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  • 1
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 14 (1980), S. 226-233 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In recent publications we have described a novel method of analysis for high-resolution NMR spectra of compounds in isotropic solution which differs from conventional procedures in that it exploits the full information content of a spectrum and does not require assignments of energy levels or transitions. We now present a further development of this technique which also makes it applicable to the NMR spectra of molecules partially oriented in liquid crystal solvents. Illustrative applications are reported for the nematic phase spectra of allyl fluoride, allyl chloride and allyl bromide. The results are discussed in terms of various theoretical models of the interplay between the internal and overall rotations of the conformationally mobile solutes.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 26 (1991), S. 157-160 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Electron impact mass spectra of the trimethylsilyl derivatives of a series of flavonoid aglycones and chalcones are reported. The spectra show prominent ions arising from fragmentation of the trimethylsilyl (TMS) groups. Inter-actions between adjacent TMS groups, and between TMS groups in the 3- or 5-position (6′-position for the chalcones) and the C-ring carbonyl, yield structurally significant ions. Few fragments associated with the retro-Diels-Alder cleavage of the C-ring characteristic of the underivatized compounds, are observed. The TMS derivatives thus provide complementary information for the identification of flavonoid aglycones and chalcones in biological systems.
    Additional Material: 1 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 22 (1993), S. 58-60 
    ISSN: 0049-8246
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: An unusually fast x-ray detector and pulse processing counting system has been devised and tested. The overall dead time of the system was determined experimentally to be 42 ns.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 25 (1987), S. 1007-1011 
    ISSN: 0749-1581
    Keywords: 13C ; 15N ; 17O NMR 13C ; 2D-EXSY ; nitrosobenzene ; activation energies ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The monomer-dimer equilibrium of nitrosobenzene in CDCI3 solution was studied in the temperature range -50 to 30 °C using 13C, 15N and 17O NMR spectroscopy. Decreasing temperature favours the dimeric azodioxy species, and below ca 10 °C both cis and trans dimers were detected in addition to the monomer. The relative abundance of the trans dimer is low (≤6%) at all temperatures and this is the first report of its existence in solution. The monomer and dimer species were characterized by their 13C and 15N shifts, and exchange between them was measured quantitatively by 13C 2D-EXSY spectra. Exchange occurred exclusively between the cis-dimer and monomer and between the trans-dimer and monomer, activation energies, ΔG≠(298.15 K) being 65.8±0.1 and 70.0±0.3 kJ mol-1, respectively.
    Additional Material: 4 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 24 (1986), S. 831-832 
    ISSN: 0749-1581
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 1H NMR spectra of 1,3-benzodithiole and eight derivatives have been analysed. Signals of the protons in positions 4 and 7 are shifted downfield compared with those for the protons in positions 5 and 6. The inter-ring proton-proton couplings have been determined.
    Additional Material: 2 Tab.
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  • 6
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 27 (1989), S. 368-376 
    ISSN: 0749-1581
    Keywords: 1H NMR ; 13C NMR ; 2,6-Dimethylnitrosobenzene ; 3,5-Dimethylnitrosobenzene ; Monomer-dimer equilibria ; Mixed azodioxy dimers ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The monomer-dimer equilibria of 2,6- and 3,5-dimethylnitrosobenzenes in CDCI3 solution were investigated by 1H and/or 13C NMR spectroscopy. The mixed systems nitrosobenzene + 2,6-dimethylnitrosobenzene and 2,6-dimethylnitrosobenzene + 3,5-dimethylnitrosobenzene were also studied, and mixed azodioxy dimers were identified. In all systems exchange occurs exclusively between dimer and monomer species, rates and activation energies being calculated from time-dependent 1H 1D spectra and/or 1H 2D-EXSY spectra measured at different temperatures.
    Additional Material: 6 Ill.
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  • 7
    ISSN: 0749-1581
    Keywords: 13C NMR ; 1H NMR ; 9-Methylenefluorenes ; Substituent effects ; Substituent-induced chemical shifts ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The two 13C NMR methyl signals of the sterically congested 9-benzylidene-1,8-dimethylfluorene (1a) have the surprisingly small separation of only 0.37 ppm; for 9-benzylidene-2,7-dimethylfluorene the corresponding methyl separation is 0.04 ppm. An alternative analysis of 1a with respect to 1,8-dimethylfluorene shows that the perturbing syn-phenyl substituent has caused a downfield ( + 0.47 ppm) 13C shift but an upfield 1H shift ( - 0.97 ppm) of the compressed 1-CH3 group. For further comparisons, NMR assignments were also made for 2,7-dimethylfluorene, 1,8-dimethylfluoren-9-one and 2-(1,1-dimethylethyl)-3,3-dimethyl-1-phenylbut-1-ene.
    Additional Material: 2 Tab.
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  • 8
    ISSN: 0749-1581
    Keywords: 13C NMR ; 1H NMR Olefins ; Substituent effects ; Substituent-induced chenical shifts (SCS) ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1H and 13C NMR signals were assigned and CH coupling constants (1J, 2J, 3J) determined for a series of α-mono-and α,α-disubstituted (1,1,3,3-tetramethyl-2-indanylidene)methanes with the following α-substituents: (mesityl)2B, n-propyl, phenyl, tert-butyl-C(=NH), cyano, (tert-butyl)2C(OH), pivaloyl, H2N-CO, PhNH-CO, carboxy, ritro, acetoxy, Me3SiO, Me3Si, PhS, PhSMe+, PhSO, PhSO2, bromo and trimethylstannyl. The 1J couplings with the olefinic proton span the range 124.3-193.7 Hz. Substituent-induced chemical shifts (SCS) of most of the nuclei with respect to the α-unsubstituted olefin obey simple additivity in the α,α-disubstituted compounds and are very similar to the SCS values along the C=N double bond in the isoelectronic (1,1,3,3-tetramethyl-2-indanylidene)amines within the error limits. The exceptions concern nuclei in the immediate vicinity of the perturbing substituent. A dominant mechanistic contribution of electric field effects appears likely for the more distant aromatic part of the indanylidene moiety. The chemical shifts of two (2,2,5,5-tetramethylcyclopentylidene)methanes are shown to be compatible with the SCS parameters from the indanylidene series.
    Additional Material: 2 Ill.
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