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Updated: May 3, 2026

Efficient Synthesis of All-Carbon Quaternary Centers via the Conjugate Addition of Functionalized Monoorganozinc Bromides
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Efficient Synthesis of All-Carbon Quaternary Centers via the Conjugate Addition of Functionalized Monoorganozinc Bromides

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π結合効果は,SN2反応を促進するのでしょうか?

Chia-Hua Wu1, Boris Galabov, Judy I-Chia Wu

  • 1Center for Computational Chemistry and Department of Chemistry, University of Georgia , Athens, Georgia 30602, United States.

Journal of the American Chemical Society
|January 24, 2014
PubMed
まとめ

パイ結合ではなく,基質-核愛性電静相互作用が,SN2反応速度を制御する. 引き寄せ力は活性化障壁を低くし,反応を加速させ,排斥力は障壁を高くし,反応を遅らせます.

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SN2 Reaction: Stereochemistry02:23

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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.
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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.
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This lesson provides an in-depth discussion of the stereochemical outcomes in an SN1 reaction.
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When the nucleophile approaches the electrophilic carbon with its lone pairs, the halide acts as a leaving group and moves away with the electron-pair bonded to the carbon. Dotted partial bonds represent the bonds being formed or broken...
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The kinetic studies of SN2 reactions suggest an essential feature of its mechanism: it is a single-step process without intermediates. Here, both the nucleophile and the substrate participate in the rate-determining step.
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