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Related Concept Videos

Mass Spectrometry: Amine Fragmentation00:55

Mass Spectrometry: Amine Fragmentation

1.7K
Amines can be identified using mass spectroscopy based on their characteristic fragmentation patterns. The molecular ions of amines undergo fragmentation via ⍺-cleavage. The ⍺-cleavage of the carbon-carbon bonds in amines generates an alkyl radical and resonance-stabilized nitrogen-containing cation.
In amines, the number of nitrogen atoms affects the mass of the molecular ion, which is described by the nitrogen rule of mass spectrometry. This rule states that a compound containing...
1.7K
Mass Spectrometry of Amines01:19

Mass Spectrometry of Amines

4.4K
In mass spectroscopy, amines undergo fragmentation to give parent ions with odd molecule weights. This observed mass spectrum follows the nitrogen rule: a molecule with an odd number of nitrogen atoms produces a parent ion with an odd molecular weight. The remaining fragments have an even mass.
Amines undergo fragmentation through α cleavage, producing nitrogen-containing cations—iminium ions—and alkyl radicals. Mass spectra of aromatic and cyclic aliphatic amines exhibit...
4.4K
Structure of Amines01:19

Structure of Amines

2.7K
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’...
2.7K
NMR Spectroscopy Of Amines01:19

NMR Spectroscopy Of Amines

9.3K
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...
9.3K

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Related Experiment Video

Updated: Aug 28, 2025

Imine Metathesis by Silica-Supported Catalysts Using the Methodology of Surface Organometallic Chemistry
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Imine Metathesis by Silica-Supported Catalysts Using the Methodology of Surface Organometallic Chemistry

Published on: October 18, 2019

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Quantification of amine functional groups on silica nanoparticles: a multi-method approach.

Ying Sun1, Filip Kunc1, Vinod Balhara1

  • 1National Research Council Canada Ottawa ON Canada K1A 0R6 Linda.Johnston@nrc-cnrc.gc.ca.

Nanoscale Advances
|September 22, 2022
PubMed
Summary

Quantifying amine groups on silica nanoparticles (NPs) is crucial for their application and environmental safety. Colorimetric assays, like ninhydrin and 4-nitrobenzaldehyde, effectively measure accessible amines on NPs, validated by NMR and XPS.

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Area of Science:

  • Materials Science
  • Nanotechnology
  • Surface Chemistry

Background:

  • Surface chemistry dictates nanomaterial behavior in applications and environmental fate.
  • Accurate quantification of surface functional groups, like amines, is vital for quality control in nanomaterial production.

Purpose of the Study:

  • To compare four methods for quantifying amine functional groups on silica nanoparticles (NPs).
  • To validate the reliability of colorimetric assays for routine analysis of accessible amines on NPs.

Main Methods:

  • Comparison of two colorimetric assays (ninhydrin and 4-nitrobenzaldehyde) for accessible amines.
  • Validation using NP dissolution followed by solution-state 1H NMR for total amine content.
  • Further validation via 19F solid-state NMR and X-ray photoelectron spectroscopy (XPS) after modification with a benzaldehyde probe.

Main Results:

  • Colorimetric assays quantified 50-100% of total amine content on various commercial silica NPs.
  • Good agreement was observed between colorimetric assays, solid-state NMR, and XPS elemental ratios.
  • Differences in amine quantification were attributed to amines located outside the XPS probing depth.

Conclusions:

  • The study validates simple colorimetric assays for efficient quantification of surface amines on silica NPs.
  • These assays are reliable for routine analysis, providing a practical alternative to more complex methods.
  • Understanding accessible vs. total amine content is important for predicting NP behavior.