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相关概念视频

Elimination Reactions02:25

Elimination Reactions

A nucleophile can react with an alkyl halide to give the substitution product by displacing the halogen. Or it can function as a base to give the elimination product by deprotonation of the neighboring carbon to form an alkene. In an elimination reaction, the substrate loses two groups from adjacent carbons forming at least one π bond. The carbon attached to the halogen is called the α carbon, while the adjacent carbon is called the β carbon; hence, these reactions are called β elimination or...
E1 Reaction: Kinetics and Mechanism02:46

E1 Reaction: Kinetics and Mechanism

Here, in contrast to the E2 reaction mechanism, we delve into the aspects of the E1 reaction mechanism, which has two steps: rate-limiting loss of the leaving group and abstraction of the beta hydrogen by a weak base. Typically, the experimental proof for the E1 mechanism is via kinetic studies or isotope studies. While the former demonstrates the first-order kinetics—the dependence of the reaction solely on substrate concentration—the latter proves the abstraction of hydrogen only in the...
Regioselectivity of Electrophilic Additions to Alkenes: Markovnikov's Rule02:17

Regioselectivity of Electrophilic Additions to Alkenes: Markovnikov's Rule

If a set of reactants can yield multiple constitutional isomers, but one of the isomers is obtained as the major product, the reaction is said to be regioselective. In such reactions, bond formation or breaking is favored at one reaction site over others.
The hydrohalogenation of an unsymmetrical alkene can yield two haloalkane products, depending on which vinylic carbon takes up the halogen. However, one product usually predominates, where hydrogen adds to the vinylic carbon bearing the...
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...
Acid Halides to Amides: Aminolysis01:07

Acid Halides to Amides: Aminolysis

Aminolysis is a nucleophilic acyl substitution reaction, where ammonia or amines act as nucleophiles to give the substitution product. Acid halides react with ammonia, primary amines, and secondary amines to yield primary, secondary, and tertiary amides, respectively.
In the first step of the aminolysis mechanism, the amine attacks the carbonyl carbon of the acyl chloride to form a tetrahedral intermediate. In the second step, the carbonyl group is re-formed with the elimination of a chloride...
IR Spectrum Peak Intensity: Dipole Moment01:20

IR Spectrum Peak Intensity: Dipole Moment

The dipole moment of a bond is the product of the partial charge on either atom and the distance between them. Dipole moments influence the efficiency of IR absorption and the peak intensity. When a bond with a dipole moment is placed in an electric field, the direction of the field determines if the bond is compressed or stretched. Electromagnetic radiation consists of an electric field component that rapidly reverses direction. It follows that polar bonds are alternately stretched and...

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相关实验视频

Updated: Jul 15, 2026

Synthesis of Antiviral Tetrahydrocarbazole Derivatives by Photochemical and Acid-catalyzed C-H Functionalization via Intermediate Peroxides (CHIPS)
06:34

Synthesis of Antiviral Tetrahydrocarbazole Derivatives by Photochemical and Acid-catalyzed C-H Functionalization via Intermediate Peroxides (CHIPS)

Published on: June 20, 2014

选择性中的一个离子依赖的切换来自于C-H激活机制的变化,这种变化发生在一种伊米达盐与IrH5的反应中.

Leah N Appelhans1, Daniele Zuccaccia, Anes Kovacevic

  • 1Department of Chemistry, 225 Prospect Street, Yale University, New Haven, Connecticut 06520-8107, USA.

Journal of the American Chemical Society
|November 17, 2005
PubMed
概括

伊米达盐中的反阴离子决定了与复合物的反应途径,在正常和异常的N-异环碳素结合之间切换. 这种离子合的质子转移机制影响了C-H激活反应的选择性.

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Synthesis of Antiviral Tetrahydrocarbazole Derivatives by Photochemical and Acid-catalyzed C-H Functionalization via Intermediate Peroxides (CHIPS)
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Synthesis of Antiviral Tetrahydrocarbazole Derivatives by Photochemical and Acid-catalyzed C-H Functionalization via Intermediate Peroxides (CHIPS)

Published on: June 20, 2014

From Molecules to Materials: Engineering New Ionic Liquid Crystals Through Halogen Bonding
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Photogeneration of N-Heterocyclic Carbenes: Application in Photoinduced Ring-Opening Metathesis Polymerization
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Published on: November 29, 2018

科学领域:

  • 有机金属化学 有机金属化学
  • 催化剂是一种催化剂.
  • 计算化学计算化学

背景情况:

  • 在有机金属化学中,N-异环碳 (NHCs) 是多功能联体.
  • NHC 的结合模式 (正常与异常) 可以显著影响反应性.
  • 催化系统中的离子配对可以影响反应通路和选择性.

研究的目的:

  • 为了研究对抗离子对2-pyridylmethyl imidazolium盐与IrH5(PPh3) 2.2.的反应途径的影响.
  • 阐明正常 (N 路径) 和异常 (AN 路径) N-异环碳化合物结合之间的机制差异.
  • 了解离子合质子转移在确定N/AN选择性的作用.

主要方法:

  • 合成离子配对的2-pyridylmethyl imidazolium盐,具有不同的对抗离子 (Br,BF4,PF6,SbF6).
  • 与IrH5(PPh3) 2进行反应研究,以确定动态产物.
  • 密度函数理论 (DFT) 计算模型反应机制.
  • 脉冲梯度旋回回声 (PGSE) 核磁共振和19F,1H-HOESY核磁共振实验以表征离子配对和产品结构.

主要成果:

  • 改变对子离子将反应产物从正常的C2结合 (N路径) 切换到异常的C5结合 (AN路径).
  • DFT计算显示,AN路径涉及C-H氧化添加到Ir(III) 形成Ir(V),与最小的离子依赖.
  • 该N路径通过异质C-H激活与离子合的质子转移进行,显示出显著的离子依赖.
  • 核磁共振实验证实了反应物和产物中离子对的形成,与计算预测一致.

结论:

  • 反抗离子在控制反应的N/AN选择性方面发挥着至关重要的作用.
  • 阴离子合质子转移是N路径中观察到的阴离子依赖的关键机械特征.
  • 正常和异常NHC的不同供体强度解释了不同的反应路径和中间氧化状态.