Mass spectral studies of 3,5-Diamino-1,2,4-thiadiazoles

1977 ◽  
Vol 30 (3) ◽  
pp. 563 ◽  
Author(s):  
CP Joshua ◽  
KN Rajasekharan
Keyword(s):  
Electron Impact ◽  
Structure Determination ◽  
Mass Spectra ◽  
Spectral Studies ◽  
Mass Spectral ◽  
Fragmentation Mechanisms

The mass spectra and fragmentation mechanisms of some 5-alkyl(or aryl)amino-3-amino-, 5-amino-3- arylamino-, 3,5-bis(arylamino)-, 4- aryl-3-arylamino-5-imino-4,5-dihydro-, and 3-alkyl(or aryl)amino-4- aryl-5-arylimino-4,5-dihydro-1,2,4-thiadiazoles and those of a 3-amino- 4-aryl-5-imino-4,5-dihydro-1,2,4-thiadiazole are discussed. The study, based on the behaviour of isomers under electron impact, attempts to evaluate the usefulness of mass spectra in structure determination of variously substituted 3,5-diamino-1,2,4-thiadiazoles.

Mass Spectral Studies on Pyrazaboles

1976 ◽  
Vol 31 (12) ◽  
pp. 1662-1666 ◽  
Author(s):  
C. E. May ◽  
K. Niedenzu ◽  
S. Trofimenko
Keyword(s):  
Electron Impact ◽  
Mass Spectra ◽  
Ring System ◽  
Hydrogen Halide ◽  
Spectral Studies ◽  
Mass Spectral ◽  
Fragmentation Patterns ◽  
Structural Entity

The mass spectra of several pyrazaboles of type 1 (R = H) have been studied. The data illustrate that electron impact causes three major fragmentation patterns for the species. Symmetrical cleavage of the pyrazabole followed by further breakdown is common to all compounds. In addition, those pyrazaboles containing H or CH3 at the C atoms of the pyrazole rings undergo an electron impact-induced rearrangement which appears to result in the formation of a species containing a B2N3 ring as a structural entity; subsequent breakdown leads to a B2N2 ring system. The mass spectra of halo- or pseudohalo-substituted pyrazaboles evidence the ready loss of hydrogen halide as a predominant feature; no rearrangement ions are observed.

Electron impact mass spectra of some vicinal trans-dihalo- and trans-hydroxyhalocholestanes

1980 ◽  
Vol 45 (6) ◽  
pp. 1720-1733 ◽  
Author(s):  
Antonín Trka ◽  
Alexander Kasal
Keyword(s):  
Mass Spectrometry ◽  
Electron Impact ◽  
Structure Determination ◽  
Mass Spectra ◽  
Electron Impact Mass ◽  
Impact Mass

Partial mass spectra of 1α, 2β-, 2α, 3β-, 3α, 4β-, 3β, 4α-, 4β, 5α-, 5α, 6β- and 6β, 7α-dihalocholestanes and -halocholestanols are given. Applicability of mass spectrometry for structure determination of these compounds types is demonstrated. Although the differences found in the appearance of their mass spectra are often only quantitative, they are characteristic enough for reliable localization of the substitution.

scholarly journals Electron Impact Ionization Mass Spectra of 3-Amino 6-Chloro2-methyl Quinazolin-4-(3H)-one Derivative

2021 ◽  
pp. 1-5
Author(s):  
Osarumwense Peter Osarodion ◽  
◽  
Omotade Treasure Ejodamen ◽  
Keyword(s):  
Electron Impact ◽  
Mass Spectra ◽  
Impact Ionization ◽  
Cyclic Compound ◽  
Electron Impact Ionization ◽  
Ionization Mass ◽  
Fragmentation Pattern ◽  
Molecular Ion ◽  
Mass Spectral ◽  
Characteristic Fragmentation

Looking at the previous studies on quinazolinones derivatives, only limited information’s are available on their mass spectral along with the preparation of novel quinazolin-4-(3H)-one derivatives The condensation of Methyl-2-amino-4-Chlorobenzoate with acetic anhydride yielded the cyclic compound 2-methyl 7-Chloro-1, 3-benzo-oxazine-4-one (1) which further produce 3-Amino-2-Methyl 7-Chloro quinazolin-4(3H)-ones (2) via the reaction with hydrazine hydrate. The compounds synthesized were unequivocally confirmed by means of Infrared, Nuclear Magnetic Resonance (1H and 13C), Gas Chromatography-Mass spectrophotometry and Elemental analysis. Discussion: The molecular ion of m/z 235 fragments to give m/z 220 by loss of –NH group. The ion of m/z 220 was broken to give m/z 206 by losing CH2 group and fragment to m/z 177 by loss of HCO. This fragmented to m/z 162 by loss of –CH3 group and then m/z 136 by loss of CN group. The loss of O gave m/z 120 which fragment to give m/z 93 by loss of –HCN and finally gave m/z 65 by loss of CO group. Conclusion: The electron impact ionization mass spectra of compound 2show a weak molecular ion peak and a base peak of m/z 235resulting from a cleavage fragmentation. Compound 2 give a characteristic fragmentation pattern. From the study of the mass spectra of compound 2, it was found that the molecular ion had fragmented to the m/z 220. The final fragmentation led to ion of m/z 93 and ion of mass m/z 65, respectively

Derivatization in Mass Spectrometry—1. Silylation

2003 ◽  
Vol 9 (1) ◽  
pp. 1-21 ◽  
Author(s):  
John M. Halket ◽  
Vladimir G. Zaikin
Keyword(s):  
Mass Spectrometry ◽  
Structure Determination ◽  
Spectral Properties ◽  
Mass Spectra ◽  
Biologically Active ◽  
Chromatographic Mobility ◽  
Mass Spectral ◽  
Silyl Derivatives ◽  
Catalytic Stability

This is the first of a series of reviews on the application of derivatization in mass spectrometry. A description is given of advances in silylation as a powerful tool used for increasing the volatility, thermal and thermo-catalytic stability, and chromatographic mobility of polar and unstable organic compounds. In addition to chemical aspects of silylation, mass spectral properties of silyl derivatives useful for structure determination and quantitation of various organic and biologically-active compounds, mainly by GC/MS, are described. Practically all tested and widely used silylating agents are described. The role of comprehensive libraries containing reference mass spectra for various silyl derivatives and search systems in structure determination is emphasized. Applications of silylation for particular analyses are summarised.

Mass spectral analysis of acetylated peptides: Implications in proteomics

2019 ◽  
Vol 26 (1) ◽  
pp. 36-45
Author(s):  
Deepika Chandra ◽  
P Gayathri ◽  
Mudita Vats ◽  
R Nagaraj ◽  
MK Ray ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Pseudomonas Syringae ◽  
Mass Spectra ◽  
De Novo ◽  
Spectral Quality ◽  
Tryptic Peptides ◽  
Mass Spectral ◽  
Human Proteins ◽  
Terminal Amino

Sequence determination of peptides using mass spectrometry plays a crucial role in the bottom-up approaches for the identification of proteins. It is crucially important to minimise false detection and validate sequence of the peptides in order to correctly identify a protein. Chemical modification of peptides followed by mass spectrometry is an option for improving the spectral quality. In silico-derived tryptic peptides with different N-terminal amino acids were designed from human proteins and synthesized. The effect of acetylation on the fragmentation of peptides was studied. N-terminal acetylation of the tryptic peptides was shown to form b1-ions, improve the abundance and occurrence of b-ions. In some cases, the intensity and occurrence of some y-ions also varied. Thus, it is demonstrated that acetylation plays an important role in improving the de novo sequencing efficiency of the peptides. The acetylation method was extended to tryptic peptides generated from the proteome of an Antarctic bacterium Pseudomonas syringae Lz4W using the proteomics work flow and mass spectra of the peptides were analysed. Comparison of the MS/MS spectra of the acetylated and unacetylated peptides revealed that acetylation helped in improving the spectral quality and validated the peptide sequences. Using this method, 673 proteins of the 1070 proteins identified were validated.

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.

Fragmentation pathways in the mass spectra of isomeric phenylazoxypyridine-N-oxides

1992 ◽  
Vol 70 (4) ◽  
pp. 1028-1032 ◽  
Author(s):  
Nigel J. Bunce ◽  
H. Stewart McKinnon ◽  
Randy J. Schnurr ◽  
Sam R. Keum ◽  
Erwin Buncel
Keyword(s):  
Mass Spectrometry ◽  
Tandem Mass Spectrometry ◽  
Electron Impact ◽  
Mass Spectra ◽  
Chemical Reduction ◽  
Ion Source ◽  
Tandem Mass ◽  
Mass Spectral Fragmentation ◽  
Fragmentation Pathways ◽  
Mass Spectral

The mass spectral fragmentation pathways of a series of phenylazoxypyridine-N-oxides have been studied under electron impact conditions using tandem mass spectrometry. Besides simple C—N cleavages, the azoxypyridine-N-oxides undergo deep-seated rearrangements directly from the molecular ion. In addition, the spectra are complicated by a purely chemical reduction of the N—O functionalities that occurs in the ion source prior to ionization.

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