在原型过渡金属-碳化合物反应中C-C和C-H插入之间的竞争
Ryan Z Hinrichs1, Jonathan J Schroden, H Floyd Davis
1Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14583, USA.
Journal of the American Chemical Society
|January 23, 2003
概括
在循环反应中,过渡金属原子在C-C和C-H键插入之间竞争. 计算和实验表明,C-C插入在较低的能量时更受欢迎,而C-H插入在更高的能量时占主导地位.
科学领域:
- 有机金属化学 有机金属化学
- 计算化学是一种计算化学.
- 反应机制的反应机制
背景情况:
- 过渡金属化学涉及复杂的反应途径.
- 了解插入反应是催化作用的关键.
- 环和为研究C-C和C-H键激活提供了模型系统.
研究的目的:
- 为了研究C-C和C-H键插入反应之间的竞争.
- 确定控制这些插入路径的能量因素.
- 将理论预测与实验观测进行比较.
主要方法:
- 使用ab initio计算来预测潜在的能源障碍.
- 研究了与环烯和烯的过渡金属反应模型.
- 测量了产品分支比率,以验证理论预测.
主要成果:
- 将中性过渡金属原子 (Y,Zr,Nb,Mo) 插入环烯的C-C键中,得到了MCH2 + C2H4.4.
- 将C-H插入环烯中产生了MC3H4 + H2.
- 实验性产品分布与计算的能源障碍保持一致.
结论:
- C-C 和 C-H 插入之间的竞争由总能量控制.
- Ab initio计算准确地预测了这些反应的相对潜在能量障碍.
- 实验结果验证了在循环烯中插入过渡金属的理论能量场景.
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.
Properties of Organometallic Compounds
Organometallic compounds are compounds that contain a carbon–metal bond. Carbon belongs to an organyl group like alkyl, aryl, allyl, or benzyl groups. The metal can be from Group I or Group II of the periodic table, a transition metal, or a semimetal.
C–C Bond Formation: Aldol Condensation Overview
Aldol condensation is an important route in synthetic organic chemistry used to generate a new carbon–carbon bond under basic or acidic conditions. The aldol condensation reaction presented in Figure 1 constitutes an aldol addition reaction followed by the dehydration process.
C–C Bond Cleavage: Retro-Aldol Reaction
The reverse of the aldol addition reaction is called the retro-aldol reaction. Here, the carbon–carbon bond in the aldol product is cleaved under acidic or basic conditions to form two molecules of carbonyl compounds. The mechanism of the reaction consists of three steps.
In the first step, as depicted in Figure 1, the base deprotonates the β-hydroxy ketone at the hydroxyl group to form an alkoxide ion.
In the first step, as depicted in Figure 1, the base deprotonates the β-hydroxy ketone at the hydroxyl group to form an alkoxide ion.
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