The role of conformational mobility in the stereospecific loss of water under electron impact

1979 ◽  
Vol 44 (12) ◽  
pp. 3595-3603 ◽  
Author(s):  
František Tureček ◽  
Vladimír Hanuš ◽  
Miloš Tichý
Keyword(s):  
Electron Impact ◽  
Mass Spectra ◽  
Molecular Ions ◽  
Conformational Mobility ◽  
Water Elimination

Mass spectra of nine of the sixteen possible diastereoisomeric 7-hydroxytricyclo[7.3.0.02,6]dodecanes are reported. The spectra differ considerably in the extent of water elimination from molecular ions. The diastereoisomers which have conformationally flexible cis-anti-cis, cis-anti-trans and cis-syn-trans skeletons exhibit abundant (M-H2O)+. ions. Molecular ions of the rigid trans-anti-trans isomers lose water to a markedly smaller extent, the main fragmentation proceeding via a skeletal cleavage. Effects of conformational mobility are emphasized.

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.

Electron impact studies. XXXII. Negative-ion mass spectra of aromatic compounds containing the =N-O- substituent

1968 ◽  
Vol 21 (8) ◽  
pp. 2031 ◽  
Author(s):  
JH Bowie ◽  
SO Lawesson ◽  
BS Larse ◽  
GE Lewis ◽  
G Schroll
Keyword(s):  
Electron Impact ◽  
Aromatic Compounds ◽  
Mass Spectra ◽  
Molecular Ions ◽  
Negative Ion ◽  
Skeletal Rearrangement ◽  
Marked Contrast ◽  
Azoxy Compounds ◽  
Positive Ion ◽  
Fragmentation Processes

The negative-ion mass spectra of aromatic azoxy compounds, nitrones, and N-oxides exhibit pronounced molecular ions and simple fragmentation processes. No skeletal-rearrangement fragments are produced upon electron impact, in marked contrast to those exhibited in the positive-ion spectra of these compounds.

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.

Mass Spectra of Fifteen Chlorinated Aromatic Fungicides

1971 ◽  
Vol 54 (1) ◽  
pp. 178-186
Author(s):  
O Hutzinger ◽  
W D Jamieson ◽  
S Safe
Keyword(s):  
Electron Impact ◽  
Mass Spectra ◽  
Molecular Ions ◽  
Chlorine Atoms ◽  
Fragmentation Patterns

Abstract Fragmentation patterns on electron impact of 15 chlorinated aromatic fungicides were investigated. In most cases strong molecular ions were obtained and the peak clusters due to the 35Cl and 37Cl isotopes and the number of chlorine atoms in the molecule were highly characteristic. Many of the polychlorinated fungicides give ions (e.g., C6Cl4, C6Cl3, C6Cl2, C6Cl, and C6 (CN)2) whose structures can be best represented as acyclic polyunsaturated moieties.

Mass Spectra of Sodium N-Alkyl and N,N-Dialkyl Dithiocarbamates and Some Related Compounds

1976 ◽  
Vol 59 (3) ◽  
pp. 622-632 ◽  
Author(s):  
Francis I Onuska ◽  
Michael E Comba
Keyword(s):  
Electron Impact ◽  
Mass Spectra ◽  
Molecular Ions ◽  
Fragmentation Behavior ◽  
Zinc Salts ◽  
Electron Impact Mass ◽  
Related Compounds ◽  
Impact Mass

Abstract Electron impact mass spectra of 8 sodium alkyl and dialkyl dithiocarbamate salts are reported with the spectra of 2 dithiocarbamate zinc salts and N′,N′-dimetliyl-N,N-dimethylthiocarbamylsulfenamide. The investigated compounds all gave molecular ions, and generalized descriptions of their fragmentation behavior are presented.

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.

Electron impact studies. XI. Mass spectra of aromatic azoxy compounds. Skeletal rearrangement upon electron impact

1967 ◽  
Vol 20 (8) ◽  
pp. 1601 ◽  
Author(s):  
JH Bowie ◽  
RG Cooks ◽  
GE Lewis
Keyword(s):  
Electron Impact ◽  
Mass Spectra ◽  
Molecular Ions ◽  
Skeletal Rearrangement ◽  
Impact Studies ◽  
Azoxy Compounds

The mass spectra of 15 aromatic azoxy compounds are reported and discussed. The spectra exhibit pronounced molecular ions, and fragmentation modes which are produced by both simple cleavage and complex skeletal reorganization processes.

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