![[DPEPhosbcpCu]PF6: A General and Broadly Applicable Copper-Based Photoredox Catalyst](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2FCDNSource%2Fteasers%2F59739.jpg&w=3840&q=50)
基于轨迹的时间解析机制,用于从环丁 Mo/W 化复合物中减少的消除
Joshua I Wheeler1, Anthony J Schaefer1, Daniel H Ess1
1Department of Chemistry and Biochemistry, Brigham Young University, Provo, Utah 84604, United States.
The journal of physical chemistry. A
|June 5, 2024
概括
直接动力学模拟揭示了有机金属反应中的非统计路径. 动态效应,不仅仅是能量景观,控制反应机制,并解释动态同位素效应 (KIEs).
科学领域:
- 有机金属化学 有机金属化学
- 计算化学的计算化学
- 反应动力学 反应动力学
背景情况:
- 潜在能景观和统计速率理论传统上用于理解有机金属反应机制.
- 这些方法往往忽略了原子和分子运动对反应路径的影响.
- 动态同位素效应 (KIE) 测量对于解释反应机制至关重要.
研究的目的:
- 通过直接动力学模拟来研究减排反应.
- 在有机金属反应中识别非统计中间体和动态控制路径.
- 阐明实验观察到的动态同位素效应 (KIEs) 背后的机制.
主要方法:
- 对气相和明确溶剂反应进行了准经典的直接动力学模拟.
- 模拟研究了从Mo和W桥接环丁烯化复合物中二的降解性消除.
- 经典分子动力学模拟估计了溶剂中的中间体的寿命.
主要成果:
- 直接动力学揭示了绕过传统的σ-和π-协调中间体的路径.
- 确定了一条直接通往旋转翻转溶剂中的中间体的途径,在几百个femtosecond内形成.
- 溶剂中的中间体的寿命估计为200-400比秒.
- 对Mo和W过渡状态的KIE计算值显示了Mo的正常值和W的小反向值.
结论:
- 反应机制受到非统计动态和溶剂效应的显著影响,而不仅仅是能源景观.
- 溶剂中的中间体可能在对 (W) 观察到的逆KIE中发挥作用.
- 动态模拟提供了更准确的机械图像,将理论计算与KIE实验数据相协调.
相关概念视频
01:18Benzene to 1,4-Cyclohexadiene: Birch Reduction Mechanism
2.2K
Birch reduction uses solvated electrons as reducing agents. The reaction converts benzene to 1,4-cyclohexadiene. The reaction proceeds by the transfer of a single electron to the ring to form a benzene radical anion. This anion is highly basic—it abstracts a proton from the alcohol to form a cyclohexadienyl radical. Another single electron transfer gives the cyclohexadienyl anion. A proton transfer from the alcohol forms 1,4-cyclohexadiene. Since this reduction occurs via radical anion...
2.2K
01:28Reduction of Benzene to Cyclohexane: Catalytic Hydrogenation
4.5K
Unlike the easy catalytic hydrogenation of an alkene double bond, hydrogenation of a benzene double bond under similar reaction conditions does not take place easily. For example, in the reduction of stilbene, the benzene ring remains unaffected while the alkene bond gets reduced. Hydrogenation of an alkene double bond is exothermic and a favorable process. In contrast, to hydrogenate the first unsaturated bond of benzene, an energy input is needed; that is, the process is endothermic. This is...
4.5K
01:11Nucleophilic Aromatic Substitution: Elimination–Addition
4.0K
Simple aryl halides do not react with nucleophiles. However, nucleophilic aromatic substitutions can be forced under certain conditions, such as high temperatures or strong bases. The mechanism of substitution under such conditions involves the highly unstable and reactive benzyne intermediate. Benzyne contains equivalent carbon centers at both ends of the triple bond, each of which is equally susceptible to nucleophilic attack. This 50–50 distribution of products is...
4.0K
00:59Reactions at the Benzylic Position: Oxidation and Reduction
3.6K
The benzylic position describes the position of a carbon atom attached directly to a benzene ring. Benzene by itself does not undergo oxidation. In contrast, the benzylic carbon is quite reactive in the presence of strong oxidizing agents such as KMnO4 or H2CrO4. Therefore, alkylbenzenes are readily oxidized to benzoic acid, irrespective of the type of alkyl groups.
3.6K
01:26Thermal and Photochemical Electrocyclic Reactions: Overview
2.3K
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.
2.3K
01:26Photochemical Electrocyclic Reactions: Stereochemistry
1.8K
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
1.8K