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関連する概念動画

Solvating Effects02:12

Solvating Effects

An understanding of the solvating effect helps rationalize the relation between solvation and acidity of the compound. In addition, this also explains the relative stability of conjugate bases for compounds with different pKa values. This lesson details, in-depth, the principle of solvating effects. The strength of an acid and the stability of its corresponding conjugate base are determined using pKa values. This observed relationship is a consequence of solvation, which is the interaction...
Predicting Products: SN1 vs. SN202:27

Predicting Products: SN1 vs. SN2

Nucleophilic substitution reactions of alkyl halides can proceed via an SN1 or an SN2 mechanism. While in SN2 reactions, the nucleophile attacks the substrate simultaneously as the leaving group departs, in SN1 reactions, the substrate first dissociates to give the carbocation intermediate. Various factors such as the structure of the substrate, the strength of the nucleophile, and the nature of the solvent promote one mechanism over the other.
With increased substitution on the alkyl halide,...
SN2 Reaction: Stereochemistry02:23

SN2 Reaction: Stereochemistry

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 observed.
Ionic Strength: Effects on Chemical Equilibria01:19

Ionic Strength: Effects on Chemical Equilibria

The addition of an inert ionic compound increases the solubility of a sparingly soluble salt. For example, adding potassium nitrate to a saturated solution of calcium sulfate significantly enhances the solubility of calcium sulfate. Le Châtelier's principle cannot predict this shift in the equilibrium. Instead, this could be explained in terms of changes in the effective concentration of the ions in solution in the presence of added inert salt.
In this solution, the primary cation—the calcium...
SN1 Reaction: Stereochemistry02:15

SN1 Reaction: Stereochemistry

This lesson provides an in-depth discussion of the stereochemical outcomes in an SN1 reaction.
In the first step of an SN1 reaction, the bond between the electrophilic carbon and the leaving group ionizes to generate the carbocation intermediate. The second step of the mechanism is the nucleophilic attack.
In the formed carbocation, the positively charged carbon is sp2 hybridized with a trigonal planar geometry. As all the three substituents lie on the same plane, a plane of symmetry for the...
SN1 Reaction: Mechanism02:25

SN1 Reaction: Mechanism

Kinetic studies of ionization of a tertiary halide in a protic solvent suggest that only the substrate participates in the rate-determining step (slow step). The nucleophile is involved only after the slowest step. The SN1 reaction takes place in a multiple-step mechanism. 
Firstly, the haloalkane ionizes to generate a carbocation intermediate and a halide ion. This heterolytic cleavage is highly endothermic with large activation energy. The ionization of the substrate, facilitated by a polar...

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関連する実験動画

Updated: Jun 19, 2026

Highly Stereoselective Synthesis of 1,6-Ketoesters Mediated by Ionic Liquids: A Three-component Reaction Enabling Rapid Access to a New Class of Low Molecular Weight Gelators
06:31

Highly Stereoselective Synthesis of 1,6-Ketoesters Mediated by Ionic Liquids: A Three-component Reaction Enabling Rapid Access to a New Class of Low Molecular Weight Gelators

Published on: November 27, 2015

イオン性S(N) 2反応におけるステリックと溶解効果

Xin Chen1, Colleen K Regan, Stephen L Craig

  • 1Department of Chemistry, Stanford University, Stanford, California 94305-5080, USA.

Journal of the American Chemical Society
|October 22, 2009
PubMed
まとめ

S(N) 2反応に対する溶解効果は,最小限のサイズ依存を示しています. アルキルクロロニトリルにおけるステリック阻害は,ガスと溶液の相では類似しており,補償された溶解効果を示唆しています.

科学分野:

  • 有機化学 オーガニック・ケミストリー
  • 物理化学 物理化学
  • コンピューティング・ケミストリー

背景:

  • ステリック効果は,有機化学における反応速度に大きな影響を与えます.
  • S(N) 2反応における溶解の役割を理解することは,反応性の予測に極めて重要です.

研究 の 目的:

  • S(N) 2反応におけるステリック効果に対する溶解の寄与を調査する.
  • モデルシステムとしてアルキルクロロニトリルを用いて,ガスと溶液相におけるステリック効果を比較する.

主な方法:

  • アルキルクロロニトリルによるクロリドイオン反応の実験的運動学的研究.
  • 偏振連続体モデルとQM/MMシミュレーションを含む理論的調査.

主要な成果:

  • ベータ炭素の置換の増加は一貫して反応性を低下させ,ステリック障害を示唆した.
  • ステリック障害の大きさは,ガス相と溶液相の両方で類似していました.
  • 移行状態の溶解エネルギーは,置換量に対する弱い依存を示した.

結論:

  • 溶解は,これらのS(N) 2反応におけるステリック効果を著しく変化させない.

さらに関連する動画

Controlling the Size, Shape and Stability of Supramolecular Polymers in Water
16:24

Controlling the Size, Shape and Stability of Supramolecular Polymers in Water

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Spin Saturation Transfer Difference NMR (SSTD NMR): A New Tool to Obtain Kinetic Parameters of Chemical Exchange Processes
11:44

Spin Saturation Transfer Difference NMR (SSTD NMR): A New Tool to Obtain Kinetic Parameters of Chemical Exchange Processes

Published on: November 12, 2016

関連する実験動画

Last Updated: Jun 19, 2026

Highly Stereoselective Synthesis of 1,6-Ketoesters Mediated by Ionic Liquids: A Three-component Reaction Enabling Rapid Access to a New Class of Low Molecular Weight Gelators
06:31

Highly Stereoselective Synthesis of 1,6-Ketoesters Mediated by Ionic Liquids: A Three-component Reaction Enabling Rapid Access to a New Class of Low Molecular Weight Gelators

Published on: November 27, 2015

Controlling the Size, Shape and Stability of Supramolecular Polymers in Water
16:24

Controlling the Size, Shape and Stability of Supramolecular Polymers in Water

Published on: August 2, 2012

Spin Saturation Transfer Difference NMR (SSTD NMR): A New Tool to Obtain Kinetic Parameters of Chemical Exchange Processes
11:44

Spin Saturation Transfer Difference NMR (SSTD NMR): A New Tool to Obtain Kinetic Parameters of Chemical Exchange Processes

Published on: November 12, 2016

  • 弱いサイズ依存は,直接的なシールドと間接的な溶解効果の補償に起因する.
  • 発見は,溶解が大きさに強く依存する他のイオン系と対照的です.