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  • Analytical Chemistry and Spectroscopy  (67)
  • Physics  (19)
  • 1975-1979  (86)
  • 1
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 2 (1975), S. 82-89 
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Identification of hydrazine monoamine oxidase inhibitor drugs such as isoniazid, iproniazid, nialamide, isocarboxazid and iproclozide is made by electron impact mass spectrometry using the direct insertion technique. The molecular ion itself, although of low relative abundance, is found in the mass spectra of all compounds studied. Relative intensities of the major fragments and data on metastable ions useful in the identification of these compounds are reported. With the aid of synthesized structurally related products, deuterium labelling of exchangeable hydrazidic and hydrazinic protons and by the use of hexadeuterated isopropylic analogues, detailed information about fragmentation patterns is obtained. Splitting processes are chiefly governed by the nature of the aromatic substituent at the hydrazidic end and the alkyl sidechain located at the second hydrazinic nitrogen. The major fragmentations occurring are loss of small neutral molecules, double rearrangement, cleavage of the N—N bond, amide bond rupture, β-cleavage to the hydrazinic nitrogen atom and McLafferty rearrangements.
    Additional Material: 1 Tab.
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  • 2
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 17 (1979), S. 2633-2637 
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 13C n.m.r. chemical shifts of a number of 1,1-disubstituted ethylenes are presented. Moreover, effects of changing temperatures on the 13C n.m.r. chemical shifts of some of these compounds as well as of three normal alkanes are given. These variations in chemical shifts are attributed to varying amounts of sterically induced shifts in the different conformational equilibria. In addition to the well-known 1,4 interaction between two alkyl groups shielding effects on the carbon atoms of the connecting bonds are also proposed. No definite explanation of this effect is presented at this time. It is further shown that no simple correlations exist between 13C n.m.r. chemical shifts and calculated total charge densities at this level. Instead, the experimental results in 1-alkenes are rationalized by assuming a linear dependence of the 13C n.m.r. chemical shifts of C-1 and C-2 via rehybridizations on changes in bond angles for small skeletal deformations caused by steric interactions. These changes in geometries, as well as conformational energies in three 1-alkenes, were calculated by means of VFF calculations. Finally. upfield shifts for both C-2 and C-4 are proposed for those conformations of 1-alkenes in which the C-3—C-4 group interacts with the pz-orbital of C-2.
    Additional Material: 4 Tab.
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  • 4
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 7 (1975), S. 415-417 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 13C NMR spectra of the most important hop bitter substances are analysed. All individual carbon atoms are assigned, except the oxygen bonded sp2 carbon atoms. Most assignments are made partly by comparison with analogous compounds and partly by reference to literature data. Cross-correlations with the 1H NMR shifts are made for two main products and confirm the correctness of the assignments. All data are in agreement with the known structures.
    Additional Material: 2 Tab.
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  • 5
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 11 (1978), S. 316-318 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The γ-effects of sulphur on 13C NMR chemical shifts have been measured in a series of steroidal compounds containing the thiophene ring in different configurations with respect to the rest of the molecule. The data constitute the first example of downfield effects exerted by sulphur on both gauche and antiperiplanar γ-carbons. The γ-gauche effect of sulphur amounts to 1.6-1.8 ppm, the γ-antiperiplanar effect from practically zero to almost 1 ppm.
    Additional Material: 1 Tab.
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  • 6
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 16 (1978), S. 2671-2673 
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 1 (1978), S. 97-97 
    ISSN: 0935-6304
    Keywords: Liquid Chromatography ; Structure and relation of polyhalogenated aromatics ; discussed ; Silica gel/aluminium oxide compared ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 8
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 2 (1979), S. 151-153 
    ISSN: 0935-6304
    Keywords: Liquid Chromatography, HPLC ; Stationary phase carrier silicagel analysis and cleaning treatment ; 0.3% metal traces may interfere ; Elution by boiling 1-12 N HCl does not attack C18 bonding in reverse phase material, extracts metals sufficiently ; Effective phase quality test by hop-α-acid chromatogram ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Trace elements in different silica gels are determined by neutron activation analysis. The presence of 20 elements in the ppm range and of 15 elements in the ppb range is established in all silica gels; even in spherical material probably obtained via an organosilicium starting material. Removal of these elements by acid treatment before and after derivatization to a reversed-phase is studied. This is only partially effective. The resulting HPLC phases are, however, much better in cases where trace elements are detrimental. Even octadecyl derivatized silicagel can withstand boiling in 12 N hydrochloric acid without loosing significant amounts of bonded organic material.
    Additional Material: 2 Tab.
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  • 9
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 2 (1979), S. 172-176 
    ISSN: 0935-6304
    Keywords: Chromatography, LC and GC ; Capillary ; Theory ; Ultimate resolution ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The expression for the resolution function, R, in terms of operating parameters for open tubular columns has been extended to include inlet contributions to the peak variance. Subsequent optimization has revealed the existence of optima in the column radius, the stationary phase thickness and the diffusion coefficient ratio in the stationary and mobile phases-in addition to the well-known optimum in the flow velocity. This implies that R at optimum becomes R=f(K)L0.6Vi-0.2, i.e. a function only of the column length, L, the inlet volume, Vi, and the concentration distribution coefficient, K. For given K, L and Vi all other parameters such as retention time and pressure drop can thus be directly computed. The information is finally consolidated in the form of contour diagrams. The text itself is cast in the form of a science fantasy.
    Additional Material: 8 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 1 (1978), S. 41-46 
    ISSN: 0935-6304
    Keywords: Chromatography ; Theory ; Chromatographic systems analysis ; Real plate number ; Fundamental interpretation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The real plate number concept is interpreted in terms of the fundamental properties of a chromatograph. It is shown that the linear relationship between the total peak width at half height, (b0.5)T, t, and k is only an approximation of the more general linear relationship between (b0.5)2T, t and (1 + k)2. In the case where the relationship between (b0.5)T, t and k approaches linearity, it is concluded, firstly, that b0 = a, i. e., b0 is a column property and independent of extra-column phenomena and, secondly, that nreal=ntheor. When the relationship becomes non-linear, b0 is determined partly by extra-column phenomena, but not in terms of a useful relationship. It is concluded that it is unnecessary to introduce the parameters a, b0 and nreal, since they all have counterparts in the established theory of chromatography. These counterparts prove to be equally useful in the practical analysis of chromatographic systems.
    Additional Material: 1 Ill.
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