Video Experimental Relacionado
Updated: Jun 1, 2026
12:22
Preparation and Use of Samarium Diiodide (SmI2) in Organic Synthesis: The Mechanistic Role of HMPA and Ni(II) Salts in the Samarium Barbier Reaction
Published on: February 4, 2013
El Ni (II) catalítico en las reacciones de SmI2: química a base de Sm (II) o Ni (0)
Kimberly A Choquette1, Dhandapani V Sadasivam, Robert A Flowers
1Department of Chemistry, Lehigh University, Bethlehem, Pennsylvania 18015, USA.
Journal of the American Chemical Society
|May 31, 2011
Resumen
Las sales catalíticas de níquel (II) mejoran las reacciones de Samario Barbier mediante la reducción a níquel (0). Este níquel ((0) luego impulsa la reacción a través de la adición oxidativa, revelando la química conocida del níquel que subyace a este proceso.
Área de la Ciencia:
- Química organometálica Química orgánica de los metales.
- La catálisis de la catálisis.
- Mecanismos de reacción Mecanismos de reacción
Sus antecedentes:
- El diioduro de samario (SmI2) es un agente reductor versátil utilizado en la síntesis orgánica.
- Se sabe que las cantidades catalíticas de sales de Ni (II) aumentan la reactividad y la selectividad en las reacciones mediadas por SmI2.
- La base mecanicista de la catálisis de Ni (II) en las reacciones SmI2 sigue siendo poco conocida.
Objetivo del estudio:
- Para aclarar el papel mecanicista del catalítico Ni (II) en la reacción de samario Barbier.
- Para investigar la interacción entre Ni(II) y SmI2 bajo condiciones de reacción.
- Para determinar la especie catalítica activa y la vía de reacción.
Principales métodos:
- Estudios espectroscópicos (por ejemplo, UV-Vis, EPR) para identificar los intermediarios.
- Mediciones cinéticas para determinar las velocidades y órdenes de reacción.
- Estudios de etiquetado isotópico para rastrear las vías de reacción.
Principales resultados:
- La reacción del samario Barbier con el Ni{II} catalítico es impulsada por la reducción del Ni{II} a Ni{0} en un paso que limita la velocidad.
- El Ni0 generado se somete a una adición oxidativa en el enlace de halogenuro de alquilo, formando una especie de organonickel.
- Se observó la formación concomitante de Ni coloidal como un proceso secundario improductivo.
Conclusiones:
- La mayor reactividad y selectividad en las reacciones de SmI2/Ni(II) Barbier se debe principalmente a la química establecida de Ni(0).
- El mecanismo de reacción involucra la reducción de Ni{II} a Ni{0}, seguida de adición oxidativa, en lugar de las características únicas de SmI2.
- Este estudio reatribuye el efecto catalítico a procesos conocidos mediados por níquel.
Más Videos Relacionados
Videos de Conceptos Relacionados
02:50Catalysis
The presence of a catalyst affects the rate of a chemical reaction. A catalyst is a substance that can increase the reaction rate without being consumed during the process. A basic comprehension of a catalysts’ role during chemical reactions can be understood from the concept of reaction mechanisms and energy diagrams.
01:27Catalysis
Catalysis influences the rate of chemical reactions by providing an alternative reaction pathway with lower activation energy. A catalyst speeds up a reaction, but it is not consumed during the process. The fundamental principle of catalysis is the ability of a catalyst to alter the reaction mechanism, often introducing a more efficient pathway than the uncatalyzed process.In a catalyzed reaction, the catalyst participates directly in the reaction mechanism. It interacts with reactants to form...
02:26Preparation and Reactions of Sulfides
Sulfides are the sulfur analog of ethers, just as thiols are the sulfur analog of alcohol. Like ethers, sulfides also consist of two hydrocarbon groups bonded to the central sulfur atom. Depending upon the type of groups present, sulfides can be symmetrical or asymmetrical. Symmetrical sulfides can be prepared via an SN2 reaction between 2 equivalents of an alkyl halide and one equivalent of sodium sulfide.
02:14SN2 Reaction: Kinetics
Kinetic Studies and Significance
In a chemical reaction, a relationship exists between the concentration of reactants and the rate at which the reaction proceeds. The study to measure this relationship is known as the kinetics of a chemical reaction. Kinetic studies are used to deduce the rate law of a chemical reaction, which provides information about the species involved during the transition state of the rate-determining step. Thus, kinetic studies help to derive the mechanism of a reaction.
In a chemical reaction, a relationship exists between the concentration of reactants and the rate at which the reaction proceeds. The study to measure this relationship is known as the kinetics of a chemical reaction. Kinetic studies are used to deduce the rate law of a chemical reaction, which provides information about the species involved during the transition state of the rate-determining step. Thus, kinetic studies help to derive the mechanism of a reaction.
01:22Alkenes via Reductive Coupling of Aldehydes or Ketones: McMurry Reaction
The radical dimerization of ketones or aldehydes gives vicinal diols through a pinacol coupling reaction. However, the behavior of titanium metals used for the reaction as a source of electrons is unusual. When the reaction is carried out in the presence of titanium, diols can be isolated at low temperatures. Else titanium further reacts with diols, forming alkenes through the McMurry reaction.
02:33Preparation and Reactions of Thiols
Thiols are prepared using the hydrosulfide anion as a nucleophile in a nucleophilic substitution reaction with alkyl halides. For instance, bromobutane reacts with sodium hydrosulfide to give butanethiol.