Video Experimental Relacionado
Updated: Jun 30, 2026
16:24
Controlling the Size, Shape and Stability of Supramolecular Polymers in Water
Published on: August 2, 2012
Reordenamiento aniónico Snieckus-Fries: efectos disolventes y papel de los agregados mixtos
Jason C Riggs1, Kanwal J Singh, Ma Yun
1Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301, USA.
Journal of the American Chemical Society
|September 19, 2008
Resumen
Este estudio detalla la generación de carbamatos de arilo liticados utilizando diisopropylamida de litio (LDA) en varios disolventes. La investigación revela que estos compuestos existen como monómeros, dímeros o trímeres, lo que influye en las reorganizaciones posteriores de Snieckus-Fries.
Área de la Ciencia:
- Química organometálica Química orgánica de los metales.
- Síntesis orgánica La síntesis orgánica.
- La espectroscopia es una técnica de espectroscopia.
Sus antecedentes:
- Los carbamatos de arilo litioados son intermediarios clave en la síntesis orgánica.
- Comprender su estado de agregación es crucial para los mecanismos de reacción.
Objetivo del estudio:
- Para investigar la formación y agregación de carbamatos de arilo litioados.
- Para dilucidar las vías mecanicistas del reordenamiento de Snieckus-Fries.
Principales métodos:
- Generación de carbamatos de arilo liticados utilizando diisopropylamida de litio (LDA) en diversos disolventes.
- Caracterización mediante espectroscopia de resonancia magnética nuclear (RMN) ((6) Li, (13) C, (15) N).
- Estudios cinéticos del reordenamiento de Snieckus y Fries.
Principales resultados:
- Los carbamatos de arilo litioados existen como monómeros, dímeros mezclados ArLi-LDA y trímeres mezclados ArLi-LDA, dependiendo de la elección del disolvente.
- El reordenamiento de Snieckus-Fries da como resultado dímeros y trímeres mezclados ArOLi-LDA.
- Los estudios de tasa apoyan los mecanismos que involucran monómeros, dímeros y trímeres.
Conclusiones:
- El disolvente dicta el estado de agregación de los carbamatos de arilo litioados.
- El estado de agregación influye en el mecanismo de reordenamiento de Snieckus-Fries.
- La espectroscopia de RMN es vital para la caracterización de estas especies de organolitio.
Videos de Conceptos Relacionados
02:25SN1 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...
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...
02:15SN1 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...
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...
02:23SN2 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.
If the substrate is an achiral molecule at the α-carbon, the inversion of configuration is not observed.
02:27Predicting 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,...
With increased substitution on the alkyl halide,...
01:16Thermal Sigmatropic Reactions: Overview
Sigmatropic rearrangements are a class of pericyclic reactions in which a σ bond migrates from one part of a π system to another. These are intramolecular rearrangements where the total number of σ and π bonds remain unchanged.
Sigmatropic shifts are classified based on an order term [i, j ], where i and j indicate the number of atoms across which each end of the σ bond migrates. Below are examples of a [3,3] sigmatropic shift in 1,5-hexadiene, referred to as...
Sigmatropic shifts are classified based on an order term [i, j ], where i and j indicate the number of atoms across which each end of the σ bond migrates. Below are examples of a [3,3] sigmatropic shift in 1,5-hexadiene, referred to as...
02:26SN2 Reaction: Transition State
An SN2 reaction of an alkyl halide is a single-step process in which bond formation between the nucleophile and the substrate and bond breaking between the substrate and the halide occurs simultaneously through a transition state without forming an intermediate.
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...
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...