Appearance Energies and Calculated Partial Mass Spectra of (23-), (2,4-) and (2,5-)Dimethylaniline Isomers

1983 ◽  
Vol 38 (10) ◽  
pp. 1084-1087 ◽  
Author(s):  
F. H. Abd El-Kader ◽  
H. M. Ahmed
Keyword(s):  
Energy Range ◽  
Internal Energy ◽  
Energy Dependence ◽  
Mass Spectra ◽  
Critical Energy ◽  
Molecular Ions ◽  
Fragment Ions ◽  
Kinetic Shift

Abstract The ionization and appearance energies for the molecular and fragment ions, respectively, of the three dimethylaniline isomers are reported. Breakdown graphs have been constructed expressing the energy dependence of the fragmentation of the isomeric molecular ions covering the internal energy range from threshold to approximately 10 eV. The kinetic shift and the critical energy for the fragments (M-H)+ and (M-CH3)+ ions are also calculated.

Photoionisationsmassenspektren von MethyI(trifluormethyl)sulfan CH3SCF3 [1]/Photoionization Mass Spectra of Methyl(trifluoromethyl)sulfan CH3SCF3 [1]

1989 ◽  
Vol 44 (1) ◽  
pp. 17-20 ◽  
Author(s):  
G. Hagenow ◽  
H.-W. Jochims ◽  
J. Sawatzki ◽  
R. Minkwitz ◽  
H. Baumgärtel
Keyword(s):  
Synchrotron Radiation ◽  
Energy Range ◽  
Ionization Potential ◽  
Photon Energy ◽  
Mass Spectra ◽  
Thermochemical Data ◽  
Photon Energy Range ◽  
Fragment Ions

Abstract The ionization potential of CH3SCF3 and the appearance potentials of fragment ions have been measured in the photon energy range 9 -19 eV using synchrotron, radiation. From these results thermochemical data of CH3SCF3, CH3SCF3+ and fragment ions have been evaluated.

Mass spectrometry of some furanocoumarins

1979 ◽  
Vol 57 (15) ◽  
pp. 1995-2003 ◽  
Author(s):  
Sheng-Yuh Tang ◽  
John C. Mcgowan ◽  
Marsha Singh ◽  
Paul Galatsis ◽  
Brian E. Ellis ◽  
...  
Keyword(s):  
Electron Impact ◽  
Mass Spectra ◽  
Kinetic Energy Release ◽  
Molecular Ions ◽  
Structural Isomers ◽  
Molecular Systems ◽  
Fragment Ions ◽  
Fragmentation Mechanisms ◽  
Impact Ionisation ◽  
Partial Success

The mass spectra of two isomeric methoxyfuranocoumarins have been investigated using electron-impact ionisation. Unambiguous distinction between the two isomers is possible through a combination of conventional mass spectra with collision-induced dissociations of the molecular ions and of selected fragment ions. The fragmentation mechanisms of these and related molecular systems were investigated in an attempt to identify the fate of each oxygen atom under electron-impact conditions. To this end, 2-pyrone, benzpyrone (coumarin), benzofuran, and some of its structural isomers were synthesised and studied via metastable spectra, collisionally activated spectra, appearance potentials, and kinetic energy release. Only partial success was achieved in this investigation, but it was possible to write a mechanistic scheme consistent with the present findings and literature data. If valid, this scheme permits identification of two of the four oxygen atoms in the methoxyfuranocoumarins.

Liquid Secondary Ion Mass Spectrometry and Collision-induced Dissociation Mass Spectrometry of Sulfonamide Derivatives of meso-Tetraphenylporphyrin

1999 ◽  
Vol 03 (03) ◽  
pp. 172-179 ◽  
Author(s):  
M. ROSÁRIO M. DOMINGUES ◽  
M. GRAÇA SANTANA-MARQUES ◽  
A. J. FERRRER-CORREIA ◽  
AUGUSTO C. TOMÉ ◽  
MARIA G. P. M. S. NEVES ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Mass Spectra ◽  
Secondary Ion Mass Spectrometry ◽  
Molecular Ions ◽  
Collision Induced Dissociation ◽  
Fragment Ions ◽  
Ion Mass Spectrometry ◽  
Derivatives Of ◽  
Secondary Ion

Liquid secondary ion mass spectrometry (LSIMS) and collision-induced dissociation (CID) were used for the characterization of sulfonamide derivatives of meso-tetraphenylporphyrin (TPP). The spectra obtained using LSIMS show abundant molecular ions and fragment ions from losses of the sulfonamide moieties. The main fragmentation observed in the LSI mass spectra and in the CID spectra of the protonated or cationized molecules involves the loss of one sulfonamide group. In addition, in the CID spectra of these compounds the fragment ions formed by the elimination of two, three and/or four sulfonamide groups are also observed. The CID spectra of the protonated or cationized molecules of these derivatives do not display the ions formed by the cleavage of the S - N bond which have been reported for other sulfonamide compounds. The LSI mass spectra and CID spectra of sulfonamide derivatives of meso-tetraphenylporphyrin provide an easy and reliable means of identification of the number and nature of sulfonamide groups in the porphyrinic ring.

Appearance Potentials of Metastable Molecular Ions

1967 ◽  
Vol 22 (1) ◽  
pp. 40-47 ◽  
Author(s):  
I. Hertel ◽  
Ch. Ottinger
Keyword(s):  
Internal Energy ◽  
Rate Constant ◽  
Molecular Ions ◽  
Energy Scale ◽  
Constant Density ◽  
Fragment Ions ◽  
Linear Threshold ◽  
Primary Fragmentation ◽  
Order Of Magnitude ◽  
Slow Rise

Differences between the appearance potentials of fragment ions formed a few μ secs after the ionization (so-called metastables) and normal fragment ions were measured. It is shown, however, that no immediate meaning regarding the primary fragmentation mechanism can be attached to these quantities. Instead, the experimental ionization curves of metastable and normal fragments were explained by a theoretical model which assumes 1) a linear threshold law, 2) a linear relation between the logarithm of the rate constant and the internal energy in the molecular ion, and 3) a constant density of populated states on the energy scale. In the case of HCN loss from benzonitrile ions, an excellent fit between the experimental and theoretical curves can then be achieved if it is assumed that an increase of 0.65 eV internal energy increases the rate constant by one order of magnitude. This is a surprisingly slow rise of k (E), compared with the few existing calculations in other cases.

Mass Spectrometric Investigation of Aliphatic Aldehydes

1981 ◽  
Vol 36 (12) ◽  
pp. 1334-1337 ◽  
Author(s):  
Th. M. El-Sherbini ◽  
S. H. Allam ◽  
M. D. Migahed ◽  
A. M. Dawoud
Keyword(s):  
Reaction Mechanisms ◽  
Mass Spectra ◽  
Molecular Ions ◽  
Spectrometric Investigation ◽  
Mass Spectrometric Investigation ◽  
Fragment Ions ◽  
Cleavage Reactions ◽  
Double Focusing ◽  
Method Show ◽  
Good Agreement

AbstractThe mass spectra of C2 to C7 n-alkanals have been measured using a double focusing mass spectrometer. The various reaction mechanisms by which the fragment ions are formed have been elucidated and discussed. Two reactions, the β-cleavage with rearrangement and the y-cleavage reactions lead, respectively, to [C2H4O]+ and [C3H5O]+ ions with significant intensities in butyraldehyde and higher n-alkanals. The electron energy distribution difference (EDD) method together with a computer programme have been used for evaluating ionization efficiency curves for the molecular ions. The ionization potentials obtained by this method show good agreement with those obtained from other electron impact and photoionization experiments.

Mass spectral studies of metal chelates. V. Mass spectra and appearance potentials of some fluorine-substituted acetylacetonates

1970 ◽  
Vol 48 (9) ◽  
pp. 1362-1370 ◽  
Author(s):  
C. Reichert ◽  
G. M. Bancroft ◽  
J. B. Westmore
Keyword(s):  
Mass Spectra ◽  
Molecular Ions ◽  
Metal Chelates ◽  
Spectral Studies ◽  
Molecular Ion ◽  
Mass Spectral ◽  
Fragment Ions ◽  
D Orbitals

The mass spectra of the hexafluoroacetylacetonates (hfacac) and trifluoroacetylacetonates (tfacac) of Al(III), Cr(III), Fe(III), Fe(II), Cu(II), and Zn(II) are reported. The main features of the spectra are discussed. Compared with the spectra of the acetylacetonates (acac), substitution of CF3 for CH3 in these complexes leads to more extensive fragmentation of the molecular ions. For example, ions corresponding to loss of •CF3 radicals are more abundant than those corresponding to loss of •CH3 radicals. The appearance potentials (a.p.'s) of the molecular ions and, where possible, of fragment ions formed from the molecular ion by loss of •CF3, •CH3, or ligand radicals are reported. The a.p.'s of the molecular ions are more sensitive to the nature of the ligand than to the metal. Thus, for the metal chelates studied here the a.p.'s of the molecular ions from ML2 and ML3 (L stands for ligand) were 9.95 ± 0.25 V for L = hfacac, 9.05 ± 0.35 V for L = tfacac, and 8.3 ± 0.35 V for L = acac. The energy required to dissociate a •CF3 or •CH3 radical from the molecular ion is sensitive to the nature and valency of the metal M, being low (relatively) for Al(III) and Fe(III), and high (relatively) for Cr(III) (inferred) and Fe(II). This variation is discussed in terms of the effect of substituent, and of interaction of metal d orbitals with the ligands.

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.

Sign in / Sign up

Export Citation Format

Share Document