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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.
¹H NMR of Conformationally Flexible Molecules: Temporal Resolution00:52

¹H NMR of Conformationally Flexible Molecules: Temporal Resolution

At room temperature, the chair conformer of cyclohexane undergoes rapid ring flipping between two equivalent chair conformers at a rate of approximately 105 times per second. These two chair conformers are in equilibrium. The rapid ring flipping results in the interconversion of the axial proton to an equatorial proton and an equatorial to the axial proton. Such interconversions are too rapid and cannot be detected on the NMR timescale. Hence, the NMR spectrometer cannot distinguish between the...
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...
Electron Paramagnetic Resonance (EPR) Spectroscopy: Organic Radicals01:17

Electron Paramagnetic Resonance (EPR) Spectroscopy: Organic Radicals

Ideally, an unpaired electron shows a single peak in the EPR spectrum due to the transition between the two spin energy states. However, coupling interactions can occur between the spins of the unpaired electron and any neighboring spin-active nuclei. This hyperfine coupling results in hyperfine splitting, where the EPR signal is split into multiplets. The signals split into 2nI + 1 peaks, where n is the number of equivalent nuclei and I is the nuclear spin. These splitting patterns provide...
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...
Double Resonance Techniques: Overview01:12

Double Resonance Techniques: Overview

Double resonance techniques in Nuclear Magnetic Resonance (NMR) spectroscopy involve the simultaneous application of two different frequencies or radiofrequency pulses to manipulate and observe two distinct nuclear spins. One important application of double resonance is spin decoupling, which selectively suppresses coupling with one type of nucleus while observing the NMR signal from another nucleus, simplifying the spectrum and enhancing resolution.
Spin decoupling is usually achieved by...

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Site Directed Spin Labeling and EPR Spectroscopic Studies of Pentameric Ligand-Gated Ion Channels
11:19

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Published on: July 4, 2016

一种稳定的N-异环基米烯的激进反应:EPR研究和DFT计算.

Boris Tumanskii1, Pauline Pine, Yitzhak Apeloig

  • 1Department of Chemistry and the Lise Meitner-Minerva Center for Computational Quantum Chemistry, Technion-Israel Institute of Technology, Haifa 32000, Israel.

Journal of the American Chemical Society
|June 9, 2005
PubMed
概括
此摘要是机器生成的。

研究人员探索了稳定的N-异环基米烯基基的附加物. 观察到旋转密度的移位,随着较重的中心原子,如和,旋转密度下降.

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科学领域:

  • 有机金属化学 有机金属化学
  • 激进化学 激进化学是什么
  • 计算化学的计算化学

背景情况:

  • 稳定的N-异环碳化合物 (NHCs) 和氨基已被确立,但它们更重的同胞氨基仍未得到充分的探索.
  • 激素 adducts 提供了一个独特的途径来研究低价值主要组元素的反应性和电子性质.
  • 了解这些物种的电子移位对于设计新材料和催化剂至关重要.

研究的目的:

  • 合成和描述一个稳定的N-异环基米烯的第一个激素添加物.
  • 为了研究电子结构和旋转密度分布在这些新的激进物种.
  • 为了比较N-异环基米烯与它们的和碳类型的行为.

主要方法:

  • 来自各种前体的新型基因物种的合成.
  • 电子偏磁共振 (EPR) 谱学用于基质特征.
  • 密度函数理论 (DFT) 计算 (B3LYP) 用于建模根 adducts.

主要成果:

  • 成功生成和表征第一个稳定的N-异环生殖基烯基基 adducts.
  • EPR光谱学证实了合成物种的激进性质.
  • DFT的计算显示,在所有研究的激素 adducts 中,未配对的电子都在五个成员的环上移位.
  • 中心原子的旋转密度以以下顺序下降:碳 > > .

结论:

  • N-异环基米烯可以形成稳定的基结添加物,扩大已知的低价值的化学成分.
  • 观察到的旋转密度 (C > Si > Ge) 的趋势归因于根 adducts 的日益增长的zwitterionic特征.
  • 这些发现为第14组中不和N-异环双价物种的电子特性和反应性提供了基本的见解.