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相关概念视频

Radical Chain-Growth Polymerization: Mechanism01:09

Radical Chain-Growth Polymerization: Mechanism

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The radical chain-growth polymerization mechanism consists of three steps: initiation, propagation, and termination of polymerization. The polymerization initiates when a free radical generated from the radical initiator adds to the unsaturated bond in the monomer. The unpaired electron of the free radical and one π electron in the unsaturated bond creates a σ bond between the free radical and the monomer. As a result, the other π electron in the unsaturated bond converts this...
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Spin–Spin Coupling: Two-Bond Coupling (Geminal Coupling)01:20

Spin–Spin Coupling: Two-Bond Coupling (Geminal Coupling)

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Two NMR-active nuclei bonded to a central atom can be involved in geminal or two-bond coupling. Geminal coupling is commonly seen between diastereotopic protons in chiral molecules and unsymmetrical alkenes, among others.
The central atom need not be NMR-active because its electrons are affected by the electron polarization of the spin-active atoms. However, spin information is transmitted less effectively than in one-bond coupling, and 2J values are usually weaker than 1J values. The energy of...
956
Hybridization of Atomic Orbitals II03:35

Hybridization of Atomic Orbitals II

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sp3d and sp3d 2 Hybridization
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Spin–Spin Coupling: One-Bond Coupling01:17

Spin–Spin Coupling: One-Bond Coupling

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Coupling interactions are strongest between NMR-active nuclei bonded to each other, where spin information can be transmitted directly through the pair of bonding electrons. While nuclei polarize their electrons to the opposite spins, the bonding electron pair has opposite spins. Configurations with antiparallel nuclear spins are expected to be lower in energy. When coupling makes antiparallel states more favorable, J is considered to have a positive value. The one-bond coupling constant, 1J,...
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Radical Chain-Growth Polymerization: Chain Branching01:17

Radical Chain-Growth Polymerization: Chain Branching

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The skeletal structure of polymers synthesized via radical polymerization is always branched. For example, the polymerization of ethylene by radical polymerization results in a low-density grade of polyethylene with a heavily branched skeletal structure. Here, the radical site abstracts hydrogen from the growing chain, and the radical site shifts from the end (a primary carbon center) to anywhere within the growing chain (a secondary carbon center). Consequently, the part of the chain from the...
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Radical Chain-Growth Polymerization: Overview01:10

Radical Chain-Growth Polymerization: Overview

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Chain-growth or addition polymerization is successive addition reactions of monomers with a polymer chain. In radical chain-growth polymerization, the reaction proceeds via a free-radical intermediate. The free radical is formed from radical initiators, which spontaneously generate free radicals by homolytic fission. Organic peroxides (such as dibenzoyl peroxide, as shown in Figure 1) or azo compounds are popular radical initiators. A low concentration ratio of radical initiator to monomer is...
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为了快速的结构多样化,动态共价螺旋交换.

Alwin Drichel1,2, Yves Garmshausen3, Stefan Hecht4,5,1,2

  • 1DWI-Leibniz Institute for Interactive Materials, Forckenbeckstr. 50, 52074, Aachen, Germany.

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概括

螺旋类动物可以通过它们的 merocyanine 形式动态交换结构. 这种由印度盐催化的动态共价交换,允许快速结构多样化和新型螺旋的合成,用于像光启动器这样的应用.

关键词:
动态共价化学 动态共价化学墨洛氨酸是什么意思斯皮洛普兰斯皮洛普兰是什么?影音摄影 (Xolography) 是一种影音摄影.

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科学领域:

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

背景情况:

  • 螺旋是光色化合物,以其可逆结构转变而闻名.
  • 动态共价化学为适应性材料和分子组装提供了途径.
  • 控制螺旋结构对于调整它们的光色和材料特性至关重要.

研究的目的:

  • 揭示和描述通过其 merocyanine 异构体的 spiropyrans 的动态共价交换.
  • 研究螺旋交叉交换的机制和影响因素.
  • 利用这种交流来合成新的螺旋衍生物,并探索它们的应用.

主要方法:

  • 通过 merocyanine 中介物研究了 spiropyran 动态共价交换.
  • 分析了迈克尔类型的加法-消除序列,用于印度部分交换.
  • 研究了反应条件和替代物模式对交换平衡的影响.
  • 作为螺旋交叉交换的催化剂使用的印度盐.

主要成果:

  • 证明螺旋酸盐经历了由 merocyanine 异构体促进的动态共价交换.
  • 确定了迈克尔类型的加除序列作为密钥交换机制.
  • 使用这种方法展示了以前无法获得的螺旋的合成,适合于双色色光启动器.
  • 通过反应条件和分子结构确定了汇率和平衡是可调节的.

结论:

  • 螺旋的动态共价交换是现场结构多样化的可行策略.
  • 这种方法使人们能够访问具有先进材料潜在应用的新型spiropyran架构.
  • 螺旋的光敏感性可以被利用来控制和偏差它们在动态系统中的热平衡.