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相关概念视频

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
Free-Radical Chain Reaction and Polymerization of Alkenes02:35

Free-Radical Chain Reaction and Polymerization of Alkenes

The conversion of alkenes to macromolecules called polymers is a reaction of high commercial importance. The structure of the polymer is defined by a repeating unit, while the terminal groups are considered insignificant. The average degree of polymerization represents the number of repeating units in the polymer molecule and is denoted by the subscript n.
Radical Reactivity: Electrophilic Radicals01:02

Radical Reactivity: Electrophilic Radicals

Radicals adjacent to electron‐withdrawing groups are called electrophilic radicals. These radicals readily react with nucleophilic alkenes. For example, the malonate radical, in which the radical center is flanked by two electron‐withdrawing groups, reacts readily with butyl vinyl ether, which consists of an electron‐donating oxygen substituent. The reaction between electrophilic malonate radical and nucleophilic vinyl ether is favored because the radical has a low‐energy SOMO, which interacts...
Radical Reactivity: Steric Effects01:10

Radical Reactivity: Steric Effects

The presence of electron-donating, electron-withdrawing, or conjugating groups adjacent to a radical center, imparts electronic stabilization to the radicals. Examples of such electronically-stabilized radicals are triphenylmethyl, tetramethylpiperidine‐N‐oxide, and 2,2‐diphenyl‐1‐picrylhydrazyl. These radicals are remarkably stable and are known as persistent radicals. Some of the persistent radicals can even be isolated and purified.
Along with electronic factors, steric factors also account...
Thermal and Photochemical Electrocyclic Reactions: Overview01:26

Thermal and Photochemical Electrocyclic Reactions: Overview

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.
Olefin Metathesis Polymerization: Ring-Opening Metathesis Polymerization (ROMP)01:16

Olefin Metathesis Polymerization: Ring-Opening Metathesis Polymerization (ROMP)

Ring-opening metathesis polymerization or ROMP involves strained cycloalkenes as starting materials. The mechanism of ROMP proceeds by reacting cycloalkene with Grubbs catalyst to give metallacyclobutane intermediate which undergoes a ring-opening reaction to form new carbene. The new carbene reacts with another molecule of cycloalkene. Repetition of these steps leads to the formation of an unsaturated open-chain polymer product. All these steps are reversible, however, relieving the ring...

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相关实验视频

Updated: Jun 20, 2026

Atom Transfer Radical Polymerization of Functionalized Vinyl Monomers Using Perylene as a Visible Light Photocatalyst
06:49

Atom Transfer Radical Polymerization of Functionalized Vinyl Monomers Using Perylene as a Visible Light Photocatalyst

Published on: April 22, 2016

可分离的光反应性多基基.

Gregory Molev1, Boris Tumanskii, Dennis Sheberla

  • 1Schulich Faculty of Chemistry and the Lise Meitner Minerva Center for Computational Quantum Chemistry, Technion-Israel Institute of Technology, Haifa 32000, Israel.

Journal of the American Chemical Society
|September 3, 2009
PubMed
概括

使用一种新的一步方法合成了稳定的silyl基. 这些基具有独特的光化学性质,其中一种类型分解为西兰和迪,而另一种类型在辐射时经历抽取.

科学领域:

  • 有机化学 有机化学
  • 激进化学 激进化学是什么
  • 摄影化学的使用.

背景情况:

  • 稳定的基是化学中的关键中间体.
  • 以前合成西基的方法是有限的.
  • 了解基的反应性和光化学对于开发新的合成路径至关重要.

研究的目的:

  • 开发一种通用和高效的单步方法,用于合成稳定的基.
  • 描述新合成的基的结构和特性.
  • 为了研究这些基的光化学行为和反应机制.

主要方法:

  • 在中,西替代二西兰与石西兰的反应.
  • 绝缘和完全表征西基,包括X射线晶体学.
  • 光化学辐射实验 (λ > 400 nm) 和 DFT 计算.

主要成果:

  • 一个新的一步合成只能产生稳定的基.
  • 两个西基, (t-Bu(2) MeSi) ((2) HSi(t-Bu(2) MeSi) ((2) Si* (1) 和 (t-Bu(2) MeSi) ((3) Si* (2),被分离并进行了表征.
  • 激素1经历光解分解,变成西兰和迪;激素2显示光稳定性,但在照射时抽象化.
  • DFT计算和辐射数据表明SOMO-1 → SOMO激发影响光反应.

更多相关视频

Reductive Electropolymerization of a Vinyl-containing Poly-pyridyl Complex on Glassy Carbon and Fluorine-doped Tin Oxide Electrodes
09:17

Reductive Electropolymerization of a Vinyl-containing Poly-pyridyl Complex on Glassy Carbon and Fluorine-doped Tin Oxide Electrodes

Published on: January 30, 2015

Depolymerizable Olefinic Polymers Based on Fused-Ring Cyclooctene Monomers
08:12

Depolymerizable Olefinic Polymers Based on Fused-Ring Cyclooctene Monomers

Published on: December 16, 2022

相关实验视频

Last Updated: Jun 20, 2026

Atom Transfer Radical Polymerization of Functionalized Vinyl Monomers Using Perylene as a Visible Light Photocatalyst
06:49

Atom Transfer Radical Polymerization of Functionalized Vinyl Monomers Using Perylene as a Visible Light Photocatalyst

Published on: April 22, 2016

Reductive Electropolymerization of a Vinyl-containing Poly-pyridyl Complex on Glassy Carbon and Fluorine-doped Tin Oxide Electrodes
09:17

Reductive Electropolymerization of a Vinyl-containing Poly-pyridyl Complex on Glassy Carbon and Fluorine-doped Tin Oxide Electrodes

Published on: January 30, 2015

Depolymerizable Olefinic Polymers Based on Fused-Ring Cyclooctene Monomers
08:12

Depolymerizable Olefinic Polymers Based on Fused-Ring Cyclooctene Monomers

Published on: December 16, 2022

结论:

  • 开发的单步方法是合成多种稳定基的通用方法.
  • 基具有明显的光化学反应性,受其电子结构的影响.
  • 光活性与特定的电子激发有关,使控制的化学转变成为可能.