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Related Concept Videos

2D NMR: Overview of Homonuclear Correlation Techniques01:16

2D NMR: Overview of Homonuclear Correlation Techniques

Homonuclear correlation spectroscopy (COSY) is a powerful technique used in Nuclear Magnetic Resonance (NMR) spectroscopy to study the correlations between nuclei of the same type within a molecule. It provides information about scalar couplings between adjacent nuclei, which helps determine connectivity and structural information. There are several COSY variants, each with its unique strengths and experimental parameters.
COSY90 is the standard two-dimensional (2D) COSY experiment that...
2D NMR: Overview of Heteronuclear Correlation Techniques01:18

2D NMR: Overview of Heteronuclear Correlation Techniques

Heteronuclear correlation spectroscopy is an analytical technique that investigates the coupling between different types of nuclei, often a proton and an X-nucleus, such as carbon-13 or nitrogen-15. This method is commonly used in nuclear magnetic resonance (NMR) spectroscopy to gain insights into complex chemical compounds' structural and compositional aspects. A typical heteronuclear correlation spectrum displays X-nucleus chemical shifts on one axis and a proton spectrum on the other axis.
¹H NMR Chemical Shift Equivalence: Homotopic and Heterotopic Protons01:03

¹H NMR Chemical Shift Equivalence: Homotopic and Heterotopic Protons

Protons in identical electronic environments within a molecule are chemically equivalent and have the same chemical shift. The replacement test is a useful tool to identify chemical equivalence and predict NMR spectra. A substituent replaces each of the protons being examined and the resulting molecules are compared. If the same molecule is obtained, the protons are equivalent or homotopic. Replacement of any hydrogens in ethane by chlorine yields chloroethane because all six protons are...
NMR Spectroscopy of Aromatic Compounds01:14

NMR Spectroscopy of Aromatic Compounds

Aromatic compounds can be identified or analyzed using proton NMR and carbon‐13 NMR. Typically, aromatic hydrogens or hydrogens directly bonded to the aromatic rings are strongly deshielded by the aromatic ring current. Therefore, they absorb in the range of 6.5–8.0 ppm in proton NMR spectra. For instance, aromatic hydrogens directly bonded to the benzene ring absorb at 7.3 ppm. However, aromatic hydrogens of larger rings absorb farther upfield or downfield than the ideal range. Consider...
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...
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.

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Atomic Scale Structural Studies of Macromolecular Assemblies by Solid-state Nuclear Magnetic Resonance Spectroscopy
14:55

Atomic Scale Structural Studies of Macromolecular Assemblies by Solid-state Nuclear Magnetic Resonance Spectroscopy

Published on: September 17, 2017

Spatially resolved solid-state 1H NMR for evaluation of gradient-composition polymeric libraries.

Johannes Leisen1, Ismael J Gomez, John A Roper

  • 1School of Chemistry and Biochemistry, ‡School of Chemical and Biomolecular Engineering, and §School of Materials Science and Engineering, Georgia Institute of Technology , Atlanta, Georgia 30332, United States.

ACS Combinatorial Science
|June 9, 2012
PubMed
Summary

Polyurethane composition gradients were analyzed using NMR microimaging and solid-state NMR. Increasing hydroxy-terminated polyacrylate resin significantly increased the rigid polymer fraction, impacting chain mobility.

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Preparation of Fungal and Plant Materials for Structural Elucidation Using Dynamic Nuclear Polarization Solid-State NMR
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Preparation of Fungal and Plant Materials for Structural Elucidation Using Dynamic Nuclear Polarization Solid-State NMR

Published on: February 12, 2019

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Last Updated: May 21, 2026

Atomic Scale Structural Studies of Macromolecular Assemblies by Solid-state Nuclear Magnetic Resonance Spectroscopy
14:55

Atomic Scale Structural Studies of Macromolecular Assemblies by Solid-state Nuclear Magnetic Resonance Spectroscopy

Published on: September 17, 2017

Preparation of Fungal and Plant Materials for Structural Elucidation Using Dynamic Nuclear Polarization Solid-State NMR
09:37

Preparation of Fungal and Plant Materials for Structural Elucidation Using Dynamic Nuclear Polarization Solid-State NMR

Published on: February 12, 2019

Area of Science:

  • Polymer Science
  • Materials Science
  • Analytical Chemistry

Background:

  • Polyurethane materials are widely used due to their tunable properties.
  • Characterizing composition-gradient materials presents unique challenges for understanding structure-property relationships.

Purpose of the Study:

  • To characterize polyurethane composition-gradient films.
  • To correlate molecular mobility and structure with component ratios.
  • To evaluate novel NMR techniques for library screening.

Main Methods:

  • (1)H NMR microimaging (magnetic resonance imaging, MRI) was employed.
  • Solid-state NMR spectroscopy, including Bloch decays and spin echoes, was utilized.
  • A 1D NMR profiler was developed for spatial analysis of static spectra.

Main Results:

  • Routine MRI revealed mobile, non-cross-linked polymer chains whose mobility decreased with increasing aliphatic polyisocyanate content.
  • Solid-state NMR identified at least three distinct fractions: rigid, intermediate, and mobile.
  • The rigid, highly cross-linked fraction significantly increased with hydroxy-terminated polyacrylate resin addition.

Conclusions:

  • NMR microimaging and solid-state NMR provide complementary information on polyurethane gradient materials.
  • The 1D NMR profiler is a valuable tool for screening composition-gradient libraries.
  • Hydroxy-terminated polyacrylate resin plays a key role in increasing the rigidity of the polyurethane network.