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Hydroboration-Oxidation of Alkenes03:08

Hydroboration-Oxidation of Alkenes

8.2K
In addition to the oxymercuration–demercuration method, which converts the alkenes to alcohols with Markovnikov orientation, a complementary hydroboration-oxidation method yields the anti-Markovnikov product. The hydroboration reaction, discovered in 1959 by H.C. Brown, involves the addition of a B–H bond of borane to an alkene giving an organoborane intermediate. The oxidation of this intermediate with basic hydrogen peroxide forms an alcohol.
8.2K
Regioselectivity and Stereochemistry of Hydroboration02:36

Regioselectivity and Stereochemistry of Hydroboration

8.1K
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...
8.1K
Reduction of Alkenes: Catalytic Hydrogenation02:13

Reduction of Alkenes: Catalytic Hydrogenation

12.0K
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...
12.0K
Reduction of Alkenes: Asymmetric Catalytic Hydrogenation02:17

Reduction of Alkenes: Asymmetric Catalytic Hydrogenation

3.3K
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...
3.3K
Alkynes to Aldehydes and Ketones: Hydroboration-Oxidation02:47

Alkynes to Aldehydes and Ketones: Hydroboration-Oxidation

18.1K
Introduction
One of the convenient methods for the preparation of aldehydes and ketones is via hydration of alkynes. Hydroboration-oxidation of alkynes is an indirect hydration reaction in which an alkyne is treated with borane followed by oxidation with alkaline peroxide to form an enol that rapidly converts into an aldehyde or a ketone. Terminal alkynes form aldehydes, whereas internal alkynes give ketones as the final product.
18.1K
Free Energy Changes for Nonstandard States03:25

Free Energy Changes for Nonstandard States

11.4K
The free energy change for a process taking place with reactants and products present under nonstandard conditions (pressures other than 1 bar; concentrations other than 1 M) is related to the standard free energy change according to this equation:
 
where R is the gas constant (8.314 J/K·mol), T is the absolute temperature in kelvin, and Q is the reaction quotient. This equation may be used to predict the spontaneity of a process under any given set of conditions.
Reaction Quotient...
11.4K

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Updated: Jul 5, 2025

Synthesis of Metal Nanoparticles Supported on Carbon Nanotube with Doped Co and N Atoms and its Catalytic Applications in Hydrogen Production
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选择性和高效的H2进化在NH3BH3水解下在零度以下的温度下.

Qing Zhang1, Chen Fang1, Yanlan Wang2

  • 1Engineering Research Center of Eco-Environment in Three Gorges Reservoir Region of Ministry of Education, College of Materials and Chemical Engineering, China Three Gorges University, Yichang, Hubei 443002, P.R. China.

iScience
|January 23, 2024
PubMed
概括

开发新的燃料催化剂对于寒冷的气候至关重要. 这项研究提出了新的金属/碳 (M-Pt/C) 纳米复合材料,用于在零度以下的温度下从氨 (NH3BH3) 水解中有效地产生气 (H2).

关键词:
应用科学 应用科学电化学 电化学 电化学

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科学领域:

  • 材料科学 材料科学 材料科学
  • 催化剂是一种催化剂.
  • 电化学 电化学 电化学

背景情况:

  • 零度以下的温度对化学反应,特别是燃料的产生带来了挑战.
  • 需要高效的催化系统来通过冷环境中的氨 (NH3BH3) 水解来实现的进化.
  • 开发方法来克服水结问题在零度以下的温度对于实际应用至关重要.

研究的目的:

  • 合成新的M-Pt/C纳米复合物 (M=Pd,Rh,Ru,Ni,Cu,Fe) 进行高效的进化.
  • 研究这些纳米复合材料在零度以下温度NH3BH3水解中的催化性能.
  • 探索这些催化剂在安全生产和在有机化学中的现场化中的应用.

主要方法:

  • 通过将商业Pt/C与各种金属合金,轻松无表面活性剂合成M-Pt/C纳米复合材料.
  • 在低至-15°C的温度下,测试NH3BH3在盐溶液中的水解中的H2演变的催化活性.
  • 使用Pd-Pt/C进行有机化合物的现场化降解.

主要成果:

  • 成功合成了M-Pt/C纳米复合材料,显示出H2进化的高效率.
  • 在零度以下温度 (-15°C) 的盐溶液中表现出有效的催化性能.
  • 展示了Pd-Pt/C在安全,按需气生成和有机合成方面的实用性.

结论:

  • 在零度以下的温度下,M-Pt/C纳米复合材料是NH3BH3水解的有效催化剂.
  • 开发的催化系统为在寒冷条件下生产气和化提供了可行的解决方案.
  • 这种方法为有机化学中传统的气瓶提供了更安全的替代方案.