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  • 1
    Electronic Resource
    Electronic Resource
    A dynamic NMR study of Z, E-isomerization in solutions of indolyl-substituted α-nitroacrylates (1978)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 11 (1978), S. 308-312 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Fast Z, E-isomerization of α-nitro-β-indolylacrylates in polar solvents has been studied by dynamic 1H NMR spectroscopy. With indolylnitroacrylates having no substituents at the ring nitrogen atom, isomerization proceeds via intermediate formation of a mesomeric anion and ionization of the N—-H bond as the rate determining step. For methyl-substituted indolylnitroacrylates, no general isomerization mechanism can be suggested, and isomerization pathways depend on the structures of isomerizing species.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270110609
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  • 2
    Electronic Resource
    Electronic Resource
    Negative ion mass spectra of a series of fluorinated β-diketones (1977)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 12 (1977), S. 93-97 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Electron capture by and the subsequent fragmentation of a series of eleven fluorinated β-diketones of general formula CF3COCH2COR has been studied in an MS-50 mass spectrometer. Consecutive loss of two HF molecules from molecular anions occurs with all compounds, as does elimination of CHF3 from [M — H]- ions. Elimination of CO occurs from either \documentclass{article}\pagestyle{empty}\begin{document}$ \left[{{\rm M - HF}} \right]_{}^{_.^ - } $\end{document} or \documentclass{article}\pagestyle{empty}\begin{document}$ \left[{{\rm M - 2HF}} \right]_{}^{_.^ - } $\end{document} ions for five compounds where R = CF3 or a cyclic substituent. Kinetic energy release in metastable transitions associated with these HF and CO eliminations has been measured. Intensities of various fragment ions are in part influenced by the ion source temperature. Interaction of \documentclass{article}\pagestyle{empty}\begin{document}$ \left[{{\rm O}} \right]_{}^{_.^ - } $\end{document} reagent ions with five of the β-diketones under chemical ionization conditions gave [M — H]- ions as the only significant ion-molecule reaction product.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210120209
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  • 3
    Electronic Resource
    Electronic Resource
    The elucidation of the mass spectral fragmentation pathway of α-methyldopamine derivatives by chlorine labelingTFA = trifluoroacetyl; TFAA = trifluoroacetic anhydride; CFAA = monochlorodifluoroacetic anhydride. (1979)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 6 (1979), S. 554-558 
    Details
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The mass spectra of the tristrifluoroacetyl derivative of α-methyldopamine and the bistrifluoroacetyl derivative of 3-O-methyl-α-methyldopamine contain important ions which can be rationalized by two alternative fragmentation pathways. These ambiguities were resolved by means of a simple chemical derivatization technique. The labile phenolic ester groups were hydrolyzed and subsequently re-esterified by reaction with chlorodifluoroacetic anhydride in the presence of ethyl acetate thereby labeling ions containing ester group(s) in the mass spectra with the diagnostic chlorine isotope ratio. This resulted in the addition of 16/18 mass units to the weights of the ions for each fluorine atom replaced by chlorine. Since it was easy to distinguish loss of the mass of a neutral molecule of trifluoroacetamide (113 mass units) from the ions of a chlorodifluoroacetoxy radical (129 mass units), the elimination of trifluoroacetamide was distinguished from that of trifluoroacetoxy radical. Derivatives were also prepared in which the chlorine label was located on the N-acyl function. The mass spectra of the chlorine labeled compounds showed that the major fragmentation pathway of tristrihaloacetyl-α-methyldopamine and bistrihaloacyl-3-O-methyl-α-methyldopamine is by loss of a neutral molecule of trihaloacetamide.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200061204
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  • 4
    Electronic Resource
    Electronic Resource
    Preparation of apolar glass capillary columns by the barium carbonate procedure (1978)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 1 (1978), S. 149-155 
    Details
    ISSN: 0935-6304
    Keywords: Gas Chromatography ; Capillary, glass ; Preparation of apolar columns ; Ba CO3 procedure optimized for thermostability acid/base behaviour and efficiency ; New, quantitative testing procedure ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: As an extension of previous reports, the barium carbonate procedure has been optimized in detail for the preparation of apolar columns. The aim was to produce optimum overall column characteristics, and to maintain them unchanged under the prolonged influence of the highest possible temperature. The main parameters under optimization were glass variety, leaching of glass surface with aqueous HCl, and amount of barium carbonate deposited, while deactivation and coating were kept constant. The basic column characteristics were adsorption properties and thermostability of deactivation, acid/base behaviour and separation efficiency. They were determined by a new, quantitative testing procedure. Intense leaching was able to eliminate almost totally the differences between glass varieties and to create a well-defined glass surface. While untreated glass, leached glass, and barium carbonate treated glass showed specific weak points in the respective column quality, the combination of leaching and barium carbonate treatment yielded the highest and most stable quality. Some technical modifications of the preparation procedure are described, including deactivation in the gas phase, and use of pentane as a solvent for static coating.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240010306
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  • 5
    Electronic Resource
    Electronic Resource
    Micro-analytical separation and evaluation of platinum metals (1978)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 1 (1978), S. 314-314 
    Details
    ISSN: 0935-6304
    Keywords: Thin Layer Chromatography, TLC ; Silicagel/org. solvents mixture ; semiquantiative determination of Ru, Rh, Pd, Ir, Pt, Au ; 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/jhrc.1240010613
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  • 6
    Electronic Resource
    Electronic Resource
    Deactivation of glass capillaries by persilylationThe term persilylation denotes complete silylation, in contrast to partial silylation achieved by common procedures.. Part 2: Practical recommendations (1979)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 2 (1979), S. 677-678 
    Details
    ISSN: 0935-6304
    Keywords: Gas chromatography ; Capillary, glass ; Surface deactivation, persllylation ; Discussion of variable parameters ; Suggested practical procedure ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240021110
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  • 7
    Electronic Resource
    Electronic Resource
    Deactivation of glass capillary columns by silylation. Part 1: Principles and basic technique (1979)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 2 (1979), S. 31-35 
    Details
    ISSN: 0935-6304
    Keywords: Gas chromatography ; Capillary, glass ; Surface deactivation, silylation ; Inertia stable to 350° ; Free acids and bases, simultaneous injection ; On-column injection ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A deactivation procedure is described based on a published method using hexamethyldisilazane in the gas phase. In addition to unusually high inertia and thermostability, the method produces truly neutral columns which allow simultaneous analysis of moderately strong free acids and bases. The silylated columns show their full potential only with on-column injection. Preliminary experimental directions are given; more elaborate directions will become available after extended optimization work.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240020110
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  • 8
    Electronic Resource
    Electronic Resource
    Splitless injection and the solvent effect (1978)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 1 (1978), S. 57-64 
    Details
    ISSN: 0935-6304
    Keywords: Gas Chromatography ; Capillary, glass ; Splitless injection, basis of ; Use for any sample ; Optimization ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Splitless injection is based on the solvent effect as a mechanism condensing large vapour clouds down to infinitely shortened bands. The effect is controlled by the parameters column temperature, volatility and amount of solvent, and rate of injection. By properly selecting the variables the effect can easily be optimized for any combination of sample and column. It is the purpose of this paper to provide the mechanistic understanding as required for this optimization, as well as some rules for the experimental realization. Potentialities and limitations of splitless injection are discussed, and the role of the solvent effect in on-column injection is emphasized.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240010112
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  • 9
    Electronic Resource
    Electronic Resource
    Argentation thin-layer chromatography of polyunsaturated fatty acid methyl esters (1978)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 1 (1978), S. 214-215 
    Details
    ISSN: 0935-6304
    Keywords: Thin layer chromatography TLC ; Ammoniacal silver ion plates for polyunsaturated fatty acid methyl esters separation ; Rf-data versus number of double bonds ; 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/jhrc.1240010413
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  • 10
    Electronic Resource
    Electronic Resource
    Gas chromatographic and mass spectrometric analysis of the products of methylation of sulfonylurea drugsAbbreviations: NMTSA = N-methyl-p-tolylsulfonamide; NMTBA = N-methyltolbutamide; MEETBA = methyl enol ether of tolbutamide; NMCBSA = N-methyl-p-chlorobenzenesulfonamide; NMCPA = N-methylchlorpropamide; MEECPA = methyl enol ether of chlorpropamide. (1976)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 3 (1976), S. 100-109 
    Details
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Gas chromatographic analysis of the products of reaction of diazomethane with tolbutamide and chlorpropamide indicates the formation of three compounds in both cases. As expected, N-methylation (at sulfonamide nitrogen) is the predominant reaction; minor amounts of O-methylated product are also observed. The third product in both cases is the N-methylsulfonamide formed by decomposition of the N-methylated sulfonylurea during gas chromatography. Electron impact and chemical ionization mass spectrometric analysis, as well as 1H nuclear magnetic resonance examination of samples collected from gas chromatography, confirm the structural assignments. Additionally, proton magnetic resonance analysis of the crude reaction products established that N-methylsulfonamides are not formed in the course of the diazomethane reaction and that the O-methylated derivatives are true products of the reaction. The use of a paramagnetic shift reagent allowed direct estimation of the ratios of N- to O-methylation, and the demonstration that these ratios are not vitiated during gas chromatographic analysis.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200030303
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