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.

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.

Electron impact studies. XVIII. Mass spectra of pyridazines, phthalazines, and related compounds

1967 ◽  
Vol 20 (12) ◽  
pp. 2677 ◽  
Author(s):  
JH Bowie ◽  
RG Cooks ◽  
PF Donaghue ◽  
JA Halleday ◽  
HJ Rodda
Keyword(s):  
High Resolution ◽  
Electron Impact ◽  
Mass Spectra ◽  
Molecular Ions ◽  
Prominent Feature ◽  
Substitution Pattern ◽  
Impact Studies ◽  
Metastable Ions ◽  
Fragmentation Patterns ◽  
Related Compounds

The mass spectra of substituted pyridazines, phthalazines, and related compounds are reported and discussed. Molecular ions are a prominent feature of all the spectra, and fragmentation modes may be usefully correlated with both the type of heterocycle and its substitution pattern. Fragmentation patterns have been substantiated by extensive high resolution studies and appropriate metastable ions.

Electron impact studies. XII. Mass spectra of substituted imidazoles

1967 ◽  
Vol 20 (8) ◽  
pp. 1613 ◽  
Author(s):  
JH Bowie ◽  
RG Cooks ◽  
S Lawesson ◽  
G Schroll
Keyword(s):  
Mass Spectrometry ◽  
Structure Elucidation ◽  
Mass Spectra ◽  
Molecular Ions ◽  
Skeletal Rearrangement ◽  
Mass Measurements ◽  
Exact Mass ◽  
Metastable Ions ◽  
Characteristic Fragmentation ◽  
Fragmentation Patterns

The mass spectra of 37 imidazoles are reported and discussed. The spectra exhibit pronounced molecular ions and characteristic fragmentation patterns. The fragmentation modes have been substantiated by deuterium labelling, exact mass measurements, and appropriate metastable ions. Skeletal rearrangement fragments are rare in these spectra; consequently mass spectrometry is useful for structure elucidation of imidazoles.

Mass spectra of α-diketones. I. Non-enolized α-diketones

1968 ◽  
Vol 21 (5) ◽  
pp. 1247 ◽  
Author(s):  
JH Bowie ◽  
RG Cooks ◽  
GE Gream ◽  
MH Laffer
Keyword(s):  
Mass Spectra ◽  
Molecular Ions ◽  
Ring Size ◽  
Mass Measurements ◽  
Exact Mass ◽  
Deuterium Labelling ◽  
Mclafferty Rearrangement ◽  
Metastable Ions ◽  
Fragmentation Patterns

The mass spectra of a series of a-diketones are reported and discussed. Fragmentation patterns have been substantiated by exact mass measurements, metastable ions, and in two cases, by deuterium labelling studies. The McLafferty rearrangement is not observed in the spectra of aliphatic α-diketones; fragmentation proceeds by α-cleavage. The fragmentation modes of those cyclic α-diketones studied depend largely on the ring size. Molecular ions are observed in all spectra.

Mass Spectra of β-Keto Esters

1972 ◽  
Vol 50 (16) ◽  
pp. 2707-2710 ◽  
Author(s):  
Larry Weiler
Keyword(s):  
Mass Spectra ◽  
Carbonyl Groups ◽  
Mass Spectral Fragmentation ◽  
Mass Spectral ◽  
Keto Esters ◽  
Fragmentation Patterns

The mass spectra of several γ-substituted β-keto esters have been recorded and interpreted. The fragmentation patterns are compared to those of α-substituted β-keto esters and are found to be very useful in differentiating the α- and γ-substituted isomers. The mass spectral fragmentation schemes are dominated by cleavages α to the carbonyl groups and by McLafferty rearrangements.

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.

Mass Spectra of Some Carbamates and Related Ureas. II

1968 ◽  
Vol 51 (2) ◽  
pp. 347-365 ◽  
Author(s):  
W R Benson ◽  
J N Damico
Keyword(s):  
Spectral Data ◽  
Relative Abundance ◽  
Mass Spectra ◽  
The Other ◽  
Methyl Isocyanate ◽  
Mass Spectral Data ◽  
Mass Spectral ◽  
Fragmentation Patterns ◽  
Sulfur Containing

Abstract Mass spectral data for fourteen carbamates, live dithiocarbamates, one thiocarbamate, and eight phenylureas are given with some interpretations. Among the compounds examined were some sulfur-containing aliphatic oxime carbamates; these lost the sulfur moieties more easily than the methyl isocyanate moiety. In the aryl IV-methylcarbamate series, the CH3NCO moiety appears to be lost most easily, as it is in pyrolysis. When l-(2-chlorophenyI)-3- methylurea is fragmented, unexpectedly the [HNC0]+ ion is found in high relative abundance. However, the remaining ureas undergo fragmentation in a manner similar to their related carbamates. Although the two ethylene bisdithiocarbamates give essentially identical fragmentation patterns, the spectra of the other four thio- and dithiocarbamates show sufficient differences so that they may be distinguished from one another.

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