The Mass Spectrometry of the Pyrolysis Products of Some Tetraalkylammonium and Bistetraalkylammonium Bromides

1974 ◽  
Vol 52 (19) ◽  
pp. 3438-3443 ◽  
Author(s):  
Ronald E. Verrall ◽  
John A. Burns
Keyword(s):  
Mass Spectra ◽  
Inductive Effect ◽  
Alkyl Halide ◽  
Substitution Reactions ◽  
Pyrolysis Products ◽  
Quaternary Nitrogen ◽  
Tetraalkylammonium Bromide ◽  
Pyrolytic Decomposition ◽  
Major Process ◽  
Positively Charged

The mass spectra of three tetraalkylammonium bromide salts and two series of bistetraalkylammonium bromide salts, one saturated and the other unsaturated, have been studied. Substitution is the major process which occurs in the pyrolytic decomposition of these quaternary ammonium bromides when placed in the probe of the mass spectrometer. This leads to the production of a tertiary amine and an alkyl halide. The substitution reactions which occur are influenced by the proximity of the bromide anion(s) to the positively charged quaternary nitrogen centers in the crystal lattice. As well, a shorter distance between the positive nitrogen centers favors substitution reaction by means of an electron inductive effect.

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.

Observation of Highly Charged Sodium Clusters

1992 ◽  
Vol 06 (23n24) ◽  
pp. 3721-3730
Author(s):  
U. Näher ◽  
H. Göhlich ◽  
T. Lange ◽  
T.P. Martin
Keyword(s):  
Cluster Size ◽  
Drift Tube ◽  
Mass Spectra ◽  
Electrostatic Model ◽  
Sodium Clusters ◽  
Upper Limit ◽  
Multiple Ionization ◽  
Charged Clusters ◽  
Singly Charged ◽  
Positively Charged

Singly charged sodium clusters have been multiply ionized in the drift tube of a TOF-mass-spectrometer. By this method multi-step photoionization of clusters can be examined mass selectively. Up to fourteenfold positively charged clusters have been observed in the mass spectra. The upper limit for multiple ionization is found to be exclusively a function of cluster size and photon energy. The energy required for each stage of ionization varies with cluster size in a manner well described by a purely classical electrostatic model.

Umwandlung von η2-Thiocarbenkomplexen des Molybdäns und Wolframs in Metalla-thia-cyclopropan-Systeme / Conversion of η2-Thiocarbene Complexes of Molybdenum and Tungsten to Metalla-thio-cyclopropane Systems

1995 ◽  
Vol 50 (12) ◽  
pp. 1839-1844
Author(s):  
C. Ogric ◽  
W. Schütt ◽  
T. Lehotkay ◽  
E. Herdtweck ◽  
F. R. Kreißl
Keyword(s):  
Crystal Structure ◽  
Carbon Atom ◽  
Sodium Azide ◽  
Mass Spectra ◽  
Sodium Thiosulfate ◽  
Substitution Reactions ◽  
Space Group ◽  
And Tungsten

Cationic η2-thiocarbene complexes of molybdenum and tungsten [Cp(CO)2Me][ BF4] (M = Mo, W; R = Ph, Tol; L = CO, PMe3) react with the germylene Ge{N(tBu)CH2CH2N(tBu)}, the plumbylene Pb{N(SiMe3)2}2, or with sodium azide and sodium thiosulfate to give neutral metalla-thia-cyclopropane complexes Cp(CO)2-. Instead of the expected cycloaddition or substitution reactions the formal addition of thiomethanolat at the carbene carbon atom is observed. On treating the corresponding trimethylphosphine substituted η2-thiocarbene complex of molybdenum [Cp(CO)(PMe3)[BF4] with diethylamine or N,N,N′,N′-tetramethylguanidine a cationic molybda-thia-cyclopropane system is formed. The products have been characterized by 1H, 13C, 31P NMR, IR and mass spectra. The crystal structure of 5a has been determined; space group with a = 1340,4(2), b - 1097,7(1), c = 1101,8(5) pm and Z = 4.

The mechanisms of α-H and proton transfers of glycine induced by Mg2+

2015 ◽  
Vol 14 (02) ◽  
pp. 1550008
Author(s):  
Qing Zhang ◽  
Xiang-Jun Meng
Keyword(s):  
Energy Barrier ◽  
Inductive Effect ◽  
Covalent Bond ◽  
Electron Cloud ◽  
Chemical Activity ◽  
The Other ◽  
Single Bond ◽  
Substitution Reactions ◽  
Neutral Complex ◽  
Proton Transfers

A MP2/6-31++G(d,p)//B3LYP/6-31++G(d,p) method was used to investigate the mechanisms of α- H and proton transfers of glycine induced by Mg 2+. Eight complexes were obtained, six of which were neutral and the other two were zwitterionic. Among them, the zwitterion with a binding energy of 159.4 kcal/mol was the most stable structure. Conformation transformations of the complexes caused by the rotation of single bond and the transfers of α- H and proton were completed via seven transition states. The inductive effect of Mg 2+ made the electron cloud of glycine deviate to Mg 2+, which activated the covalent bond involving the transferred proton. The neutral complex can be turned into the zwitterionic one by the transfers of both carboxyl hydrogen and α- H , and the energy barrier of each reaction was less than 9.2 kcal/mol. After the transfer of α- H , a delocalized π bond was formed in glycine skeleton and the α- C atom took 0.19 positive charges. So the chemical activity of the glycine enhanced, and glycine was readily available for addition and nucleophilic substitution reactions. The path from the most stable glycine conformer G1 to the zwitterionic conformation I is G1 → G1–G3 → G3 → G3–G4 → G4 → G2–G4 → G2 → VI → I–VI → I, and the highest energy barrier of this path is 9.2 kcal/mol.

The Mass Spectra of Imidoyl Halides and Bromoiminium Bromides

1973 ◽  
Vol 51 (1) ◽  
pp. 132-138 ◽  
Author(s):  
J. Gal ◽  
B. A. Phillips ◽  
R. Smith
Keyword(s):  
Mass Spectrometer ◽  
Alkyl Group ◽  
Mass Spectra ◽  
Halogen Atom ◽  
Fragmentation Pattern ◽  
Inlet System ◽  
Molecular Ion ◽  
Major Process ◽  
Hydrogen Rearrangement

The mass spectra of imidoyl halides 1–6 and bromoiminium bromides 7–9 have been studied and their fragmentation pattern discussed. Loss of halogen atom from the molecular ion of imidoyl halides to form a N-alkylnitrilium ion is a major process. When the N-alkyl group is larger than methyl the fragmentation of N-alkylnitrilium ions with hydrogen rearrangement to give the [PhC≡NH]+ ion becomes important. Thermolysis of bromoiminium bromides in the inlet system of the mass spectrometer produces imidoyl bromides via dealkylation (or dehydrobromination) and α,α-dibromobenzylamines via addition of bromide to the C=N bond.

Detection of Adducts with Matrix Clusters in the Positive and Negative Ion Mode MALDI-TOF Mass Spectra of Phospholipids

2009 ◽  
Vol 64 (3) ◽  
pp. 331-334 ◽  
Author(s):  
Marijana Petković ◽  
Jürgen Schiller ◽  
Matthias Müller ◽  
Rosmarie Süß ◽  
Klaus Arnold ◽  
...  
Keyword(s):  
Mass Spectra ◽  
Negative Ion ◽  
Dihydroxybenzoic Acid ◽  
Maldi Tof Ms ◽  
Maldi Tof ◽  
Maldi Tof Mass Spectra ◽  
Negative Ion Mode ◽  
Charged Ions ◽  
Positively Charged ◽  
Tof Ms

It is usually accepted that neutral phospholipids (PLs) generate singly positively charged ions, whereas negative PLs are easily detectable in the negative ion mode when analysed by matrix-assisted laser desorption and ionisation time-offlight mass spectrometry (MALDI-TOF MS). In this study, we demonstrate that some caution is required in the interpretation of MALDI-TOF mass spectra of PLs, since also neutral PLs have appeared to be detectable in the negative ion mode as well. Neutral and negatively charged phospholipids can generate adducts with the most commonly used matrix - 2,5-dihydroxybenzoic acid - yielding singly negatively charged ions that are detectable in the spectra. This further contributes to the complexity of the spectra and potentially leads to severe misinterpretation, particularly when unknown mixtures of PLs are analysed by MALDI-TOF MS.

Collection of ion-trap mass spectra of sulfonylurea pyrolysis products

1995 ◽  
Vol 30 (2) ◽  
pp. 333-338
Author(s):  
Guido C. Galletti ◽  
Giovanni Dinelli ◽  
Giuseppe Chiavari
Keyword(s):  
Mass Spectra ◽  
Ion Trap ◽  
Pyrolysis Products

The Behavior of 1-Phenyl-2-benzimidazolinethione and 1-Phenyl-2-benzimidazolinone upon Electron Impact and Pyrolysis

1974 ◽  
Vol 52 (13) ◽  
pp. 2359-2366 ◽  
Author(s):  
Denis C. K. Lin ◽  
Michael L. Thomson ◽  
Don C. DeJongh
Keyword(s):  
Mass Spectrum ◽  
Electron Impact ◽  
Mass Spectra ◽  
Path Loss ◽  
Starting Material ◽  
Base Peak ◽  
Pyrolysis Products

The mass spectra of 1-phenyl-2-benzimidazolinethione (3) and 1-phenyl-2-benzimidazolinone (4) have been compared with their pyrolysis products and similarities have been found. In the 70 eV mass spectrum of 3, the base peak results from the loss of H•; at low ionizing voltages, this path and a competing path, loss of S, are the only ones which remain. At 650° in a stream of N2, 1-phenylbenzimidazole (8, 20%) formed from the loss of S and benzimidazo-[2,1-b]benzothiazole (5, 11%) formed by loss of H2. The major fragmentation paths in the mass spectrum of 4 are loss of CHO• and NCO•. At 950°, phenazine (6, 35%) formed by loss of CH2O, and carbazole (7, 14%) formed by loss of HNCO. In each pyrolysis, 65–70% of the starting material was recovered or accounted for.

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