Mass spectra of bis(trimethylsilyl)- and bis(trimethylgermyl)carbodiimide

The mass spectral fragmentation patterns of bis(trimethylsilyl)- and bis(trimethylgermyl)carbodiimides are compared. Metastable confirmed transitions involve elimination of neutral fragments apparently containing Si=N and/or Si=C bonds. The fragmentation pathways are similar for the germyl analogue but no proof of a fragment containing a Ge=C bond was observed.

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Mass Spectra of β-Keto Esters

Canadian Journal of Chemistry ◽

10.1139/v72-433 ◽

1972 ◽

Vol 50 (16) ◽

pp. 2707-2710 ◽

Cited By ~ 2

Author(s):

Larry Weiler

Keyword(s):

Mass Spectra ◽

Carbonyl Groups ◽

Mass Spectral Fragmentation ◽

Mass Spectral ◽

Keto Esters ◽

Fragmentation Patterns

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

Canadian Journal of Chemistry ◽

10.1139/v92-137 ◽

1992 ◽

Vol 70 (4) ◽

pp. 1028-1032 ◽

Cited By ~ 7

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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Mass Spectrometry of Bis-Quinolizidine Alkaloids: FAB-MS of Oxo-Substituted Sparteines

International Journal of Analytical Chemistry ◽

10.1155/2011/652589 ◽

2011 ◽

Vol 2011 ◽

pp. 1-5 ◽

Cited By ~ 1

Author(s):

Beata Jasiewicz ◽

Elżbieta Wyrzykiewicz

Keyword(s):

Mass Spectrometry ◽

Mass Spectra ◽

Collision Induced Dissociation ◽

Quinolizidine Alkaloids ◽

Positional Isomers ◽

Mass Spectral Fragmentation ◽

Fragmentation Pathways ◽

Mass Spectral

The unpublished in the literature FAB mass spectral fragmentation of seven oxosparteines (i.e., 2-oxosparteine, 15-oxosparteine, 17-oxosparteine, 2,17-dioxosparteine, 2,13-dioxosparteine, 2-oxo-13-hydroxysparteine, and 2-oxo-17-hydroxysparteine) is investigated. Fragmentation pathways, elucidation of which was assisted by FAB/collision-induced dissociation (CID) mass spectra measurements, are discussed. The data obtained create the basis for distinguishing positional isomers.

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Triazolopyridine nucleosides. II. Glycosylations of 3-oxo-s-triazolo[4,3-a]pyridines with accompanying conversions into 2-oxo-s-triazolo[1,5-a]pyridine nucleosides

Canadian Journal of Chemistry ◽

10.1139/v77-116 ◽

1977 ◽

Vol 55 (5) ◽

pp. 831-840 ◽

Cited By ~ 3

Author(s):

Brian Maurice Lynch ◽

Suresh Chandra Sharma

Keyword(s):

General Structure ◽

Spectroscopic Properties ◽

Mass Spectral Fragmentation ◽

Mass Spectral ◽

H Nmr ◽

Pyridine Nitrogen ◽

Methyl Derivatives ◽

Fragmentation Patterns ◽

Ribose Moiety ◽

C Nmr

3-Oxo-s-triazolo[4,3-a]pyridine and various C-methyl derivatives (general structure 1) have been converted into the 2-β-D-ribofuranosyl species 2 and thence 4 via Friedel–Crafts catalyzed reaction with tetra-O-acetyl-β-D-ribofuranose, followed by deblocking. During the course of these reactions, rearrangements into the isomeric 3-β-D-ribofuranosyl-2-oxo-s-triazolo[1,5-a]-pyridines occur through ring-opening of the pyridine rings yielding species 3 and 5. The proportion of rearrangement products is dependent upon the position and number of the C-methyl substituents.Structural assignments for these compounds are based upon comparisons of spectroscopic properties (1H nmr, 13C nmr, uv) with model compounds from each isomeric series; structural assignments for these models are based on unequivocal mass-spectral fragmentation patterns. Unlike related triazolopyridine nucleosides with the ribose moiety attached to a pyridine nitrogen (Lynch and Sharma (1976)), there are no unusual aspects in the conformations of the nueleosides of types 4 and 5.

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Differentiation of the Isomeric o-(m- and p-) Nitro-(Chloro- and Bromo-)Benzyl-2,4-(and 2,1-) Disubstituted 2-Thiocytosinium Halides by Electron Impact Ionisation and Fast Atom Bombardment Mass Spectrometry

European Journal of Mass Spectrometry ◽

10.1255/ejms.996 ◽

2009 ◽

Vol 15 (4) ◽

pp. 497-506 ◽

Cited By ~ 2

Author(s):

Tomasz Pospieszny ◽

Elżbieta Wyrzykiewicz

Keyword(s):

Mass Spectrometry ◽

Mass Spectra ◽

Fast Atom Bombardment ◽

Collision Induced Dissociation ◽

Mass Measurements ◽

Fragmentation Pathways ◽

Mass Spectral ◽

Fragment Ions ◽

Accurate Mass Measurements ◽

Impact Ionisation

Electron ionisation (EI) and fast atom bombardment (FAB) mass spectral fragmentations of nine 2,4-(and 2,1-) disubstituted o-( m- and p-)nitro-(chloro- and bromo-)-2-thiocytosinium halides are investigated. Fragmentation pathways, whose elucidation is assisted by accurate mass measurements and metastable transitions [EI-mass spectrometry (MS)], as well as FAB/collision-induced dissociation (CID) mass spectra measurements are discussed. The correlations between the abundances of the (C11H10N4SO2)+1–3; (C11H10N3SCl)+4–6 and (C11H10N3SBr)+7–9 ions and the selected fragment ions (EI-MS), as well as (C18H16N5SO4)+1–3; (C18H16N3SCl2)+4–6 and (C18H16N3SBr2) + 7–9 ions and the selected ions (C7H6NO2)+1–3; (C7H6Cl)+ 4–6; (C7H6Br)+ 7–9 (FAB-MS) are discussed. The data obtained can be used for distinguishing isomers.

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