有没有观察到三重烯的反应?
Monica Kosa1, Miriam Karni, Yitzhak Apeloig
1The Schulich Faculty of Chemistry and The Lise Meitner-Minerva Center for Computational Quantum Chemistry, Technion-Israel Institute of Technology, Haifa 32000, Israel.
Journal of the American Chemical Society
|May 22, 2013
概括
这项研究研究了烯的反应性,发现分子内C-H键插入发生在单个状态,而不是三重状态,与之前的信念相反. 这挑战了使用C-H插入作为三重烯行为证据的使用.
科学领域:
- 有机化学 有机化学
- 计算化学的计算化学
- 反应机制 反应机制
背景情况:
- 以前的研究表明,由于分子内C-H键插入,烯1表现出三重电子状态反应性.
- 这一结论是基于实验观测和对相对单元和三元状态能量的计算预测.
研究的目的:
- 通过计算来调查分子内C-H键插入是否表明三重状态的烯反应性.
- 为了确定单体和三体烯插入反应的反应途径和能量障碍.
主要方法:
- 在B3LYP/6-31+G (d,p) 层面的密度函数理论 (DFT) 计算.
- 使用了包括SCS-MP2/cc-PVTZ在内的Ab initio方法进行比较和验证.
- 一个模型烯, (iPr3Si) ((tBuMe2Si) Si: (9),被用来表示烯1.
主要成果:
- 单体乙烯9插入C-H键,其激活屏障明显较低 (22.7 kcal/mol),相比于三体乙烯9 (34.6 kcal/mol).
- 单片插入的计算反应速度比室温三片插入快10^910^12倍.
- 这些发现表明,分子内C-H插入反应主要通过单片状态进行.
结论:
- 观察到的1和2烯的分子内C-H键插入反应发生在单个状态,而不是三重状态.
- 内分子C-H插入不是三重烯反应性的可靠指标,即使三重状态接近同能或基本状态.
- 必须继续使用替代方法来寻找真正的三重烯反应的明确证据.
相关概念视频
Preparation and Reactions of Sulfides
Sulfides are the sulfur analog of ethers, just as thiols are the sulfur analog of alcohol. Like ethers, sulfides also consist of two hydrocarbon groups bonded to the central sulfur atom. Depending upon the type of groups present, sulfides can be symmetrical or asymmetrical. Symmetrical sulfides can be prepared via an SN2 reaction between 2 equivalents of an alkyl halide and one equivalent of sodium sulfide.
Diels–Alder Reaction Forming Cyclic Products: Stereochemistry
The Diels–Alder reaction is one of the robust methods for synthesizing unsaturated six-membered rings. The reaction involves a concerted cyclic movement of six π electrons: four π electrons from the diene and two π electrons from the dienophile.
Cycloaddition Reactions: Overview
Cycloadditions are one of the most valuable and effective synthesis routes to form cyclic compounds. These are concerted pericyclic reactions between two unsaturated compounds resulting in a cyclic product with two new σ bonds formed at the expense of π bonds. The [4 + 2] cycloaddition, known as the Diels–Alder reaction, is the most common. The other example is a [2 + 2] cycloaddition.
Diels–Alder Reaction Forming Bridged Bicyclic Products: Stereochemistry
Diels–Alder reactions between cyclic dienes locked in an s-cis configuration and dienophiles yield bridged bicyclic products.
Preparation and Reactions of Thiols
Thiols are prepared using the hydrosulfide anion as a nucleophile in a nucleophilic substitution reaction with alkyl halides. For instance, bromobutane reacts with sodium hydrosulfide to give butanethiol.
[4+2] Cycloaddition of Conjugated Dienes: Diels–Alder Reaction
The Diels–Alder reaction is an example of a thermal pericyclic reaction between a conjugated diene and an alkene or alkyne, commonly referred to as a dienophile. The reaction involves a concerted movement of six π electrons, four from the diene and two from the dienophile, forming an unsaturated six-membered ring. As a result, these reactions are classified as [4+2] cycloadditions.

