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相关概念视频

Bond Dissociation Energy and Activation Energy02:13

Bond Dissociation Energy and Activation Energy

Bond energy is the energy required to break a bond homolytically. These values are usually expressed in units of kcal/mol or kJ/mol and are referred to as bond dissociation energies when given for specific bonds or average bond energies when indicated for a given type of bond over many compounds. Firstly, the bond dissociation energy for a single bond is weaker than that of a double bond, which in turn is weaker than that of a triple bond. Secondly, hydrogen forms relatively strong bonds with...
Photochemical Electrocyclic Reactions: Stereochemistry01:26

Photochemical Electrocyclic Reactions: Stereochemistry

The absorption of UV–visible light by conjugated systems causes the promotion of an electron from the ground state to the excited state. Consequently, photochemical electrocyclic reactions proceed via the excited-state HOMO rather than the ground-state HOMO. Since the ground- and excited-state HOMOs have different symmetries, the stereochemical outcome of electrocyclic reactions depends on the mode of activation; i.e., thermal or photochemical.
Selection Rules: Photochemical Activation
ortho–para-Directing Activators: –CH3, –OH, –⁠NH2, –OCH301:11

ortho–para-Directing Activators: –CH3, –OH, –⁠NH2, –OCH3

All ortho–para directors, excluding halogens, are activating groups. These groups donate electrons to the ring, making the ring carbons electron-rich. Consequently, the reactivity of the aromatic ring towards electrophilic substitution increases. For instance, the nitration of anisole is about 10,000 times faster than the nitration of benzene. The electron-donating effect of the methoxy group in anisole activates the ortho and para positions on the ring and stabilizes the corresponding...
Radical Formation: Homolysis00:54

Radical Formation: Homolysis

A bond is formed between two atoms by sharing two electrons. When this bond is broken by supplying sufficient energy, either two electrons can be taken up by one atom forming ions by the cleavage called heterolysis, or the two electrons are shared by two atoms, with one each creating radicals by the cleavage called homolysis.
Cycloaddition Reactions: MO Requirements for Thermal Activation01:16

Cycloaddition Reactions: MO Requirements for Thermal Activation

Thermal cycloadditions are reactions where the source of activation energy needed to initiate the reaction is provided in the form of heat. A typical example of a thermally-allowed cycloaddition is the Diels–Alder reaction, which is a [4 + 2] cycloaddition. In contrast, a [2 + 2] cycloaddition is thermally forbidden.
Cycloaddition Reactions: MO Requirements for Photochemical Activation01:12

Cycloaddition Reactions: MO Requirements for Photochemical Activation

Some cycloaddition reactions are activated by heat, while others are initiated by light. For example, a [2 + 2] cycloaddition between two ethylene molecules occurs only in the presence of light. It is photochemically allowed but thermally forbidden.

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相关实验视频

Updated: Jul 13, 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)

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了解和利用C-H债券激活的方法

Jay A Labinger1, John E Bercaw

  • 1Arnold and Mabel Beckman Laboratories of Chemical Synthesis, California Institute of Technology, Pasadena, California 91125, USA. jal@its.caltech.edu

Nature
|May 31, 2002
PubMed
概括

科学家正在利用过渡金属推进碳- (C-H) 键的选择性转化. 这项研究承诺更高效的化学合成和更清洁的利用丰富的资源.

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.
  • 可持续化学 可持续化学

背景情况:

  • 碳- (C-H) 键是丰富的,但惰性,对化学合成构成挑战.
  • 过渡金属催化已经成为激活C-H键的强大工具.
  • 在过去的二十年中,在了解CH激活机制方面取得了重大进展.

研究的目的:

  • 审查过渡金属催化C-H键激活的进展.
  • 讨论这些方法在化学合成和转化中的实际应用的潜力.
  • 突出目前正在进行的催化系统的开发,以实现高效和清洁的基资源利用.

主要方法:

  • 关于过渡金属催化C-H键激活的文献综述.
  • 对反应机制,选择性和条件的分析.
  • 评估精细化学合成和原料替代中的当前和潜在应用.

主要成果:

  • 在温和条件下,在过渡金属中心报告了大量选择性C-H键激活的例子.
  • 我们已经对这些有机金属反应的机制,优势和局限性有了更深入的了解.
  • 有前途的新催化系统证明了实际的C-H激活策略的可行性.

更多相关视频

Application of Elemental Lanthanides in the Selective C-F Activation of Trifluoromethylated Benzofulvenes Providing Access to Various Difluoroalkenes
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Application of Elemental Lanthanides in the Selective C-F Activation of Trifluoromethylated Benzofulvenes Providing Access to Various Difluoroalkenes

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Versatile CO2 Transformations into Complex Products: A One-pot Two-step Strategy
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Versatile CO2 Transformations into Complex Products: A One-pot Two-step Strategy

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相关实验视频

Last Updated: Jul 13, 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

Application of Elemental Lanthanides in the Selective C-F Activation of Trifluoromethylated Benzofulvenes Providing Access to Various Difluoroalkenes
10:10

Application of Elemental Lanthanides in the Selective C-F Activation of Trifluoromethylated Benzofulvenes Providing Access to Various Difluoroalkenes

Published on: July 28, 2018

Versatile CO2 Transformations into Complex Products: A One-pot Two-step Strategy
07:36

Versatile CO2 Transformations into Complex Products: A One-pot Two-step Strategy

Published on: November 9, 2019

结论:

  • 有机金属化学为高效和选择性的C-H键激活提供了显著的潜力.
  • 进一步开发催化系统对于实现基转化中的实际应用至关重要.
  • 这些进步为更清洁,更有效地利用地球资源铺平了道路.