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相关概念视频

Photochemical Electrocyclic Reactions: Stereochemistry01:26

Photochemical Electrocyclic Reactions: Stereochemistry

2.2K
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
2.2K
Cycloaddition Reactions: MO Requirements for Photochemical Activation01:12

Cycloaddition Reactions: MO Requirements for Photochemical Activation

2.6K
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.
2.6K
Thermal and Photochemical Electrocyclic Reactions: Overview01:26

Thermal and Photochemical Electrocyclic Reactions: Overview

2.9K
Electrocyclic reactions are reversible reactions. They involve an intramolecular cyclization or ring-opening of a conjugated polyene. Shown below are two examples of electrocyclic reactions. In the first reaction, the formation of the cyclic product is favored. In contrast, in the second reaction, ring-opening is favored due to the high ring strain associated with cyclobutene formation.
2.9K
[3,3] Sigmatropic Rearrangement of 1,5-Dienes: Cope Rearrangement01:21

[3,3] Sigmatropic Rearrangement of 1,5-Dienes: Cope Rearrangement

3.3K
The Cope rearrangement is classified as a [3,3] sigmatropic shift in 1,5-dienes, leading to a more stable, isomeric 1,5-diene. The reaction involves a concerted movement of six electrons, four from two π bonds and two from a σ bond, via an energetically favorable chair-like transition state.
3.3K
Thermal Electrocyclic Reactions: Stereochemistry01:17

Thermal Electrocyclic Reactions: Stereochemistry

2.5K
The stereochemistry of electrocyclic reactions is strongly influenced by the orbital symmetry of the polyene HOMO. Under thermal conditions, the reaction proceeds via the ground-state HOMO.
Selection Rules: Thermal Activation
Conjugated systems containing an even number of π-electron pairs undergo a conrotatory ring closure. For example, thermal electrocyclization of (2E,4E)-2,4-hexadiene, a conjugated diene containing two π-electron pairs, gives trans-3,4-dimethylcyclobutene.
2.5K
Radical Formation: Homolysis00:54

Radical Formation: Homolysis

4.2K
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.
4.2K

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相关实验视频

Updated: Jan 11, 2026

Determination of the Photoisomerization Quantum Yield of a Hydrazone Photoswitch
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Determination of the Photoisomerization Quantum Yield of a Hydrazone Photoswitch

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通过直接的光异构化来操纵动态共价键.

Neil D Dolinski1, Alex E Crolais2, Nicholas R Boynton1

  • 1Pritzker School of Molecular Engineering, University of Chicago Chicago Illinois 60637 USA stuartrowan@uchicago.edu n.dolinski@columbia.edu.

Chemical science
|November 10, 2025
PubMed
概括

研究人员开发出光敏感的利索克萨 (BIOx) 分子,在可见光下增强醇结合. 这项创新使动态聚合物网络和有机凝中的光触发硬化成为可能.

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Direct Imaging of Laser-driven Ultrafast Molecular Rotation
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科学领域:

  • 材料科学 材料科学 材料科学
  • 聚合物化学 聚合物化学
  • 有机化学 有机化学

背景情况:

  • 光是控制动态共价化学的有吸引力的刺激,因为光的可用性和时空控制.
  • 动态共价化学为先进材料提供独特的特性,但需要精确的控制机制.

研究的目的:

  • 开发一种新的可光异构化的二醇 (BIOx) 提亚-迈克尔 (tM) 受体.
  • 为了研究光引起的醇结合和系统平衡 (Keq) 的增加.
  • 为了将这些光响应单元纳入动态聚合物网络,以获得光触发材料特性.

主要方法:

  • 合成可光异构化的二醇 (BIOx) -迈克尔 (tM) 受体.
  • 用可见光 (455-470nm) 照射,以诱导光异构和硫醇结合.
  • 在现场照片NMR实验量化Keq.的变化.
  • 计算研究以阐明增加Keq的机制.
  • 融入动态聚合物网络,形成有机凝.

主要成果:

  • 开发了BIOx tM受体,在可见光照射时显示了增加的醇结合.
  • 图像NMR证实了各种电子替代BIOx tM受体的Keq显著增加.
  • 在E-异构体中,固体相互作用被确定为增强Keq的驱动力.
  • 显示光强度可以调整系统的响应.
  • 开发的器官凝显示可逆的,按需的,光触发的硬化.

结论:

  • 可光异构化的BIOx tM受体提供了光控制的动态共价化学机制.
  • 绝缘效应在推动光学诱导的结合增加方面发挥着至关重要的作用.
  • 开发的材料为创建智能,光敏的聚合物网络和有机凝提供了潜力.