Video Experimental Relacionado

Updated: Apr 21, 2026

Preparation and Reactivity of a Triphosphenium Bromide Salt: A Convenient and Stable Source of PhosphorusI

Preparation and Reactivity of a Triphosphenium Bromide Salt: A Convenient and Stable Source of PhosphorusI

Published on: November 22, 2016

Degenerar la sustitución nucleófila en las sales de fosfonio

Elizabeth V Jennings¹, Kirill Nikitin, Yannick Ortin

¹Centre for Synthesis and Chemical Biology, School of Chemistry and Chemical Biology, University College Dublin , Dublin 4, Ireland.

Journal of the American Chemical Society

|November 12, 2014

Resumen

La sustitución de haluros degenerados en cationes de halofosfonio se produce a través de un mecanismo de dos pasos que involucra un intermediario pentacoordinado. Estudios experimentales y computacionales revelan barreras energéticas y efectos estéricos que influyen en esta importante reacción química.

Área de la Ciencia:

Química de los organofosforados Química de los organofosforados
Mecanismos de reacción Mecanismos de reacción
Química computacional es la química computacional.

Sus antecedentes:

Las reacciones de sustitución de haluros degenerados en cationes de halofosfonio tetracoordinados son fundamentales en la química de los organofosforos.
Comprender el mecanismo y las barreras energéticas es crucial para predecir la reactividad y diseñar nuevas rutas sintéticas.

Objetivo del estudio:

Para dilucidar el mecanismo y determinar las barreras energéticas de la sustitución de haluro degenerado en cationes de halofosfonio.
Para investigar la influencia de los sustituyentes en las velocidades de reacción y la estereocímica.
Para comparar hallazgos experimentales con predicciones computacionales para obtener conocimientos mecanicistas.

Principales métodos:

Se emplearon técnicas de Resonancia Magnética Nuclear (RMN) de Temperatura Variable (VT) y Espectroscopia de Intercambio (EXSY).Técnicas de Resonancia Magnética Nuclear (RMN) fueron empleadas.
Un nuevo diseño experimental que utiliza un sustituto quiral ((s) Bu) para resolver sales degeneradas.
Se desarrollaron enfoques de química computacional para modelar el sistema de reacción y analizar los perfiles de energía.

Principales resultados:

Se apoyó fuertemente un mecanismo de dos pasos que involucra el ataque por la espalda y la disociación para formar un intermediario de dihalofosforano pentacoordinado.
Las barreras energéticas determinadas experimentalmente oscilaron entre <9 y casi 20 kcal mol(-1), excluyendo la pseudorotación de Berry.
Los cloruros de clorofosfonio exhibieron barreras energéticas más bajas que los análogos de bromo debido a la mayor accesibilidad de los intermediarios pentacoordinados.
Los sustitutos voluminosos (Me < Et < (i) Pr < (t) Bu) retrasaron la reacción, lo que es consistente con un mecanismo asociativo y un obstáculo estérico.
Se observaron cinéticas de primer orden, atribuidas a la presencia de pares de iones en solución.
Más parcelas de O'Ferrall-Jencks indicaron un pozo potencial poco profundo para el intermediario de la bípirámide trigonal.

Conclusiones:

El estudio confirma un mecanismo asociativo de dos pasos para la sustitución de haluros degenerados en cationes de halofosfonio.
Las barreras energéticas están influenciadas por la identidad halogenada y la masa estérica de los sustituyentes.
Los datos computacionales y experimentales proporcionan una comprensión completa de la vía de reacción y las estructuras intermedias.

Más Videos Relacionados

Preparation of N-2-alkoxyvinylsulfonamides from N-tosyl-1,2,3-triazoles and Subsequent Conversion to Substituted Phthalans and Phenethylamines

Preparation of N-2-alkoxyvinylsulfonamides from N-tosyl-1,2,3-triazoles and Subsequent Conversion to Substituted Phthalans and Phenethylamines

Published on: January 3, 2018

Chemical Triphosphorylation of Oligonucleotides

Chemical Triphosphorylation of Oligonucleotides

Published on: June 2, 2022

Videos de Conceptos Relacionados

Nucleophilic Aromatic Substitution of Aryldiazonium Salts: Aromatic SN1

Nucleophilic Aromatic Substitution of Aryldiazonium Salts: Aromatic S_N1

Treating arylamines with nitrous acid gives aryldiazonium salts that are effective substrates in nucleophilic aromatic substitution reactions. The diazonio group in these salts can be easily displaced by different nucleophiles, yielding a wide variety of substituted benzenes. The leaving group departs as nitrogen gas, and this easy elimination is the driving force for the substitution reaction.
In the Sandmeyer reaction, for example, the diazonio group is replaced by a chloro, bromo,...

Nucleophilic Substitution Reactions

Nucleophilic Substitution Reactions

Historical perspective
In 1896, the German chemist Paul Walden discovered that he could interconvert pure enantiomeric (+) and (-) malic acids through a series of reactions. This conversion suggested the involvement of optical inversion during the substitution reaction. Further, in 1930, Sir Christopher Ingold described for the first time two different forms of nucleophilic substitution reactions, which are known as SN1 (nucleophilic substitution unimolecular) and SN2 (nucleophilic substitution...

Nucleophiles

Nucleophiles

The word “nucleophile” has a Greek root and translates to nucleus-loving. Nucleophiles are either negatively charged or neutral species with a pair of electrons in a high-energy occupied molecular orbital (HOMO). As these species tend to donate electron pairs, nucleophiles are considered Lewis bases as well. Negatively charged species, like OH−, Cl−, or HS−, with one or several pairs of electrons, are typically nucleophiles. Similarly, neutral species such as...

Reactions of α-Halocarbonyl Compounds: Nucleophilic Substitution

Reactions of α-Halocarbonyl Compounds: Nucleophilic Substitution

Nucleophilic substitution in α-halocarbonyl compounds can be achieved via an SN2 pathway. The reaction in α-haloketones is generally carried out with less basic nucleophiles. The use of strong basic nucleophiles leads to the generation of α-haloenolate ions, which often participate in other side reactions.

Diazonium Group Substitution: –OH and –H

Diazonium Group Substitution: –OH and –H

Nitrous acid, a weak acid, is prepared in situ via the reaction of sodium nitrite with a strong acid under cold conditions. This nitrous acid prepared in situ reacts with primary arylamines to form arenediazonium salts. Such reactions are known as diazotization reactions. As shown in Figure 1, the formation of arenediazonium salts begins with the decomposition of nitrous acid in an acidic solution to give nitrosonium ions.

Nucleophilic Aromatic Substitution: Addition–Elimination (SNAr)

Nucleophilic Aromatic Substitution: Addition–Elimination (S_NAr)

Nucleophilic substitution in aromatic compounds is feasible in substrates bearing strong electron-withdrawing substituents positioned ortho or para to the leaving group. The reaction proceeds via two steps: the addition of the nucleophile and the elimination of the leaving group.
The reaction begins with an attack of the nucleophile on the carbon that holds the leaving group. This results in the delocalization of the π electrons over the ring carbons. The resonance interaction between...