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相关概念视频

Woodward–Hoffmann Selection Rules and Microscopic Reversibility01:34

Woodward–Hoffmann Selection Rules and Microscopic Reversibility

3.2K
Electrocyclic reactions, cycloadditions, and sigmatropic rearrangements are concerted pericyclic reactions that proceed via a cyclic transition state. These reactions are stereospecific and regioselective. The stereochemistry of the products depends on the symmetry characteristics of the interacting orbitals and the reaction conditions. Accordingly, pericyclic reactions are classified as either symmetry-allowed or symmetry-forbidden. Woodward and Hoffmann presented the selection criteria for...
3.2K
Thermal and Photochemical Electrocyclic Reactions: Overview01:26

Thermal and Photochemical Electrocyclic Reactions: Overview

2.4K
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.
2.4K
[3,3] Sigmatropic Rearrangement of 1,5-Dienes: Cope Rearrangement01:21

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

2.8K
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.
2.8K
Thermal Electrocyclic Reactions: Stereochemistry01:17

Thermal Electrocyclic Reactions: Stereochemistry

2.1K
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.
2.1K
Cycloaddition Reactions: Overview01:16

Cycloaddition Reactions: Overview

2.7K
Cycloadditions are one of the most valuable and effective synthesis routes to form cyclic compounds. These are concerted pericyclic reactions between two unsaturated compounds resulting in a cyclic product with two new σ bonds formed at the expense of π bonds. The [4 + 2] cycloaddition, known as the Diels–Alder reaction, is the most common. The other example is a [2 + 2] cycloaddition.
2.7K
Cycloaddition Reactions: MO Requirements for Thermal Activation01:16

Cycloaddition Reactions: MO Requirements for Thermal Activation

3.6K
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.
3.6K

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相关实验视频

Updated: Jul 30, 2025

Unraveling Entropic Rate Acceleration Induced by Solvent Dynamics in Membrane Enzymes
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由溶剂选择驱动的可逆宏循环到宏循环间转换

Fei Wang1, Xiangling Shi1, Yi Zhang1

  • 1State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, People's Republic of China.

Journal of the American Chemical Society
|May 12, 2023
PubMed
概括
此摘要是机器生成的。

研究人员开发了一种用于自组装宏循环的新型单合成方法. 溶剂的选择控制了不同大小的宏循环产品的形成,使得 [1 + 1] 和 [2 + 2] 结构之间的可逆互转成为可能.

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Solid-phase Synthesis of [4.4] Spirocyclic Oximes
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Unraveling Entropic Rate Acceleration Induced by Solvent Dynamics in Membrane Enzymes

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Depolymerizable Olefinic Polymers Based on Fused-Ring Cyclooctene Monomers
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Solid-phase Synthesis of [4.4] Spirocyclic Oximes
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科学领域:

  • 超分子化学
  • 有机合成
  • 材料科学

背景情况:

  • 宏观循环对宏观循环的相互转换提供了多种结构可能性.
  • 在不同大小的宏观循环之间实现可控,可逆的相互转换是一个重大挑战.

研究的目的:

  • 为自组装的宏循环开发一个简单的单合成.
  • 通过溶剂操纵研究宏循环大小和相互转换的控制.

主要方法:

  • 在α,α'-连接的寡二甲基和二胺之间发生的凝结反应.
  • 使用各种溶剂 (甲醇,乙醇,,DMSO,DMF,MeCN) 来影响产品的分销.
  • 宏循环产品的表征 ([1 + 1] 和 [2 + 2] 组合).

主要成果:

  • 一个胺桥接的寡二甲基 (3) 和二胺很容易形成 [2 + 2] 宏循环,独立于溶剂.
  • 根据溶剂的选择,将3与2,2'-oxybis(ethylamine) (14) 的凝结产生 [1 + 1] 或 [2 + 2] 的宏循环.
  • 特定的溶剂 (甲醇,乙醇,) 偏好 [1 + 1] 产品,而其他溶剂 (DMSO,DMF,MeCN) 偏好 [2 + 2] 产品,通常是沉物.
  • 通过改变溶剂,由热力学和可溶性因素驱动,可以实现 [1 + 1] 和 [2 + 2] 大循环之间的可逆互转.

结论:

  • 已经建立了一种多功能的一合成自组装宏循环的方法.
  • 证明了溶剂控制的可逆宏观循环相互转换,为结构多样性提供了新的策略.
  • 这些发现强调了热力学和可溶性参数在指导自组装过程中的重要性.