在SmI2的反应中的催化Ni (II):基于Sm (II) 或Ni (0) 的化学反应?
Kimberly A Choquette1, Dhandapani V Sadasivam, Robert A Flowers
1Department of Chemistry, Lehigh University, Bethlehem, Pennsylvania 18015, USA.
Journal of the American Chemical Society
|May 31, 2011
概括
催化 (II) 盐通过降解为 (II) 增强萨马巴比埃反应. 这种(0) 然后通过氧化添加驱动反应,揭示了这种过程背后的已知化学成分.
科学领域:
- 有机金属化学 有机金属化学
- 催化剂是一种催化剂.
- 反应机制 反应机制
背景情况:
- 二氧化 (SmI2) 是一种用于有机合成的多功能还原剂.
- 已知有大量的Ni (II) 盐的催化剂可增强SmI2介导反应中的反应性和选择性.
- 在SmI2反应中Ni (II) 催化作用的机理基础仍然不太清楚.
研究的目的:
- 阐明催化Ni (II) 在萨玛巴比耶反应中的机械作用.
- 在反应条件下研究Ni(II) 与SmI2之间的相互作用.
- 为了确定活性催化物种和反应途径.
主要方法:
- 谱学研究 (例如,UV-Vis,EPR) 以确定中间体.
- 动力测量以确定反应速度和顺序.
- 同位素标记研究,以追踪反应途径.
主要成果:
- 巴比尔与催化Ni(II) 的反应是由Ni(II) 减少为Ni(0) 在速度限制的步骤中驱动的.
- 生成的Ni(0) 经过氧化添加到化键中,形成一个有机物种.
- 观察到同时形成的合性Ni(0) 是一种非生产性的副作用过程.
结论:
- 在SmI2/Ni(II) 巴比埃反应中增强的反应性和选择性主要是由于已建立的Ni(0) 化学.
- 反应机制涉及Ni(II) 降解为Ni(0),其次是氧化添加,而不是独特的SmI2特性.
- 这项研究将催化效应重新归因于已知的介导过程.
相关概念视频
Catalysis
The presence of a catalyst affects the rate of a chemical reaction. A catalyst is a substance that can increase the reaction rate without being consumed during the process. A basic comprehension of a catalysts’ role during chemical reactions can be understood from the concept of reaction mechanisms and energy diagrams.
Catalysis
Catalysis influences the rate of chemical reactions by providing an alternative reaction pathway with lower activation energy. A catalyst speeds up a reaction, but it is not consumed during the process. The fundamental principle of catalysis is the ability of a catalyst to alter the reaction mechanism, often introducing a more efficient pathway than the uncatalyzed process.In a catalyzed reaction, the catalyst participates directly in the reaction mechanism. It interacts with reactants to form...
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.
SN2 Reaction: Kinetics
Kinetic Studies and Significance
In a chemical reaction, a relationship exists between the concentration of reactants and the rate at which the reaction proceeds. The study to measure this relationship is known as the kinetics of a chemical reaction. Kinetic studies are used to deduce the rate law of a chemical reaction, which provides information about the species involved during the transition state of the rate-determining step. Thus, kinetic studies help to derive the mechanism of a reaction.
In a chemical reaction, a relationship exists between the concentration of reactants and the rate at which the reaction proceeds. The study to measure this relationship is known as the kinetics of a chemical reaction. Kinetic studies are used to deduce the rate law of a chemical reaction, which provides information about the species involved during the transition state of the rate-determining step. Thus, kinetic studies help to derive the mechanism of a reaction.
Alkenes via Reductive Coupling of Aldehydes or Ketones: McMurry Reaction
The radical dimerization of ketones or aldehydes gives vicinal diols through a pinacol coupling reaction. However, the behavior of titanium metals used for the reaction as a source of electrons is unusual. When the reaction is carried out in the presence of titanium, diols can be isolated at low temperatures. Else titanium further reacts with diols, forming alkenes through the McMurry reaction.
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.


