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相关概念视频

Reduction of Alkenes: Asymmetric Catalytic Hydrogenation02:17

Reduction of Alkenes: Asymmetric Catalytic Hydrogenation

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Catalytic hydrogenation of alkenes is a transition-metal catalyzed reduction of the double bond using molecular hydrogen to give alkanes. The mode of hydrogen addition follows syn stereochemistry.
The metal catalyst used can be either heterogeneous or homogeneous. When hydrogenation of an alkene generates a chiral center, a pair of enantiomeric products is expected to form. However, an enantiomeric excess of one of the products can be facilitated using an enantioselective reaction or an...
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Reduction of Alkynes to cis-Alkenes: Catalytic Hydrogenation02:24

Reduction of Alkynes to cis-Alkenes: Catalytic Hydrogenation

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Introduction
Like alkenes, alkynes can be reduced to alkanes in the presence of transition metal catalysts such as Pt, Pd, or Ni. The reaction involves two sequential syn additions of hydrogen via a cis-alkene intermediate.
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Reduction of Alkenes: Catalytic Hydrogenation02:13

Reduction of Alkenes: Catalytic Hydrogenation

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Alkenes undergo reduction by the addition of molecular hydrogen to give alkanes. Because the process generally occurs in the presence of a transition-metal catalyst, the reaction is called catalytic hydrogenation.
Metals like palladium, platinum, and nickel are commonly used in their solid forms — fine powder on an inert surface. As these catalysts remain insoluble in the reaction mixture, they are referred to as heterogeneous catalysts.
The hydrogenation process takes place on the...
11.6K
Olefin Metathesis Polymerization: Overview01:13

Olefin Metathesis Polymerization: Overview

2.0K
Recently, the development of olefin metathesis polymerization advanced the field of polymer synthesis. Simply put, the reorganization of substituents on their double bonds between two olefins in the presence of a catalyst is known as the olefin metathesis reaction. The use of metathesis reaction for polymer synthesis is called olefin metathesis polymerization.
Ruthenium-based Grubbs catalyst is the most commonly used catalyst for olefin metathesis polymerization. Grubbs catalyst consists...
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Regioselectivity and Stereochemistry of Hydroboration02:36

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A significant aspect of hydroboration–oxidation is the regio- and stereochemical outcome of the reaction.
Hydroboration proceeds in a concerted fashion with the attack of borane on the π bond, giving a cyclic four-centered transition state. The –BH2 group is bonded to the less substituted carbon and –H to the more substituted carbon. The concerted nature requires the simultaneous addition of –H and –BH2 across the same face of the alkene giving syn...
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Electrophilic Addition of HX to 1,3-Butadiene: Thermodynamic vs Kinetic Control01:23

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2.3K
The addition of a hydrogen halide to 1,3-butadiene gives a mixture of 1,2- and 1,4-adducts. Since more substituted alkenes are more stable, the 1,4-adduct is expected to be the major product. However, the product distribution is strongly influenced by temperature; low temperature favors the 1,2-adduct, whereas the 1,4-adduct is predominant at high temperature.
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使用隔离的双金属-位控制乙烯化反应途径

Yong Yuan1, Tianyou Mou1, Sooyeon Hwang2

  • 1Chemistry Division, Brookhaven National Laboratory, Upton, New York 11973, United States.

Journal of the American Chemical Society
|March 29, 2025
PubMed
概括

这项研究在ZSM-5焦岩中引入了孤立的-位,以有效地化乙烯. 最佳的-协调 (CN 3) 显著提高了C3氧化物生产的催化速率和选择性.

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科学领域:

  • 不同质的催化
  • 材料科学
  • 化学工程

背景情况:

  • 在生产C3氧化物方面,乙烯水合是至关重要的.
  • 开发高效的无配体异质催化剂仍然是一个挑战.
  • 现有的催化剂通常具有较低的活性和选择性.

研究的目的:

  • 在ZSM-5中设计孤立的- (Rh-Co) 位点.
  • 增强乙烯水合基的催化活性和选择性.
  • 在反应条件下保持催化剂的稳定性.

主要方法:

  • 用不同的Co/Al比率合成Co-ZSM-5.
  • 引入Rh以形成可调节的协调号码 (CN) 的孤立Rh-Co集群.
  • 在现场表征和密度函数理论 (DFT) 的计算.

主要成果:

  • 调整Co/Al比率控制了Co物种的大小和随后的Rh-Co协调.
  • 一个孤立的Rh1Co3位点 (Rh-Co CN为3) 呈现出最高的化率.
  • 最佳协调增强了对反应中间体的结合,提高了性能.

结论:

  • 在ZSM-5中隔离的Rh-Co位点是有效的无配体乙烯水合基.
  • 通过二次金属 (Co) 的协调调节是控制单个Rh原子催化剂通路的关键.
  • 这种方法为设计先进的异质催化剂提供了一个有前途的策略.