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  • 1
    Electronic Resource
    Electronic Resource
    A Theoretical Study of Thionitrosyl Azide (N3—N=S), Thiazyl Azide (N3—S≡N) and Nitrosyl Azide (N3—N=O) (1996)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 129 (1996), S. 1373-1377 
    Details
    ISSN: 0009-2940
    Keywords: Thionitrosyl azide ; Thiazyl azide ; Nitrosyl azide ; Tetranitrogen sulfide ; Calculations, ab initio ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Stimulated by the recent detection of nitrosyl azide (N3—N=O), we investigated the stability of the sulfur analogues thionitriosyl azide (N3—N=S) and thiazyl azide (N3—S≡N) by using ab initio MO calculations up to the QCISD(T)/6-311+G(d)//QCISD/6-311G(d) + ZPE level. Both azides have a similar energy content. While thionitrosyl azide is not stable with respect to N2 elimination, thiazyl azide resists to this process by an energy barrier of about 110 kJ/mol. The NS and N3 fragments resulting from homolytic cleavage lie about 100 kJ/mol above the azides. The five-membered ring is thermodynamically much more stable than both azides but kinetically unstable with respect to cheletropic decomposition yielding N2S + N2. Overall, trans-thiazyl azide is the most likely candidate for experimental observation of, for example, the reaction of NS+ salts with the azide anion. IR wavenumbers of the azides were also predicted.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19961291110
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  • 2
    Electronic Resource
    Electronic Resource
    Formation and identification of ionized and neutral cumulenes, RN=C=C=C=NH, by tandem mass spectrometry (1993)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 28 (1993), S. 1161-1166 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Using a combination of mass spectrometric techniques, it is shown that 5-amino-4-cyanoisoxazole molecular ions (1+·), lose isocyanic acid HN=O, not fulminic acid, HC≡N → O. Metastable ion fragmentations (unimolecular and collision induced) and deuterium-labelling experiments are in agreement with the formation of a cumulenic structure, HN=C=C=C=NH (3a+·). The hitherto unreported molecules HNCCCNH are also shown to be stable when formed in the low-pressure gas phase of the mass spectrometer by using the technique of neutralization-reionization mass spectrometry. The arguments developed for the characterization of 3a+· have also been extended to the methylated and phenylated analogues 3b+· and 3c+· [RN=C=C=C=NH+·, R = CH3 or C6H5]. On flash-vacuum pyrolysis at 700°C, 1 also loses HN=C=O producing the cumulene 3a, which is in turn readily tautomerized into malononitrile via wall collisions.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210281030
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  • 3
    Electronic Resource
    Electronic Resource
    Gas-phase unimolecular chemistry of ethyl butyl ketone cations (1993)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 28 (1993), S. 1189-1196 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Mass spectra of the four isomeric ethylbutyl ketones, C2H5CO-n-C4H9 (1), C2H5CO-iso-C4H9 (2), C2H5CO-sec-C4H9 (3) and C2H5 CO-t-C4H9 (4), are reported. The structure of the fragment ions produced from precursors of both high and low internal energy were identified by collision experiments in a six-sector mass spectrometer. Metastable molecular ions 1+· and 2+· behave identically in expelling CH3·, C3H6 and C2H5· to produce the same fragment ions: [C2H5C(OH)CHCHCH3]+, [C2H5C(OH)=CH2]+· and a mixture of [CHOHCHCHC2H5]+ and [CHOHCHC(CH3)2]+, respectively. The key isomerization step between 1+· and 2+· is a 1,2-enol-olefin shift. Metastable molecular ions 3+· and 4+· give essentially ethene and ethyl losses, respectively; the fragment ions are [C2H5C(OH)CHCH3]+· and [t-C4H9CO]+. Keto-enol isomerization also occurs to a significant extent for ions 1+· and 2+· and 3+·. In contrast, 1,2- or 1,3-ethylhydroxycarbene migrations are only marginal processes.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210281034
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  • 4
    Electronic Resource
    Electronic Resource
    Characterization of iminopropadienone ions and neutrals in a tandem mass spectrometer (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. 667-670 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Radical-cations of iminopropadienones (RN=C=C=C=O+·) have been generated by dissociative ionization of isoxazle precursors a structurally characterized by collisional activation mass spectrometry; the corresponding neutral cumulenes have also been produced in a tandem mass spectrometer by neutralization and/or flash-vacuum pyrolysis experiments.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290061108
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  • 5
    Electronic Resource
    Electronic Resource
    Characterization of new diimines of carbon suboxide by tandem mass spectrometry (1994)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 8 (1994), S. 329-332 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Bis-aryliminopropadiene radical-cations, [ArN=C=C=C=NAr′]+·, have been generated by dissociative ionization of isoxazolopyrimidine precursors and structurally characterized by collisional activation mass spectrometry; the corresponding neutral cumulenes have also been produced in neutralization-reionization experiments.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290080410
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  • 6
    Electronic Resource
    Electronic Resource
    A new hybrid mass spectrometer for the investigation of ion/molecule reactions (1995)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 9 (1995), S. 795-799 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: An RF-only quadrupole collision cell, fitted with retardation and acceleration lenses, has been installed in a field-free region of a large-scale tandem mass spectrometer. This new arrangement has allowed decelerated, mass-selected ions (ca. 5 eV kinetic energy) to react with reagent gases and reaccelerated, mass-selected products (ca. 8 keV) to be subsequently identified by collisional activation mass spectrometry. The system was tested by looking at ion/molecule reactions of cyclobutanone molecular ions, previously studied by FTICR mass spectrormetry.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290090916
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  • 7
    Electronic Resource
    Electronic Resource
    Polycarbon sulfides CnS (n = 2-6) and corresponding hydrides HCnS.. Neutralization-reionization mass spectrometry and ab initio molecular orbital study (1995)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 9 (1995), S. 203-208 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: A series of polycarbon sulfide radical cations, CnS+· (n = 2-6), have been detected in the 70 eV electron impact mass spectrum of benzothiazole. Application of collisional activation and neutralization-reionization mass spectrometry indicates their connectivity and the stability of the corresponding neutral molecules CnS in the gas phase. Closed shell HCnS+ ions (n = 2-6) and the corresponding radicals HCnS. have similarly been identified in the dilute gas phase of the mass spectrometer. The experimental results are supported by ab initio molecular orbital calculations at the QCISD(T)/6-311G** (based on additivity approximation) + ZPVE level.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290090305
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  • 8
    Electronic Resource
    Electronic Resource
    Identification of C4H9O+ isomers by collisional activation mass spectrometry (1988)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 2 (1988), S. 176-179 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: C4H9O+ ions have been produced in the high pressure ion source of a triple sector mass spectrometer either by protonation of C4H8O isomers using methane as the reagent gas, or by methylation of C3H6O isomers using iodomethane or chloromethane as reagent gas. The collisional activation spectra of these mass selected C4H9O+ ions (m/z 73) allow the identification of several stable isomers in the gas phase.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290020903
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  • 9
    Electronic Resource
    Electronic Resource
    Characterization of [C6H7N]+· radical cations by tandem mass spectrometry (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. 135-139 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Collisional Activation, charge-stripping and neutralization/reionozation mass spectra allow the identification of six [C6H7N]+· isomers, namely the molecular ions of the three isomeric picolines, 1+·-;3+·, ionized 2- and 4-methylene dihydropyridines, b - c, and ionized pyridinium methylide, a. The implication of the distonic forms a and b in some fragmentation reactions of funct of onalized (position 2) pyyridines is briefly discussed. Molecular orbital calculations indicate the b〉a〉1+· stability sequence.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290060212
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  • 10
    Electronic Resource
    Electronic Resource
    Electron impact and chemical ionization mass spectrometry of heterocumulenes produced by flash vacuum pyrolysis (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. 249-253 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Heterocumulenes such as ketenes, propadienones and comulogs of isocyanates are produced by flash vacuum pyrolysis of Meldrum's acid. Real-time monitoring of the pyrolysis products is performed by methods of tandem mass spectrometry. In particular, chemical ionization is show, for the first time, to generate protonated moleculular ions of these kinetically unstable neutral molecules which can be identified by collisional activation experiments.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290060405
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