Mass spectrometric studies. X. Phenacylpyridinium enol-betaines

1972 ◽  
Vol 25 (2) ◽  
pp. 345 ◽  
Author(s):  
IC Calder ◽  
QN Porter ◽  
CM Richards
Keyword(s):  
Hydrogen Atom ◽  
Mass Spectra ◽  
Parent Compound ◽  
Molecular Ions ◽  
Mass Spectrometric ◽  
Deuterium Labelling ◽  
E 92

Phenylpyridinium enol-betaines have mass spectra containing abundant molecular ions which decompose by loss of a hydrogen atom to give intense M- 1 species. Both ions eliminate CO and CHO units, and the courses of the various decompositions have been established by making use of deuterium labelling. The ion at m/e 92 in the spectrum of the parent compound is best described by an azatropylium structure.

Mass Spectrometric Studies. XIII. Spirocyclic Glycidic Esters

1979 ◽  
Vol 32 (9) ◽  
pp. 1983 ◽  
Author(s):  
J Baldas ◽  
D Iakovidis ◽  
QN Porter
Keyword(s):  
Mass Spectra ◽  
Alkoxy Group ◽  
Mass Spectrometric ◽  
Deuterium Labelling ◽  
Ring Contraction ◽  
Ring Junction

The mass spectra of a series of spirocyclic glycidic esters derived from cyclo-butanones, -pentanones, -hexanones, -heptanones and -octanones show the following characteristic fragmentations: (i) a rearrangement involving migration of the ester alkoxy group to the ring junction, followed by elision of the group COCR=O (R = H or Me), and (ii) loss of the alkoxycarbonyl group by α-fission, followed by ring-contraction and loss of the elements of acetaldehyde. The major fragmentations are supported by deuterium-labelling experiments, and a number of minor decompositions are described.

Epoxidation of 4,4-dimethyl-A-homo-4a-cholestene derivatives and a study of electron impact mass spectra of the epoxidation products

1982 ◽  
Vol 47 (1) ◽  
pp. 315-337 ◽  
Author(s):  
Helena Velgová ◽  
Antonín Trka
Keyword(s):  
Electron Impact ◽  
Mass Spectra ◽  
Molecular Ions ◽  
Mass Spectrometric ◽  
Characteristic Decomposition ◽  
Conformational Effects ◽  
Electron Impact Mass ◽  
Decomposition Pathway ◽  
Impact Mass

The effect of the substituent in the position 3 on the epoxidation of some 4,4-dimethyl-A-homo-4a-cholestene derivatives was investigated. The stereochemistry of the epoxidation is affected mainly by sterical and conformational effects. The mass spectrometric behaviour of epoxides IV-XI, XV-XX, XXIII and XXIV and of 4a,5-unsaturated 3-ketones XXI and XXVI was also studied. The double-transannular cleavage represents a common and characteristic decomposition pathway of molecular ions of these compounds.

Mass Spectrometric Studies. XIV. Nitrochalcones

1979 ◽  
Vol 32 (10) ◽  
pp. 2249 ◽  
Author(s):  
J Baldas ◽  
QN Porter
Keyword(s):  
Oxygen Transfer ◽  
Mass Spectra ◽  
Nitro Compounds ◽  
Molecular Ions ◽  
Mass Spectrometric ◽  
Hydrogen Atoms ◽  
Carbon Carbon Bond ◽  
Nitro Derivatives ◽  
Anchimeric Assistance ◽  
Hydroxy Groups

The mass spectra of chalcone, of its 2-, 2'-, 3-, 3'- and 4-nitro derivatives, and of a number of deuterated analogues, are described. Fragmentation of the 2-nitro isomer is very simple on account of anchimeric assistance to a carbon-carbon bond fission from the nitro group. The 2'-nitro isomer shows complex fragmentation resulting from oxygen transfer to the α,β-double bond. The 3-, 3'-, and 4-nitro compounds fragment in ways similar to that of chalcone itself, except for losses of hydroxy groups from their molecular ions. The origins of the transferred hydrogen atoms are shown by labelling experiments, and structures are suggested for the ions formed.

Studies in Mass Spectrometry. II. Random Hydrogen Rearrangement in Aromatic Molecular Ions

1962 ◽  
Vol 15 (4) ◽  
pp. 771 ◽  
Author(s):  
CG Macdonald ◽  
JS Shannon
Keyword(s):  
Mass Spectrometry ◽  
Aromatic Compounds ◽  
Mass Spectra ◽  
Molecular Ions ◽  
Mass Spectrometric ◽  
Deuterium Exchange ◽  
Molecular Ion ◽  
Hydrogen Rearrangement ◽  
Aromatic Hydrogen

To provide data for investigations by, inter alia, mass-spectrometric methods into the deuterium exchange of the aromatic hydrogen of some coal fractions, a study was made which confirmed the occurrence of completely random hydrogen rearrangement prior to or during the elimination of C2H2 in the molecular ions of benzene-1,2,3-d3, benzene-l,3,5-d3, naphthalene-1,2,3,4-d4, naphthalene-1,4,5,8-d4, and phenanthrene-9,10-d2, and in the phenyl ions derived from o-bromobenzene-d, m-bromobenzene-d, and p-chlorobenzene-d, Similar but incomplete hydrogen rearrangement was found to occur in the molecular ion of carbazole-N-d prior to or during elimination of HCN. Such rearrangements, for which mechanistic considerations are presented, must be taken into account when the mass spectra of deuterium-substituted aromatic compounds are being interpreted.

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.

The mass spectra of acridones

1967 ◽  
Vol 20 (6) ◽  
pp. 1179 ◽  
Author(s):  
JH Bowie ◽  
RG Cooks ◽  
RH Prager ◽  
HM Thredgold
Keyword(s):  
Mass Spectrometry ◽  
High Resolution ◽  
Structure Determination ◽  
Mass Spectra ◽  
Molecular Ions ◽  
Skeletal Rearrangement ◽  
Deuterium Labelling ◽  
Naturally Occurring ◽  
Fragmentation Patterns

The mass spectra of 34 acridones have been determined and interpreted with the aid of both high-resolution measurements and deuterium labelling studies. The spectra contain pronounced molecular ions and are free of skeletal rearrangement fragments. The fragmentation patterns are dependent on the nature and position of substituents, and therefore mass spectrometry can be a useful aid to structure determination in this class of naturally occurring compounds.

Inductive effect in EI-mass spectra of some 5,6-dihalogenides and 5,6-halohydrins of 5α-cholestan-3β-ol and 3β-acetoxy-5α-cholestane

1982 ◽  
Vol 47 (11) ◽  
pp. 2946-2960 ◽  
Author(s):  
Antonín Trka ◽  
Alexander Kasal
Keyword(s):  
Mass Spectra ◽  
Inductive Effect ◽  
Molecular Ions ◽  
Hydroxyl Group ◽  
Halogen Atoms ◽  
Derivatives Of

Partial EI-mass spectra of 3β-hydroxy- and 3β-acetoxy-5α-cholestanes substituted in positions 5α-, 6β- or 5α,6β- with a hydroxyl group or halogen atoms (fluorine, chlorine, bromine) are presented. The molecular ions of 5α,6β-disubstituted derivatives of 3β-hydroxy-5α-cholestane (or of its 3-acetate) are considerably more stable than the corresponding monosubstituted derivatives if at least one of the pair of the vicinal substituents is chlorine or fluorine. This increase in stability, most striking in 5α- and 6β-fluoro compounds, is explained by the inductive effect.

Mass spectra of 4,4-dimethyl-A-homo-4a,6-cholestadien-3-ols, 4,4-dimethyl-A-homo-5-cholestene-3,4a-diols and their derivatives

1982 ◽  
Vol 47 (10) ◽  
pp. 2768-2778
Author(s):  
Antonín Trka ◽  
Helena Velgová
Keyword(s):  
Carbon Atom ◽  
Electron Impact ◽  
Mass Spectra ◽  
Molecular Ions

Partial electron impact induced mass spectra are given of 3α-hydroxy-, 3β-hydroxy-, 3β-methoxy-, 3α-acetoxy- and 3β-acetoxy-4,4-dimethyl-A-homo-4a,6-cholestadienes, 3α,5α-epoxy-4,4-dimethyl-A-homo-5-cholestane, isomeric 4,4-dimethyl-A-homo-5-cholestene-3α(β),4aα(β)-diols, their 3-acetoxy derivatives and 3-methyl ethers. The fragmentation of the molecular ions of these substances involves the usual elimination of substituents (in the form of H2O, CH3OH, CH3COOH, CH2CO), but the most abundant and characteristic ions are products of the contraction of ring A (to a six- or five-membered one), accompanied by expulsion of a fragment containing the carbon atom C(4) with both methyls.

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