相关实验视频
Updated: Jun 12, 2025

11:51
Facile Preparation of 4-Substituted Quinazoline Derivatives
Published on: February 15, 2016
11.9K
在隔离的林中非辐射失活.
Floriane Sturm1, Christoph Herok1, Ingo Fischer1
1Institute of Physical and Theoretical Chemistry, University of Würzburg, Am Hubland, D-97074 Würzburg, Germany.
The journal of physical chemistry. A
|September 20, 2024
概括
奇诺林的光物理 奇诺林的光物理
科学领域:
- 摄影化学的使用.
- 分子光谱学 分子光谱学
- 物理化学 物理化学
背景情况:
- 多环芳含碳化合物 (PANHs) 在大气和燃烧化学中至关重要.
- 了解像诺林这样的PANHs的兴奋状态动态对于预测它们的环境命运和反应性至关重要.
- 之前的研究已经探讨了氨酸的光物理,但详细的皮秒动力学仍然不太了解.
研究的目的:
- 为了研究氨酸S2 1(ππ*) 状态的兴奋状态光物理.
- 使用先进的光谱技术来确定S2状态的失活路径和寿命.
- 阐明内部转换和系统间交叉在素放松动态中的作用.
主要方法:
- 皮秒时间分辨率的光电子成像光谱学.
- 多光子电离谱在自由喷气膨胀中的多光子电离谱.
- 在波长范围 (312.2279.7 nm) 上激发诺林的S2状态.
主要成果:
- 确定了S2的起源在~32,200 cm-1与相关的振动结构.
- 时间分辨率图像显示了一个短寿命组件 (ps寿命) 和一个具有偏移的长寿命组件.
- S2 状态的寿命从原始状态的 45 ps 减少到更高能量时的 11 ps,这表明快速停用.
结论:
- 短暂的组成部分归因于S2 1(ππ*) 状态.
- 具有偏移的长寿命组件从三元组 (T1状态) 分配给来自三元组的电离.
- 禁用可能通过内部转换到S1 1 ((nπ*) 状态进行,然后通过跨系统交叉到三重状态.
相关概念视频
Deactivation Processes: Jablonski Diagram
605
Luminescence, the emission of light by a substance that has absorbed energy, is a process that involves the interaction of molecules with light. The energy-level diagram, or Jablonski diagram, is a graphical representation of these interactions, illustrating the various states and transitions a molecule can undergo. In a typical Jablonski diagram, the lowest horizontal line represents the ground-state energy of the molecule, which is usually a singlet state. This state represents the energies...
605
meta-Directing Deactivators: –NO2, –CN, –CHO, –⁠CO2R, –COR, –CO2H
5.5K
All meta-directing substituents are deactivating groups. These substituents withdraw electrons from the aromatic ring, making the ring less reactive toward electrophilic substitution. For example, the nitration of nitrobenzene is 100,000 times slower than that of benzene because of the deactivating effect of the nitro group. The first step in an electrophilic aromatic substitution is the addition of an electrophile to form a resonance-stabilized carbocation. The energy diagrams for...
5.5K
Oxidation of Phenols to Quinones
2.9K
In the presence of oxidizing agents, phenols are oxidized to quinones. Quinones can be easily reduced back to phenols using mild reducing agents. The electron-donating hydroxyl group enhances the reactivity of the aromatic ring, enabling oxidation of the ring even in the absence of an α hydrogen.
o-hydroxy phenols are oxidized to o-quinones and p-hydroxy phenols to p-quinones. Such redox reactions involve the transfer of two electrons and two protons. The reversible redox...
o-hydroxy phenols are oxidized to o-quinones and p-hydroxy phenols to p-quinones. Such redox reactions involve the transfer of two electrons and two protons. The reversible redox...
2.9K
ortho–para-Directing Deactivators: Halogens
5.5K
Halogens are ortho–para directors. They are more electronegative than carbon. Therefore, as ring substituents, they can withdraw electrons through the inductive effect and deactivate the aromatic ring towards electrophilic substitution. Halogens also have an electron-donating resonance effect on the ring, which influences the orientation of the incoming electrophile. If an electrophile attacks at the ortho or the para position, the halogen donates electrons and stabilizes the intermediate...
5.5K
The Electron Transport Chain
16.3K
The electron transport chain or oxidative phosphorylation is an exothermic process in which free energy released during electron transfer reactions is coupled to ATP synthesis. This process is a significant source of energy in aerobic cells, and therefore inhibitors of the electron transport chain can be detrimental to the cell's metabolic processes.
Inhibitors of the electron transport chain
Rotenone, a widely used pesticide, prevents electron transfer from Fe-S cluster to ubiquinone or Q...
Inhibitors of the electron transport chain
Rotenone, a widely used pesticide, prevents electron transfer from Fe-S cluster to ubiquinone or Q...
16.3K
Radical Chain-Growth Polymerization: Overview
2.4K
Chain-growth or addition polymerization is successive addition reactions of monomers with a polymer chain. In radical chain-growth polymerization, the reaction proceeds via a free-radical intermediate. The free radical is formed from radical initiators, which spontaneously generate free radicals by homolytic fission. Organic peroxides (such as dibenzoyl peroxide, as shown in Figure 1) or azo compounds are popular radical initiators. A low concentration ratio of radical initiator to monomer is...
2.4K

