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相关概念视频

Thermal and Photochemical Electrocyclic Reactions: Overview01:26

Thermal and Photochemical Electrocyclic Reactions: Overview

2.3K
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.
2.3K
¹H NMR: Long-Range Coupling01:27

¹H NMR: Long-Range Coupling

1.7K
The coupling interactions of nuclei across four or more bonds are usually weak, with J values less than 1 Hz. While these are usually not observed in spectra, the presence of multiple bonds along the coupling pathway can result in observable long-range coupling.
In alkenes, spin information is communicated via σ–π overlap, as seen in allylic (four-bond) and homoallylic (five-bond) couplings. These coupling interactions are stronger when the σ bond is parallel to the alkene...
1.7K
Thermal Electrocyclic Reactions: Stereochemistry01:17

Thermal Electrocyclic Reactions: Stereochemistry

2.0K
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.
2.0K
Spin–Spin Coupling: Three-Bond Coupling (Vicinal Coupling)01:22

Spin–Spin Coupling: Three-Bond Coupling (Vicinal Coupling)

1.0K
Vicinal or three-bond coupling is commonly observed between protons attached to adjacent carbons. Here, nuclear spin information is primarily transferred via electron spin interactions between adjacent C‑H bond orbitals. This generally favors the antiparallel arrangement of spins, so 3J values are usually positive.
The extent of coupling depends on the C‑C bond length, the two H‑C‑C angles, any electron-withdrawing substituents, and the dihedral angle between the...
1.0K
Photochemical Electrocyclic Reactions: Stereochemistry01:26

Photochemical Electrocyclic Reactions: Stereochemistry

1.8K
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
1.8K
Spin–Spin Coupling: Two-Bond Coupling (Geminal Coupling)01:20

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

981
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...
981

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相关实验视频

Updated: Jun 11, 2025

Mizoroki-Heck Cross-coupling Reactions Catalyzed by Dichloro{bis[1,1',1''-phosphinetriyltripiperidine]}palladium Under Mild Reaction Conditions
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Mizoroki-Heck Cross-coupling Reactions Catalyzed by Dichloro{bis[1,1',1''-phosphinetriyltripiperidine]}palladium Under Mild Reaction Conditions

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在Triferrocenylpnictogens中的电子合.

Corina Stoian1, Fawaz Al Hussein1, Wesley R Browne2

  • 1Institute for Inorganic Chemistry and Crystallography, Faculty of Biology and Chemistry, University of Bremen, Leobener Straße 7, Bremen 28359, Germany.

ACS organic & inorganic Au
|October 7, 2024
PubMed
概括
此摘要是机器生成的。

研究人员研究了新的混合价值铁复合物,特别是三铁烯基物质 (Fc3E). 他们在相关的离子体中发现了弱电子合,这表明了穿越空间的电子传输机制.

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Synthetic Methodology for Asymmetric Ferrocene Derived Bio-conjugate Systems via Solid Phase Resin-based Methodology
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The Synthesis, Characterization and Reactivity of a Series of Ruthenium N-triphosPh Complexes
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The Synthesis, Characterization and Reactivity of a Series of Ruthenium N-triphosPh Complexes
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科学领域:

  • 有机金属化学 有机金属化学
  • 电化学 电化学 电化学
  • 材料科学 材料科学 材料科学

背景情况:

  • 具有铁基单元的混合价值复合体对于推进电子转移理论至关重要.
  • 该系列的三烯烯基物质 (Fc3E) 被扩展到更重的类似物 (E = As,Sb,Bi).

研究的目的:

  • 调查桥梁原子 (As,Sb,Bi) 对三烯烯基物质电子性质的影响.
  • 了解导致这些化合物中大量氧化还原分裂的因素.

主要方法:

  • 电化学研究来分析氧化还原分裂 (ΔE).
  • 合成化合物的结构特征.
  • 光谱电化学研究探测电子合.

主要成果:

  • 电化学研究揭示了静电贡献对氧化还原分裂的显著影响.
  • 对Fc3As.As.观察到溶剂稳定效应.
  • 结构和光谱电化学数据表明[Fc3E]+电离子中的电子合较弱.

结论:

  • 桥梁原子显著影响三烯烯基物质的电化学性质.
  • 由于电子合较弱,建议在氧化物种中使用穿越空间的电子转移机制.