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Related Concept Videos

NMR Spectroscopy Of Amines01:19

NMR Spectroscopy Of Amines

8.9K
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...
8.9K
Mass Spectrometry of Amines01:19

Mass Spectrometry of Amines

4.2K
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...
4.2K
Physical Properties of Amines01:26

Physical Properties of Amines

3.2K
Amines with low molecular weight are usually gaseous at room temperature, while those with high molecular weight are liquid or solids in nature. Usually, low molecular weight amines have a rotten fish-like smell. Diamines typically have a pungent smell. For instance, cadaverine and putrescine, depicted in Figure 1, are two molecules responsible for decaying tissue.
3.2K
Structure of Amines01:19

Structure of Amines

2.6K
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’...
2.6K
Mass Spectrometry: Amine Fragmentation00:55

Mass Spectrometry: Amine Fragmentation

1.6K
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...
1.6K
Atomic Emission Spectroscopy: Lab01:29

Atomic Emission Spectroscopy: Lab

174
AES is a powerful analytical technique, especially effective when used with plasma sources, producing abundant spectra in characteristic emission lines. The Inductively Coupled Plasma (ICP), in particular, yields superior quantitative analytical data due to its high stability, low noise, low background, and minimal interferences under optimal experimental conditions. However, newer air-operated microwave sources are emerging as promising alternatives that could be more cost-effective than...
174

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Studying Local Electrostatics by Terahertz Spectroscopy Using Amines as a Probe.

Simon Schulke1, Melinda Nolten1, Gerhard Schwaab1

  • 1Physical Chemistry 2, Ruhr-Univeristy Bochum, Universitaetsstraße 150, 44801, Bochum, Germany.

Chemphyschem : a European Journal of Chemical Physics and Physical Chemistry
|October 28, 2023
PubMed
Summary

Amines act as sensitive, label-free probes for local protonation. Terahertz-FTIR spectroscopy quantifies protonation-induced spectral changes, correlating amine titration spectra with pKa values.

Keywords:
AminesHydrationLocal ElectrostaticsTHz SpectroscopyTitration

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Area of Science:

  • Physical Chemistry
  • Spectroscopy
  • Biophysical Chemistry

Background:

  • Previous studies demonstrated zwitterion glycine's utility as a protonation probe.
  • The concept of using molecular vibrations to sense protonation requires broader validation.

Purpose of the Study:

  • To investigate the generalizability of using molecular probes for local protonation.
  • To assess the efficacy of amines as label-free protonation sensors.
  • To correlate Terahertz-FTIR spectral changes with pKa values for solvated amines.

Main Methods:

  • pH-dependent Terahertz-FTIR (THz-FTIR) spectroscopy was employed.
  • Spectra of solvated Diethylamine (DEA), Triethylamine (TEA), and Diisopropylamine (DiPA) were measured.
  • Intensity changes in THz-FTIR spectra were precisely quantified.

Main Results:

  • Significant intensity changes were observed in THz-FTIR spectra upon amine protonation.
  • These spectral changes were quantifiable and correlated with amine pKa values.
  • The study successfully linked amine titration spectra in the THz range to their respective pKa values.

Conclusions:

  • Amines serve as effective, label-free probes for local protonation.
  • Terahertz spectroscopy offers a precise method for quantifying protonation-induced spectral alterations.
  • This approach holds potential for label-free probing of biomolecular charge states in aqueous environments.