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Related Concept Videos

¹H NMR: Long-Range Coupling01:27

¹H NMR: Long-Range Coupling

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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...
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Spin–Spin Coupling: Three-Bond Coupling (Vicinal Coupling)01:22

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

1.6K
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...
1.6K
Spin–Spin Coupling: Two-Bond Coupling (Geminal Coupling)01:20

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

1.9K
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...
1.9K
Spin–Spin Coupling: One-Bond Coupling01:17

Spin–Spin Coupling: One-Bond Coupling

1.6K
Coupling interactions are strongest between NMR-active nuclei bonded to each other, where spin information can be transmitted directly through the pair of bonding electrons. While nuclei polarize their electrons to the opposite spins, the bonding electron pair has opposite spins. Configurations with antiparallel nuclear spins are expected to be lower in energy. When coupling makes antiparallel states more favorable, J is considered to have a positive value. The one-bond coupling constant, 1J,...
1.6K
Spin–Spin Coupling Constant: Overview01:08

Spin–Spin Coupling Constant: Overview

1.6K
In bromoethane, the three methyl protons are coupled to the two methylene protons that are three bonds away. In accordance with the n+1 rule, the signal from the methyl protons is split into three peaks with 1:2:1 relative intensities. The methylene protons appear as a quartet, with the relative intensities of 1:3:3:1.
Qualitatively, any spin plus-half nucleus polarizes the spins of its electrons to the minus-half state. Consequently, the paired electron in the hydrogen–carbon bond must...
1.6K
NMR Spectroscopy: Spin–Spin Coupling01:08

NMR Spectroscopy: Spin–Spin Coupling

3.5K
The spin state of an NMR-active nucleus can have a slight effect on its immediate electronic environment. This effect propagates through the intervening bonds and affects the electronic environments of NMR-active nuclei up to three bonds away; occasionally, even farther. This phenomenon is called spin–spin coupling or J-coupling. Coupling interactions are mutual and result in small changes in the absorption frequencies of both nuclei involved. While nuclei of the same element are involved...
3.5K

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Application of a Coupling Agent to Improve the Dielectric Properties of Polymer-Based Nanocomposites
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Coupling strength versus coupling impact in nonidentical bidirectionally coupled dynamics.

Petroula Laiou1, Ralph G Andrzejak2

  • 1Department of Information and Communication Technologies, Universitat Pompeu Fabra, Barcelona, 08018 Spain.

Physical Review. E
|February 18, 2017
PubMed
Summary
This summary is machine-generated.

We introduce "coupling impact" to define symmetric interactions in complex networks with nonidentical dynamics. This new measure accurately detects symmetry, unlike traditional coupling strength, by considering individual dynamics

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Area of Science:

  • Complex systems
  • Network science
  • Nonlinear dynamics

Background:

  • Real-world networks often feature heterogeneous nodes with distinct properties.
  • Defining symmetric interactions in networks with coupled, nonidentical dynamics is challenging due to asymmetry in individual node properties.
  • Traditional coupling strength measures are insufficient for characterizing symmetry in such systems.

Purpose of the Study:

  • To introduce and validate a new metric, "coupling impact," for defining symmetric interactions in networks of coupled nonidentical dynamics.
  • To address the limitations of coupling strength in asymmetric interaction scenarios.
  • To provide a method for accurately assessing the influence one dynamic has on another.

Main Methods:

  • A data-driven approach analyzing signals from pairs of coupled model dynamics.
  • Utilizing two distinct connectivity measures to evaluate interactions.
  • Introducing the concept of coupling impact, which incorporates both coupling strength and individual dynamics' energy.

Main Results:

  • The proposed coupling impact metric correctly identifies symmetric interactions between coupled dynamics, irrespective of their asymmetry.
  • Coupling strength alone fails to accurately detect symmetry in nonidentical dynamics.
  • The coupling impact reveals the true influence of one dynamic on another.

Conclusions:

  • Coupling impact offers a robust method for defining and detecting symmetric interactions in heterogeneous network dynamics.
  • This approach enhances the characterization of real-world networks by accurately quantifying inter-dynamics influence.
  • The findings enable a more precise understanding of symmetry in complex, asymmetric systems.