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相关概念视频

Disubstituted Cyclohexanes: cis-trans Isomerism02:37

Disubstituted Cyclohexanes: cis-trans Isomerism

Depending upon the different spatial orientation of the substituents, the disubstituted cycloalkanes exhibit two types of stereoisomers. The cis isomers have the substituents on the same side of the ring, whereas the trans isomers have the substituents on the opposite sides. These stereoisomers exhibit different physical properties and cannot be interconverted without breaking the carbon-carbon bonds.
In cyclohexane, the substituents can occupy different positions generating distinct isomers.
Stereoisomerism of Cyclic Compounds02:33

Stereoisomerism of Cyclic Compounds

In this lesson, we delve into the role of ring conformation and its stability, which determines the spatial arrangement and, consequently, the molecular symmetry and stereoisomerism of cyclic compounds. 1,2-Dimethylcyclohexane is used as a case study to evaluate the possible number of stereoisomers. Here, given the multiple (n = 2) chiral centers, there are 2n = 4 possible configurations that lack a plane of symmetry, as the ring skeleton exists in a non-planar chair conformation. In addition,...
Structure of Conjugated Dienes01:16

Structure of Conjugated Dienes

Introduction
Conjugated dienes are compounds characterized by the presence of alternating double and single bonds. In a conjugated system like 1,3-butadiene, the unhybridized 2p orbital on each carbon overlaps continuously, allowing the π electrons to be delocalized across the entire molecule. In contrast, this type of overlap does not occur in cumulated and isolated dienes, such as 2,3-pentadiene and 1,4-pentadiene, respectively. Instead, the π electrons remain localized between the double...
[3,3] Sigmatropic Rearrangement of 1,5-Dienes: Cope Rearrangement01:21

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

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.
Five-Membered Heterocyclic Aromatic Compounds: Overview01:13

Five-Membered Heterocyclic Aromatic Compounds: Overview

Heterocyclic aromatic compounds are cyclic compounds that are aromatic and have one or more heteroatoms—atoms other than carbon, in the ring. Depending upon the number of atoms present in the ring, they can be either five or six-membered. Examples of five-membered heterocyclic aromatic compounds include pyrrole, furan, thiophene, and imidazole. Pyrrole consists of one nitrogen atom having one lone pair of electrons. Furan and thiophene have one oxygen and one sulfur heteroatom, respectively.
Aromatic Hydrocarbon Cations: Structural Overview01:18

Aromatic Hydrocarbon Cations: Structural Overview

Cycloheptatriene is a neutral monocyclic unsaturated hydrocarbon that consists of an odd number of carbon atoms and an intervening sp3 carbon in the ring. The three double bonds in the ring correspond to 6 π electrons, which is a Huckel number, and therefore satisfies the criteria of 4n + 2 π electrons. However, the intervening sp3 carbon disrupts the continuous overlap of p orbitals. As a result, cycloheptatriene is not aromatic.
Removing one hydrogen from the intervening CH2 group with both...

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Synthesis of Cyclic Polymers and Characterization of Their Diffusive Motion in the Melt State at the Single Molecule Level
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非平面芳香化合物. 非平面芳香化合物. 5. 5. 5. 这是一个很大的问题. 一种合成cis-10b,10c-dimethyl-10b,10c-dihydropyrenes的方法.

G J Bodwell1, J N Bridson, S L Chen

  • 1Department of Chemistry, Memorial University of Newfoundland, St. John's, NF, Canada A1B 3X7. gbodwell@mun.ca

Journal of the American Chemical Society
|July 18, 2001
PubMed
概括
此摘要是机器生成的。

研究人员通过绑定方法合成了cis-10b,10c-dimethyl-10b,10c-dihydropyrene (DMDHP). X射线结晶学揭示了其独特的cis-DMDHP骨架,显示出比trans-DMDHP更大的键交替.

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科学领域:

  • 有机化学 有机化学
  • 超分子化学 超分子化学
  • 晶体学 晶体学是指结晶学.

背景情况:

  • 二烯是具有独特结构性质的多环芳,具有独特的结构性质.
  • 对于合成化学来说,了解替代二烯的立体化学和电子结构至关重要.

研究的目的:

  • 为了合成和表征一个被严重替代的10b,10c-二甲基-10b,10c-二二烯 (DMDHP) 的cis异构体.
  • 用X射线晶体学实验确定cis-DMDHP骨的结构参数.
  • 将实验结果与之前的计算研究 (MMPI和DFT) 进行比较.

主要方法:

  • 使用可能可拆卸的带合成cis-DMDHP (20).
  • 隔离和净化cis-同位素与其价值同位素脱离平衡.
  • 对cis-DMDHP的X射线晶体结构的确定 (20).
  • 与现有的MMPI和DFT计算数据进行比较.

主要成果:

  • 单独合成DMDHP的 cis异构体 (20).
  • DMDHP (20) 与其价值同位素syn-[2.2]metacyclophanediene (19) 在平衡状态下存在.
  • 对X射线结构的确定为cis-DMDHP骨架提供了第一个实验数据.
  • 在cis-DMDHP的 [14] 烯中观察到的键交替比trans-DMDHP框架更大.
  • 实验结果与之前的MMPI计算非常相匹配.
  • DFT计算预测了一个比观察到的更对称和债券均等的结构.

结论:

  • 这项研究为cis-DMDHP骨架提供了第一个实验结构数据.
  • 实验结果验证了先前的MMPI计算,但与DFT预测有所不同.
  • 结果提供了关于二二烯系统的电子和结构细微差别的见解.