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

¹H NMR: Interpreting Distorted and Overlapping Signals01:02

¹H NMR: Interpreting Distorted and Overlapping Signals

1.1K
Spin systems where the difference in chemical shifts of the coupled nuclei is greater than ten times J are called first-order spin systems. These nuclei are weakly coupled, and their chemical shifts and coupling constant can generally be estimated from the well-separated signals in the spectrum.
As Δν decreases and the signals move closer, the doublets appear increasingly distorted. The intensities of the inner lines increase at the cost of those of the outer lines as the signals are...
1.1K
Spin–Spin Coupling Constant: Overview01:08

Spin–Spin Coupling Constant: Overview

964
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...
964
Spin–Spin Coupling: One-Bond Coupling01:17

Spin–Spin Coupling: One-Bond Coupling

1.0K
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,...
1.0K
Spin–Spin Coupling: Two-Bond Coupling (Geminal Coupling)01:20

Spin–Spin Coupling: Two-Bond Coupling (Geminal Coupling)

1.1K
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...
1.1K
Atomic Nuclei: Nuclear Spin State Population Distribution01:14

Atomic Nuclei: Nuclear Spin State Population Distribution

1.0K
Near absolute zero temperatures, in the presence of a magnetic field, the majority of nuclei prefer the lower energy spin-up state to the higher energy spin-down state. As temperatures increase, the energy from thermal collisions distributes the spins more equally between the two states. The Boltzmann distribution equation gives the ratio of the number of spins predicted in the spin −½ (N−) and spin +½ (N+) states.
1.0K
Spin–Spin Coupling: Three-Bond Coupling (Vicinal Coupling)01:22

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

1.1K
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...
1.1K

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

Accelerating geometry optimization <i>via</i> Grassmann-DIIS extrapolation.

Physical chemistry chemical physics : PCCP·2026
Same author

Benchmarking Nanoscale Noncovalent Complexes at the Two-Hundred-Atom Scale with Converged Local CCSD(T).

The journal of physical chemistry. A·2026
Same author

Crystal Structure and Morphology-Controlled Synthesis of Co<sub>1-<i>x</i></sub>Mn<sub><i>x</i></sub>P Nanocrystals and Their Composition-Dependent Electrocatalytic Activity for the Hydrogen Evolution Reaction.

ACS applied materials & interfaces·2026
Same author

Water-Mediated Isomerization in the Stepwise Hydration of the Nitrobenzene Radical Cation with 1-6 Water Molecules.

The journal of physical chemistry. A·2026
Same author

Theoretical Analysis of the <i>n</i><sub>1</sub>ν<sub>1</sub> + ν<sub>3</sub> Combination Bands in Hydrogen Bihalide Anions, XHX<sup>-</sup>, X = {F, Cl, Br, and I}.

The journal of physical chemistry. A·2025
Same author

Grassmann extrapolation via direct inversion in the iterative subspace.

The Journal of chemical physics·2025
Same journal

Anharmonic phonons via quantum thermal bath simulations.

The Journal of chemical physics·2026
Same journal

Quantum simulation of alignment dependent differential cross sections in co-propagating molecular beams at cold collision energies.

The Journal of chemical physics·2026
Same journal

Non-additive ion effects on the coil-globule equilibrium of a generic polymer in aqueous salt solutions.

The Journal of chemical physics·2026
Same journal

Insights into the unexpected small reduction of the temperature of maximum density of water by lithium chloride addition.

The Journal of chemical physics·2026
Same journal

Optical frequency comb double-resonance spectroscopy of the 9030-9175 cm-1 states of ethylene.

The Journal of chemical physics·2026
Same journal

Time reversal breaking of colloidal particles in cells.

The Journal of chemical physics·2026
查看所有相关文章

相关实验视频

Updated: Jul 28, 2025

Computation of Atmospheric Concentrations of Molecular Clusters from ab initio Thermochemistry
12:11

Computation of Atmospheric Concentrations of Molecular Clusters from ab initio Thermochemistry

Published on: April 8, 2020

8.2K

对于旋转不受限制的开系统的格拉斯曼插值方法.

Jake A Tan1, Ka Un Lao1

  • 1Department of Chemistry, Virginia Commonwealth University, Richmond, Virginia 23284, USA.

The Journal of chemical physics
|June 1, 2023
PubMed
概括
此摘要是机器生成的。

格拉斯曼插值 (G-Int) 被扩展到自旋不受限制的开系统. 这种方法为自相一致的场计算提供了准确的初步猜测,提高了效率,并使直接的原子电荷计算成为可能.

更多相关视频

Excitonic Hamiltonians for Calculating Optical Absorption Spectra and Optoelectronic Properties of Molecular Aggregates and Solids
08:04

Excitonic Hamiltonians for Calculating Optical Absorption Spectra and Optoelectronic Properties of Molecular Aggregates and Solids

Published on: May 27, 2020

8.5K
Line Shape Analysis of Dynamic NMR Spectra for Characterizing Coordination Sphere Rearrangements at a Chiral Rhenium Polyhydride Complex
10:52

Line Shape Analysis of Dynamic NMR Spectra for Characterizing Coordination Sphere Rearrangements at a Chiral Rhenium Polyhydride Complex

Published on: July 27, 2022

2.8K

相关实验视频

Last Updated: Jul 28, 2025

Computation of Atmospheric Concentrations of Molecular Clusters from ab initio Thermochemistry
12:11

Computation of Atmospheric Concentrations of Molecular Clusters from ab initio Thermochemistry

Published on: April 8, 2020

8.2K
Excitonic Hamiltonians for Calculating Optical Absorption Spectra and Optoelectronic Properties of Molecular Aggregates and Solids
08:04

Excitonic Hamiltonians for Calculating Optical Absorption Spectra and Optoelectronic Properties of Molecular Aggregates and Solids

Published on: May 27, 2020

8.5K
Line Shape Analysis of Dynamic NMR Spectra for Characterizing Coordination Sphere Rearrangements at a Chiral Rhenium Polyhydride Complex
10:52

Line Shape Analysis of Dynamic NMR Spectra for Characterizing Coordination Sphere Rearrangements at a Chiral Rhenium Polyhydride Complex

Published on: July 27, 2022

2.8K

科学领域:

  • 计算化学计算化学
  • 量子化学 是一个量子化学.

背景情况:

  • 格拉斯曼插值 (G-Int) 方法提供了高效的密度矩阵插值.
  • 旋转不受限制的开系统需要对α和β旋转密度矩阵进行单独的插值.

研究的目的:

  • 扩展和评估G-Int方法对自旋不受限制的开系统的性能.
  • 评估G-Int密度矩阵作为自相一致场 (SCF) 计算的初始猜测的实用性.
  • 探索使用G-Int密度矩阵直接计算原子电荷.

主要方法:

  • 将G-Int应用于自旋不受限制的开系统,特别是CO●+和烯.
  • 将G-Int性能与传统的SCF猜测方案进行比较.
  • 使用Mulliken和ChElPG群体分析与G-Int密度矩阵直接计算原子电荷.

主要成果:

  • 对于α和β旋转密度矩阵的Frobenius规范误差被发现是可比的.
  • G-Int密度矩阵显著超过了传统的SCF猜测方案.
  • 根据准确性要求,使用G-Int密度矩阵可以直接进行SCF能量评估,而无需代.
  • 首次使用自旋不受限制的G-Int密度矩阵用于直接的原子电荷计算.

结论:

  • 扩展的G-Int方法对于旋转不受限制的开系统是有效的.
  • G-Int为SCF计算提供了卓越的初始猜测,提高了计算效率.
  • 该方法可以直接计算原子电荷,扩大其在电子结构分析中的应用.