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Oxidation of Alkenes: Syn Dihydroxylation with Osmium Tetraoxide02:44

Oxidation of Alkenes: Syn Dihydroxylation with Osmium Tetraoxide

13.2K
Alkenes are converted to 1,2-diols or glycols through a process called dihydroxylation. It involves the addition of two hydroxyl groups across the double bond with two different stereochemical approaches, namely anti and syn. Dihydroxylation using osmium tetroxide progresses with syn stereochemistry.
13.2K
Preparation of Epoxides03:00

Preparation of Epoxides

9.6K
Overview
Epoxides result from alkene oxidation, which can be achieved by a) air, b) peroxy acids, c) hypochlorous acids, and d) halohydrin cyclization.
Epoxidation with Peroxy Acids
Epoxidation of alkenes via oxidation with peroxy acids involves the conversion of a carbon–carbon double bond to an epoxide using the oxidizing agent meta-chloroperoxybenzoic acid, commonly known as MCPBA. Since the O–O bond of peroxy acids is very weak, the addition of electrophilic oxygen of peroxy acids to...
9.6K
Acid-Catalyzed Ring-Opening of Epoxides02:24

Acid-Catalyzed Ring-Opening of Epoxides

9.3K
Epoxides that are three-membered ring systems are more reactive than other cyclic and acyclic ethers. The high reactivity of epoxides originates from the strain present in the ring. This ring strain acts as a driving force for epoxides to undergo ring-opening reactions either with halogen acids or weak nucleophiles in the presence of mild acid. The acid catalyst converts the epoxide oxygen, a poor leaving group, into an oxonium ion, a better leaving group, making the reaction feasible. The...
9.3K
Sharpless Epoxidation02:57

Sharpless Epoxidation

5.3K
The conversion of allylic alcohols into epoxides using the chiral catalyst was discovered by K. Barry Sharpless and is known as Sharpless epoxidation. The use of a chiral catalyst enables the formation of one enantiomer of the product in excess. This chiral catalyst is mainly a chiral complex of titanium tetraisopropoxide and tartrate ester (specific stereoisomer). The stereoisomer used in the chiral catalyst dictates the formation of the enantiomer of the product. In other words, the use of...
5.3K
Olefin Metathesis Polymerization: Overview01:13

Olefin Metathesis Polymerization: Overview

2.7K
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 of a...
2.7K
Oxidative Cleavage of Alkenes: Ozonolysis01:46

Oxidative Cleavage of Alkenes: Ozonolysis

13.3K
In ozonolysis, ozone is used to cleave a carbon–carbon double bond to form aldehydes and ketones, or carboxylic acids, depending on the work-up.
Ozone is a symmetrical bent molecule stabilized by a resonance structure.
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Updated: Mar 3, 2026

Development of Heterogeneous Enantioselective Catalysts using Chiral Metal-Organic Frameworks MOFs
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グループIVとVのフレームワークで置換されたゼオライト触媒に対するオレフィンエポキシデーションの周期的な傾向:動力学およびスペクトル学の研究

Daniel T Bregante1, David W Flaherty1

  • 1Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States.

Journal of the American Chemical Society
|April 29, 2017
PubMed
まとめ
この要約は機械生成です。

グループIVとVのゼオライトのより強いルイス酸部位は,過酸化水素 (H2O2) をより効果的に活性化することによって,オレフィンエポキシデーションの選択性と速度を高めます. この研究は,エポキシデーション性能の改善のための触媒設計を明確にします.

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Tuning the Acidity of Pt/ CNTs Catalysts for Hydrodeoxygenation of Diphenyl Ether
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Imine Metathesis by Silica-Supported Catalysts Using the Methodology of Surface Organometallic Chemistry
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科学分野:

  • 異質な触媒
  • 材料科学
  • 物理化学

背景:

  • フレームに置き換えられたゼオライトとグループIVおよびVの移行金属は,オレフィンエポキシデーションの確立された触媒である.
  • その選択性と反応速度を制御する正確な構造-特性関係は,まだ十分に理解されていません.

研究 の 目的:

  • オレフィンエポキシデーションのためのグループIVとVのゼオライト触媒の選択性と周回率を決定する基本的な性質を明らかにする.
  • エポキシデーションと過酸化水素分解の経路に関与する活性酸素種と反応機構を特定する.

主な方法:

  • 動力学,熱力学,およびin situ UV対光譜測定の組み合わせ
  • 反応中間物質 (水酸化物,過酸化物,超酸化物) の分析
  • Z-スティルベンのエポキシデーション産物の同位体分布を含む製品分析

主要な成果:

  • より強いルイス酸性は,より高いエポキシデーション選択性と速度,およびエポキシデーションとH2O2分解の両方のより低いエンタルピックバリアと相関する.
  • エポキシデーションに有効な種は,それぞれグループIVおよびVの金属に対してM-OOH/-O2−およびM-O2−として識別された.
  • エポキシデーションとH2O2分解は,同様のEley-Ridealメカニズムに従います. 選択性は,ルイス酸強度とリガンドから金属への電荷移転 (LMCT) エネルギーに指数関数的に依存しています.

結論:

  • より多くの電子性活性酸素種 (より低いLMCTエネルギー) は,電子豊富なオレフィンのエポキシデーションのためのより高い反応性と選択性につながる.
  • Tiベースの触媒は,最適な電子特性により,初期の移行金属の中で最も高い活性を示します.
  • ルイス酸の強度を増やすことは,H2O2分解を最小限に抑えながら,エポキシデーションの反応性と選択性を同時に高めるための重要な戦略です.