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Videos de Conceptos Relacionados

¹H NMR: Complex Splitting01:13

¹H NMR: Complex Splitting

A proton M that is coupled to a proton X results in doublet signals for M. However, NMR-active nuclei can be simultaneously coupled to more than one nonequivalent nucleus. When M is coupled to a second proton A, such as in styrene oxide, each peak in the doublet is split into another doublet.
Splitting diagrams or splitting tree diagrams are routinely used to depict such complex couplings. While drawing splitting diagrams, the splitting with the larger coupling constant is usually applied first.
Spin–Spin Coupling: Two-Bond Coupling (Geminal Coupling)01:20

Spin–Spin Coupling: Two-Bond Coupling (Geminal Coupling)

Two NMR-active nuclei bonded to a central atom can be involved in geminal or two-bond coupling. Geminal coupling is commonly seen between diastereotopic protons in chiral molecules and unsymmetrical alkenes, among others.
The central atom need not be NMR-active because its electrons are affected by the electron polarization of the spin-active atoms. However, spin information is transmitted less effectively than in one-bond coupling, and 2J values are usually weaker than 1J values. The energy of...
Spin–Spin Coupling: Three-Bond Coupling (Vicinal Coupling)01:22

Spin–Spin Coupling: Three-Bond Coupling (Vicinal Coupling)

Vicinal or three-bond coupling is commonly observed between protons attached to adjacent carbons. Here, nuclear spin information is primarily transferred via electron spin interactions between adjacent C‑H bond orbitals. This generally favors the antiparallel arrangement of spins, so 3J values are usually positive.
The extent of coupling depends on the C‑C bond length, the two H‑C‑C angles, any electron-withdrawing substituents, and the dihedral angle between the involved orbitals. The...
¹H NMR: Long-Range Coupling01:27

¹H NMR: Long-Range Coupling

The coupling interactions of nuclei across four or more bonds are usually weak, with J values less than 1 Hz. While these are usually not observed in spectra, the presence of multiple bonds along the coupling pathway can result in observable long-range coupling.
In alkenes, spin information is communicated via σ–π overlap, as seen in allylic (four-bond) and homoallylic (five-bond) couplings. These coupling interactions are stronger when the σ bond is parallel to the alkene π orbitals.
Noncovalent Attractions in Biomolecules02:35

Noncovalent Attractions in Biomolecules

Noncovalent attractions are associations within and between molecules that influence the shape and structural stability of complexes. These interactions differ from covalent bonding in that they do not involve sharing of electrons.
Four types of noncovalent interactions are hydrogen bonds, van der Waals forces, ionic bonds, and hydrophobic interactions.
Hydrogen bonding results from the electrostatic attraction of a hydrogen atom covalently bonded to a strong-electronegative atom like oxygen,...
Complexation Equilibria: The Chelate Effect01:19

Complexation Equilibria: The Chelate Effect

In complexation reactions, metal atoms or cations interact with ligands to form donor-acceptor adducts called metal complexes. Ligands that bind through one donor site are monodentate, ligands with two donor sites are bidentate, and those with more than two donor sites are polydentate ligands. For example, ethylene diamine is a bidentate ligand that binds through two nitrogen donor atoms, forming a five-membered ring. EDTA is a polydentate ligand that binds through four oxygen and two nitrogen...

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Video Experimental Relacionado

Updated: Jul 10, 2026

Construction and Systematical Symmetric Studies of a Series of Supramolecular Clusters with Binary or Ternary Ammonium Triphenylacetates
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Construction and Systematical Symmetric Studies of a Series of Supramolecular Clusters with Binary or Ternary Ammonium Triphenylacetates

Published on: February 15, 2016

Enlaces de hidrógeno cuádruples complementarios en copolímeros supramoleculares.

G B W L Ligthart1, Haruki Ohkawa, Rint P Sijbesma

  • 1Laboratory of Macromolecular and Organic Chemistry, Eindhoven University of Technology, P.O. Box 513, 5600 MB, Eindhoven, The Netherlands.

Journal of the American Chemical Society
|January 20, 2005
PubMed
Resumen

Este estudio introduce un nuevo copolímero supramolecular que utiliza enlaces cuádruples de hidrógeno. Estos polímeros avanzados mantienen un alto grado de polimerización en diversas composiciones, superando a los sistemas existentes.

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Efficient Synthesis of All-Carbon Quaternary Centers via the Conjugate Addition of Functionalized Monoorganozinc Bromides
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Construction and Systematical Symmetric Studies of a Series of Supramolecular Clusters with Binary or Ternary Ammonium Triphenylacetates
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Área de la Ciencia:

  • Química supramolecular de las moléculas.
  • La ciencia de los polímeros es la ciencia de los polímeros.
  • Química orgánica es la química orgánica.

Sus antecedentes:

  • Los polímeros supramoleculares se basan en interacciones no covalentes para su estructura y propiedades.
  • Los sistemas anteriores a menudo mostraban una estabilidad limitada o tolerancia a la composición.
  • La unión cuádruple de hidrógeno ofrece un reconocimiento molecular robusto y direccional.

Objetivo del estudio:

  • Desarrollar un copolímero supramolecular utilizando un motivo específico de enlace cuádruple de hidrógeno.
  • Investigar el impacto de las unidades de enlace de hidrógeno complementarias en las propiedades de los polímeros.
  • Para evaluar la estabilidad y el rango de composición del copolímero supramolecular resultante.

Principales métodos:

  • Síntesis de ureido-pirimidinonona y monómeros de 2,7-diamido-1,8-naftiridina.
  • La polimerización a través de interacciones de enlaces cuádruples de hidrógeno.
  • Caracterización de las propiedades del polímero, incluyendo el grado de polimerización (DP) y la tolerancia de la composición.

Principales resultados:

  • Formación exitosa de un copolímero supramolecular a través de enlaces cuádruples de hidrógeno.
  • Se ha demostrado un alto grado de polimerización (DP) para el copolímero.
  • El copolímero mantuvo un alto DP en una amplia gama de composiciones monoméricas.

Conclusiones:

  • El enlace cuádruple de hidrógeno proporciona una plataforma robusta para la síntesis de copolímero supramolecular.
  • El sistema desarrollado exhibe una tolerancia de composición superior en comparación con los polímeros de enlace de hidrógeno complementarios anteriores.
  • Este trabajo abre caminos para el diseño de materiales avanzados con propiedades sintonizables.