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Woodward–Hoffmann Selection Rules and Microscopic Reversibility01:34

Woodward–Hoffmann Selection Rules and Microscopic Reversibility

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...
Diels–Alder vs Retro-Diels–Alder Reaction: Thermodynamic Factors01:31

Diels–Alder vs Retro-Diels–Alder Reaction: Thermodynamic Factors

The Diels–Alder reaction is thermally reversible, meaning that the reaction reverts to the starting diene and dienophile under suitable temperatures. The forward reaction gives a cyclohexene derivative and is favored at low to medium temperatures. The reverse process, also called retro-Diels–Alder reaction, is a ring-opening process favored at high temperatures.
C–C Bond Cleavage: Retro-Aldol Reaction00:57

C–C Bond Cleavage: Retro-Aldol Reaction

The reverse of the aldol addition reaction is called the retro-aldol reaction. Here, the carbon–carbon bond in the aldol product is cleaved under acidic or basic conditions to form two molecules of carbonyl compounds. The mechanism of the reaction consists of three steps.
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Crossed Aldol Reactions: Overview01:04

Crossed Aldol Reactions: Overview

Crossed aldol addition is the reaction between two different carbonyl compounds under acidic or basic conditions. Here, both the carbonyl compounds function as nucleophiles and electrophiles. As shown in Figure 1, such a reaction yields a mixture of products, two of which are formed via self-condensation, while the remaining two are formed via crossed-condensation. Without adjustment, the reaction's usefulness in organic chemistry is decreased.
Structuralism01:26

Structuralism

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Theory of Attribution I: Correspondent Inference Theory

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相关实验视频

Updated: Jun 30, 2026

Irrelevant Stimuli and Action Control: Analyzing the Influence of Ignored Stimuli via the Distractor-Response Binding Paradigm
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Published on: May 14, 2014

结构性研究对回复-迪尔斯-阿尔德反应. 实验和理论研究实验和理论研究

David Birney1, Tang Kuan Lim, Joanne H P Koh

  • 1Contribution from the School of Chemistry, University of Melbourne, Parkville, Vic 3010, Australia, and Texas Tech University, Lubbock, Texas 79409-1061.

Journal of the American Chemical Society
|May 2, 2002
PubMed
概括

在研究反复-迪尔斯-阿尔德反应时,这项研究发现,反应性循环载荷管道表现出更长的碳-碳键. 这种键延长与反应性相关,为反应机制提供了洞察力.

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Dissociation of the Confounding Influences of Expectancy and Integrative Difficulty Residing in Anomalous Sentences in Event-related Potential Studies
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RBDT: A Computerized Task System based in Transposition for the Continuous Analysis of Relational Behavior Dynamics in Humans
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相关实验视频

Last Updated: Jun 30, 2026

Irrelevant Stimuli and Action Control: Analyzing the Influence of Ignored Stimuli via the Distractor-Response Binding Paradigm
12:12

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Published on: May 14, 2014

Dissociation of the Confounding Influences of Expectancy and Integrative Difficulty Residing in Anomalous Sentences in Event-related Potential Studies
05:22

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科学领域:

  • 有机化学 有机化学
  • 物理化学 物理化学
  • 计算化学的计算化学

背景情况:

  • 逆-迪尔斯-阿尔德 (rDA) 反应是有机化学中的一个基本的转化.
  • 了解影响rDA反应性的基态结构特征对于合成设计至关重要.

研究的目的:

  • 为了研究地面状态结构与反复-迪尔斯-阿尔德反应倾向之间的关系.
  • 阐明循环载荷管道中的结构参数如何与它们在rDA反应中的反应性相关.

主要方法:

  • 使用低温X射线晶体学来确定精确的分子几何形状.
  • 密度函数理论 (DFT) 的计算 (B3LYP/6-31G(d,p)) 在地面和过渡状态上进行.
  • 测量了碳-碳 (13C-13C) 合常量,以探测结合特性.

主要成果:

  • 能够接受rDA的循环载荷管道与它们的和类型相比,表现出明显更长的碳-碳键 (a和b键).
  • 碳-碳键延长的程度和循环载荷管道的反应性之间观察到直接的相关性.
  • 预计将经历异步rDA反应的循环载荷导管显示了不同程度的键延长,反映了过渡状态的键断裂特征.

结论:

  • 基态结构参数,特别是碳-碳键长度,可以作为反复-迪尔斯-阿尔德反应性的可靠指标.
  • 循环载荷管道中键延长的程度提供了对它们接受rDA反应的倾向的定量见解.
  • 计算和实验方法的结合提供了对rDA反应中的结构-反应性关系的全面理解.