在1,2-二乙烯的E-Z异体化中,通过加冕基烯子进行了阴离子识别的光敏化
Ken Kokubo1, Hidenobu Kakimoto, Takumi Oshima
1Department of Applied Chemistry, Faculty of Engineering, Osaka University, Toyonaka, Osaka 560-0043, Japan.
Journal of the American Chemical Society
|June 6, 2002
概括
皇冠乙烯作为三重敏感剂增强了1,2-二乙烯的Z/E异体化. 金属离子添加显著增加Z/E同位素比率,证明了阴离子识别的敏感化效应.
科学领域:
- 摄影化学的使用.
- 有机化学 有机化学
- 超分子化学 超分子化学
背景情况:
- 光敏化异构化是有机化学中的一个关键反应.
- 皇冠乙烯以其结合金属离子的能力而闻名.
- 了解光化学反应上的阴离子效应对于开发新合成方法至关重要.
研究的目的:
- 研究金属离子对1,2-二乙烯光敏化异构的作用.
- 探索皇冠乙醇三重敏感剂在阴子识别敏感化中的作用.
- 确定阴离子结合如何影响三重能量和能量转移比率.
主要方法:
- 1,2-二乙烯的光敏感化使用15和18个环冠芬.
- 添加和土金属离子 (Li +,Na +,Mg2 +,Ca2 +).
- 使用光谱技术分析Z/E异构体比率.
主要成果:
- 与无金属反应 (Z/E = 1.5-2.1) 相比,加离子增加了1,2-二乙烯的Z/E异构体比率,增加到大约10.
- 特定的金属离子显示出增强的效果:Li+ (2.9) 和Mg2+ (5.3) 与敏感剂1a;Na+ (8.2) 和Ca2+ (9.8) 与敏感剂1b.
- 阴离子结合改变了三重能量 (ET) 和感应剂的PhiE/Phiz比率.
结论:
- 冠乙的阴离子识别敏感化有效控制了1,2-二乙烯的Z/E异构.
- 观察到的三倍能量和能量传输效率的变化是导致异构体比率的增强的原因.
- 这项研究突出了利用超分子相互作用调整光化学反应的新方法.
相关概念视频
E2 Reaction: Stereochemistry and Regiochemistry
Elimination reactions of alkyl halides can yield one or more alkenes depending on the specific regiochemical and stereochemical considerations. While the regiochemistry of the reaction governs the location of the double bond in the product, the stereochemical requirements often influence the geometry.
When a substrate with two different β hydrogens undergoes an E2 elimination, the presence of a strong base can yield two regioisomeric alkenes. The more-substituted alkene is the major product and...
When a substrate with two different β hydrogens undergoes an E2 elimination, the presence of a strong base can yield two regioisomeric alkenes. The more-substituted alkene is the major product and...
E1 Reaction: Kinetics and Mechanism
Here, in contrast to the E2 reaction mechanism, we delve into the aspects of the E1 reaction mechanism, which has two steps: rate-limiting loss of the leaving group and abstraction of the beta hydrogen by a weak base. Typically, the experimental proof for the E1 mechanism is via kinetic studies or isotope studies. While the former demonstrates the first-order kinetics—the dependence of the reaction solely on substrate concentration—the latter proves the abstraction of hydrogen only in the...
E1 Reaction: Stereochemistry and Regiochemistry
One of the critical aspects of the E1 reaction mechanism, as also observed in E2, is the regiochemistry, with multiple regioisomers obtained as products. In the example discussed, the presence of water as a weak base favors elimination over substitution to generate two alkenes. Given that alkenes’ stability increases with the number of alkyl groups across the double bond, typically, E1 reactions lead to the Zaitsev product, for this is more substituted and stable than the Hofmann product.
¹³C NMR: Distortionless Enhancement by Polarization Transfer (DEPT)
When proton-coupled carbon-13 spectra are simplified by a broadband proton decoupling technique, structural information about the coupled protons is lost. Distortionless enhancement by polarization transfer (DEPT) is a technique that provides information on the number of hydrogens attached to each carbon in a molecule. While the DEPT experiment utilizes complex pulse sequences, the pulse delay and flip angle are specifically manipulated. The resulting signals have different phases depending on...
Chemical Ionization (CI) Mass Spectrometry
The molecular ion peak of a molecule in the mass spectrum provides vital information for molecular identification. However, conventional electron impact ionization can lead to the rapid dissociation of some molecular ions before they reach the detector. A milder ionization method is required to increase the lifetime of such ionized analyte molecules. Chemical ionization (CI) is a gas-phase protonation reaction useful for mass-analyzing analyte molecules that are easily protonated to yield the...
Photochemical Electrocyclic Reactions: Stereochemistry
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
Selection Rules: Photochemical Activation


