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  • Analytical Chemistry and Spectroscopy  (14)
  • 1
    Digitale Medien
    Digitale Medien
    Features of Si rearrangement in the structural analysis by mass spectrometry (1988)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 16 (1988), S. 439-442 
    Details
    ISSN: 1052-9306
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Attention is drawn to the general nature of rearrangement processes which in silylated organic compounds by non-bonded interactions of the ionized Si centre with nucleophilic functional groups produce significant amounts of recombination products under electron impact conditions. Several typical examples involving different functional groups are shown to illustrate the appearance of the resulting characteristics.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bms.1200160186
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  • 2
    Digitale Medien
    Digitale Medien
    Charge separation and ion-pair formation in cations subsequent to electron-impact (1969)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 2 (1969), S. 1033-1035 
    Details
    ISSN: 0030-493X
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Investigation of metastable ion transitions shows, that spontaneous charge separations (loss of an electron from a cation) and ion-pair formations (loss of negative ions from positive ones)are taking place in conventional mass spectrometry. Such processes may be important factors in formation of doubly charged ions.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/oms.1210021012
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  • 3
    Digitale Medien
    Digitale Medien
    Elimination reactions of ions in the gas phase. IVPart III: Th. Kuster and J. Seibl, Org. Mass Spectrom. 11, 458 (1976). - Comparative investigation of water elimination in odd and even electron hydroxyl cations of 6-undecanol (1976)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 11 (1976), S. 644-651 
    Details
    ISSN: 0030-493X
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Reactivity differences between odd ([M]+) and even electron ions (α-cleavage product) were studied by comparing water elimination mechanisms in 6-undecanol. The compounds specifically labelled with deuterium in positions 6, 5 + 7, 4 + 8 and 3 + 9 were made, and a detailed investigation of tghe metastable ion transitions carried out. A highly specific 1,4 elimination of water without preceding intramolecular hydrogen exchange occurs from [M]+, but equal amounts of 1,3 and 1,4 elimination of water preceded by specific hydrogen exchange between -OH and the hydrocarbon chain occurs from the α-cleavage ion [M - C5H11]+. To make such distinctions a thorough examination of metastable ions is essential.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/oms.1210110612
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  • 4
    Digitale Medien
    Digitale Medien
    Elimination reactions of ions in the gas phase. VPart IV: Th. Kuster and J. Seibl, Org. Mass Spectrom. 11, 644 (1976). - elimination of water in hydroxybornanes and related compounds (1978)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 13 (1978), S. 275-279 
    Details
    ISSN: 0030-493X
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Results of an investigation of deuterium labelled methylated norborneols and dihydrocarveols are presented to show that the 1,2 elimination of water in borneol and isoborneol is triggered by an initial ring cleavage reaction. Other eliminations of water in borneol and isoborneol are elucidated by specific and stereospecific deuterium labelling in different positions.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/oms.1210130509
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  • 5
    Digitale Medien
    Digitale Medien
    McLafferty reactions in even-electron ions?Dedicated to Professor Dr H. Bretschneider on the occasion of his 80th birthday. (1985)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 20 (1985), S. 649-661 
    Details
    ISSN: 0030-493X
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Within the scope of a comparative study of the reactivities of odd- versus even-electron ions, the possible significance of the well-known McLafferty reaction for structural analysis in even-electron ions is investigated. In order not to compare reactions of different types with one another, a selective set of experimentally verifiable features is specified which must be met by a degradation reaction to justify its classification as a true McLafferty process. The literature is critically reviewed in the light of this restrictive specification and some ambiguous examples have been reinvestigated, applying modern techniques of selective metastable ion scrutiny together with specific 2H labelling. Only in a few specific cases are even-electron ions found to decay in a McLafferty fashion according to the postulated criteria, indicating a rather limited effectiveness of the reaction as a source of structural information in this field. Fundamental problems in unequivocally pinning down a very specific mechanistic course of a reaction are encountered in spite of using sensitive new techniques of measurement.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/oms.1210201102
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  • 6
    Digitale Medien
    Digitale Medien
    A new versatile matrix for fast atom bombardment analysis (1984)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 19 (1984), S. 581-582 
    Details
    ISSN: 0030-493X
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/oms.1210191111
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  • 7
    Digitale Medien
    Digitale Medien
    Zur Massenspektrometrie von Nitrophenylverbindungen - I. Nitrophenylphydrazone Aromatischer Aldehyde und Ketone und Verweandte Verbindungen (1968)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 1 (1968), S. 713-737 
    Details
    ISSN: 0030-493X
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Fragmentation under electron impact of phenylhydrazones of aromatic aldehydes and ketones, of nitrostilbenes, nitrobenzalacetophenones and analogous compounds is determined by intramolecular oxidation reactions. Oxygen transfer from the o-nitrogroup on to the hydrazon- or stilbene-double bond is taking place; degradation of the resulting rearrangement products provides some of the most characteristic features in the mass spectra of such compounds. The spectra of 20 out of 40 compounds investigated are presented and discussed. Several other rearrangement reactions are observed. An additional conjugated double bond in the hydrazone chain completely changes the reactivity under electron impact. Even saturated substituents (cyclopropyl) can be drastically affected in their mode of fragmentation by an o-substituted nitrogroup.
    Notizen: Die Fragmentierung von Nitrophenylhydrazonen aromatischer Aldehyde und Ketone, von Nitrostillbenen, Nitrobenzalacetophenonen und analogen Verbindungen unter Elektronenbeschuss wird entscheidend durch intramolekulare Oxidationsreaktionen beeinflusst, sofern sich eine Nitrogruppe in o-Stellung zum ungesättigten substituenten befindet. Es findet eine Sauerstoffübertragung von der o-Nitrogruppe auf die Hydrazon- oder Stilbendoppelbindung statt; ein wesentlicher Teil der charakterisierenden Fragmente in den Massenspektren dieser Verbindungen stammt aus dem Zerfall dieser Sauerstoffübertragungsprodukte. 20 Spektren von 40 untersuchten Verbindungen werden präsentiert und diskutiert. Eine Reihe weiterer umlagerungsreaktionen werden beobahtet. Eine konjugierte zusätzliche Dopplbindung in der Hydrazonkette ändert die Reaktivität der Verbindung vollsändig. auch die Fragmentierung gesättigter Substituenten (Cyclopropyl) kann durch eine o-Nitrogruppe entscheidend beeinflusst werden.
    Zusätzliches Material: 15 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/oms.1210010511
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  • 8
    Digitale Medien
    Digitale Medien
    Elimination reactions of ions in the gas phase (1976)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 11 (1976), S. 458-467 
    Details
    ISSN: 0030-493X
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The loss of water from the molecular ion of 2-adamantanol was investigated using specifically labelled deuterium derivatives, and, in particular that stereospecifically labelled in position 4. Water is lost predominantly in a stereospecific 1, 3 fashion by two clearly distinguishable mechanisms. Determination of metastable ion characteristics proved to be essential for drawing this distinction.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/oms.1210110503
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  • 9
    Digitale Medien
    Digitale Medien
    Letters to the editor (1982)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 17 (1982), S. 448-460 
    Details
    ISSN: 0030-493X
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 14 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/oms.1210170910
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  • 10
    Digitale Medien
    Digitale Medien
    Mechanisms of water elimination and other degradations of 2-hydroxy-5-ketobornane cations in the gas phaseElimination reactions of ions in the gas phase - VI. For Part V see Ref. 1. (1981)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 16 (1981), S. 215-220 
    Details
    ISSN: 0030-493X
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The mechanisms of water elimination in 2-hydroxy-5-ketobornanes have been investigated and compared with those in borneol and isoborneol in order to ascertain whether and how such processes are affected by incorporation of a remote second functional group of lower ionization energy. Analysis of metastable ion peak shapes and specific labelling with 2H and 18O are employed as methods for differentiating between individual reaction paths. In addition, those degradation reactions which give rise to the most prominent fragments and pattern differences in the mass spectra of the epimeric keto alcohols were scrutinized. The elimination of water is shown to exhibit entirely different features due to the presence of the carbonyl group. The other most important degradation reactions all proceed by hydrogen transfer from the hydroxyl group onto the charged product and concomitant loss of the hydroxyl oxygen in a neutral entity. The results are interpreted in terms of initial charge radical localization on the carbonyl group initiating the relevant chemical reactions. Peak shape analysis proves a very valuable, and at times the only useful way to distinguish individual reactions.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/oms.1210160506
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