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相关概念视频

VSEPR Theory and the Basic Shapes02:52

VSEPR Theory and the Basic Shapes

Overview of VSEPR Theory
Predicting Molecular Geometry02:27

Predicting Molecular Geometry

VSEPR Theory for Determination of Electron Pair Geometries
¹³C NMR: Distortionless Enhancement by Polarization Transfer (DEPT)01:20

¹³C NMR: Distortionless Enhancement by Polarization Transfer (DEPT)

When proton-coupled carbon-13 spectra are simplified by a broadband proton decoupling technique, structural information about the coupled protons is lost. Distortionless enhancement by polarization transfer (DEPT) is a technique that provides information on the number of hydrogens attached to each carbon in a molecule. While the DEPT experiment utilizes complex pulse sequences, the pulse delay and flip angle are specifically manipulated. The resulting signals have different phases depending on...
Electrospray Ionization (ESI) Mass Spectrometry01:12

Electrospray Ionization (ESI) Mass Spectrometry

Higher molecular weight biomolecules are nonvolatile compounds that may decompose before ionizing or vaporizing during mass analysis with conventional electron impact ionization methods. Accordingly, electrospray ionization (ESI) is the favored method for vaporizing and ionizing biomolecules as it circumvents rapid fragmentation and enables the recording of mass signals for the entire biomolecule.
ESI utilizes electrical energy to transfer ions from the liquid phase of the sample into the...
¹H NMR of Conformationally Flexible Molecules: Variable-Temperature NMR01:15

¹H NMR of Conformationally Flexible Molecules: Variable-Temperature NMR

The axial and equatorial protons in cyclohexane can be distinguished by performing a variable-temperature NMR experiment. In this process, except for one proton, the remaining eleven protons are replaced by deuterium. The deuterium substitution avoids the possible peak splitting caused by the spin-spin coupling between the adjacent protons. The remaining proton flips between the axial and equatorial positions.
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...

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Updated: Jul 13, 2026

Spatial Separation of Molecular Conformers and Clusters
10:37

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计算和ESR研究电子附着到decafluorocyclopentane,octafluorocyclobutane和hexafluorocyclopropane:分子的电子亲和力及其稳定的负离子的结构,根据13C和19F高精度合常量确

Adel M ElSohly1, Gregory S Tschumper, Richard A Crocombe

  • 1Department of Chemistry and Biochemistry, The University of Mississippi, University, Mississippi 38677, USA.

Journal of the American Chemical Society
|July 28, 2005
PubMed
概括

电子自旋共振 (ESR) 研究显示, perfluorocycloalkane 基离子表现出非局部化单独占用的分子轨道 (SOMOs). 计算分析证实了它们的pi*性质,并澄清了这些独特的含物种中的高价值性.

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08:44

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科学领域:

  • 物理化学 物理化学
  • 量子化学 是一个量子化学.
  • 频谱学是一种光谱学.

背景情况:

  • 研究了高环基的基态负离子的电子结构.
  • 专注于六cyclopropane (c-C3F6*-),八cyclopobutane (c-C4F8*-),以及十cyclopentane (c-C5F10*-). 这三种类型的环是最常见的.

研究的目的:

  • 为了描述 perfluorocycloalkane 基离子的电子特性和结构.
  • 确定单独占用的分子轨道 (SOMO) 的性质,并澄清超价值.

主要方法:

  • 高分辨率电子自旋共振 (ESR) 光谱测量超细合常量 (hfcc).
  • 量子化学计算包括B3LYP密度函数理论和MP2扰动理论.
  • 对同位素19F和13Chfcc值的分析.

主要成果:

  • 对于c-C3F6*-,c-C4F8*-和c-C5F10*-的实验性19F hfcc值分别为198.6,147.6和117.9G.
  • 对于c-C4F8*-的实验13C hfcc是5.2 G. 这是一个值.
  • 索莫在相当的化物上脱局,通过碳原子的节点平面,与D (nh) 结构一致.

结论:

  • perfluorocycloalkane 基离子的特征是作为 pi* 的物种.
  • 使用MP2理论的计算结果与实验19F hfcc值密切匹配.
  • 这项研究阐明了这些 perfluorinated 循环离子的高价值性.