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関連する概念動画

π Electron Effects on Chemical Shift: Aromatic and Antiaromatic Compounds01:14

π Electron Effects on Chemical Shift: Aromatic and Antiaromatic Compounds

In aromatic compounds, such as benzene, the circulation of (4n + 2) π-electrons sets up a diamagnetic or diatropic ring current around the perimeter of the molecule. This current induces a magnetic field that opposes the external field inside the ring and reinforces it on the outside. The protons in benzene are deshielded and exhibit high chemical shifts in the range 6.5–8.5 ppm. The shielding effect at the center of the ring is evident in complex aromatic molecules, such as annulenes. In...
Aromatic Hydrocarbon Anions: Structural Overview01:18

Aromatic Hydrocarbon Anions: Structural Overview

Neutral hydrocarbons like cyclopentadiene with an odd number of carbon atoms and one intervening CH2 group in the ring are not aromatic. Cyclopentadiene with 4 π electrons does not satisfy the 4n + 2 π electron rule. Additionally, the intervening CH2 group is sp3 hybridized and lacks a vacant p orbital, thereby interrupting the overlap of p orbitals in a continuous manner and preventing the delocalization of π electrons throughout the ring.
Due to the absence of continuous overlap of p...
Electrophilic Aromatic Substitution: Overview01:16

Electrophilic Aromatic Substitution: Overview

In an electrophilic aromatic substitution reaction, an electrophile substitutes for a hydrogen of an aromatic compound.
Criteria for Aromaticity and the Hückel 4n + 2 Rule01:20

Criteria for Aromaticity and the Hückel 4n + 2 Rule

Like benzene, cyclobutadiene and cyclooctatetraene are cyclic compounds with alternate single and double bonds. However, their chemical behavior differs from benzene, as they are unstable and not aromatic. So, what are the structural characteristics of unsaturated compounds categorized as aromatic?
For the first time, Eric Hückel, a German chemical physicist, derived a set of structural features for a compound to be classified as aromatic. This is now known as Hückel’s rule or the 4n + 2 rule.
Electrophilic Addition of HX to 1,3-Butadiene: Thermodynamic vs Kinetic Control01:23

Electrophilic Addition of HX to 1,3-Butadiene: Thermodynamic vs Kinetic Control

The addition of a hydrogen halide to 1,3-butadiene gives a mixture of 1,2- and 1,4-adducts. Since more substituted alkenes are more stable, the 1,4-adduct is expected to be the major product. However, the product distribution is strongly influenced by temperature; low temperature favors the 1,2-adduct, whereas the 1,4-adduct is predominant at high temperature.
Frost Circles for Different Conjugated Systems01:18

Frost Circles for Different Conjugated Systems

The inscribed polygon method is consistent with Hückel’s 4n + 2 rule and helps to learn whether the given cyclic compound is aromatic or not. The compound is stable and aromatic if every bonding molecular orbital (MO) is completely filled with a pair of electrons. However, if the non-bonding or antibonding orbitals are filled with electrons, the compound is unstable and not aromatic. Consider the Frost circle diagrams for cycloalkenes containing 4 to 8 carbons.

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関連する実験動画

Updated: May 27, 2026

Novel Techniques for Observing Structural Dynamics of Photoresponsive Liquid Crystals
10:35

Novel Techniques for Observing Structural Dynamics of Photoresponsive Liquid Crystals

Published on: May 29, 2018

関連電子ダイナミクス:芳香度を制御する方法

Inga S Ulusoy1, Mathias Nest

  • 1Technische Universität München, Theoretische Chemie, Lichtenbergstrasse 4, 85747 Garching, Germany. inga.ulusoy@mytum.de

Journal of the American Chemical Society
|November 5, 2011
PubMed
まとめ

研究者らは,レーザーパルスで電子のダイナミクスを操作することによって,分子芳香度を制御することを実証した. この研究は,ベンゼルを芳香状態から非芳香状態に切り替え,分子制御に関する新しい洞察を提供します.

科学分野:

  • 量子化学とは,量子化学である.
  • 分子ダイナミクス 分子ダイナミクス
  • レーザー物理学 レーザー物理学

背景:

  • アロマティック性は化学の基本的な概念であり,分子安定性と反応性にとって極めて重要です.
  • 分子の電子ダイナミクスを制御することは,化学的性質を操作するための経路を提供します.
  • 暫定的な非芳香的状態を理解することは,新しい分子変換の鍵です.

研究 の 目的:

  • レーザー誘発電子ダイナミクスを用いて分子芳香性の制御された切り替えを実証する.
  • ベンゼンにおける芳香的基底状態から非芳香的状態への移行を調査する.
  • 分子電子特性を操作するための理論的枠組みを提供すること.

主な方法:

  • 分子波関数の伝播をシミュレートするための時間依存構成相互作用 (TDCI) 方法.
  • レーザーパルス設計の最適制御理論 (OCT) は,特定の状態移行を達成するためのものです.
  • アロマティック性の基準として,債券注文とミュリケンチャージの分析.

主要な成果:

  • オーダーメイドのレーザーパルスを使って,アロマティックな基底状態から2つの異なるノンアロマティックな状態にベンゼンを成功裏に切り替えました.
  • 非芳香的状態を特徴付け,局所結合と炭素原子の部分電荷を明らかにした.

さらに関連する動画

Preparation of a Corannulene-functionalized Hexahelicene by Copper(I)-catalyzed Alkyne-azide Cycloaddition of Nonplanar Polyaromatic Units
09:35

Preparation of a Corannulene-functionalized Hexahelicene by Copper(I)-catalyzed Alkyne-azide Cycloaddition of Nonplanar Polyaromatic Units

Published on: September 18, 2016

Using Cyclic Voltammetry, UV-Vis-NIR, and EPR Spectroelectrochemistry to Analyze Organic Compounds
11:44

Using Cyclic Voltammetry, UV-Vis-NIR, and EPR Spectroelectrochemistry to Analyze Organic Compounds

Published on: October 18, 2018

関連する実験動画

Last Updated: May 27, 2026

Novel Techniques for Observing Structural Dynamics of Photoresponsive Liquid Crystals
10:35

Novel Techniques for Observing Structural Dynamics of Photoresponsive Liquid Crystals

Published on: May 29, 2018

Preparation of a Corannulene-functionalized Hexahelicene by Copper(I)-catalyzed Alkyne-azide Cycloaddition of Nonplanar Polyaromatic Units
09:35

Preparation of a Corannulene-functionalized Hexahelicene by Copper(I)-catalyzed Alkyne-azide Cycloaddition of Nonplanar Polyaromatic Units

Published on: September 18, 2016

Using Cyclic Voltammetry, UV-Vis-NIR, and EPR Spectroelectrochemistry to Analyze Organic Compounds
11:44

Using Cyclic Voltammetry, UV-Vis-NIR, and EPR Spectroelectrochemistry to Analyze Organic Compounds

Published on: October 18, 2018

  • ノンアロマティック状態のリングシステム内で,アト秒の時間スケールで電子の移位を観測した.

    • 結論:

    • 分子アロマティック性は,電子波関数を精密に操作することによって,動的に制御することができます.
    • レーザーで最適化された電子ダイナミクスは,一時的なノンアロマティック分子構成にアクセスし制御するための経路を提供します.
    • この研究は,分子電子構造と反応性の超高速制御の可能性を広げています.