Formation of 2-substituted benzofuran fragment ions from 6-alkyl- and 6-aryldibenzo(d,f)(1,3)dioxepine derivatives under electron ionization-a useful precursor ion for isomeric differentiation

2009 ◽  
Vol 44 (2) ◽  
pp. 245-251 ◽  
Author(s):  
Michela Begala ◽  
Graziella Tocco ◽  
Gabriele Meli ◽  
Gianni Podda ◽  
Silvana A. M. Urru
Keyword(s):  
Electron Ionization ◽  
Fragment Ions ◽  
Isomeric Differentiation

Unimolecular Gas-Phase Reactions of Diethyl Phthalate, Isophthalate, and Terephthalate upon Electron Ionization

2003 ◽  
Vol 56 (5) ◽  
pp. 473 ◽  
Author(s):  
Susumu Tajima ◽  
Masashi Mamada ◽  
Satoshi Nakajima ◽  
Yutaka Takahashi ◽  
Nico M. M. Nibbering
Keyword(s):  
Gas Phase ◽  
Molecular Ions ◽  
Ion Source ◽  
Electron Ionization ◽  
Diethyl Phthalate ◽  
Gas Phase Reactions ◽  
Fragment Ions ◽  
Metastable Fragmentation ◽  
Primary Fragmentation ◽  
Ion Kinetic Energy

Unimolecular gas-phase reactions of diethyl phthalate (1), isophthalate (2), and terephthalate (3), upon electron ionization, have been investigated by use of mass-analyzed ion kinetic energy (MIKE) spectrometry and deuterium labelling. The metastable molecular ions (1)+ decompose to give exclusively the ions m/z 176 ([M – CH3CH2OH]+) and not the ions by the loss of CH3CH2O as proposed earlier in the literature. The metastable molecular ions (2)+ and (3)+ fragment differently from (1)+ and lead not only to the formation of the major fragment ions m/z 194 ([M − CH2CH2]+) via a McLafferty rearrangement but also to minor fragment ions m/z 193 ([M – CH2CH3]+).Yet, molecular ions decomposing in the ion source all show as primary fragmentation channel the loss of CH3CH2O to give the ions at m/z 177, which further dissociate to give the ions at m/z 149 through the loss of C2H4 or CO, indicating the resulting ions are +COC6H4COOH and +C6H4COOCH2CH3. The +COC6H4COOH ions decompose into the m/z 121, 93, and 65 ions by the consecutive losses of three carbon monoxide molecules, respectively. Prior to the second CO loss, a migration of the OH group to the benzene ring occurs. During the metastable fragmentation of the +C6H4COOCH2CH3 ions no ethoxy migration occurs, in contrast to the methoxy migration taking place in the metastable decomposition of the lower homologue +C6H4COOCH3 ions.

scholarly journals Gas Chromatography Electron Ionization Mass Spectral Analysis of Thio Analogues of Pyrimidine Bases: 5-Bromo-2,4-di-o-(m- and p-) chloro- (bromo-)benzylthiouracils and 6-methyluracils

2012 ◽  
Vol 2012 ◽  
pp. 1-8
Author(s):  
G. Bartkowiak ◽  
E. Wyrzykiewicz ◽  
G. Schroeder
Keyword(s):  
Gas Chromatography ◽  
Electron Ionization ◽  
Gas Chromatography Mass Spectrometry ◽  
Ionization Mass ◽  
Structural Isomers ◽  
Mass Spectral Fragmentation ◽  
Mass Spectral ◽  
Fragment Ions ◽  
Accurate Mass Measurements ◽  
Pyrimidine Bases

Electron ionization (EI) mass spectral fragmentation routes of twelve 5-bromo-2,4-di-o-(m- and p-) chloro- (bromo-)benzyl-thiouracils and 6-methyluracils are investigated. The compounds studied are analyzed using gas chromatography/mass spectrometry (GC/MS). Fragmentation pathways, whose elucidation is assisted by accurate mass measurements and metastable transitions, are discussed. Correlation between the abundances of the selected fragment ions of the compounds investigated is discussed. The data obtained make grounds for distinction of structural isomers.

The Influence of the C-4′ Substituent on the Formation of Benzoyl Ions during Electron Ionization-Induced Decomposition of Some 2-Phenyl-1,3,4-Oxadiazoles

2002 ◽  
Vol 8 (4) ◽  
pp. 295-298 ◽  
Author(s):  
Rafał Frahski ◽  
Krystian Eitner ◽  
Grzegorz Schroeder ◽  
Volodymir Rybachenko
Keyword(s):  
Charge Density ◽  
Phenyl Ring ◽  
Molecular Ions ◽  
Electron Ionization ◽  
Ion Current ◽  
Fragment Ions ◽  
Induced Decomposition ◽  
Linear Correlations ◽  
Positively Charged

The effect of the C-4′ substituent for the formation of benzoyl ions during electron ionization-induced decomposition of some 2-phenyl-1,3,4-oxadiazoles is studied. The formation of these ions occurs via an azirane ion. The sums of the abundances of benzoyl ions and abundances of fragment ions derived from them, expressed as a percentage of total-ion current, were compared with the calculated charge density on both C-4′ atoms and atoms connected with C-4′ atoms. Linear correlations were found for both molecular and intermediate azirane ions. In the case of substituents which are less likely to be positively charged, the peaks of benzoyl ions have higher relative intensities. It is deduced that ionization in the phenyl ring strongly affects the formation of benzoyl ions from molecular ions of the studied compounds.

Structural Characterization and Differentiation of Isomeric ω-Bromoalkoxy Derivatives of (E)-Chalcone by Means of Mass Spectrometry

2008 ◽  
Vol 14 (1) ◽  
pp. 37-47 ◽  
Author(s):  
Zdzisława Nowakowska
Keyword(s):  
Mass Spectrometry ◽  
Electrospray Ionization ◽  
Structural Characterization ◽  
Molecular Ions ◽  
Electron Ionization ◽  
Cone Voltage ◽  
Fragment Ions ◽  
The Difference ◽  
Derivatives Of

Mass spectrometry with electron ionization and electrospray ionization have been applied to characterize and differentiate the isomeric ortho-, meta- or para-( E)-bromoalkyloxychalcones 1–15. The difference in the values of μ1–μ5 (i.e. the ratio of abundances of the selected fragment ions to those of the molecular ions) in the series of isomeric chalcones studied and the so-called “in-source” fragmentation induced by increasing cone voltage have been found to be important and reliable indicators differentiating the isomers studied.

Reduction Reactions in the Ion Source in Electron Ionization Mass Spectrometry

2020 ◽  
Vol 75 (13) ◽  
pp. 1685-1692
Author(s):  
D. M. Mazur ◽  
M. E. Zimens ◽  
Th. B. Latkin ◽  
N. V. Ul’yanovskii ◽  
V. B. Artaev ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Ion Source ◽  
Electron Ionization ◽  
Electron Ionization Mass Spectrometry ◽  
Ionization Mass Spectrometry ◽  
Ionization Mass ◽  
Reduction Reactions

Scattering of Low-Energy (5-12 eV) C2D4•+ Ions from Room-Temperature Carbon Surfaces

2008 ◽  
Vol 73 (6-7) ◽  
pp. 755-770 ◽  
Author(s):  
Andriy Pysanenko ◽  
Ján Žabka ◽  
Zdeněk Herman
Keyword(s):  
Survival Probability ◽  
Room Temperature ◽  
Incident Angle ◽  
Pyrolytic Graphite ◽  
Carbon Surface ◽  
Translational Energy ◽  
Energy Distributions ◽  
Surface Mass ◽  
Fragment Ions ◽  
Product Ions

The scattering of the hydrocarbon radical cation C2D4•+ from room-temperature carbon (highly oriented pyrolytic graphite, HOPG) surface was investigated at low incident energies of 6-12 eV. Mass spectra, angular and translational energy distributions of product ions were measured. From these data, information on processes at surfaces, absolute ion survival probability, and kinematics of the collision was obtained. The projectile ion showed both inelastic, dissociative and reactive scattering, namely the occurrence of H-atom transfer reaction with hydrocarbons present on the room-temperature carbon surface. The absolute survival probability of the ions for the incident angle of 30° (with respect to the surface) decreased from about 1.0% (16 eV) towards zero at incident energies below 10 eV. Estimation of the effective surface mass involved in the collision process led to m(S)eff of about 57 a.m.u. for inelastic non-dissociative collisions of C2D4•+ and of about 115 a.m.u. for fragment ions (C2D3+, C2D2•+) and ions formed in reactive surface collisions (C2D4H+, C2D2H+, contributions to C2D3+ and C2D2•+). This suggested a rather complex interaction between the projectile ion and the hydrocarbon-covered surface during the collision.

Comparison of isomeric C3H7O+ ion mobilities using fragment ions from 2-butanol and tert-butanol in He and Ne

2020 ◽  
Vol 739 ◽  
pp. 137045
Author(s):  
Kazunari Takaya ◽  
Yuya Hasegawa ◽  
Tetsuo Koizumi
Keyword(s):  
Tert Butanol ◽  
Fragment Ions

Fragment Ions of Dimethylsilane Produced by Hot Tungsten Wires

2006 ◽  
Vol 45 (10B) ◽  
pp. 8204-8207 ◽  
Author(s):  
Satoru Yoshimura ◽  
Akinori Toh ◽  
Satoshi Sugimoto ◽  
Masato Kiuchi ◽  
Satoshi Hamaguchi
Keyword(s):  
Fragment Ions

Electron-impact dissociation ofCD3+andCH3+ions producingCD2+,CH+, andC+fragment ions

2009 ◽  
Vol 79 (5) ◽  
Author(s):  
E. M. Bahati ◽  
M. Fogle ◽  
C. R. Vane ◽  
M. E. Bannister ◽  
R. D. Thomas ◽  
...  
Keyword(s):  
Electron Impact ◽  
Electron Impact Dissociation ◽  
Fragment Ions
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