Video Experimental Relacionado
Updated: Jul 4, 2026
09:22
Self-assembling Morphologies Obtained from Helical Polycarbodiimide Copolymers and Their Triazole Derivatives
Published on: February 7, 2017
La formación de Cucurbit[n]uril procede por ciclo-oligomerización de crecimiento gradual
Wei-Hao Huang1, Peter Y Zavalij, Lyle Isaacs
1Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742, USA.
Journal of the American Chemical Society
|June 6, 2008
Resumen
Los oligómeros de glicoluril y nor-seco-cucurbit[n]urils se forman con una cantidad limitada de formaldehído. Los oligómeros acíclicos pentámero y hexámero se unen a los huéspedes, expandiendo las cavidades para moléculas más grandes, revelando un mecanismo de ciclo-oligomerización de crecimiento escalonado en la formación de cucurbiturilo.
Área de la Ciencia:
- Química supramolecular de las moléculas.
- Síntesis orgánica La síntesis orgánica.
- Ingeniería de Cristal Ingeniería de Cristal.
Sus antecedentes:
- Cucurbit[n]urils (CB[n]) son compuestos macrocíclicos típicamente sintetizados con una proporción de 1:2 de glicoluril a formaldehído.
- Las reacciones de condensación incompletas producen mezclas de análogos CB[n] y oligómeros de glicolurilo lineales o cíclicos.
Objetivo del estudio:
- Para aislar y caracterizar los oligómeros acíclicos de glicolurilo formados bajo condiciones de formaldehído sub-estoiquiométrico.
- Investigar las propiedades de unión al huésped y las características estructurales de estos oligómeros.
- Para aclarar el mecanismo de la formación de cucurbit[n]uril.
Principales métodos:
- Purificación cromatográfica de oligómeros de glicolurilo (del dímero al hexámero).
- Caracterización del estado de solución (NMR, MS).
- Cristalografía de rayos X para la determinación estructural.
- Estudios de vinculación de huéspedes.
- Experimentos de re-envío de productos.
Principales resultados:
- Aislamiento y caracterización estructural de los oligómeros de glicolurilo en forma de C (dimero-hexámero).
- Los oligómeros acíclicos pentámero y hexámero exhiben capacidades de unión de huéspedes similares a las de CB[6], con una cavidad expandida que acomoda huéspedes más grandes.
- La nueva presentación de productos reveló preferencias para tamaños de anillos específicos durante la formación de CB[n].
- Se propuso un esquema mecanicista integral para la síntesis de CB[n].
Conclusiones:
- Se pueden aislar y caracterizar los oligómeros de glicoluril, incluidos los pentámeres y hexámeres acíclicos.
- Estos oligómeros poseen propiedades únicas de unión de huéspedes, lo que demuestra la adaptabilidad al tamaño de la cavidad.
- La formación de CB[n] y compuestos relacionados se produce a través de una vía de ciclo-oligomerización de crecimiento escalonado.
Más Videos Relacionados
Videos de Conceptos Relacionados
00:57Cationic Chain-Growth Polymerization: Mechanism
The cationic polymerization mechanism consists of three steps: initiation, propagation, and termination. In the initiation step of the polymerization process, the π bond of a monomer gets protonated by the Lewis acid catalyst, which is formed from boron trifluoride and water. The protonation of the π bond generates a carbocation stabilized by the electron‐donating group. In the propagation step, the π bond of the second monomer acts as a nucleophile and attacks the generated carbocation,...
01:03Step-Growth Polymerization: Overview
Step-growth or condensation polymerization is a stepwise reaction of bi or multifunctional monomers to form long-chain polymers. As all the monomers are reactive, most of the monomers are consumed at the early stages of the reaction to form small chains of reactive oligomers, which then combine to form long polymer chains in the late stages. Hence, the reaction has to proceed for a long time to achieve high molecular weight polymers.
Many natural and synthetic polymers are produced by...
Many natural and synthetic polymers are produced by...
01:17Radical Chain-Growth Polymerization: Chain Branching
The skeletal structure of polymers synthesized via radical polymerization is always branched. For example, the polymerization of ethylene by radical polymerization results in a low-density grade of polyethylene with a heavily branched skeletal structure. Here, the radical site abstracts hydrogen from the growing chain, and the radical site shifts from the end (a primary carbon center) to anywhere within the growing chain (a secondary carbon center). Consequently, the part of the chain from the...
01:16Cycloaddition Reactions: Overview
Cycloadditions are one of the most valuable and effective synthesis routes to form cyclic compounds. These are concerted pericyclic reactions between two unsaturated compounds resulting in a cyclic product with two new σ bonds formed at the expense of π bonds. The [4 + 2] cycloaddition, known as the Diels–Alder reaction, is the most common. The other example is a [2 + 2] cycloaddition.
02:28Cycloalkanes
Cycloalkanes are saturated cyclic hydrocarbons with carbon atoms arranged in the form of rings. They have two fewer hydrogen atoms than the corresponding acyclic alkane; therefore, their general formula is CnH2n. The structural formulas of cycloalkanes are simplified using the line-angle representation. The regular polygons are used to represent the cycloalkane rings, with each side representing a carbon-carbon bond.
The IUPAC nomenclature of cycloalkanes follows similar rules that apply to...
The IUPAC nomenclature of cycloalkanes follows similar rules that apply to...
01:23Urea Cycle
The urea cycle describes how liver cells convert ammonia to urea. Ammonia is a toxic waste product of protein catabolism. Land animals must convert ammonia into the less toxic urea which can be safely eliminated by the kidneys through urine. Marine animals excrete ammonia directly, and the surrounding water dilutes the ammonia to safe levels.