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Related Concept Videos

¹H NMR: Interpreting Distorted and Overlapping Signals01:02

¹H NMR: Interpreting Distorted and Overlapping Signals

Spin systems where the difference in chemical shifts of the coupled nuclei is greater than ten times J are called first-order spin systems. These nuclei are weakly coupled, and their chemical shifts and coupling constant can generally be estimated from the well-separated signals in the spectrum.
As Δν decreases and the signals move closer, the doublets appear increasingly distorted. The intensities of the inner lines increase at the cost of those of the outer lines as the signals are slanted or...
NMR Spectroscopy: Spin–Spin Coupling01:08

NMR Spectroscopy: Spin–Spin Coupling

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 in...
Two-Dimensional (2D) NMR: Overview01:12

Two-Dimensional (2D) NMR: Overview

The 1D NMR spectrum of large and complex molecules like natural products has complicated splitting patterns and overlapping signals, which can be easily interpreted using 2-dimensional (2D) NMR. Unlike 1D NMR, 2D NMR has two frequency axes that provide the coupling information between the nucleus A and nucleus B in a molecule. The process from which 2D spectra are obtained has four steps.
The first step is the preparation period, during which nucleus A is excited with a radiofrequency pulse.
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.
Spin–Spin Coupling Constant: Overview01:08

Spin–Spin Coupling Constant: Overview

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 have a...
Double Resonance Techniques: Overview01:12

Double Resonance Techniques: Overview

Double resonance techniques in Nuclear Magnetic Resonance (NMR) spectroscopy involve the simultaneous application of two different frequencies or radiofrequency pulses to manipulate and observe two distinct nuclear spins. One important application of double resonance is spin decoupling, which selectively suppresses coupling with one type of nucleus while observing the NMR signal from another nucleus, simplifying the spectrum and enhancing resolution.
Spin decoupling is usually achieved by...

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Related Experiment Video

Updated: Jun 23, 2026

In Situ Monitoring of Diffusion of Guest Molecules in Porous Media Using Electron Paramagnetic Resonance Imaging
06:34

In Situ Monitoring of Diffusion of Guest Molecules in Porous Media Using Electron Paramagnetic Resonance Imaging

Published on: September 2, 2016

Quantitative analysis of diffusional pore coupling from T2-store-T2 NMR experiments.

Marc Fleury1, Jawed Soualem

  • 1IFP, Petrophysics Department, 1-4 avenue de Bois Préau, 92852 Rueil-Malmaison, France. marc.fleury@ifp.fr

Journal of Colloid and Interface Science
|May 15, 2009
PubMed
Summary

A new coupling factor quantifies pore connectivity in porous media using T(2)-store-T(2) NMR. This method enhances understanding of pore-to-pore exchange, improving characterization of complex systems.

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Site Directed Spin Labeling and EPR Spectroscopic Studies of Pentameric Ligand-Gated Ion Channels
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Last Updated: Jun 23, 2026

In Situ Monitoring of Diffusion of Guest Molecules in Porous Media Using Electron Paramagnetic Resonance Imaging
06:34

In Situ Monitoring of Diffusion of Guest Molecules in Porous Media Using Electron Paramagnetic Resonance Imaging

Published on: September 2, 2016

Site Directed Spin Labeling and EPR Spectroscopic Studies of Pentameric Ligand-Gated Ion Channels
11:19

Site Directed Spin Labeling and EPR Spectroscopic Studies of Pentameric Ligand-Gated Ion Channels

Published on: July 4, 2016

Area of Science:

  • Geophysics
  • Materials Science
  • Physical Chemistry

Background:

  • Low field Nuclear Magnetic Resonance (NMR) T(2) distribution is a key technique for pore size distribution analysis in porous media.
  • NMR relaxation measures magnetization decay (T(2) relaxation time) influenced by molecular diffusion and liquid-solid interactions within pore spaces.

Purpose of the Study:

  • To introduce and validate a quantitative coupling factor for analyzing diffusional pore-to-pore exchange in multimodal porous systems.
  • To enhance the characterization of pore connectivity using the T(2)-store-T(2) technique.

Main Methods:

  • Utilized the T(2)-store-T(2) technique, employing 2D inverse Laplace transforms to generate T(2)-T(2) maps.
  • Developed an analytical solution for diffusional coupling between two pore populations and defined a coupling factor.
  • Applied the methodology to bimodal pore structures including clay gels, shaly sandstones, and carbonates.

Main Results:

  • Off-diagonal peaks in T(2)-T(2) maps indicate system coupling.
  • The proposed coupling factor effectively quantifies the degree of pore population coupling.
  • The T(2)-store-T(2) method, with the coupling factor, provides satisfactory quantitative analysis even in systems with broad pore size distributions.

Conclusions:

  • The coupling factor offers a simplified understanding of complex pore coupling phenomena derived from T(2)-store-T(2) NMR.
  • The methodology reveals limitations in interpreting 1D T(2) data solely as pore size distribution.
  • The study demonstrates the technique's applicability across various geological porous media, revealing varying degrees of pore coupling.