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  • 1990-1994  (8)
  • 1970-1974  (5)
  • Analytical Chemistry and Spectroscopy  (13)
  • 1
    Electronic Resource
    Electronic Resource
    Quantitative determination of sulfur compounds in FCC gasolines by AED. A study of the effect of catalyst type and catalytic conditions on sulfur distribution (1993)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 13-17 
    Details
    ISSN: 0935-6304
    Keywords: GC-AED ; Sulfur ; FCC gasoline ; Compound-independent calibration ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The identification and quantification of sulfur-containing compounds in gasoline has become an area of interest because of impending legislation regulating total sulfur levels in these fuels. To study the effects of catalyst type and catalytic conditions on gasoline sulfur distribution, a method has been developed employing both the compound-independent and element-specific response of the atomic emission detector (AED). Calibration and quantification can be accomplished even where standards are not available, owing to the nature of the AED response.Compounds were separated on a thick film polydimethylsiloxane column. An external calibration curve was applied to the area responses of individual sulfur components in the sulfur chromatogram, and the concentrations of each were calculated. Summation of these sulfur concentrations over the gasoline range yields the total sulfur content of the gasoline.The method is applicable to the determination of these compounds in raw crude oils, finished gasolines, fluid cracking catalyst (FCC) unit gasolines, and fluid catalytic cracking “model” compound studies. A prefractionating column was employed to remove heavy (〉C13) materials; prefractionation is not, however, necessary for distilled or commercial gasoline samples. Detection limits, linearity, detector stability, and accuracy are discussed.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240160103
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  • 2
    Electronic Resource
    Electronic Resource
    1,4 elimination of C6H6 in the mass spectral fragmentation of 1-phenyltetralin (1971)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 5 (1971), S. 99-101 
    Details
    ISSN: 0030-493X
    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/oms.1210050114
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  • 3
    Electronic Resource
    Electronic Resource
    Compounds with bridgehead nitrogen. Part 72For Part 71, see Ref. 1. - NMR spectra and stereochemistry of 8,9,10,11,11a,11b,12,13-octahydro-7aH-quino [1,2-c][1,3]benzoxazines and perhydropyrido [1,2-c][1,3]benzoxazines. NMR chemical shifts of methylene group protons adjacent to a nitrogen atom (1993)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 31 (1993), S. 505-508 
    Details
    ISSN: 0749-1581
    Keywords: Octahydro-7aH-quino[1,2-c][1,3]benzoxazines ; Perhydropyrido[1,2-c][1,3]benzoxazines ; 1H and 13C NMR ; Conformation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The positions of conformational equilibria in the four diastereoisomers of 8,9,11,11a,11b,12,13-octahydro-7aH-quino [1,2-c] [1,3] benzoxazines were investigated using 13C and 1H NMR spectroscopy. Comparison of the NMR chemical shifts of these isomers with those in the corresponding isomers of perhydropyrido [1,2-c] [1,3]benzoxazine shows the effect on NMR shifts of fusion of the aromatic ring on to the fully saturated system. The Δδ values are discussed in terms of degree of overlap of the nitrogen lone pair orbitals with the aromatic π-system.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260310516
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  • 4
    Electronic Resource
    Electronic Resource
    NMR coupling of 13C and 19F with 14N in nitro compounds (1990)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 28 (1990), S. 16-20 
    Details
    ISSN: 0749-1581
    Keywords: Nitro compounds ; 13C NMR ; 14N NMR ; 19F NMR ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 13C and 14N NMR spectra of a variety of highly nitrated aliphatic, aromatic and heterocyclic compounds were obtained. The proton decoupled 13C peaks of the nitro-substituted carbons in most of these compounds were split into the multiplets expected for coupling with spin 1 nuclei with negligible quadrupolar broadening. In addition, the 19F spectra of some fluoronitroaliphatic compounds showed that the 19F signals were also split into the expected multiplets from coupling with the 14N of the nitro groups.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260280105
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  • 5
    Electronic Resource
    Electronic Resource
    13C NMR spectra of allosteric effectors of hemoglobin (1994)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 32 (1994), S. 182-183 
    Details
    ISSN: 0749-1581
    Keywords: 13C NMR ; HETCOR ; Urea and thiourea derivatives Hemoglobin ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Carbon-13 NMR studies were performed for a series of allosteric effectors of hemoglobin. Spectral assignments were made by comparison of 1H-decoupled 13C spectra; for selected cases, 2D HETCOR experiments were applied. High regularity in the chemical shifts of the similar fragments of these structures was found.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260320309
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  • 6
    Electronic Resource
    Electronic Resource
    Compounds with bridgehead nitrogen 68For Part 67, see Ref. 1. - NMR spectra and stereochemistry of perhydropyrido [1,2-c] [1,3]oxazines (1992)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 30 (1992), S. 129-132 
    Details
    ISSN: 0749-1581
    Keywords: Perhydropyrido[1,2-c][1,3]oxazines ; 1H and 13C NMR ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Low-temperature 13C NMR spectroscopy shows perhydropyrido [1,2-c] [1,3]oxazine to adopt a conformational equilibrium in CD2Cl2-CFCl3 solution containing 98% trans fused conformer in equilibrium with 2% O-outside-cis fused conformer at 203 K. A similar equilibrium position is adopted by the trans-(H-4,H-4a)-4-methylperhydropyrido[1,2-c][1,3]oxazine, whereas the C-4 epimer adopts exclusively the trans fused conformation.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260300207
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  • 7
    Electronic Resource
    Electronic Resource
    Raman studies of nucleic acids. IX: A salt-induced structural transition in poly(rG) (1973)
    Chichester [u.a.] : Wiley-Blackwell
    Journal of Raman Spectroscopy 1 (1973), S. 207-215 
    Details
    ISSN: 0377-0486
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Raman spectra of poly(rG), obtained from neutral aqueous solutions containing excess sodium counterions, are qualitatively different than spectra obtained from salt-free solutions. In the presence of a two-fold molar excess of Na+ (per phosphate group) the Raman spectrum of poly(iG) closely resembles that of the gel of Guo-5′-P and is characteristic of an ordered helical structure in which guanine residues are hydrogen bonded to one another. In the absence of added salt the spectrum of poly(rG) is characterized by unusual guanine ring frequencies which suggests a tautomeric or ionic modification of the ordinary (keto-amino) ring structure. Both the high-salt and no-salt forms of poly(rG) represent stable secondary structures as evidenced by the conformationally sensitive phosphodiester frequencies and by the absence of significant spectral changes on heating the solutions.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jrs.1250010208
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  • 8
    Electronic Resource
    Electronic Resource
    Enhancement of Cα hydrogen vibrations in the resonance Raman spectra of amides (1994)
    Chichester [u.a.] : Wiley-Blackwell
    Journal of Raman Spectroscopy 25 (1994), S. 537-543 
    Details
    ISSN: 0377-0486
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Ultraviolet resonance Raman (UVRR) spectra of polypeptides and proteins exhibit a band at ca. 1390 cm-1 whose intensity is sensitive to helical content. The assignment of this band, designated amide S, has been contentious. To study the vibrational origin of amide S, relevant amide model compounds and their selectively deuterated iso-topomers were synthesized. N-Methylacetamide, N-methylpropionamide and N-methylisobutyramide possess a methyl, methylene and methine group, respectively, adjacent to the amide carbonyl. The UVRR spectrum of the natural abundance species show resonantly enhanced vibrational bands in the region 1350-1380 cm-1. These bands disappear on deuteration of the (C)Cα. hydrogen atoms, while the amide III modes shift up to a common position (ca. 1335 cm-1) and increase in intensity. These results suggest that amide S can be assigned to a (C)Cα hydrogen bending vibration, which acquires resonance intensity by vibrational mixing with the CN stretch of the nearby amide III mode. Variation of this mixing with the Cα—H/C=O dihedral angle can explain the sensitivity of amide III to protein secondary structure. Additional UVRR and Fourier transform IR data reveal that (C)Cα-deuteration has a smaller effect on the amide I, I′, II and II′ vibrational modes. Finally, it is established that UVRR spectra for NMA in H2O and D2O show an absence of torsional fundamentals or overtones. These results are interpreted as indicating an energy barrier to cxcited-state isomerization, which argues against an alternative assignment of amide S to the amide V overtone.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jrs.1250250715
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  • 9
    Electronic Resource
    Electronic Resource
    Dinucleotide binding to RNase probed with UV resonance Raman spectroscopy (1991)
    Chichester [u.a.] : Wiley-Blackwell
    Journal of Raman Spectroscopy 22 (1991), S. 205-209 
    Details
    ISSN: 0377-0486
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Raman spectra are reported for ribonuclease and its complexes with the dideoxynucleotides dCpdC, dCpdA and dCpdG, using 240-250-nm excitation to enhance the purine and pyrimidine modes, as well as tyrosine and phenylalanine modes of the protein. Spectral perturbations associated with binding were examined via difference spectroscopy. Consistent with the crystal structure of CpA* bound to RNase, the 3′-cytidine was inferred to be hydrogen bonded to a protein donor via the N-3 ring atom, but not via the carbonyl O atom, since the 1526 cm-1 band shifts up on binding, as it does when aqueous CMP is protonated, and the C=O stretch shifts from 1655 to 1670 cm-1, an effect attributable to polarization via the N-3 hydrogen bond. The effect of binding on the spectra of the 5′-purine rings is limited to intensity changes, an augmentation of the adenine 1578 cm-1 band and a diminution of the guanine 1330 cm-1 band, consistent with only weak interactions with the protein. Binding of dCpdC intensifies the 1615 cm-1 protein band, suggesting environmental changes for tyrosine or phenylalanine residues. No spectral perturbation was observed on mixing RNase with dGpdC or dGpdG, consistent with weak or non-specific binding of dinucleotides lacking a pyrimidine in the 3′-position.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jrs.1250220403
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  • 10
    Electronic Resource
    Electronic Resource
    Hemoglobin resonance Raman excitation profiles with a tunable dye laser (1973)
    Chichester [u.a.] : Wiley-Blackwell
    Journal of Raman Spectroscopy 1 (1973), S. 387-392 
    Details
    ISSN: 0377-0486
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Resonance Raman spectra have been obtained for oxy hemoglobin within the α absorption band, corresponding to the first π - π* transition, using a tunable dye (Rhodamine 6 G) laser. The excitation profiles demonstrate resonance at the electronic origin (0-0), as well as at the vibronic side-band (0-1) frequency, as predicted by theory. The wavelength dependence of the Raman intensity follows the molar absorptivity, rather than its square. It is suggested, however, that this form of the wavelength dependence may be an artifact of the transition from resonance to pre-resonance scattering.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jrs.1250010411
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