Video Experimental Relacionado
Updated: Feb 28, 2026
12:08
Catalytic Reactions at Amine-Stabilized and Ligand-Free Platinum Nanoparticles Supported on Titania During Hydrogenation of Alkenes and Aldehydes
Published on: June 24, 2022
4.1K
Cambiar entre la catálisis de unión de aniones y la aminocatálisis con un catalizador de doble función de rotaxano
Katarzyna Eichstaedt1, Javier Jaramillo-Garcia1, David A Leigh1
1School of Chemistry, University of Manchester , Oxford Road, Manchester M13 9PL, U.K.
Journal of the American Chemical Society
|June 20, 2017
Resumen
Este estudio revela un catalizador rotaxano conmutable que cambia entre la aminocatálisis y la catálisis de unión de aniones. Su estado "apagado" para una reacción es el estado "encendido" para la otra, controlado por la posición del macrociclo.
Área de la Ciencia:
- Química supramolecular
- Catálisis
- Química orgánica
Sus antecedentes:
- Los catalizadores conmutables ofrecen una reactividad ajustable para transformaciones químicas complejas.
- Las máquinas moleculares basadas en rotaxano proporcionan plataformas para la actividad catalítica controlada.
Objetivo del estudio:
- Demostrar un catalizador de rotaxano de doble función con capacidad de aminocatálisis y de unión de aniones.
- Elucidar el mecanismo de cambio entre estados catalíticos basado en la posición del macrociclo.
Principales métodos:
- Síntesis y caracterización de un rotaxano conmutable [2].
- Investigando la actividad catalítica tanto en la aminocatálisis como en las reacciones de unión de aniones.
- Utilizando el movimiento del macrociclo inducido por estímulos para controlar la función catalítica.
Principales resultados:
- El rotaxano exhibe estados "encendido" y "apagado" mutuamente excluyentes para la aminocatálisis y la catálisis de unión aniónica.
- La catálisis de unión aniónica implica un enlace cooperativo CH-hidrógeno por grupos de triazolio para estabilizar los intermedios.
- La activación secuencial de los sitios catalíticos permite procesos de reacción en tándem.
Conclusiones:
- Los rotaxanos conmutables pueden diseñarse como catalizadores moleculares sofisticados con funciones ortogonales.
- El control del posicionamiento del macrociclo es clave para modular la actividad catalítica y permitir la catálisis secuencial.
Videos de Conceptos Relacionados
02:17Reduction of Alkenes: Asymmetric Catalytic Hydrogenation
3.9K
Catalytic hydrogenation of alkenes is a transition-metal catalyzed reduction of the double bond using molecular hydrogen to give alkanes. The mode of hydrogen addition follows syn stereochemistry.
The metal catalyst used can be either heterogeneous or homogeneous. When hydrogenation of an alkene generates a chiral center, a pair of enantiomeric products is expected to form. However, an enantiomeric excess of one of the products can be facilitated using an enantioselective reaction or an...
The metal catalyst used can be either heterogeneous or homogeneous. When hydrogenation of an alkene generates a chiral center, a pair of enantiomeric products is expected to form. However, an enantiomeric excess of one of the products can be facilitated using an enantioselective reaction or an...
3.9K
01:22Heterogeneous Catalysis
9
Heterogeneous catalysis involves a catalyst in a different phase from the reactants. It is a process where the catalyst and the reactants are in distinct phases, typically solid and gas or liquid.Most heterogeneous catalysts are metals, metal oxides, or acids. The list includes transition metals like iron (Fe), cobalt (Co), nickel (Ni), palladium (Pd), platinum (Pt), chromium (Cr), manganese (Mn), tungsten (W), silver (Ag), and copper (Cu). These metals possess partially vacant d orbitals that...
9
02:24Reduction of Alkynes to cis-Alkenes: Catalytic Hydrogenation
9.2K
Introduction
Like alkenes, alkynes can be reduced to alkanes in the presence of transition metal catalysts such as Pt, Pd, or Ni. The reaction involves two sequential syn additions of hydrogen via a cis-alkene intermediate.
Like alkenes, alkynes can be reduced to alkanes in the presence of transition metal catalysts such as Pt, Pd, or Ni. The reaction involves two sequential syn additions of hydrogen via a cis-alkene intermediate.
9.2K
01:13Introduction to Mechanisms of Enzyme Catalysis
11.1K
For many years, scientists thought that enzyme-substrate binding took place in a simple "lock-and-key" fashion. This model stated that the enzyme and substrate fit together perfectly in one instantaneous step. However, current research supports a more refined view scientists call induced fit. The induced-fit model expands upon the lock-and-key model by describing a more dynamic interaction between enzyme and substrate. As the enzyme and substrate come together, their interaction causes...
11.1K
02:50Catalysis
31.1K
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.
31.1K
01:11ortho–para-Directing Activators: –CH3, –OH, –NH2, –OCH3
7.8K
All ortho–para directors, excluding halogens, are activating groups. These groups donate electrons to the ring, making the ring carbons electron-rich. Consequently, the reactivity of the aromatic ring towards electrophilic substitution increases. For instance, the nitration of anisole is about 10,000 times faster than the nitration of benzene. The electron-donating effect of the methoxy group in anisole activates the ortho and para positions on the ring and stabilizes the corresponding...
7.8K