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  • 1
    Electronic Resource
    Electronic Resource
    Effect of protonation exothermicity on the chemical ionization mass spectra of some alkylbenzenes (1981)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 16 (1981), S. 423-427 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The H2, N2/H2, CO2/H2, N2O/H2, CO/H2 and CH4 chemical ionization mass spectra of thirteen C8 to C11 alkylbenzenes are reported. Characteristic hydride and alkide ion abstraction reactions are observed with all reagent gases. The major fragmentation reactions of [MH]+ are olefin elimination to form a protonated arene and arene elimination to form an alkyl ion. From the effect of structure and protonation exothermicity it is concluded that rearrangement of primary alkyl groups to the more stable secondary or tertiary structure occurs prior to alkyl ion formation. A detailed fragmentation mechanism for protonated arenes is proposed. The ‘effective’ proton affinity of the methane-derived reagent system is estimated to be ∼556 kJ mol-1.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210161002
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  • 2
    Electronic Resource
    Electronic Resource
    An energy-resolved study of the fragmentation of ionized 1-Penten-3-ol (1984)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 19 (1984), S. 573-576 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A detailed energy-resolved study of the fragmentation of CH2=CHCH(OH)CD2CD3 (1-d5) has been carried out using metastable ion studies and charge exchange techniques, combined with collision-induced dissociation studies to establish the structures of fragment ions. At low internal energies (metastable ions) the molecular ion of 1-d5 rearranges to the 3-pentanone structure and fragments by loss of C2H5 or C2D5 leading to the acyl structure, [CH3CH2C≡O]+ or [CD3CD2C≡O]+, for the fragment ion. However, with increasing internal energy of the molecular ion this rearrangement process decreases rapidly in importance and loss of C2D5 by direct cleavage, leading to [CH2=CHCH=OH]+, becomes the dominant fragmentation reaction. As a result the [C3H5O]+ ion seen in the electron impact mass spectrum of 1-penten-3-ol has predominantly the protonated acrolein structure.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210191109
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  • 3
    Electronic Resource
    Electronic Resource
    Effect of protonation exothermicity on the reaction of gaseous Brønsted acids with halobenzene derivativesTaken, in part, from the MSc. Thesis of W. G. Liauw, University of Toronto (1981). (1981)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 16 (1981), S. 383-387 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The protonation of haloaromatics by [N2H]+ and [CO2H]+ has been studied by chemical ionization mass spectrometry. In general, the fragmentation reactions following protonation by [CO2H]+ are similar to those observed following protonation by [CH5]+, while the fragmentation reactions induced by protonation by [N2H]+ are intermediate between those observed on reaction with [CH5]+ and with [H3]+. These results are consistent with the conclusion that the fragmentation mode is determined by the protonation exothermicity since the proton affinity of CO2 is the same as that of CH4 while the proton affinity of N2 is intermediate between that of CH4 and H2.
    Additional Material: 6 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210160904
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  • 4
    Electronic Resource
    Electronic Resource
    Site of protonation in the chemical ionization mass spectra of olefinic methyl esters (1980)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 15 (1980), S. 244-248 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The H2 and CH4 chemical ionization mass spectra of the olefinic esters methyl acrylate, methyl methacrylate, methyl crotonate, methyl 3-butenoate, methyl 2-methyl-2-butenoate, methyl 3-methyl-2-butenoate and methyl cinnamate have been determined. In addition to the expected loss of CH3OH from [MH]+, in many cases the protonated molecules also show loss of CO or CH2CO with methoxy group migration to the positive ion centre, indicative of protonation at the double bond. These rearrangement reactions, which have analogies in electron impact mass spectra, result in chemical ionization mass spectra of isomeric molecules which show more substantial differences than the electron impact mass spectra. In the case of methyl cinnamate, isotopic labelling experiments show considerable interchange of the added proton with the ortho and meta phenyl hydrogens prior to CH3OH or CH2CO loss, although the extent of interchange is not the same for both cases.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210150507
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  • 5
    Electronic Resource
    Electronic Resource
    Energy redistribution following proton transfer chemical ionization (1984)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 19 (1984), S. 343-344 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210190710
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  • 6
    Electronic Resource
    Electronic Resource
    Mass spectral behavior of n-alkynesTaken, in part, from the MSc thesis of R. S. Mercer, University of Toronto, 1985. Dedicated to Professor Dr. H.-D. Beckey on the occasion of his 65th birthday. (1986)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 21 (1986), S. 717-722 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 70 e V-electron impact mass spectra of the C7-C10 n-alkynes have been determined as well as the metastable ion spectra of the molecular ions and the [CS2]+ and [N2O]+ charge exchange mass spectra of the C7-C9 n-alkynes. The metastable ion mass spectra provide only a limited opportunity to distinguish between isomers; however, the 70-eV EI mass spectra of isomeric compounds permit a ready distinction between isomers. The [CS2]+ charge exchange mass spectra of isomeric compounds also show substantial differences. The [N2O]+ charge exchange mass spectra do not show the enhancement of β-fission fragments observed in field ionization experiments, despite representing ions of similar internal energy, and it is concluded that field dissociation is responsible for the β-fission fragments in the field ionization experiments.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210211017
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  • 7
    Electronic Resource
    Electronic Resource
    Negative-ion-negative-ion neutralization-reionization (-NR-)This paper is dedicated to Professor Allan Maccoll on the occasion of his 75th birthday. (1989)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 24 (1989), S. 620-624 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: There are four neutralization-reionization processes which can be studied. In the first two, gaseous cations are collisionally reduced and the resulting fast neutrals are either oxidized by collisional electron removal (NR) or reduced further by collisional electron attachment (NR-). In the third and fourth processes, gaseous anions are collisionally oxidized and the resulting fast neutrals are either oxidized further by collisional electron removal (-NR) or reduced by collisional electron attachment (-NR-). These four processes are illustrated briefly using the interrelated species [SF5]+ and [SF5]-. Negative-ion-negative-ion neutralization-reionization (-NR-) processes are illustrated for [CH3O]-, [C2H5O]-, [CO3]- and [HCO3]- and compared with -NR processes. In addition, collisional electron attachment ionization of fast neutrals formed in unimolecular fragmentation of cations is illustrated. The -NR- studies of [CO3]- and [HCO3]- show that both CO3 and HCO3 are stable neutral species with lifetimes greater than 0.7 μs.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210240818
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