scholarly journals A study of hydrogen rearrangement reactions in the molecular ion of 1,2-dimethoxyethane by MIKE spectrometry.

1986 ◽  
Vol 34 (5) ◽  
pp. 279-286 ◽  
Author(s):  
Seiji Tobita ◽  
Kenichi Tonokura ◽  
Susumu Tajima
Keyword(s):  
Molecular Ion ◽  
Rearrangement Reactions ◽  
Hydrogen Rearrangement

Rearrangement Reactions in the Electron Impact Fragmentation of Isobutene

1974 ◽  
Vol 52 (9) ◽  
pp. 1813-1820 ◽  
Author(s):  
Margaret S.-H. Lin ◽  
Alex. G. Harrison
Keyword(s):  
Mass Spectrum ◽  
Internal Energy ◽  
Electron Impact ◽  
Electron Energy ◽  
Skeletal Isomerization ◽  
Molecular Ion ◽  
Impact Fragmentation ◽  
Rearrangement Reactions ◽  
Average Internal Energy

The detailed mass spectrum of isobutene has been examined using both D and 13C labelling. It is shown that at low average internal energies of the molecular ion complete randomization of hydrogens and of carbons occurs prior to fragmentation to form C3H5+. As the average internal energy of the molecular ion increases (by increasing the ionizing electron energy) the extent of both carbon and hydrogen randomization decreases. Carbon scrambling is complete in the molecular ion prior to fragmentation to form C2 ions under all conditions studied. The results are consistent with a skeletal isomerization of the isobutene molecular ion by a mechanism involving a series of 1,3 ring closures to form methylcyclopropane type ions.

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.

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.

Is the collision induced loss of ethene from the (M – H+)− ion of butyrophenone a γ-hydrogen rearrangement?

1986 ◽  
Vol 64 (4) ◽  
pp. 764-768 ◽  
Author(s):  
Michael B. Stringer ◽  
Dennis J. Underwood ◽  
John H. Bowie ◽  
John L. Holmes ◽  
Alexander A. Mommers ◽  
...  
Keyword(s):  
Collisional Activation ◽  
Hydrogen Atoms ◽  
Rearrangement Reactions ◽  
Hydrogen Rearrangement ◽  
Hydrogen Scrambling

The (M – H+)− ion of butyrophenone undergoes the following reactions on collisional activation: losses of CH3•, CH4, (C,H5•), C2H4, C3H7•, (CO + CH4), together with formation of C6H5− and C4H5O−. Labelling studies (13C and 2H) show that the losses of CH3•, C3H7• and the formation of C6H5− and C4H5O− are specific and occur without hydrogen scrambling. All other reactions involve prior or accompanying hydrogen rearrangement. In particular, the loss of C2H4 is very complex: it involves loss of ethyl carbon atoms, but all hydrogen atoms are involved via specific rearrangement reactions. The phenyl–alkyl H rearrangements which are noted for this process occur after collisional activation of the (M – H+)− ion.

Interaction of heterocycles and nucleophiles. II. Sigma complexes formed from methoxide ion and Methoxy-3,5-dinitropyridines in dimethyl sulphoxide

1970 ◽  
Vol 23 (5) ◽  
pp. 957 ◽  
Author(s):  
MEC Biffin ◽  
J Miller ◽  
AG Moritz ◽  
DB Paul
Keyword(s):  
Dimethyl Sulphoxide ◽  
No Conversion ◽  
Solvation Effects ◽  
Sigma Complexes ◽  
Sigma Complex ◽  
Methoxide Ion ◽  
Rearrangement Reactions

Contrasting behaviour is observed when 2- and 4-methoxy-3,5-dinitropyridine interact with methoxide ion in dimethyl sulphoxide. The 4-methoxy compound affords both methine and acetal sigma complexes, the latter being thermodynamically more stable. The interconversion is catalysed by methanol. Labelling experiments have established that the sigma complex from the 2-methoxypyridine is formed by addition at C6; no conversion into the acetal could be effected. These observations are rationalized in terms of differential steric and solvation effects. Demethylation and rearrangement reactions of 4-methoxy-3,5-dinitropyridine are reported.

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