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  • 1
    Electronic Resource
    Electronic Resource
    Studies of consecutive reactions of quinones in a reversed geometry mass spectrometer (1981)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 16 (1981), S. 312-322 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Consecutive reactions involving the ejection of molecules of carbon monoxide from quinone systems have been studied. Using a reversed geometry double focusing mass spectrometer, the individual steps of a consecutive reaction may be separated into different field free regions. The structure of ions formed in the ion source may be compared with those formed from the fragmentation of metastable ions in a field free region by studying differences in the pattern of translational energies released when they break. In the case of anthraquinone it is found that two structures exist for the [M—CO]+· ion. Critical energy measurements strengthen this argument. Furthermore, 18O labelling has been used to distinguish between the loss of carbon monoxide from different positions on the molecular ion of 1-hydroxyanthraquinone.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210160710
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  • 2
    Electronic Resource
    Electronic Resource
    Translational energy released in decompositions of metastable ions: A simple criterion for distinction between steroid epimers by mass spectrometry (1981)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 16 (1981), S. 465-466 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210161010
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  • 3
    Electronic Resource
    Electronic Resource
    The elimination of carbon monoxide from molecular ions of phenol and other [C6H6O]+· isomers (1982)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 17 (1982), S. 81-85 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Phenol and five acyclic isomeric compounds have been investigated using electron impact and field ionization techniques, mass analysed ion kinetic energy spectrometry and collision induced dissociation mass analysed ion kinetic energy spectrometry. The kinetic energy release data corresponding to the elimination of carbon monoxide from the molecular ions show that at least two structures of the reactant ion are involved. The electron impact and field ionization collision induced dissociation mass analysed ion kinetic energy spectra indicate that under electron impact conditions, the phenol ion partially isomerizes to another ion structure. An isomerization of about 40% to the structure of cis-2-hexen-4-yn-1-al is in good accordance with the spectral data.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210170206
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  • 4
    Electronic Resource
    Electronic Resource
    Consecutive reactions arising from the molecular ions of 14α-equilenin and 14β-isoequilenin (1982)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 17 (1982), S. 131-135 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: It is shown that two configurational steroidal isomers, 14α-equilenin and 14β-isoequilenin, may be easily distinguished by the unimolecular mass analysed ion kinetic energy spectra of their corresponding molecular ions. Furthermore, many of the peaks in these spectra are found to be due to consecutive reactions, whereby product ions of an initial reaction are themselves reactive and can undergo further fragmentation. In each of these cases, the individual steps of the reaction sequence have been separated in the different field free regions of a reversed geometry, double focusing mass spectrometer. Isotopic labelling with 18O in the 17-position has also helped to clarify reaction sequences.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210170306
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  • 5
    Electronic Resource
    Electronic Resource
    Cyclization of dimethyl oxalate upon electron impact (1981)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 16 (1981), S. 34-36 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Isotope labelling experiments and also consecutive fragmentation investigations of metastable ions, a novel technique in mechanistic studies, have been carried out to elucidate structure and genesis of the m/z 45 ions from dimethyl oxalate as well as dimethyl carbonate. It is shown that the formation of the m/z 45 ions, \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm{CH}}_{\rm{3}} \mathop {\rm{O}}\limits^{\rm{ + }} = {\rm{CH}}_{\rm{2}} $\end{document}, in the mass spectra of these compounds arises via single step processes. Mechanisms involving hydrogen transfer and subsequent formation of cyclic intermediates which then collapse to give \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm{CH}}_{\rm{3}} \mathop {\rm{O}}\limits^{\rm{ + }} = {\rm{CH}}_{\rm{2}} $\end{document} directly from molecular ions are suggested. No evidence was found for a two-step fragmentation route to m/z 45 from the molecular ions of either dimethyl oxalate or dimethyl carbonate.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210160110
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  • 6
    Electronic Resource
    Electronic Resource
    The elimination of masses 27 and 28 from the [M—OH]+ ion of 2-nitrotoluene (1984)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 19 (1984), S. 306-310 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The expulsion of neutral fragments of masses 27 and 28 from metastable [M — OH]+ ions derived from 2-nitrotoluene has been observed. The relative abundances of the resulting fragment ions, together with the kinetic energy released in each process, has been compared with similar fragmentation of [C7H6NO]+ ions derived from other precursor molecules. In this way, the nature of the neutral fragments and the structure of the [M — OH]+ ions from 2-nitrotoluene has been investigated. The most likely structure is the 1,2-benzisoxazolenium cation although the coexistence of other structures cannot be ruled out on the present evidence.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210190703
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  • 7
    Electronic Resource
    Electronic Resource
    The structures of [C5H5O]+ ions formed from isomers of nitrophenol in the gaseous phase (1982)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 17 (1982), S. 331-334 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Translational energy release measurments on metastable ions are used in the comparison of the structures of isomeric ions. Metastable ions, m2+, formed from m1+ ions as the result of a high energy process in the ion source are compared with isomeric metastable ions formed as daughters from fragmentation of metastable m1+ ions in a field. In the case of o-, m- and p-nitrophenol the structure of the [C5H5O]+ ions formed from [C6H5O]+ ions by these two independent methods is different as verified by comparison of the behaviour of [C5H5O]+ ions formed from several other compounds.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210170709
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  • 8
    Electronic Resource
    Electronic Resource
    Translational energy release and stereochemistry of steroids 4 - Epimeric 3-keto and 3-hydroxy steroidsPresented in part at the 29th Annual Conference on Mass Spectrometry and Allied Topics. Minneapolis, Minnesota USA (24-29 May 1981); for Part 3 see Ref. 8. (1984)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 19 (1984), S. 321-325 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The translational energy, T, released during CH3· loss from the molecular ions of epimeric steroid ketones and from both molecular and [M-H2O]+· ions of epimeric alcohols of the androstane, pregnane and cholestane series, differing in the mode of the A/B ring junction, has been measured. These data provide a simple and rapid method for identifying the configuration of the epimeric centres. Of the compounds studied, it is found in 3-hydroxy steroids that the 5β-isomers release the smaller amounts of translational energy for CH3· loss. In most of the 3-keto steroids investigated, the opposite is found, i.e. the larger T values are observed for the 5β-isomers. Exceptions occur when further keto groups are introduced at the 11- or 17-positions. A small range of epimeric pairs of 17-hydroxy, 17-keto and 4-keto steroids have also been studied, the 5β-isomer giving the lower T value in each case. The importance of hydroxy and keto groups at the various sites within the steroid structure in determining the T values is discussed.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210190706
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