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Related Concept Videos

Mass Spectrometry: Molecular Fragmentation Overview01:20

Mass Spectrometry: Molecular Fragmentation Overview

5.2K
The ionization of a molecule into a molecular ion inside the mass spectrometer causes instability in the molecule's structure due to the loss of an electron. This eventually leads to the fragmentation or breaking of some bonds in the molecule. The fragmentation occurs predominantly at specific bonds to yield relatively stable fragments.
One type of fragmentation pattern is the cleavage of a single bond in the molecular ion. The cleavage leads to a radical and a cation. The cleavage can occur at...
5.2K
Mass Spectrometry: Carboxylic Acid, Ester, and Amide Fragmentation01:01

Mass Spectrometry: Carboxylic Acid, Ester, and Amide Fragmentation

2.6K
The fragmentation patterns observed for compounds such as carboxylic acids, esters, and amides in the mass spectra include ⍺-cleavage and McLafferty rearrangement. Fragmentation by ⍺-cleavage preferentially occurs at the carbon-carbon bond at the ⍺-position next to the carboxylic group to generate a neutral radical and a cation. Long chain compounds with hydrogen at their γ-carbon undergo McLafferty rearrangement to give a radical cation and a neutral alkene.
For example,...
2.6K
Mass Spectrometry: Alcohol Fragmentation01:03

Mass Spectrometry: Alcohol Fragmentation

4.7K
Alcohols (R-OH) ionize to lose one non-bonded electron from the oxygen atom, forming molecular ions. Due to their tendency to fragment rapidly, the intensity of the molecular ion peak in the mass spectrum is weak or sometimes absent. The fragmentation patterns for alcohols occur in two ways, i.e. ⍺-cleavage and dehydration. During ⍺-cleavage, the bond at the ⍺-position adjacent to the hydroxyl group cleaves to give a resonance-stabilized cation and a radical. However,...
4.7K
Mass Spectrometry: Long-Chain Alkane Fragmentation01:18

Mass Spectrometry: Long-Chain Alkane Fragmentation

2.5K
The molecular ions of linear alkanes prefer to fragment at the carbon-carbon bond away from the end of the chain since the cleavage of an inner bond creates a stable carbocation and a stable radical. Consequently, the mass signals of linear alkanes feature intense peaks in the middle of the mass-to-charge ratio plot with weaker peaks on either end. The fragmentation of each carbon-carbon bond with the release of a methyl group in each splitting leads to prominent peaks in the mass spectra...
2.5K
Mass Spectrometry: Alkene Fragmentation00:59

Mass Spectrometry: Alkene Fragmentation

3.7K
Alkenes lose one electron from the unsaturated π bond upon ionization and form stable molecular ions. Further fragmentation of alkenes occurs through three different reaction pathways. The most prominent fragmentation is the cleavage at the allylic position. The resultant allylic carbocation is resonance stabilized. In the mass spectra of terminal alkenes, this fragment appears at a mass-to-charge ratio of 41. In the internal alkenes, where there are two choices of allylic cleavage, the...
3.7K
Mass Spectrometry: Aromatic Compound Fragmentation01:23

Mass Spectrometry: Aromatic Compound Fragmentation

2.5K
Upon ionization, aromatic compounds generate a molecular ion that is observed as a prominent peak in their mass spectra. For example, the molecular ion peak for benzene appears at a mass-to-charge ratio of 78, while toluene is observed at a mass-to-charge ratio of 92. The molecular ion benzene is highly stable and does not readily undergo further fragmentation due to the significant amount of energy required to disrupt the aromatic stability of the benzene ring. In contrast, the molecular ion...
2.5K

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Updated: May 5, 2026

Spatial Separation of Molecular Conformers and Clusters
10:37

Spatial Separation of Molecular Conformers and Clusters

Published on: January 9, 2014

11.0K

Molecular electrostatic potentials by systematic molecular fragmentation.

David M Reid1, Michael A Collins

  • 1Research School of Chemistry, Australian National University, Canberra, ACT 0200, Australia.

The Journal of Chemical Physics
|December 11, 2013
PubMed
Summary
This summary is machine-generated.

A new method estimates molecular electrostatic potential directly from electron density using systematic fragmentation. This approach accurately predicts molecular interactions and binding energies, proving useful in computational chemistry and drug discovery.

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Area of Science:

  • Computational Chemistry
  • Molecular Modeling
  • Quantum Chemistry

Background:

  • Estimating molecular electrostatic potential (MEP) is crucial for understanding molecular interactions.
  • Accurate MEP calculation often requires computationally intensive methods.

Purpose of the Study:

  • To present a simple and accurate method for estimating MEP.
  • To demonstrate the method's utility in predicting binding energies.

Main Methods:

  • Systematic molecular fragmentation approach.
  • Direct estimation of MEP from electron density.
  • Validation using organic molecules and ions.

Main Results:

  • The method accurately estimates MEP in and around molecules.
  • Established accuracy for diverse organic molecules and ions.
  • Successfully estimated binding energy of water in ubiquitin.

Conclusions:

  • The presented method offers an efficient way to calculate MEP.
  • This approach has practical applications in computational chemistry and molecular simulations.