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  • Articles  (2,891)
  • Analytical Chemistry and Spectroscopy  (1,753)
  • Organic Chemistry  (853)
  • Industrial Chemistry
  • 2000-2004  (13)
  • 1995-1999  (733)
  • 1990-1994  (1,706)
  • 1965-1969  (439)
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  • Articles  (2,891)
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  • 1
    Electronic Resource
    Electronic Resource
    Electrophoric labelling of nucleosides for sensitive analysis by negative ion chemical ionization gas chromatography/mass spectrometry (1992)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 21 (1992), S. 441-450 
    Details
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The formation and analytical utility of several electrophone derivatives of native and oxidatively modified nucleosides of deoxythymidine and deoxyguanosine were studied. Derivatives include the incorporation of trimethylsilyl, acetyl or perfluoroacyl groups together with pentafluorobenzyl. Acetylation followed by pentafluorobenzylation was the most favourable method. In general, the combined information from the electron impact, positive ion chemical ionization and negative ion chemical ionization spectra was well suited for structure elucidation purposes. The acetyl-pentafluorobenzyl derivative of deoxythymidine was prepared in quantitative yield and was very sensitive on analysis by gas chromatography negative ion chemical ionization. Injection of 0.45 fmol of 3′,5′-bis(O-acetyl)-3-pentafluorobenzyl-deoxythymidine, in multiple ion detection experiments, gave a response with a signal-to-noise ratio larger than 10.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200210905
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  • 2
    Electronic Resource
    Electronic Resource
    Identification of Diels-Alder regioisomers by mass spectrometry coupled with theoretical calculations (1993)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 28 (1993), S. 752-758 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Differences in the mass spectra of Diels-Alder cyclohexene regioisomers are explained with the aid of a simple model based on the relative stability differences of the open-chain structures resulting from the alternative cleavage of the C(1)-C(2) and the C(5)-C(6) bonds of the 1-substituted cyclohexene ring. Theoretical SCF-MO calculations at a semi-empirical level proved to be useful tools for determining the relative stabilities of these open-chain radical cation structures and hence in the interpretation of mass spectra and the correct assignment of regioisomer structures from these spectra.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210280705
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  • 3
    Electronic Resource
    Electronic Resource
    Structure of the intermediate formed in the synthesis of symmetrical pyrylium ions (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 731-741 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The synthesis of symmetrical blocked pyrylium derivatives by reaction of a cyclic aromatic ketone with ethyl orthoformate goes through an intermediate which can be isolated under certain conditions. This intermediate is unstable when starting from 1-tetralone derivatives but, surprisingly, it can be isolated easily when the synthesis is performed with 1-indanone derivatives. Further, in the latter case, this intermediate cyclizes hardly into the expected blocked pyrylium derivative. Its ionic structure was demonstrated by mass spectrometry and by 500 MHz 1H and 13C NMR techniques including heteronuclear H-C COSY and DEPT polarization transfer experiments. Hydrolysis of this intermediate in aqueous ethanol solution forms, in acidic or basic media, a pseudo-base, which in the latter case presents strong similarities with that obtained by the base-catalysed ring-opening of a blocked pyrylium ion. In both acidic and basic solutions, the pseudo-base obtained by the two sources shows identical UV-visible absorption spectra. The difficulty of the intermediate (g) originating from 1-indanone derivatives in cyclizing into the blocked pyrylium structure, in contrast to the intermediate formed from 1-tetralone derivatives, is tentatively explained.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610081106
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  • 4
    Electronic Resource
    Electronic Resource
    Letter to the editor (1991)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 5 (1991), S. 218-221 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290050416
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  • 5
    Electronic Resource
    Electronic Resource
    Surface-enhanced Raman spectroscopy of γ-aminobutyric acid on silver colloid surfaces (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Biospectroscopy 3 (1997), S. 449-455 
    Details
    ISSN: 1075-4261
    Keywords: surface-enhanced Raman spectroscopy ; γ-aminobutyric acid ; Raman spectra ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: The surface-enhanced Raman spectroscopy (SERS) of γ-aminobutyric acid (GABA) adsorbed on silver colloids in H2O and D2O were recorded and analyzed. When the concentration is greater than 10-3 M, the adsorbed species is the anionic form of the amino acid that interacts with the surface through both functional groups. According to the vibrational interpretation of the spectra, it is assumed that at concentrations in the order of or less than 10-3 M, GABA undergoes chemical transformations, which increase upon dilution, and spectra are recorded that are the result of the competitive adsorption between the amino acid in its anionic form and the products resulting from the chemical transformations. © 1997 John Wiley & Sons, Inc. Biospectroscopy 3: 449-455, 1997
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Methylmercury(II) complexes with 2-mercaptopyridinecarboxylic acids (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 6 (1992), S. 501-505 
    Details
    ISSN: 0268-2605
    Keywords: Methylmercury ; complexes ; pyridinecarboxylic acids ; stability constants ; mass spectra ; IR spectra ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The stability constants of the complexes [MeHgL]-(H2L = 2-mercaptopyridine-3-carboxylic acid, 2-mercaptopyridine-4-carboxylic acid, 2-mercaptopyridine-5-carboxylic acid and 2-mercaptopyridine-6-carboxylic acid) have been obtained by differential pulse polarography. The values of log β1 are in the range 14.14-14.96 at 20°C and ionic strength 0.1 mol dm-3. The complexes MeHgHL have been isolated and characterized by chemical analysis and mass and IR spectrometry.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aoc.590060605
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  • 7
    Electronic Resource
    Electronic Resource
    Application of B-E time-of-flight mass spectrometry to the detection of high-energy neutral atoms following the photoexcitation of Ar19+ (1993)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 28 (1993), S. 523-526 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A novel instrument which combines high-resolution double-focusing mass spectrometry with time-of-flight detection was applied to the study of cluster ion photofragmentation. Using this apparatus, kinetic energy measurements were made on neutral photofragments following the excitation of Ar19+ at 532 nm. The results show that one and possibly two argon atoms with high centre of mass kinetic energies emerge from the cluster within a few picoseconds of the photon being absorbed.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210280509
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  • 8
    Electronic Resource
    Electronic Resource
    Investigation of the effects of cooling after laser desorption before post-ionization (1994)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 29 (1994), S. 78-84 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: To evaluate the necessity for cooling laser-desorbed molecules to obtain molecular ions and minimal fragmentation, mass spectra of a series of methoxybenzenes were measured in two different experimental configurations. In one geometry, laser-desorbed molecules were entrained in a pulsed supersonic jet before ionization. In the other, the molecules were ionized directly after laser desorption. The samples were ionized with laser-generated vacuum ultraviolet radiation in a single-photon process or ultraviolet radiation in a multi-photon process.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210290203
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  • 9
    Electronic Resource
    Electronic Resource
    Solution phase 1H and 13C-NMR studies of some 1,4,8,11,15,18,22,25-octa-alkylphthalocyanines (1991)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 29 (1991), S. 1053-1060 
    Details
    ISSN: 0749-1581
    Keywords: Octa-alkylphthalocyanines ; phthalocyanines ; 1H NMR ; 13C NMR ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Solution state 1H NMR and 13C NMR spectral data are reported for 1,4,8,11,15,18,22,25-octahexylphthalocyanine, its zinc metallated analogue, and 1,4,8,11,15,18,22,25-octanonylphthalocyanine. Full 1H and 13C NMR signal assignments for these compounds have been made using one and two dimensional techniques supported by T1 measurements. 13C NMR spectra of the two metal-free derivatives show only three signals in the aromatic region at 100 MHz but the expected four resonances at 22.5 MHz. The apparent absence of one of these at 100 MHz is ascribed to a fast exchange process, originating from N—H⃛N⇌N⃛H—N tautomerism.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260291014
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  • 10
    Electronic Resource
    Electronic Resource
    13C NMR analysis of sultones and sulphonate-sulphate anhydrides (1990)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 28 (1990), S. 998-1002 
    Details
    ISSN: 0749-1581
    Keywords: 13C NMR ; Sultones ; Sulphonate-sulphate anhydrides ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 13C NMR spectra of 20 compounds belonging to several types of monocyclic sultones and related ‘carbyl sulphates,’ including a series of fluorinated β-sultones (1,2-oxathietane 2,2-dioxides), are reported. Chemical shift increment systems with n-alkanes as reference molecules are established for non-fluorinated sultones: they show a much less pronounced deshielding effect on the carbon α to oxygen in β-sultones than in the other series. Chemical shifts for the parent β-sultone, predicted in two ways (linear or cyclic model compound), are found to be almost consistent with a purely additive scheme. In fluorinated β-sultones the α-substituent increments relative to perfluoroethanesultone are also derived.
    Additional Material: 8 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260281116
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