the bonding electron pair has opposite spins. Configurations with antiparallel nuclear spins are expected to be lower in energy. When coupling makes antiparallel states more favorable, J is considered to have a positive value. The one-bond coupling constant, 1J,...
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.
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...

您也可能阅读

相关文章

通过共同作者、期刊和引用图与本文相关的文章。

排序
Same author

Niobium and vanadium iminophosphinimide complexes.

Chemical communications (Cambridge, England)·2002
Same author

Terminal phosphide and dinitrogen molybdenum compounds obtained from pnictide-bridged precursors.

Inorganic chemistry·2002
Same author

On the origin of selective nitrous oxide N-N bond cleavage by three-coordinate molybdenum(III) complexes.

Journal of the American Chemical Society·2001
Same author

Coordination chemistry of a chelating amidoximato ligand.

Inorganic chemistry·2001
Same author

In pursuit of the molybdenum(III) tris(thiolate) fragment: unusual structure of a dimolybdenum mu-nitrido complex.

Inorganic chemistry·2001
Same author

Role of the arginine-nitric oxide pathway in the regulation of vascular smooth muscle cell proliferation.

Proceedings of the National Academy of Sciences of the United States of America·2001

相关实验视频

Updated: Jun 19, 2026

Functionalization of Single-walled Carbon Nanotubes with Thermo-reversible Block Copolymers and Characterization by Small-angle Neutron Scattering
09:12

Functionalization of Single-walled Carbon Nanotubes with Thermo-reversible Block Copolymers and Characterization by Small-angle Neutron Scattering

Published on: June 1, 2016

作为终端连接体的原子碳:对具有固态 (13) C NMR 数据和质子转移自我交换动力学的碳基离子的研究.

J B Greco1, J C Peters, T A Baker

  • 1Departments of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, Massachusetts 02139-4307, USA.

Journal of the American Chemical Society
|July 18, 2001
PubMed
概括

这项研究详细描述了碳胺离子及其结合酸的特征,揭示了独特的结合和反应性. 这些发现促进了对有机金属化合物及其潜在应用的理解.

更多相关视频

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

Covalent Immobilization of Proteins for the Single Molecule Force Spectroscopy
11:13

Covalent Immobilization of Proteins for the Single Molecule Force Spectroscopy

Published on: August 20, 2018

相关实验视频

Last Updated: Jun 19, 2026

Functionalization of Single-walled Carbon Nanotubes with Thermo-reversible Block Copolymers and Characterization by Small-angle Neutron Scattering
09:12

Functionalization of Single-walled Carbon Nanotubes with Thermo-reversible Block Copolymers and Characterization by Small-angle Neutron Scattering

Published on: June 1, 2016

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

Covalent Immobilization of Proteins for the Single Molecule Force Spectroscopy
11:13

Covalent Immobilization of Proteins for the Single Molecule Force Spectroscopy

Published on: August 20, 2018

科学领域:

  • 有机金属化学 有机金属化学
  • 无机化学 无机化学
  • 频谱学是一种光谱学.
  • 计算化学计算化学

背景情况:

  • 在过渡金属复合体中探索低坐标碳物种.
  • 了解金属碳化物系统中的电子结构和粘合.

研究的目的:

  • 为了描述一种新型的碳聚离子的结构和结合,[CMo(N[R]Ar) ((3)) ](-).
  • 为了研究碳基离子及其合酸,HCMo(N[R]Ar) 的化学反应性和动力性质.
  • 通过光谱和计算方法阐明碳化物和甲基类物种之间的电子差异.

主要方法:

  • 单晶X射线晶体学用于结构确定.
  • 溶液和固态碳-13核磁共振 (NMR) 光谱学.
  • 密度函数理论 (DFT) 计算用于电子结构分析.
  • 对质子转移自我交换反应的动力学研究.

主要成果:

  • 对于碳化物离子和甲基来说,观察到相同的Mo-C键长度,尽管化学转移和NMR参数存在显著差异.
  • 固态 (13) C 核磁共振显示,与甲基相比,碳化物具有更大的化学转移异构性 (CSA) 和更小的 (95) Mo-(13) C 合常量.
  • DFT的计算表明,碳化物中Mo-C重叠群增加了.
  • 甲基呈现了大约30的pK (a) 在THF中,两种物种都经历了快速的质子转移自我交换 (k = 7 x 10 (6) M (-1) s (-1)).
  • 碳化物表现出作为强有力的还原剂和核爱体的反应性,形成新的碳-和碳-键.

结论:

  • 碳聚离子 ([CMo(N[R]Ar) ((3)) ((-)) 拥有独特的电子特性,与其甲基联酸不同,尽管结构参数相似.
  • 该化合物表现出丰富的反应性,作为一种强大的还原剂和多功能核爱好者.
  • 这项研究提供了对金属碳化物物种化学的基本见解,以及它们在合成应用中的潜力.