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相关概念视频

¹H NMR: Complex Splitting01:13

¹H NMR: Complex Splitting

A proton M that is coupled to a proton X results in doublet signals for M. However, NMR-active nuclei can be simultaneously coupled to more than one nonequivalent nucleus. When M is coupled to a second proton A, such as in styrene oxide, each peak in the doublet is split into another doublet.
Splitting diagrams or splitting tree diagrams are routinely used to depict such complex couplings. While drawing splitting diagrams, the splitting with the larger coupling constant is usually applied first.
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...
Chemical Ionization (CI) Mass Spectrometry01:21

Chemical Ionization (CI) Mass Spectrometry

The molecular ion peak of a molecule in the mass spectrum provides vital information for molecular identification. However, conventional electron impact ionization can lead to the rapid dissociation of some molecular ions before they reach the detector. A milder ionization method is required to increase the lifetime of such ionized analyte molecules. Chemical ionization (CI) is a gas-phase protonation reaction useful for mass-analyzing analyte molecules that are easily protonated to yield the...
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 Signal Integration: Overview00:58

¹H NMR Signal Integration: Overview

The intensity of a signal, which can be represented by the area under the peak, depends on the number of protons contributing to that signal. The area under each peak is shown as a vertical line called an integral, with the integral value listed under it, as seen in the proton NMR spectrum of benzyl acetate. Each integral value is divided by the smallest integral value to obtain the ratio of the number of protons producing each signal. The ratio reveals the relative number of protons and not...
Insensitive Nuclei Enhanced by Polarization Transfer (INEPT)01:15

Insensitive Nuclei Enhanced by Polarization Transfer (INEPT)

Insensitive Nuclei Enhanced by Polarization Transfer (INEPT) is an advanced Nuclear Magnetic Resonance (NMR) technique specifically designed to detect and enhance the signals of low-abundance nuclei, such as carbon-13 and nitrogen-15, in small molecules. The fundamental principle behind INEPT is the transfer of polarization from a more abundant and highly polarizable nucleus, typically hydrogen-1, to the low-abundance nucleus of interest. This process effectively boosts the NMR signal of the...

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相关实验视频

Updated: Jul 9, 2026

Ethylene Polymerizations Using Parallel Pressure Reactors and a Kinetic Analysis of Chain Transfer Polymerization
07:28

Ethylene Polymerizations Using Parallel Pressure Reactors and a Kinetic Analysis of Chain Transfer Polymerization

Published on: November 27, 2015

催化聚合:通过直接的NMR观测 (EBI) Zr ((MeB ((C6F5) 3) 催化剂物种的扩散,终结和表皮化动态的确定.

Douglass R Sillars1, Clark R Landis

  • 1Department of Chemistry, University of Wisconsin, 1101 University Avenue, Madison, WI 53706, USA.

Journal of the American Chemical Society
|August 14, 2003
PubMed
概括

这项研究详细介绍了一种使用新方法生成的活体聚烯催化剂. 研究人员直接观察了异构化和表构化,揭示了对金属催化机制的新见解.

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Analysis of Complex Molecules and Their Reactions on Surfaces by Means of Cluster-Induced Desorption/Ionization Mass Spectrometry
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Analysis of Complex Molecules and Their Reactions on Surfaces by Means of Cluster-Induced Desorption/Ionization Mass Spectrometry

Published on: March 1, 2020

Thermochemical Studies of Ni(II) and Zn(II) Ternary Complexes Using Ion Mobility-Mass Spectrometry
16:11

Thermochemical Studies of Ni(II) and Zn(II) Ternary Complexes Using Ion Mobility-Mass Spectrometry

Published on: June 8, 2022

相关实验视频

Last Updated: Jul 9, 2026

Ethylene Polymerizations Using Parallel Pressure Reactors and a Kinetic Analysis of Chain Transfer Polymerization
07:28

Ethylene Polymerizations Using Parallel Pressure Reactors and a Kinetic Analysis of Chain Transfer Polymerization

Published on: November 27, 2015

Analysis of Complex Molecules and Their Reactions on Surfaces by Means of Cluster-Induced Desorption/Ionization Mass Spectrometry
07:53

Analysis of Complex Molecules and Their Reactions on Surfaces by Means of Cluster-Induced Desorption/Ionization Mass Spectrometry

Published on: March 1, 2020

Thermochemical Studies of Ni(II) and Zn(II) Ternary Complexes Using Ion Mobility-Mass Spectrometry
16:11

Thermochemical Studies of Ni(II) and Zn(II) Ternary Complexes Using Ion Mobility-Mass Spectrometry

Published on: June 8, 2022

科学领域:

  • 有机金属化学 有机金属化学
  • 聚合物科学 聚合物科学
  • 催化剂是一种催化剂.

背景情况:

  • 金属催化剂对于olefin聚合是非常重要的.
  • 了解生物聚合动力学和副作用反应对于催化剂设计至关重要.
  • 在金属催化中直接观察异构化和表构化机制仍然具有挑战性.

研究的目的:

  • 为了产生和表征一个活的聚烯催化剂与一个聚烯尾巴.
  • 直接测量生物催化剂的传播动力学和物种化.
  • 研究金属催化聚合物的异构化和表皮化过程.

主要方法:

  • 活体聚烯催化剂的合成,通过对 (EBI) ZrMe2 处理 B ((C6F5) 3) 和烯.
  • 在现场的NMR光谱 (1H,19F,13C) 用于催化剂表征和动力学研究.
  • 用同位素标记的 (1-13C-和1,1-2H-2,3-13C-) 进行机械阐明.

主要成果:

  • 一个活的聚烯催化剂 (3) 与一个聚烯尾巴成功生成.
  • 在和活催化剂度 (k = 2.6 M-1 s-1 在-40°C) 中,传播动力学遵循一阶速率定律.
  • 维尼利丁终结,1,3-异构化和链末端表皮化被观察到的速率相似,提供了直接的机械证据.

结论:

  • 这项研究提供了第一个直接观察1,3-异构化和链末化在金属催化中.
  • 观察到的异构化和表皮化速率支持了涉及三级基中间体和反面切换的拟议机制.
  • 这项工作促进了对活烯聚合物的复杂反应途径的理解.