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Updated: Jun 1, 2025

Development of Heterogeneous Enantioselective Catalysts using Chiral Metal-Organic Frameworks MOFs
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Development of Heterogeneous Enantioselective Catalysts using Chiral Metal-Organic Frameworks MOFs

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基酸离子对对基酸离子对催化剂激活的立体和电子作用:一项理论研究

Wijitra Meelua1,2, Tanchanok Wanjai2, Julianna Oláh3

  • 1Demonstration School, University of Phayao, Phayao 56000, Thailand.

ACS omega
|January 20, 2025
PubMed
概括

金属类催化剂的催化剂

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Catalytic Reactions at Amine-Stabilized and Ligand-Free Platinum Nanoparticles Supported on Titania During Hydrogenation of Alkenes and Aldehydes12:08

Catalytic Reactions at Amine-Stabilized and Ligand-Free Platinum Nanoparticles Supported on Titania During Hydrogenation of Alkenes and Aldehydes

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Imine Metathesis by Silica-Supported Catalysts Using the Methodology of Surface Organometallic Chemistry09:37

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Regioselectivity and Stereochemistry of Hydroboration02:36

Regioselectivity and Stereochemistry of Hydroboration

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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E1 Reaction: Stereochemistry and Regiochemistry02:43

E1 Reaction: Stereochemistry and Regiochemistry

One of the critical aspects of the E1 reaction mechanism, as also observed in E2, is the regiochemistry, with multiple regioisomers obtained as products. In the example discussed, the presence of water as a weak base favors elimination over substitution to generate two alkenes. Given that alkenes’ stability increases with the number of alkyl groups across the double bond, typically, E1 reactions lead to the Zaitsev product, for this is more substituted and stable than the Hofmann product.
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Radical Reactivity: Steric Effects01:10

Radical Reactivity: Steric Effects

The presence of electron-donating, electron-withdrawing, or conjugating groups adjacent to a radical center, imparts electronic stabilization to the radicals. Examples of such electronically-stabilized radicals are triphenylmethyl, tetramethylpiperidine‐N‐oxide, and 2,2‐diphenyl‐1‐picrylhydrazyl. These radicals are remarkably stable and are known as persistent radicals. Some of the persistent radicals can even be isolated and purified.
Along with electronic...
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E2 Reaction: Stereochemistry and Regiochemistry02:43

E2 Reaction: Stereochemistry and Regiochemistry

Elimination reactions of alkyl halides can yield one or more alkenes depending on the specific regiochemical and stereochemical considerations. While the regiochemistry of the reaction governs the location of the double bond in the product, the stereochemical requirements often influence the geometry.
When a substrate with two different β hydrogens undergoes an E2 elimination, the presence of a strong base can yield two regioisomeric alkenes. The more-substituted alkene is the major...
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Regioselectivity and Stereochemistry of Acid-Catalyzed Hydration02:34

Regioselectivity and Stereochemistry of Acid-Catalyzed Hydration

The rate of acid-catalyzed hydration of alkenes depends on the alkene's structure, as the presence of alkyl substituents at the double bond can significantly influence the rate.
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Regioselectivity of Electrophilic Additions-Peroxide Effect

In the presence of organic peroxides, the addition of hydrogen bromide to an alkene yields the isomer that is not predicted by Markovnikov’s rule. For example, the addition of hydrogen bromide to 2-methylpropene in the presence of peroxides gives 1-bromo-2-methylpropane. This addition reaction proceeds via a free radical mechanism, which reverses the regioselectivity. The free radical reaction mechanism involves three stages: initiation, propagation, and termination.
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