Rearrangements and “Flat-Topped Metastable Ions” in the Mass Spectra of Substituted Nitrobenzenes1

1966 ◽  
Vol 88 (21) ◽  
pp. 5023-5025 ◽  
Author(s):  
Maurice M. Bursey ◽  
F. W. McLafferty
Keyword(s):  
Mass Spectra ◽  
Metastable Ions

Electron impact studies. VI. Mass spectra of esters and thioesters. Skeletal rearrangement on electron impact

1967 ◽  
Vol 20 (4) ◽  
pp. 689 ◽  
Author(s):  
JH Bowie ◽  
RG Cooks ◽  
P Jakobsen ◽  
S Lawesson ◽  
G Schroll
Keyword(s):  
Carbon Dioxide ◽  
Carbon Monoxide ◽  
High Resolution ◽  
Electron Impact ◽  
Mass Spectra ◽  
Skeletal Rearrangement ◽  
Unsaturated Esters ◽  
Impact Studies ◽  
Unsaturated Alcohols ◽  
Metastable Ions

The mass spectra of representative series of simple alkyl acetoacetates, alkyl acetothioacetates, and some unsaturated esters derived from unsaturated alcohols or phenols are reported and discussed. The fragmentation schemes have been established by high resolution measurements, appropriate metastable ions, and by deuterium and 18O labelling. Many of the spectra show significant skeletal rearrangement fragments arising from either loss of carbon monoxide or carbon dioxide.

Squaraine chemistry. On the anomalous mass spectra of bis(4-dimethylaminophenyl)squaraine and its derivatives

1986 ◽  
Vol 64 (8) ◽  
pp. 1607-1619 ◽  
Author(s):  
Kock-Yee Law ◽  
F. Court Bailey ◽  
Lynn J. Bluett
Keyword(s):  
Electron Impact ◽  
Mass Spectra ◽  
Mass Number ◽  
Equal Mass ◽  
Transfer Reactions ◽  
Ionization Mass ◽  
Structure Property ◽  
Fragment Ions ◽  
Structure Property Relationship ◽  
Metastable Ions

The electron impact (EI) mass specra of bis(4-dimethylaminophenyl)squaraine 1 and its derivatives 2–14 have been studied. Ions of mass number higher than the molecular ion, which are shown to be precursors of fragment ions of lower mass numbers, are observed. From the structure–property relationship, these ions are assigned to [Formula: see text] and [Formula: see text] where CH2R is the alkyl group in the N,N-dialkylanilino moiety of squaraine. Evidence is provided that the formation of [Formula: see text] and [Formula: see text] is the result of alkyl transfer and H transfer reactions within a squaraine aggregate rather than intermolecular vapor phase reactions in the mass spectrometer. This molecular aggregate is later shown to be a trimer by analysis of metastable ion data and chemical ionization mass spectrometry. The fragmentation sequence of this trimeric species is elucidated with the assistance of metastable ions. Results show that the trimer may break down to monomelic and dimeric species upon electron impact; alternatively, the four-membered ring of the central squaraine in the trimer may cleave to generate two species of approximately equal mass number. These two species usually dominate the mass spectrum and further fragment into [Formula: see text] and [Formula: see text] Detailed fragmentation schemes for [Formula: see text] and [Formula: see text] are proposed and discussed.

Spectroscopie de masse des gem-diesters cycliques. Fragment anhydride

1972 ◽  
Vol 50 (10) ◽  
pp. 1535-1538
Author(s):  
Krzysztof Jankowski ◽  
Jean Couturier ◽  
Jean-Yves Daigle
Keyword(s):  
Mass Spectra ◽  
Metastable Ions ◽  
Fragmentation Patterns

Mass spectra of four gem-diesters on three-, four-, five-, and six-member rings are analyzed. The fragmentation patterns of the investigated compounds supported by metastable ions are illustrated by Schemes 1–5 and Tables. A new fragment anhydride is proposed.

Detector for the Metastable Ions Observed in the Mass Spectra of Organic Compounds

1968 ◽  
Vol 39 (8) ◽  
pp. 1163-1167 ◽  
Author(s):  
N. R. Daly ◽  
A. McCormick ◽  
R. E. Powell
Keyword(s):  
Organic Compounds ◽  
Mass Spectra ◽  
Metastable Ions

Mechanism and structure in chemical ionization mass spectrometry: tricyclic flavanoid compounds

1973 ◽  
Vol 26 (7) ◽  
pp. 1577 ◽  
Author(s):  
JW Clark-Lewis ◽  
CN Harwood ◽  
MJ Lacey ◽  
JS Shannon
Keyword(s):  
Mass Spectrometry ◽  
Mass Spectra ◽  
Chemical Ionization ◽  
Ionization Mass Spectrometry ◽  
Chemical Ionization Mass Spectrometry ◽  
Ionization Mass ◽  
Fragmentation Pathways ◽  
Fragment Ions ◽  
Metastable Ions ◽  
Fragmentation Patterns

The chemical ionization mass spectra of a series of tricyclic flavanoid compounds have been examined using isobutane and hydrogen as reagent gases and the fragmen- tation modes have been correlated systematically in terms of structure. The technique produces simple fragmentation patterns and abundant metastable ions. The use of deuterium as reagent gas reveals the influence of extraneous water on the spectra and facilitates the interpretation of the fragmentation pathways. The fragment ions appear to arise from isomeric progenitors protonated at different sites in the molecules.

The mass spectra of trifluoroacetyl-2,5-diketopiperazines. I. cyclo-(-Gly-X), cyclo-(-Ala-X) (X = Gly, Val, Leu, Ile), and cyclo-(-Ala-Ala)

1979 ◽  
Vol 57 (15) ◽  
pp. 2037-2051 ◽  
Author(s):  
George P. Slater ◽  
Lawrence R. Hogge
Keyword(s):  
Mass Spectrum ◽  
Mass Spectra ◽  
High Resolution Data ◽  
Fragmentation Pathways ◽  
Molecular Ion ◽  
Metastable Ions ◽  
Fragmentation Patterns ◽  
The Individual ◽  
Derivatives Of ◽  
Resolution Data

The trifluoroacetyl derivatives of the 2,5-diketopiperazines cyclo-(-Gly-X), cyclo-(-Ala-X) (X = Gly, Val, Leu, Ile), and cyclo-(-Ala-Ala) were examined by GC–MS. The molecular ion was readily detectable only for TFA-cyclo-(-Gly-Gly) (m/e 306, 9%). For those compounds containing a valyl or leucyl/isoleucyl residue the ion of highest mass in the spectrum was formed by elimination of C3H6 or C4H8, respectively, from the molecular ion. In the TFA-cyclo-(-Gly-X) series this ion corresponded to the molecular ion of TFA-cyclo-(Gly-Gly) (m/e 306), and in the TFA-cyclo-(-Ala-X) series, to the molecular ion of TFA-cyclo-(-Ala-Gly) (m/e 320). The fragmentation patterns proposed for these compounds are based on the further degradation of these parent ions so that each compound within a series has a similar mass spectrum. However, sufficient differences were detectable in the various spectra to permit identification of the individual DKP's.Many of the fragmentation pathways devised to explain the mass spectra were supported by high resolution data and appropriate metastable ions.

Metastable Ions and Isotope Effects in the Mass Spectra of Methane and the Deuteromethanes

1971 ◽  
Vol 54 (9) ◽  
pp. 3834-3845 ◽  
Author(s):  
Lorin P. Hills ◽  
Marvin L. Vestal ◽  
Jean H. Futrell
Keyword(s):  
Mass Spectra ◽  
Isotope Effects ◽  
Metastable Ions

Fragmentation and rearrangement processes in the mass spectra of perhalogenoaromatic compounds. Part X. Pentafluorophenyl dimethyl derivatives of group V

1976 ◽  
Vol 54 (9) ◽  
pp. 1478-1486 ◽  
Author(s):  
Timothy R. B. Jones ◽  
Jack M. Miller ◽  
J. Lowell Peterson ◽  
Devon W. Meek
Keyword(s):  
Mass Spectra ◽  
Energy Spectra ◽  
Group V ◽  
Fragmentation Pathways ◽  
Transfer Processes ◽  
Metastable Ions ◽  
Ion Kinetic Energy ◽  
Derivatives Of ◽  
Rearrangement Processes ◽  
Resolution Study

A comprehensive low-resolution study of the mass spectra of the compounds C6F5M(CH3)2, where M = N, P, As, is described, fragmentation pathways being assigned with the aid of normal metastable ions and mass analyzed ion kinetic energy spectra (mikes). A comparison of these spectra has re-affirmed the absence of halogen transfer processes for atoms such as N which are incapable of providing the necessary vacant orbitals apparently prerequisite in the mechanisms. The influence of increased coordination to phosphorus and effects on halogen transfer processes are discussed with respect to the mass spectra of the compounds C6F5PX(CH3)2, X = O, S, Se and the gold adducts C6F5P(CH3)2•AuX, X = Cl, Br, I.

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