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  • Analytical Chemistry and Spectroscopy  (19)
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  • 1
    Electronic Resource
    Electronic Resource
    An NMR study of some substituted 1,3- and 1,4-bistrifluoromethylbenzenes (1973)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 5 (1973), S. 479-481 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Contrary to an earlier report, the metallation of 1,3-bistrifluoromethylbenzene with n-butyllithium is found to take place at the 4- and 2-positions. Lithiation of 1,4-bistrifluoromethylbenzene and subsequent carboxylation gives exclusively the 2-carboxylic acid. Structures are assigned on the basis of PMR data (100 and 220 MHz). The effects of coupling between aromatic protons and trifluoromethyl groups and the aromatic chemical shifts brought about by esterification are discussed for a series of bistrifluoromethylbenzoic acids.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270051008
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  • 2
    Electronic Resource
    Electronic Resource
    High-resolution nuclear magnetic resonance spectra of phenanthrenes-IVFor part III, see Ref. 1. Phenyl derivatives of phenanthrene (1970)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 2 (1970), S. 259-270 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Proton magnetic resonance spectra at 60 MHz are reported for 9, 9′-biphenanthryl, 1-phenylfluoranthene, 9-benzylphenanthrene, 1-, 4- and 9-phenylphenanthrenes and 9-methyl-10-phenylphenanthrene, all in CS2 solution. Approximate values of some of the chemical shifts and coupling constants were extracted from the overlapped and often collapsed AB, ABC ABCD and AA′BB′C (phenyl) spin systems. By comparison with data for phenanthrene itself, estimates have been made for the dihedral angle, θ, between the planes of the phenyl ring and the phenanthrene nucleus in phenylphenanthrenes. These lead, except for 9-phenylphenanthrene for which the angle derived from H(10) by PMR is higher than UV suggests, to plausible values for θ: 90°, 75°, 40° and 45 to 60°, for 4-phenyl, 9-methyl-10-phenyl-, 1- and 9-phenylphenanthrenes, respectively.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270020306
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  • 3
    Electronic Resource
    Electronic Resource
    Nuclear magnetic resonance and the conformation of some derivatives of Michler's ketone (1975)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 7 (1975), S. 154-159 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1H NMR spectra are reported for Michler's ketone and twenty of its derivatives, along with 13C chemical shifts for five of the compounds. 1H chemical shifts show only small changes with increasing substitution at the sterically hindered 2-position. Estimates of the dihedral angle between the benzene ring and C—CO—C planes have been obtained from the chemical shifts of C=O and 4-C for ketones 1, 3, 5, 15 and 16. These angles are both internally consistent and very similar to dihedral angles determined by other methods for corresponding compounds in the benzophenone series.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270070403
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  • 4
    Electronic Resource
    Electronic Resource
    Correlation of molecular orbital indices of reactivity and proton chemical shifts: Acenaphtho[1,2-b]- and -[1,2-c]thiophens (1973)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 5 (1973), S. 95-97 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Nuclear magnetic resonance proton chemical shifts may be correlated with free valence, a representative reactivity index, for fluoranthene and two novel sulphur heterocyclic analogues, acenaphtho[1,2-b]- and -[1,2-c]thiophens. Such correlations arise fortuitously, however, and an attempt to explain them in terms of intrinsic properties of the Hückel-McWeeny theory of proton shielding is proved to be fallacious.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270050209
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  • 5
    Electronic Resource
    Electronic Resource
    Annual reports on NMR spectroscopy, volume 6A, edited by E. F. Mooney. Academic Press, London, 1975, £15·00, $40.00 (1976)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 8 (1976), S. A7 
    Details
    ISSN: 0030-4921
    Keywords: 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/mrc.1270080718
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  • 6
    Electronic Resource
    Electronic Resource
    Rayleigh instability of stationary phase films in capillary column chromatography (1987)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 10 (1987), S. 128-136 
    Details
    ISSN: 0935-6304
    Keywords: Gas chromatography ; Capillary columns ; Coating of capillaries, static and dynamic ; Rayleigh instability ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The film of stationary phase on the wall of a capillary column and that of the phase solution during both static and dynamic coating is subject to Rayleigh instability, which is quite independent of so-called wettability. A theory is developed which shows that the logarithmic growth rate of Rayleigh instabilities is proportional to the surface tension and to the third power of the film thickness, and inversely to the viscosity and to the fourth power of the capillary diameter. Determination of the variation of the viscosities of stationary phase solutions with concentration in coating solvents, and the variation of the viscosities of neat stationary phases with temperature, both revealed that heating and/or diluting changed the viscosities of phases with π-electron-containing, groups much more than for polydimethylsiloxanes. Rayleigh instability is therefore more important during coating of phenyl-containing phases such as OV-17, and later during column operation. The efficiencies of capillary columns of different diameters coated with a number of phases under different conditions of temperature and coating rate, and then operated at different temperatures were in good agreement with the predictions of the theory.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240100305
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  • 7
    Electronic Resource
    Electronic Resource
    Analysis of chemical additives in polypropylene films using capillary supercritical fluid chromatography (1989)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 12 (1989), S. 688-691 
    Details
    ISSN: 0935-6304
    Keywords: Capillary supercritical fluid chromatography, CSFC ; Polymer extraction ; Additive analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240121014
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  • 8
    Electronic Resource
    Electronic Resource
    Deactivation of fused silica capillary columns with cyanopropylhydrosiloxanes (1985)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 8 (1985), S. 741-747 
    Details
    ISSN: 0935-6304
    Keywords: Gas chromatography ; Fused silica capillary columns ; Deactivation ; Cyanopropylhydrosiloxanes ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A method is described for surface deactivation and modification of fused silica capillary columns with a cyanopropyl-containing reagent. The deactivation procedure involved a dehydrocondensation reaction between a bis(cyanopropyl)methylhydropolysiloxane reagent and surface silanol groups at an optimum temperature of only 250°C. Actual critical surface tension measurements were made using the capillary rise method. Excellent deactivation for acidic and basic compounds at the low ng level, and wettability for nonpolar and polar polysiloxane stationary phases were obtained. A procedure was developed to remove acidic impurities that are present in polar stationary phases.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240081109
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  • 9
    Electronic Resource
    Electronic Resource
    Deactivation of small diameter fused silica capillary columns with organosilicon hydrides (1986)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 9 (1986), S. 506-514 
    Details
    ISSN: 0935-6304
    Keywords: Supercritical fluid chromatography, SFC ; Deactivation ; Gas chromatography, GC ; Small diameter capillary columns ; Organosilicon hydrides ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Small diameter fused silica capillary columns (50-75 μm i.d.) were deactivated at relatively low temperatures (250-300°C) with a mixture of polymethylhydrosiloxanes and several lowmolecular-weight organosilicon hydrides. Reproducible surface deactivations of highest quality were achieved with the polymethylhydrosiloxane (PMHS) reagent. Deactivations performed with PMHS via dynamic coating with neat or diluted reagent were evaluated by gas chromatography. Deactivations achieved with organosiloxane mono-, tri-, and tetrahydrides were also evaluated and compared. Low-molecular-weight organosilicon hydride deactivations were less time consuming and required lower head pressures for filling and coating columns with the reagent. Critical surface tensions of capillary surfaces modified with PMHS and the low-molecular-weight organosilicon hydrides gave support to the dehydrocondensation reaction between silica surface silanols and silyhydride bonds of the reagents. Slopes from Zisman plots indicated that coverage of the surface ranged from highest for the polymer (PMHS) to lowest for the monomers (TMS and PMDS). Efficiency measurements showed the influence that surface modification had on the uniformity and stability of the coated capillary columns. Well-deactivated capillary columns permitted the chromatography of polar solutes using supercritical carbon dioxide as mobile phase.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240090904
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  • 10
    Electronic Resource
    Electronic Resource
    Preparation of robust tapered restrictors for capillary supercritical fluid chromatography (1988)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 11 (1988), S. 289-291 
    Details
    ISSN: 0935-6304
    Keywords: Supercritical fluid chromatography, SFC ; Capillary columns ; Restrictor ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240110314
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