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Related Concept Videos

NMR Spectroscopy Of Amines01:19

NMR Spectroscopy Of Amines

11.2K
In proton NMR spectroscopy, primary amines and secondary amines showcase their N–H protons as a broad signal in the chemical shift range between δ 0.5 and 5 ppm. The exact position in this range depends on several factors, including sample concentration, hydrogen bonding, and the type of solvent used. Since amine protons undergo fast proton exchange in solution, the protons are labile and therefore do not participate in any splitting with adjacent protons. Thus, the observed peak is...
11.2K
NMR Spectroscopy of Aromatic Compounds01:14

NMR Spectroscopy of Aromatic Compounds

6.4K
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.
6.4K
NMR Spectroscopy of Benzene Derivatives01:34

NMR Spectroscopy of Benzene Derivatives

11.3K
Simple unsubstituted benzene has six aromatic protons, all chemically equivalent. Therefore, benzene exhibits only a singlet peak at δ 7.3 ppm in the 1H NMR spectrum. The observed shift is far downfield because the aromatic ring current strongly deshields the protons. Any substitution on the benzene ring makes the aromatic protons nonequivalent, and the protons split each other. The peak is, therefore, no longer a singlet and the splitting pattern and their associated coupling...
11.3K
NMR Spectroscopy: Chemical Shift Overview01:15

NMR Spectroscopy: Chemical Shift Overview

3.3K
The position of the absorption signal of a sample is reported relative to the position of the signal of tetramethylsilane (TMS), which is added as an internal reference while recording spectra. The difference between the absorption frequencies of the sample and TMS (in Hz) is divided by the spectrometer operating frequency (in MHz) to obtain a dimensionless quantity called the chemical shift. It is reported on the δ (delta) scale and expressed in parts per million.
For instance, the proton...
3.3K
NMR Spectroscopy: Spin–Spin Coupling01:08

NMR Spectroscopy: Spin–Spin Coupling

3.3K
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...
3.3K
NMR and Mass Spectroscopy of Carboxylic Acids01:30

NMR and Mass Spectroscopy of Carboxylic Acids

5.3K
In ¹H NMR spectroscopy, acidic protons (–COOH) of carboxylic acids are highly deshielded and absorb far downfield, at around 9–12 ppm. The chemical shift value depends on the concentration and solvent used.
While α protons of carboxylic acids absorb at 2–2.5 ppm, β protons absorb further upfield.
Carboxylic acids are easily identified by dissolving them in deuterium oxide, which results in a rapid exchange of the acidic protons with deuterium. This leads to the...
5.3K

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Related Experiment Video

Updated: Feb 9, 2026

Transport Properties of Ibuprofen Encapsulated in Cyclodextrin Nanosponge Hydrogels: A Proton HR-MAS NMR Spectroscopy Study
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Transport Properties of Ibuprofen Encapsulated in Cyclodextrin Nanosponge Hydrogels: A Proton HR-MAS NMR Spectroscopy Study

Published on: August 15, 2016

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Indirect covariance NMR spectroscopy.

Fengli Zhang1, Rafael Brüschweiler

  • 1Carlson School of Chemistry and Biochemistry, Clark University, Worcester, Massachusetts 01610, USA.

Journal of the American Chemical Society
|October 14, 2004
PubMed
Summary

A new nuclear magnetic resonance (NMR) technique enables spin correlations without direct detection. This covariance NMR method advances biomolecular NMR and analytical chemistry, particularly for molecules with insensitive spins.

Area of Science:

  • Biomolecular NMR Spectroscopy
  • Analytical Chemistry
  • Metabolomics

Background:

  • Traditional NMR methods often require direct detection of all spin species, which can be challenging for molecules with insensitive nuclei.
  • Analyzing complex biological molecules and mixtures, such as amino acids and peptides, necessitates advanced spectroscopic techniques.
  • The field of metabolomics relies on sensitive and efficient methods for identifying and quantifying small molecules.

Purpose of the Study:

  • To introduce a novel nuclear magnetic resonance (NMR) scheme for establishing homonuclear spin correlations.
  • To demonstrate a method that bypasses the need for direct detection of specific spin species.
  • To expand the analytical capabilities for molecules containing insensitive spins in biomolecular NMR and analytical chemistry.

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Assessing Hepatic Metabolic Changes During Progressive Colonization of Germ-free Mouse by 1H NMR Spectroscopy
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Assessing Hepatic Metabolic Changes During Progressive Colonization of Germ-free Mouse by 1H NMR Spectroscopy

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Assessment of Cardiac Function and Energetics in Isolated Mouse Hearts Using 31P NMR Spectroscopy
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Assessment of Cardiac Function and Energetics in Isolated Mouse Hearts Using 31P NMR Spectroscopy

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Related Experiment Videos

Last Updated: Feb 9, 2026

Transport Properties of Ibuprofen Encapsulated in Cyclodextrin Nanosponge Hydrogels: A Proton HR-MAS NMR Spectroscopy Study
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Transport Properties of Ibuprofen Encapsulated in Cyclodextrin Nanosponge Hydrogels: A Proton HR-MAS NMR Spectroscopy Study

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Assessing Hepatic Metabolic Changes During Progressive Colonization of Germ-free Mouse by 1H NMR Spectroscopy
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Assessing Hepatic Metabolic Changes During Progressive Colonization of Germ-free Mouse by 1H NMR Spectroscopy

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Assessment of Cardiac Function and Energetics in Isolated Mouse Hearts Using 31P NMR Spectroscopy
11:38

Assessment of Cardiac Function and Energetics in Isolated Mouse Hearts Using 31P NMR Spectroscopy

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Main Methods:

  • Development of a covariance NMR scheme.
  • Experimental validation using a 13C-edited Total Correlation Spectroscopy (TOCSY) experiment.
  • Application to a mixture of amino acids and uniformly 13C-labeled cyclic decapeptide antamanide.

Main Results:

  • Successful establishment of homonuclear spin correlations without direct spin detection.
  • Demonstration of the covariance NMR method's efficacy on complex biological samples.
  • Proof-of-concept for analyzing molecules with challenging spin properties.

Conclusions:

  • The presented covariance NMR method offers a powerful new approach for molecular analysis.
  • This technique significantly enhances the study of molecules with insensitive spins.
  • It opens new avenues for research in biomolecular NMR, analytical chemistry, and metabolomics.