Mass spectral fragmentation pattern of 2,2′‐bipyridyls Part XI. 2,2′‐Iminodipyridine
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Abstract The base peak in the mass spectrum of 2,2′‐iminodipyridine is due to the M‐1 ion. There are several minor fragmentation routes from the molecular ion but the principal pathway involves rupture of the central bonds. J. Heterocyclic Chem. , 14, 1103 (1977)Keywords:
Fragmentation
Polyatomic ion
The mass spectra of 8, 8-dicyanoheptafulvene and its derivatives, which are considered to belong to a non-benzenoid aromatic compound, were measured. The high degree of aromaticity of 8, 8-dicyanoheptafulvenes was made clear by mass spectrometry. Low mass regions of dicyanoheptafulvene showed the elimination of hydrogen cyanide from parent ion and rearrangement to phenylpropiolonitrile ion. The mass spectra of methoxy dicyanoheptafulvenes showed fragmentation quite different from that of 8, 8-dicyanoheptafulvenes. The structures and fragmentation processes of dicyanoheptafulvenes were discussed.
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Hydrogen cyanide
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High mass
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The mass spectra of 8, 8-dicyanoheptafulvene and its derivatives, which are considered to belong to a nonbenzenoid aromatic compound, were measured. The high degree of aromaticity of8, 8-dicyanotheptafulvene was made clear by masss pectrometry. Low mass regions of dicyanoheptofalvene showed the elimination of HCN from parent ion and rearrangement to phenvlpropiolonitrile ion. The mass spectra of methoxy-dicyanoheptafulvenes showed fragmentation quite different from that 8, 8-dieyanoheptafulvenes. The structure and fragmentation processes of dieyanoheptafulvenes were discussed.
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The mechanism of radiation damage to 2,5-diketopiperazine (DKP, C 4 H 6 N 2 O 2 ) molecules in the gas phase upon interaction with He 2+ ions with an energy Ep = 4 keV/u has been investigated. The relative cross sections of various elementary processes occurring in single collisions of DKP with ions have been measured for the first time. The channels of fragmentation processes of singly charged ions have been studied experimentally. The DFT method was used to calculate the geometry of molecules and singly charged DKP ions, as well as the energies of the main experimentally observed channels of fragmentation of these ions. Keywords: electron capture, dipeptides, molecular ion fragmentation.
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The production rate of negative ions in collisions between neutral, singly and multiply charged ions with clusters or small molecules is a crucial parameter to study the fragmentation of the targets as a function of the excitation energy (CIDEC method). We report on high production yields of negative ions in collisions between Fq+(q = 1-3) ions and fullerene C60 and adenine molecules. The dynamics of the formation of the negative ion in such collisions is discussed.
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Excitation function
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Abstract The potent endectocide 23‐( O ‐methyloximino)‐F28249α and related compounds were identified and characterized by mass spectrometry. The fragmentation pathway of 23‐( O ‐methyloximino)‐F28249α was identified by its high‐resolution mass spectrum and the electron impact unit mass spectra of its homologs. This fragmentation pathway is presented and discussed.
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High mass
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The mass spectral fragmentation of the cyclodipeptides were investigated. The main fragmentation processes for the peptides were almost the same. In the case of compounds that have the large side chains, the cyclic skeletal ions generated by the loss of the side chain group were followed by the further fragmentations. The important ions arising from cycloglycylglycine in 70 eV-mass spectrum were of m/z 86 [M-CO] and of m/z 71 [M-NHCO] from which further fragmentations occurred. The metastable ion spectrum by B/E linked scan method indicated that the m/z 30 (the most abundant ion in 70 eV-mass spectrum) was formed from the process via the ion of m/z 86.
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The doubly charged ion mass spectra of anhydropisatin, 4-methoxyanhydropisatin, 3, 8, 9-trimethoxypterocarpen and 3, 4, 8, 9-tetramethoxypterocarpen were determined, and the fragmentation was explained by assuming that the paired electrons were partially localized in the fragmentations and by comparing the spectra with that of 3-(CD3)-anhydropisatin. Conventional mass spectra of these compounds were very simple, but the doubly charged ion spectra were sufficiently characteristic for the reliable identification.
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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.
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