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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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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

C-H 債券のアクティベーションを理解し,活用する

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
まとめ

科学者は,移行金属を用いた炭素-水素 (C-H) 結合の選択的変換を進めています. この研究は,より効率的な化学合成と,豊富なアルカン資源のよりクリーンな利用を約束しています.

科学分野:

  • 有機金属化学 有機金属化学
  • カタリシス カタリシス カタリシス
  • 持続可能な化学

背景:

  • 炭素-水素 (C-H) 結合は豊富ですが,惰性であり,化学合成に挑戦しています.
  • 移行金属触媒は,C-H結合の活性化のための強力なツールとして登場しました.
  • 過去20年間で,C-H活性化メカニズムを理解する上で大きな進展がみられた.

研究 の 目的:

  • 移行金属で触媒化されたC-H結合の活性化における進歩をレビューする.
  • 化学合成とアルカン変換における実用的な応用のためのこれらの方法の可能性を議論する.
  • 効率的かつクリーンなアルカンの資源利用のための触媒システムの進行中の開発を強調する.

主な方法:

  • 移行金属触媒によるC-H結合活性化に関する文献のレビュー.
  • 反応機構,選択性,および条件の分析.
  • 微細化学合成および原料の代替における現在のおよび潜在的なアプリケーションの評価.

主要な成果:

  • 穏やかな条件下で移行金属の中心部で選択的なC-H結合活性化の多くの例が報告されています.
  • これらの有機金属反応のメカニズム,利点,および限界のより深い理解が達成されました.

さらに関連する動画

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

関連する実験動画

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

  • 新しい有望な触媒システムは,実用的なC-H活性化戦略の実現可能性を示しています.

    • 結論:

    • 有機金属化学は,効率的かつ選択的なC-H結合活性化のための大きな可能性を秘めています.
    • 触媒システムのさらなる開発は,アルカンの変換における実用的な応用を実現するために不可欠です.
    • これらの進歩は,地球上のアルカン資源のよりクリーンでより効率的な利用への道を開く.