Video Experimental Relacionado
Updated: May 21, 2026
![Cercosporin-Photocatalyzed [4+1]- and [4+2]-Annulations of Azoalkenes Under Mild Conditions](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2FCDNSource%2Fteasers%2F60786.jpg&w=3840&q=50)
07:12
Cercosporin-Photocatalyzed [4+1]- and [4+2]-Annulations of Azoalkenes Under Mild Conditions
Published on: July 17, 2020
Efectos regiocímicos en la estabilidad molecular: una evaluación mecanoquímica de los triazoles 1,4- y
Johnathan N Brantley1, Sai Sriharsha M Konda, Dmitrii E Makarov
1Department of Chemistry and Biochemistry, The University of Texas, Austin, Texas 78712, USA.
Journal of the American Chemical Society
|June 12, 2012
Resumen
La irradiación por ultrasonido desencadena la ciclorreversión de las cadenas de poli (metilacrilato) que contienen triazoles 1,4- y 1,5-disubstituidos. El isómero 1,5 sufre una degradación más rápida debido a una mayor deformabilidad mecánica.
Área de la Ciencia:
- Química de Polímeros La química de los polímeros es la química de los polímeros.
- Ciencia de los materiales Ciencia de los materiales.
- Química Física es la química física.
Sus antecedentes:
- Los 1,2,3-triazoles son versátiles bloques de construcción en la síntesis de polímeros.
- Las reacciones inducidas por ultrasonido ofrecen nuevas vías para la modificación de polímeros.
- Comprender los efectos regioquímicos en la degradación de polímeros es crucial para el diseño de materiales.
Objetivo del estudio:
- Para investigar la ciclorreversión inducida por ultrasonido de cadenas de poli (metilacrilato) funcionalizadas con 1,4- y 1,5-disubstituidos 1,2,3-triazoles.
- Para comparar las tasas de degradación de polímeros que contienen diferentes regioisómeros de triazol.
- Para dilucidar la influencia de la estructura isomérica en la deformabilidad mecánica y la cinética de reacción.
Principales métodos:
- Síntesis de poli (metilacrilato) a través de la química de "clic" utilizando triazoles 1,4- y 1,5-disubstituidos.
- Sonificación de soluciones de polímeros en acetonitrilo.
- Análisis espectroscópico (por ejemplo, RMN, UV-Vis) y etiquetado químico para monitorear la ciclorreversión.
- Estudios cinéticos para determinar las constantes de velocidad de reacción.
- Modelado computacional utilizando la teoría extendida de Bell.
Principales resultados:
- Síntesis exitosa de poli (metilacrilato) con los triazoles 1,4- y 1,5-disubstituidos.
- La irradiación por ultrasonido indujo la ciclorreversión formal de las unidades de triazol en ambos tipos de polímeros.
- El isómero de triazol 1,5-disubstituido exhibió una constante de velocidad de ciclo-reversión 1,2 veces más rápida en comparación con el 1,4-isómero.
- Los estudios computacionales apoyaron los hallazgos experimentales, correlacionando las tasas de degradación con la deformabilidad mecánica.
Conclusiones:
- La regioquímica de los sustituyentes de triazol tiene un impacto significativo en la cinética de degradación inducida por ultrasonido del poli (metilacrilato).
- El aumento de la deformabilidad mecánica del 1,5-regioisómero facilita una ciclorreversión más rápida bajo sonication.
- Este estudio proporciona información sobre las relaciones estructura-propiedad de los polímeros que contienen triazol y su respuesta a los estímulos mecánicos.
Videos de Conceptos Relacionados
02:30Stability of Substituted Cyclohexanes
This lesson discusses the stability of substituted cyclohexanes with a focus on energies of various conformers and the effect of 1,3-diaxial interactions.
The two chair conformations of cyclohexanes undergo rapid interconversion at room temperature. Both forms have identical energies and stabilities, each comprising equal amounts of the equilibrium mixture. Replacing a hydrogen atom with a functional group makes the two conformations energetically non-equivalent.
For example, in...
The two chair conformations of cyclohexanes undergo rapid interconversion at room temperature. Both forms have identical energies and stabilities, each comprising equal amounts of the equilibrium mixture. Replacing a hydrogen atom with a functional group makes the two conformations energetically non-equivalent.
For example, in...
01:18Directing and Steric Effects in Disubstituted Benzene Derivatives
When disubstituted benzenes undergo electrophilic substitution, the product distribution depends on the directing effect of both substituents. When the directing effects of both substituents reinforce each other, a single product is obtained. For example, bromination of p-nitrotoluene occurs ortho to the methyl group and meta to the nitro group, which is the same position, resulting in a single product. However, if the directing effects of the two groups oppose each other, the more strongly...
02:34Regioselectivity and Stereochemistry of Acid-Catalyzed Hydration
The rate of acid-catalyzed hydration of alkenes depends on the alkene's structure, as the presence of alkyl substituents at the double bond can significantly influence the rate.
02:43E1 Reaction: Stereochemistry and Regiochemistry
One of the critical aspects of the E1 reaction mechanism, as also observed in E2, is the regiochemistry, with multiple regioisomers obtained as products. In the example discussed, the presence of water as a weak base favors elimination over substitution to generate two alkenes. Given that alkenes’ stability increases with the number of alkyl groups across the double bond, typically, E1 reactions lead to the Zaitsev product, for this is more substituted and stable than the Hofmann product.
01:10Radical Reactivity: Steric Effects
The presence of electron-donating, electron-withdrawing, or conjugating groups adjacent to a radical center, imparts electronic stabilization to the radicals. Examples of such electronically-stabilized radicals are triphenylmethyl, tetramethylpiperidine‐N‐oxide, and 2,2‐diphenyl‐1‐picrylhydrazyl. These radicals are remarkably stable and are known as persistent radicals. Some of the persistent radicals can even be isolated and purified.
Along with electronic factors, steric factors also account...
Along with electronic factors, steric factors also account...
02:17Regioselectivity of Electrophilic Additions to Alkenes: Markovnikov's Rule
If a set of reactants can yield multiple constitutional isomers, but one of the isomers is obtained as the major product, the reaction is said to be regioselective. In such reactions, bond formation or breaking is favored at one reaction site over others.
The hydrohalogenation of an unsymmetrical alkene can yield two haloalkane products, depending on which vinylic carbon takes up the halogen. However, one product usually predominates, where hydrogen adds to the vinylic carbon bearing the...
The hydrohalogenation of an unsymmetrical alkene can yield two haloalkane products, depending on which vinylic carbon takes up the halogen. However, one product usually predominates, where hydrogen adds to the vinylic carbon bearing the...