Video Experimental Relacionado
Updated: Jul 14, 2026
10:44
Isolating Free Carbenes, their Mixed Dimers and Organic Radicals
Published on: April 19, 2019
Los rotores iónicos. preparación, estructura y estudio dinámico de RMN 2D en estado sólido del
James R Gardinier1, Perry J Pellechia, Mark D Smith
1Department of Chemistry, Marquette University, Milwaukee, Wisconsin 53201, USA.
Journal of the American Chemical Society
|September 8, 2005
Resumen
Los investigadores sintetizaron una nueva sal de borato, un miembro perdido de una serie isoelectrónica. Este compuesto de organoboron exhibe una rápida rotación de su anillo central de fenileno en estado sólido, a diferencia de su análogo de carbono.
Área de la Ciencia:
- Química organometálica Química orgánica de los metales.
- Química del boro y su química.
- Espectroscopia de RMN en estado sólido.
Sus antecedentes:
- La serie isoelectrónica [p-(Ph3EC2) 2C6H4] (E = grupo 13-15 elemento) fue previamente incompleta.
- Comprender la dinámica de los componentes moleculares en los compuestos organometálicos en estado sólido es crucial para la ciencia de los materiales.
Objetivo del estudio:
- Para sintetizar y caracterizar una nueva sal de borato, [Li(THF) [4]2[p-(Ph3BC2) 2C6H4].
- Para investigar la dinámica de rotación del enlazador central de fenileno en estado sólido.
- Para comparar la dinámica de rotación con su análogo basado en carbono.
Principales métodos:
- Generación in situ de p- ((LiC2) 2C6H4 a partir de butillitio y dialquinilbenceno.
- Reacción con 2 equivalentes de trifenilborano (BPh3) para obtener la sal de borato objetivo.
- Espectroscopia de resonancia magnética nuclear (RMN) de espín 2D de estado sólido de temperatura variable para estudiar el movimiento molecular.
Principales resultados:
- Se obtuvieron altos rendimientos de la sal de borato objetivo, [Li(THF) [4]2[p-(Ph3BC2) 2C6H4].
- Se encontró que el enlace central de fenileno en estado sólido estaba girando libremente.
- La velocidad de rotación observada a temperatura ambiente es al menos 20 veces más rápida que la del análogo de carbono.
Conclusiones:
- La síntesis exitosa de [Li(THF) [4]2[p-(Ph3BC2) 2C6H4] completa las series isoelectrónicas.
- La mayor movilidad rotacional del enlazador de fenileno se atribuye a las repulsiones coulombinas que minimizan las interacciones intermoleculares.
- Este estudio proporciona información sobre las relaciones estructura-propiedad en los compuestos de organoboron y su dinámica de estado sólido.
Videos de Conceptos Relacionados
00:48¹H NMR of Labile Protons: Deuterium (²H) Substitution
This lesson illustrates the role of deuterium substitution in simplifying the NMR spectrum of compounds comprising labile protons. One method employed is the use of deuterium. Amongst the three isotopes of hydrogen, deuterium (2H) has a nucleus composed of one proton and one neutron. When the D2O solvent is added to a pure dry ethanol solution, its labile proton is substituted with deuterium.
01:16Structure of Conjugated Dienes
Introduction
Conjugated dienes are compounds characterized by the presence of alternating double and single bonds. In a conjugated system like 1,3-butadiene, the unhybridized 2p orbital on each carbon overlaps continuously, allowing the π electrons to be delocalized across the entire molecule. In contrast, this type of overlap does not occur in cumulated and isolated dienes, such as 2,3-pentadiene and 1,4-pentadiene, respectively. Instead, the π electrons remain localized between the double...
Conjugated dienes are compounds characterized by the presence of alternating double and single bonds. In a conjugated system like 1,3-butadiene, the unhybridized 2p orbital on each carbon overlaps continuously, allowing the π electrons to be delocalized across the entire molecule. In contrast, this type of overlap does not occur in cumulated and isolated dienes, such as 2,3-pentadiene and 1,4-pentadiene, respectively. Instead, the π electrons remain localized between the double...
01:24π Molecular Orbitals of 1,3-Butadiene
Conjugated dienes have lower heats of hydrogenation than cumulated and isolated dienes, making them more stable. The enhanced stabilization of conjugated systems can be understood from their π molecular orbitals.
The simplest conjugated diene is 1,3-butadiene: a four-carbon system where each carbon is sp2-hybridized and has an unhybridized p orbital that contains an unpaired electron. According to molecular orbital theory, atomic orbitals combine to form molecular orbitals such that the number...
The simplest conjugated diene is 1,3-butadiene: a four-carbon system where each carbon is sp2-hybridized and has an unhybridized p orbital that contains an unpaired electron. According to molecular orbital theory, atomic orbitals combine to form molecular orbitals such that the number...
01:29Diels–Alder Reaction: Characteristics of Dienes
The Diels–Alder reaction brings together a diene and a dienophile to form a six-membered ring. Both components have unique characteristics that influence the rate of the reaction.
Characteristics of the diene
Conformation
The simplest example of a diene is 1,3-butadiene, an acyclic conjugated π system. At room temperature, the molecule exists as a mixture of s-cis and s-trans conformers by virtue of rotation around the carbon–carbon single bond. Although the s-trans isomer is more stable, the...
Characteristics of the diene
Conformation
The simplest example of a diene is 1,3-butadiene, an acyclic conjugated π system. At room temperature, the molecule exists as a mixture of s-cis and s-trans conformers by virtue of rotation around the carbon–carbon single bond. Although the s-trans isomer is more stable, the...
![[3,3] Sigmatropic Rearrangement of 1,5-Dienes: Cope Rearrangement](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2Ffiles%2Fmedia%2Fscience-education%2Fscience-education-thumbs%2F12422.jpg&w=3840&q=75)
01:21[3,3] Sigmatropic Rearrangement of 1,5-Dienes: Cope Rearrangement
The Cope rearrangement is classified as a [3,3] sigmatropic shift in 1,5-dienes, leading to a more stable, isomeric 1,5-diene. The reaction involves a concerted movement of six electrons, four from two π bonds and two from a σ bond, via an energetically favorable chair-like transition state.
01:28Stability of Conjugated Dienes
Introduction
A comparison of the enthalpies of hydrogenation of dienes reveals that conjugated dienes release less heat on hydrogenation, rendering them more stable than their nonconjugated analogs.
A comparison of the enthalpies of hydrogenation of dienes reveals that conjugated dienes release less heat on hydrogenation, rendering them more stable than their nonconjugated analogs.