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Related Concept Videos

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...
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 Of Amines01:19

NMR Spectroscopy Of Amines

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 broad and...
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...
Structure of Amines01:19

Structure of Amines

The hybridized nitrogen atom in amines possesses a lone pair of electrons and is bound to three substituents with a bond angle of around 108°, which is less than the tetrahedral angle of 109.5°. However, the C–N–H bond angle is slightly larger at 112°, with a carbon–nitrogen bond length of 147 pm. This carbon–nitrogen bond length of of amines is longer than the carbon–oxygen bond of alcohols (143 pm) but shorter than alkanes’ carbon–carbon bond (154 pm). These aspects are illustrated in Figure...
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.

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Related Experiment Video

Updated: May 31, 2026

Structure and Coordination Determination of Peptide-metal Complexes Using 1D and 2D 1H NMR
14:44

Structure and Coordination Determination of Peptide-metal Complexes Using 1D and 2D 1H NMR

Published on: December 16, 2013

EAD-MS/MS-driven intelligent structure prediction and NMR fast structure elucidation framework for nitazene analogs.

Cui-Mei Liu1, Yu Du2, Bo-Yu Huang3

  • 1Key Laboratory of Drug Monitoring and Control, Drug Intelligence and Forensic Center, Ministry of Public Security, Beijing 100193, China.

Forensic Science International
|May 29, 2026
PubMed
Summary

New software using mass spectrometry aids in identifying potent nitazene analog opioids. This tool, combined with NMR, speeds up structural analysis for better control of these new psychoactive substances.

Keywords:
Electron-activated dissociation (EAD)Mass spectrometry and intelligent elucidation (MSIE)NMR characteristicsNitazene analogs

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

Published on: September 17, 2017

Related Experiment Videos

Last Updated: May 31, 2026

Structure and Coordination Determination of Peptide-metal Complexes Using 1D and 2D 1H NMR
14:44

Structure and Coordination Determination of Peptide-metal Complexes Using 1D and 2D 1H NMR

Published on: December 16, 2013

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:

  • Forensic Chemistry
  • Analytical Chemistry
  • Pharmacology

Background:

  • Nitazene analogs, a new class of potent opioids with a 2-benzylbenzimidazole core, are emerging as significant new psychoactive substances (NPS).
  • In China, nitazene analogs were designated as the third NPS class subject to generic control as of July 1, 2025, following fentanyl analogs and synthetic cannabinoids.
  • Effective control requires rapid identification and structural elucidation methods.

Purpose of the Study:

  • To develop an automated mass spectrometry intelligent elucidation (MSIE) software for the rapid identification and structure prediction of nitazene analogs.
  • To establish a comprehensive structure confirmation workflow utilizing NMR spectroscopy.
  • To create an integrated MS-NMR platform for robust technical support in the generic control of nitazene analogs.

Main Methods:

  • Developed MSIE software utilizing mass spectrometry fragmentation pathways and characteristic fragment ions from 14 nitazene substances under electron-activated dissociation (EAD).
  • Established a structure confirmation workflow based on Nuclear Magnetic Resonance (NMR) spectroscopic characteristics.
  • Integrated mass spectrometry (MS) and NMR techniques into a unified analytical platform.

Main Results:

  • The MSIE software demonstrated capability for rapid early warning and structure prediction of nitazene analogs.
  • The NMR-based workflow significantly reduced the time required for structural verification of these compounds.
  • The integrated MS-NMR platform provides reliable data for forensic and pharmaceutical analysis.

Conclusions:

  • The developed automated MSIE software and integrated MS-NMR platform offer efficient solutions for the identification and structural verification of nitazene analogs.
  • These advancements provide crucial technical support for the generic control of nitazene analogs, addressing challenges in forensic and pharmaceutical settings.
  • The study highlights the importance of advanced analytical techniques in managing the emergence of new psychoactive substances.