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Related Concept Videos

Mass Spectrometry: Molecular Fragmentation Overview01:20

Mass Spectrometry: Molecular Fragmentation Overview

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...
Introduction to Electrophilic Addition Reactions of Alkenes02:24

Introduction to Electrophilic Addition Reactions of Alkenes

The double bond in a simple, unconjugated alkene is a region of high electron density that can act as a weak base or a nucleophile. The filled π orbital (HOMO) of the double bond can interact with the empty LUMO of an electrophile. A bonding interaction occurs when the electrophile attacks between the two carbons; the electrophile then accepts a pair of electrons from the π bond and undergoes addition across the double bond, yielding a single product.
Addition and elimination reactions can be...
Mass Spectrometry: Alkene Fragmentation00:59

Mass Spectrometry: Alkene Fragmentation

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...
α-Alkylation of Ketones via Enolate Ions01:10

α-Alkylation of Ketones via Enolate Ions

Ketones with α protons are deprotonated by strong bases like lithium diisopropylamide (LDA) to form enolate ions. The anion is stabilized by resonance, and its hybrid structure exhibits negative charges on the carbonyl oxygen and the α carbon. This ambident nucleophile can attack an electrophile via two possible sites: the carbonyl oxygen, known as O-attack, or the α carbon, known as C-attack. The nucleophilic attack via the carbanionic site is preferred. This is due to the strong interaction...
Mass Spectrometry: Carboxylic Acid, Ester, and Amide Fragmentation01:01

Mass Spectrometry: Carboxylic Acid, Ester, and Amide Fragmentation

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, the fragmentation of...
Carbocations02:10

Carbocations

Carbocations are one of the reaction intermediates formed during several nucleophilic substitutions or elimination reactions. A carbocation is an electron-deficient species with the central carbon atom having six electrons and three bonded atoms. The central carbon in a carbocation is sp2 hybridized with trigonal planar geometry. It has an empty p orbital perpendicular to the plane of the structure that can accept electrons. Thus, carbocations act as strong electrophiles and may react with any...

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Dissociative electron attachment to β-alanine.

Violaine Vizcaino1, Peter Bartl, David Gschliesser

  • 1Institut für Ionenphysik and Angewandte Physik, Universität Innsbruck, Technikerstrasse 25, A-6020 Innsbruck, Austria. violaine.vizcaino@uibk.ac.at

Chemphyschem : a European Journal of Chemical Physics and Physical Chemistry
|April 22, 2011
PubMed
Summary
This summary is machine-generated.

Dissociative electron attachment to beta-alanine fragments molecules, revealing key bond cleavages and reaction pathways. This study details electron-induced reactions in amino acids, providing insights into their chemical behavior.

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Area of Science:

  • Physical Chemistry
  • Chemical Physics
  • Molecular Physics

Background:

  • Amino acids are fundamental biological molecules.
  • Understanding their electron-induced fragmentation is crucial for various applications.
  • Beta-alanine (βA) is a non-proteinogenic amino acid with unique properties.

Purpose of the Study:

  • To investigate the dissociative electron attachment (DEA) process in gas-phase beta-alanine.
  • To identify and quantify fragment ions produced by DEA.
  • To elucidate the underlying fragmentation mechanisms and energetics.

Main Methods:

  • Measured absolute ion yields for various fragments as a function of incident electron energy (0-15 eV).
  • Calculated theoretical threshold energies for decomposition reactions using the G4(MP2) method.
  • Investigated metastable anion decays using the mass-analyzed ion kinetic energy (MIKE) scan technique.

Main Results:

  • The dominant DEA pathway in beta-alanine involves the loss of a hydrogen atom.
  • Multiple complex bond cleavages were observed, leading to a variety of fragment ions.
  • Metastable decay of the (βA-H)(-) anion was characterized.
  • Calculated threshold energies provide insights into the energetics of fragmentation pathways.

Conclusions:

  • Dissociative electron attachment to beta-alanine exhibits complex fragmentation patterns.
  • The study provides a detailed understanding of electron-molecule interactions in beta-alanine.
  • Comparisons with alpha-alanine and other amino acids highlight similarities and differences in DEA processes.