Video Experimental Relacionado
Updated: Feb 19, 2026
08:56
Synthesis of a Borylated Ibuprofen Derivative Through Suzuki Cross-Coupling and Alkene Boracarboxylation Reactions
Published on: November 30, 2022
3.5K
Generación y estructura de radicales únicos de boriranilo
John C Walton1, Timothy R McFadden2, Dennis P Curran2
1EaStCHEM School of Chemistry, University of St. Andrews , St. Andrews, Fife KY16 9ST, United Kingdom.
Journal of the American Chemical Society
|November 4, 2017
Resumen
Los radicales de boriranilo, derivados de los boraciclopropanos de anillo de tres miembros, se detectaron por primera vez utilizando la espectroscopia EPR. Se caracterizó su carácter π plano y su reactividad, proporcionando información sobre las energías de disociación de enlaces boro-hidrógeno.
Área de la Ciencia:
- Química del organoboron
- La Química Radical
- Espectroscopia
Sus antecedentes:
- Los boraciclopropanos de anillo de tres miembros (boriranos) son compuestos novedosos sintetizados a través de un método recientemente desarrollado.
- Los sustituyentes de carbenos N-heterocíclicos (NHC) se incorporan a estas estructuras de borirano.
- Comprender la reactividad y las propiedades de las especies radicales transitorias es crucial en la síntesis química.
Objetivo del estudio:
- Preparación y caracterización de los boriranos con sustituyentes NHC.
- Para detectar y estudiar por primera vez los radicales de boriranilo.
- Investigar la cinética de abstracción del átomo H y la energía de disociación del enlace B-H (BDE) en estos sistemas.
Principales métodos:
- Síntesis de boriranos sustituidos por NHC utilizando una nueva vía sintética.
- Abstracción selectiva de átomos de hidrógeno de átomos de boro mediante el uso de radicales t-butoxilo.
- Detección y caracterización de los radicales boriranilo mediante espectroscopia de resonancia paramagnética de electrones (EPR).
- Experimentos de competencia para determinar las constantes de velocidad para la abstracción del átomo H.
Principales resultados:
- Los radicales de boriranilo fueron generados y detectados con éxito por espectroscopia EPR.
- Los parámetros de EPR indicaron que los radicales de boriranilo poseen un carácter π plano.
- La constante de velocidad para la abstracción de átomos de H de los NHC-boranos es aproximadamente dos órdenes de magnitud inferior a la de los NHC-boranos.
- La energía de disociación del enlace B-H (BDE) de un NHC-borirano se estimó en alrededor de 95 kcal mol-1.
Conclusiones:
- Este estudio informa de la primera detección y caracterización exitosas de los radicales de boriranilo.
- Los hallazgos proporcionan información valiosa sobre la estructura electrónica y la reactividad de estos nuevos radicales que contienen boro.
- El estimado B-H BDE ofrece información sobre la estabilidad y las aplicaciones potenciales de los NHC-boriranos en las reacciones químicas.
Videos de Conceptos Relacionados
03:08Hydroboration-Oxidation of Alkenes
11.7K
In addition to the oxymercuration–demercuration method, which converts the alkenes to alcohols with Markovnikov orientation, a complementary hydroboration-oxidation method yields the anti-Markovnikov product. The hydroboration reaction, discovered in 1959 by H.C. Brown, involves the addition of a B–H bond of borane to an alkene giving an organoborane intermediate. The oxidation of this intermediate with basic hydrogen peroxide forms an alcohol.
11.7K
02:36Regioselectivity and Stereochemistry of Hydroboration
9.5K
A significant aspect of hydroboration–oxidation is the regio- and stereochemical outcome of the reaction.
Hydroboration proceeds in a concerted fashion with the attack of borane on the π bond, giving a cyclic four-centered transition state. The –BH2 group is bonded to the less substituted carbon and –H to the more substituted carbon. The concerted nature requires the simultaneous addition of –H and –BH2 across the same face of the alkene giving syn stereochemistry.
Hydroboration proceeds in a concerted fashion with the attack of borane on the π bond, giving a cyclic four-centered transition state. The –BH2 group is bonded to the less substituted carbon and –H to the more substituted carbon. The concerted nature requires the simultaneous addition of –H and –BH2 across the same face of the alkene giving syn stereochemistry.
9.5K
01:07Radicals: Electronic Structure and Geometry
5.1K
This lesson delves into the geometry of a radical, which is influenced by the electronic structure of the molecule. The principle is similar to that of a lone pair, where the unpaired electron influences the geometry at the radical center.
Accordingly, the structure of a trivalent radical lies between the geometries of carbocations and carbanions. An sp2-hybridized carbocation is trigonal planar, while an sp3-hybridized carbanion is trigonal pyramidal. Here, the difference in geometry is...
Accordingly, the structure of a trivalent radical lies between the geometries of carbocations and carbanions. An sp2-hybridized carbocation is trigonal planar, while an sp3-hybridized carbanion is trigonal pyramidal. Here, the difference in geometry is...
5.1K
01:11Radical Reactivity: Overview
2.8K
Radicals, the highly reactive species, gain stability by undergoing three different reactions. The first reaction involves a radical-radical coupling, in which a radical combines with another radical, forming a spin‐paired molecule. The second reaction is between a radical and a spin‐paired molecule, generating a new radical and a new spin‐paired molecule. The third reaction is radical decomposition in a unimolecular reaction, forming a new radical and a spin‐paired...
2.8K
01:03Radical Formation: Overview
2.7K
A bond can be broken either by heterolytic bond cleavage to form ions or homolytic bond cleavage to yield radicals. A fishhook arrow is used to represent the motion of a single electron in homolytic bond cleavage. There are two main sources from which radicals can be formed:
Radicals from spin-paired molecules:
Radicals can be obtained from spin-paired molecules either by homolysis or electron transfer. While two radicals are formed in the former, an electron is added in the...
Radicals from spin-paired molecules:
Radicals can be obtained from spin-paired molecules either by homolysis or electron transfer. While two radicals are formed in the former, an electron is added in the...
2.7K
00:47Radical Formation: Addition
2.3K
Radicals can be formed by adding a radical to a spin-paired molecule. This is typically observed with unsaturated species, where the addition of a radical across the π bond leads to the production of a new radical by dissolving the π bond. For example, the addition of a Br radical to an alkene yields a carbon-centered radical.
Similar to charge conservation in chemical reactions, spin conservation is implicit for radical reactions. Accordingly, the product formed must possess an...
Similar to charge conservation in chemical reactions, spin conservation is implicit for radical reactions. Accordingly, the product formed must possess an...
2.3K