軸性キラルバイススピロピランの熱均衡中のサイクル運動学
Pintu K Kundu1, Avishai Lerner, Kristina Kučanda
1Department of Organic Chemistry and ∥Chemical Research Support, Weizmann Institute of Science , Rehovot 76100, Israel.
Journal of the American Chemical Society
|July 30, 2014
まとめ
研究者らは,新しい分子ローターとフォトスイッチ化合物を合成した. その3つのダイアステロエーマーが相互変換し,その運動性を研究することで,活性化バリアが明らかになり,交換可能な分子にとって化学環境の重要性を強調しました.
科学分野:
- 超分子化学 超分子化学
- オーガニック・シンセシス オーガニック・シンセシス
- 物理化学 物理化学
背景:
- 分子ローターとフォトスイッチは,高度な機能材料の開発において重要な構成要素です.
- 分子イソメアのダイナミックな行動と相互変換を理解することは,材料の性質を制御する鍵です.
研究 の 目的:
- 分子ローターとフォトスイッチの機能を統合した新しい化合物を合成し,特徴づけること.
- 合成された分子のダイアステロエーマー相互変換経路と運動学を調査する.
- 観察された反応を支配する活性化バリアを決定し,その環境依存性を理解する.
主な方法:
- ハイブリッド分子ローター・フォトスイッチ化合物の合成.
- 個々のダイアステレオメアの分離と特徴付け.
- ダイアステロエーマー均衡をモニタリングするための運動学的研究.
- 相互変換反応の活性化バリアを計算するための計算分析.
主要な成果:
- 分子ローターとフォトスイッチの両方の特徴を示す化合物の合成が成功しました.
- 3つの異なるダイアステロエーマーを識別する.
- ダイアステロエーマー相互変換を制御する可逆周期反応の観察.
- スキーム内のすべての反応段階における活性化バリアの定量化.
結論:
- 分子スイッチの性質と行動は,周囲の化学環境によって大きく影響を受けます.
- 発見は,新しい切り替え可能な分子と反応性のある材料の合理的な設計のための重要な洞察を提供します.
- ダイアステレオメア相互変換の理解は,分子装置の機能を制御するために不可欠です.
関連する概念動画
01:17Thermal Electrocyclic Reactions: Stereochemistry
1.6K
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.
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.
1.6K
00:52¹H NMR of Conformationally Flexible Molecules: Temporal Resolution
991
At room temperature, the chair conformer of cyclohexane undergoes rapid ring flipping between two equivalent chair conformers at a rate of approximately 105 times per second. These two chair conformers are in equilibrium. The rapid ring flipping results in the interconversion of the axial proton to an equatorial proton and an equatorial to the axial proton. Such interconversions are too rapid and cannot be detected on the NMR timescale. Hence, the NMR spectrometer cannot distinguish between the...
991
01:16Thermal Sigmatropic Reactions: Overview
1.6K
Sigmatropic rearrangements are a class of pericyclic reactions in which a σ bond migrates from one part of a π system to another. These are intramolecular rearrangements where the total number of σ and π bonds remain unchanged.
Sigmatropic shifts are classified based on an order term [i, j ], where i and j indicate the number of atoms across which each end of the σ bond migrates. Below are examples of a [3,3] sigmatropic shift in...
Sigmatropic shifts are classified based on an order term [i, j ], where i and j indicate the number of atoms across which each end of the σ bond migrates. Below are examples of a [3,3] sigmatropic shift in...
1.6K
01:16Cycloaddition Reactions: MO Requirements for Thermal Activation
29.7K
Thermal cycloadditions are reactions where the source of activation energy needed to initiate the reaction is provided in the form of heat. A typical example of a thermally-allowed cycloaddition is the Diels–Alder reaction, which is a [4 + 2] cycloaddition. In contrast, a [2 + 2] cycloaddition is thermally forbidden.
29.7K
01:15¹H NMR of Conformationally Flexible Molecules: Variable-Temperature NMR
1.3K
The axial and equatorial protons in cyclohexane can be distinguished by performing a variable-temperature NMR experiment. In this process, except for one proton, the remaining eleven protons are replaced by deuterium. The deuterium substitution avoids the possible peak splitting caused by the spin-spin coupling between the adjacent protons. The remaining proton flips between the axial and equatorial positions.
1.3K
01:26Thermal and Photochemical Electrocyclic Reactions: Overview
2.1K
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.
2.1K