由二甲 (hexamethyldisilazide) 介导的乙烯溶解的动力学和机制
Xuyang He1, J Jacob Morris, Bruce C Noll
1Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556-5670, USA.
Journal of the American Chemical Society
|October 13, 2006
概括
二 ((hexamethyldisilazide) 与 propiophenone 反应形成乙烯酸盐. 一个关键的中间体经历了分子内质子转移,在速度限制步骤中观察到道化.
科学领域:
- 有机金属化学 有机金属化学
- 反应机制研究 反应机制研究
- 光谱和晶体分析分析.
背景情况:
- 在有机合成中,了解醇酶化的机制至关重要.
- 胺复合物是去反应的有效基.
- 在介导反应中中间体的作用需要详细的研究.
研究的目的:
- 为了阐明由二 (hexamethyldisilazide) 介导的烯乙烯化机制.
- 描述反应中间体并确定速度限制步骤.
- 研究同位素替代对反应动力学的影响.
主要方法:
- 和二 (hexamethyldisilazide) 在烯中对烯的反应.
- 使用溶液NMR (1H,扩散顺序的NMR),紫外线光谱学,红外光谱学和X射线晶体学进行表征.
- 动力学研究,包括测量同位素效应和计算研究.
主要成果:
- 形成一种 (E) - 和 (Z) - 乙烯酸盐的混合物, [(HMDS) ((2) Mg ((2) mu-HMDS) {mu-OC ((Ph) = CHCH ((3))) ].
- 一个三坐标单体中间体的识别和表征, (HMDS) 2Mg{eta}1−O=CPhCH2CH3}.
- 被确定为速度限制步骤的质子转移,具有显著的初级动同位素效应 (k ⋅ H / k ⋅ D) = 18.9) 和道道的证据.
结论:
- 乙醇化通过单个中间体进行,涉及分子内质子转移.
- 量子力学道在环境温度下对反应速率做出了重大贡献.
- 这项研究提供了详细的机理洞察力,了解胺促进的胺乙烯醇化.
相关概念视频
04:01Factors Affecting Solubility
Compared with pure water, the solubility of an ionic compound is less in aqueous solutions containing a common ion (one also produced by dissolution of the ionic compound). This is an example of a phenomenon known as the common ion effect, which is a consequence of the law of mass action that may be explained using Le Chȃtelier’s principle. Consider the dissolution of silver iodide:
02:30Stability of Substituted Cyclohexanes
This lesson discusses the stability of substituted cyclohexanes with a focus on energies of various conformers and the effect of 1,3-diaxial interactions.
The two chair conformations of cyclohexanes undergo rapid interconversion at room temperature. Both forms have identical energies and stabilities, each comprising equal amounts of the equilibrium mixture. Replacing a hydrogen atom with a functional group makes the two conformations energetically non-equivalent.
For example, in...
The two chair conformations of cyclohexanes undergo rapid interconversion at room temperature. Both forms have identical energies and stabilities, each comprising equal amounts of the equilibrium mixture. Replacing a hydrogen atom with a functional group makes the two conformations energetically non-equivalent.
For example, in...
02:37Disubstituted Cyclohexanes: cis-trans Isomerism
Depending upon the different spatial orientation of the substituents, the disubstituted cycloalkanes exhibit two types of stereoisomers. The cis isomers have the substituents on the same side of the ring, whereas the trans isomers have the substituents on the opposite sides. These stereoisomers exhibit different physical properties and cannot be interconverted without breaking the carbon-carbon bonds.
In cyclohexane, the substituents can occupy different positions generating distinct isomers.
In cyclohexane, the substituents can occupy different positions generating distinct isomers.
02:45E2 Reaction: Kinetics and Mechanism
SN2 substitutions and E2 eliminations of alkyl halides proceed via a concerted pathway. While the nucleophile attacks the alpha carbon in SN2 reactions, it functions as a strong base and abstracts a beta hydrogen in the E2 mechanism. The rate-limiting transition state in E2 elimination reactions is characterized by partially broken carbon–hydrogen and carbon–halogen bonds and a partially formed pi bond between the alpha and beta carbons. The beta hydrogen and halide are eliminated...
00:57Cationic Chain-Growth Polymerization: Mechanism
The cationic polymerization mechanism consists of three steps: initiation, propagation, and termination. In the initiation step of the polymerization process, the π bond of a monomer gets protonated by the Lewis acid catalyst, which is formed from boron trifluoride and water. The protonation of the π bond generates a carbocation stabilized by the electron‐donating group. In the propagation step, the π bond of the second monomer acts as a nucleophile and attacks the generated carbocation,...
01:05Mechanism of Ciliary Motion
The ciliary structures were first seen in 1647 by Antonie Leeuwenhoek while observing the protozoans. In lower organisms, these appendages are responsible for cell movement, while in higher organisms, these appendages help in the movement of the extracellular fluids within the body cavities.
The cilia are made up of microtubules in a 9+2 arrangement, with nine microtubule doublet ring bundles, surrounding a pair of central singlet microtubule bundles. The doublet microtubule bundles are...
The cilia are made up of microtubules in a 9+2 arrangement, with nine microtubule doublet ring bundles, surrounding a pair of central singlet microtubule bundles. The doublet microtubule bundles are...