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Related Concept Videos

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: 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.
NMR Spectroscopy of Benzene Derivatives01:37

NMR Spectroscopy of Benzene Derivatives

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 constants depend...
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...
¹H NMR of Conformationally Flexible Molecules: Variable-Temperature NMR01:15

¹H NMR of Conformationally Flexible Molecules: Variable-Temperature NMR

The axial and equatorial protons in cyclohexane can be distinguished by performing a variable-temperature NMR experiment. In this process, except for one proton, the remaining eleven protons are replaced by deuterium. The deuterium substitution avoids the possible peak splitting caused by the spin-spin coupling between the adjacent protons. The remaining proton flips between the axial and equatorial positions.
¹H NMR of Conformationally Flexible Molecules: Temporal Resolution00:52

¹H NMR of Conformationally Flexible Molecules: Temporal Resolution

At room temperature, the chair conformer of cyclohexane undergoes rapid ring flipping between two equivalent chair conformers at a rate of approximately 105 times per second. These two chair conformers are in equilibrium. The rapid ring flipping results in the interconversion of the axial proton to an equatorial proton and an equatorial to the axial proton. Such interconversions are too rapid and cannot be detected on the NMR timescale. Hence, the NMR spectrometer cannot distinguish between the...

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Related Experiment Video

Updated: May 23, 2026

High Resolution Physical Characterization of Single Metallic Nanoparticles
09:56

High Resolution Physical Characterization of Single Metallic Nanoparticles

Published on: June 28, 2019

Quantitative structural characterization of POSS and octavinyl-POSS nanocomposites by solid state NMR.

Huipeng Zhao1, Jie Shu, Qun Chen

  • 1Shanghai Key Laboratory of Magnetic Resonance, Department of Physics, East China Normal University, Shanghai 200062, China.

Solid State Nuclear Magnetic Resonance
|April 17, 2012
PubMed
Summary

Quantitative cross polarization (QCP) in solid-state NMR accurately determines silicon ratios in Polyhedral Oligomeric Silsesquioxane (POSS). This efficient NMR method also quantifies vinyl groups in POSS nanocomposites.

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Last Updated: May 23, 2026

High Resolution Physical Characterization of Single Metallic Nanoparticles
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Characterization of Nanocrystal Size Distribution using Raman Spectroscopy with a Multi-particle Phonon Confinement Model
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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

Area of Science:

  • Materials Science
  • Analytical Chemistry
  • Solid-State NMR Spectroscopy

Background:

  • Polyhedral Oligomeric Silsesquioxane (POSS) is a versatile nanomaterial with tunable properties.
  • Accurate characterization of silicon-containing structures is crucial for material development.
  • Existing methods for quantifying specific functional groups in POSS can be time-consuming or indirect.

Purpose of the Study:

  • To develop and validate an efficient solid-state NMR method for quantitative analysis of POSS.
  • To determine the ratio of different silicon (29Si) atoms in chloromethylphenyl isobutyl POSS.
  • To accurately quantify reacted vinyl groups in octavinyl-POSS nanocomposites.

Main Methods:

  • Quantitative Cross Polarization (QCP) solid-state NMR was employed.
  • Optimized cross-polarization and depolarization with reciprocity relations were utilized for (29)Si/(1)H spin systems.
  • The method was applied to both neat POSS and POSS-perfluoropolyether nanocomposites.

Main Results:

  • The ratio of different (29)Si atoms in chloromethylphenyl isobutyl POSS was accurately determined.
  • The average number of reacted vinyl groups in octavinyl-POSS nanocomposites was directly and accurately derived.
  • The QCP method demonstrated significant time savings compared to direct polarization NMR experiments.

Conclusions:

  • Quantitative Cross Polarization (QCP) solid-state NMR is a valuable technique for the precise characterization of silicon-based materials.
  • This NMR approach offers a more direct and efficient alternative to conventional methods for analyzing POSS structures and functionalization.
  • The developed method has broad applicability for quantitative analysis of silicon-related structures in bulk materials.