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関連する概念動画

Relative Reactivity of Carboxylic Acid Derivatives01:13

Relative Reactivity of Carboxylic Acid Derivatives

3.9K
Carboxylic acid derivatives such as acid halides, anhydrides, esters, and amides undergo nucleophilic acyl substitution reactions with varying degrees of reactivity.
A key factor in assessing the reactivity of the acid derivatives is the basicity of the substituent or the leaving group. The lower the basicity of the leaving group, the higher the reactivity of the derivative. The basicity of the leaving group follows this order:
Halide ions < Acyloxy ions < Alkoxy ions < Amine ions
3.9K
Leaving Groups02:14

Leaving Groups

9.8K
The nature of leaving groups strongly influences the outcome of a nucleophilic substitution reaction.
In general, in a nucleophilic substitution reaction, a nucleophile displaces a functional group, called the leaving group, from the substrate to give a substituted product. A leaving group departs the substrate molecule through heterolytic cleavage, taking the pair of electrons with it to become a relatively stable weak base in the form of an anion or a neutral molecule.  
In a...
9.8K
SN2 Reaction: Stereochemistry02:23

SN2 Reaction: Stereochemistry

12.0K
In an SN2 reaction, the nucleophilic attack on the substrate and departure of the leaving group occurs simultaneously through a transition state. As the nucleophile approaches the substrate from the back-side, the configuration of the substrate carbon changes from tetrahedral to trigonal bipyramidal and then back to tetrahedral, leading to an inversion in the configuration of the product.
If the substrate is an achiral molecule at the α-carbon, the inversion of configuration is not...
12.0K
E2 Reaction: Stereochemistry and Regiochemistry02:43

E2 Reaction: Stereochemistry and Regiochemistry

13.9K
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...
13.9K
E1 Reaction: Kinetics and Mechanism02:46

E1 Reaction: Kinetics and Mechanism

18.0K
Here, in contrast to the E2 reaction mechanism, we delve into the aspects of the E1 reaction mechanism, which has two steps: rate-limiting loss of the leaving group and abstraction of the beta hydrogen by a weak base. Typically, the experimental proof for the E1 mechanism is via kinetic studies or isotope studies. While the former demonstrates the first-order kinetics—the dependence of the reaction solely on substrate concentration—the latter proves the abstraction of hydrogen only...
18.0K
Preparation and Reactions of Sulfides02:26

Preparation and Reactions of Sulfides

5.9K
Sulfides are the sulfur analog of ethers, just as thiols are the sulfur analog of alcohol. Like ethers, sulfides also consist of two hydrocarbon groups bonded to the central sulfur atom. Depending upon the type of groups present, sulfides can be symmetrical or asymmetrical. Symmetrical sulfides can be prepared via an SN2 reaction between 2 equivalents of an alkyl halide and one equivalent of sodium sulfide.
5.9K

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Regioselective O-Glycosylation of Nucleosides via the Temporary 2',3'-Diol Protection by a Boronic Ester for the Synthesis of Disaccharide Nucleosides
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Regioselective O-Glycosylation of Nucleosides via the Temporary 2',3'-Diol Protection by a Boronic Ester for the Synthesis of Disaccharide Nucleosides

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同じ残基を持つグルコシドの反応性の顕著な差異

Tianmeng Duo1, Kyle Robinson1, Ian R Greig1

  • 1Department of Chemistry, University of British Columbia , 2036 Main Mall, Vancouver, British Columbia V6T 1Z1, Canada.

Journal of the American Chemical Society
|October 17, 2017
PubMed
まとめ
この要約は機械生成です。

酵素の相互作用ではなく,固有の分子特性から生じる,酵素反応の速度の百万倍の違いを示しています. 非酵素化水解も大きな速度の変化を示した.

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Hierarchical and Programmable One-Pot Oligosaccharide Synthesis
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Hierarchical and Programmable One-Pot Oligosaccharide Synthesis

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A Straightforward Method for Glucosinolate Extraction and Analysis with High-pressure Liquid Chromatography HPLC
10:09

A Straightforward Method for Glucosinolate Extraction and Analysis with High-pressure Liquid Chromatography HPLC

Published on: March 15, 2017

26.9K

関連する実験動画

Last Updated: Feb 20, 2026

Regioselective O-Glycosylation of Nucleosides via the Temporary 2',3'-Diol Protection by a Boronic Ester for the Synthesis of Disaccharide Nucleosides
08:46

Regioselective O-Glycosylation of Nucleosides via the Temporary 2',3'-Diol Protection by a Boronic Ester for the Synthesis of Disaccharide Nucleosides

Published on: July 26, 2018

9.2K
Hierarchical and Programmable One-Pot Oligosaccharide Synthesis
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A Straightforward Method for Glucosinolate Extraction and Analysis with High-pressure Liquid Chromatography HPLC
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科学分野:

  • 生物化学
  • 酵素学
  • 有機化学

背景:

  • β-グルコシダゼは,炭水化物の代謝において重要な酵素である.
  • 基質の特異性と反応メカニズムを理解することは,酵素の機能の鍵です.
  • 同位体化合物は,非常に異なる反応性プロファイルを示すことができます.

研究 の 目的:

  • アリル2-デオキシ-2-フッ素β-グルコシドの2つの同位体の酵素性水解の速度における有意な差異を調査する.
  • 非酵素分解と分子特性を調べることで,これらの速度差の起源を明らかにする.
  • 観測された反応性に対する基底状態と移行状態の影響の寄与を決定する.

主な方法:

  • β-グルコシダースを用いた酵素水解の動力学
  • 非酵素 (自発的) 水解の研究
  • 反応メカニズムを調査するO-ラベリング実験.
  • レントゲン結晶学と量子化学計算

主要な成果:

  • 2つの同位体基板とβ-グルコシダースの反応速度の差は10倍であった.
  • 非酵素化水解は105倍速度の差を示し,固有の基板特性が原因であることを示した.
  • O-ラベリングは代替の核愛性アリル置換メカニズムを除外した.
  • X線と計算による研究は,基底状態の不安定化と移行状態の安定化が反応性の違いに等しく寄与することを明らかにした.

結論:

  • β-グルコシダース活性における劇的な速度の差異は,主に同位体基質の固有特性による.
  • 基本状態の不安定化と移行状態の安定化の両方が,反応性を調節する上で重要な,ほぼ等しい役割を果たします.
  • pKaのような単純な均衡測定は,複雑な酵素反応における脱出グループ能力を予測するのに不十分である.