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  • 1
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: The molecular ions generated by electron-impact from olefins of the general structure I, II and III fragment mainly via the McLafferty rearrangement. Even under mild ionization conditions, however, they undergo isomerization before fragmentation takes place.The origin and mode of formation of an ion generated simultaneously by decay of the molecular ion and the McLafferty ion were investigated by means of 13C- and D-labelling.The influence of branching at the γ-, ω-, or ∊-positions of the double bond in type I-olefins was studied.
    Notes: Bei Olefinen der allgemeinen Struktur I, II und III erleidet das unter Elektronenbeschuss erzeugte Molekülion neben der als Hauptreaktion ablaufenden McLafferty-Umlagerung auch bei milden Anregungsbedingungen eine vor der Fragmentierung eintretende Isomerisierung.Es wurde versucht, Herkunft und Entstehungsweg eines sowohl beim Abbau des Molekülions als auch des McLafferty-Ions gebildeten gemeinsamen Bruchstückes mit Hilfe von 13C- und D-Markierung zu klären.Der Einfluss einer Verzweigungstelle in γ-, ω- oder ∊-Position zur Doppelbindung bei Olefinen vom Typ I auf deren Verhalten im Massenspektrometer wurde untersucht.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Intense rearrangement processes involving migrations of hydrogen atoms and the phenyl group were observed in the electron impact induced fragmentation of 1-benzyl-3,3-dimethyldiaziridine. The following ions are observed: (i) m/z 146: a two-step fragmentation involving hydrogen transfer followed by loss of NH2; (ii) m/z 119: C - N1 bond fission followed by a 1-4 phenyl shift and loss of CH3N2; (iii) m/z 106: a process involving reciprocal hydrogen migration between the methyl and benzylic methylene groups; (iv) m/z 58: hydrogen transfer from benzylic methylene and subsequent loss of PhCHN. The origin of these ions has been confirmed by measurements of metastable transitions in 1-benzyl-3,3-dimethyldiaziridine, and on specifically deuterated and substituted diaziridines. The structure of the ions at m/z 119 and m/z 106 has been deduced by means of collisional activation spectrometry.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
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  • 3
    Publication Date: 2019-03-29
    Description: Solfatara crater is locatedwithin the Campi Flegrei caldera to the west of Naples (Italy). It is one of the largest fumarolic manifestations known, and the rocks hosting the hydrothermal system are affected by intense hydrothermal alteration. Alteration can result in changes of degassing behavior, and in the formation of a cap rock thereby increasing the probability of phreatic eruptions. Here, we investigate the effects of alunitic (solfataric) alteration on the mineralogy, the physical properties (porosity, density, permeability) and the mechanical properties (strength) of the rocks involved, aswell as its influence on fragmentation and ejection behavior. Our results showthat the pristine mineralogy of deposits fromthe vicinity of the Solfatara cryptodome and from Pisciarelli is almost completely replaced by amorphous silica and alunite. The differences in the degree of alteration among the samples series are reflected in the investigated properties and behavior aswell as in the analysis of the experimentally generated particles. Alunitic alteration increases porosity and permeability,whereas it reduces density, elastic wave velocity and strength leading to higher fragmentation and ejection speeds for the sample series examined in this study. Our results also show that alteration results in the generation of a high fraction of fines (particle sizes b10 μm) during fragmentation, mainly composed of alunite crystals. Due to their potential for inducing chronic disease, dispersion of such material should represent a serious health hazard on a local scale and the evaluation of precautions should be considered.
    Description: Published
    Description: 128-143
    Description: 3V. Proprietà dei magmi e dei prodotti vulcanici
    Description: JCR Journal
    Keywords: Solfataric alteration ; Phreatic eruption ; Fragmentation ; Permeability
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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