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  • 1
    Electronic Resource
    Electronic Resource
    Analysis of the IGLO bond contributions to the 13C shielding tensors in the local bond frame (1987)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 31 (1987), S. 45-55 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new method is presented to analyze the IGLO (individual gauge for localized orbitals) bond contributions in 13C chemical shielding. The IGLO bond contributions calculated in the molecular frame are rotated to a local bond frame, in which one component is selected along the bond. This procedure removes the explicit angular dependence of the IGLO bond contributions and allows a comparison of the bond contributions in different molecules.The results provide a new method to study the electronic basis of shielding interactions. The problems associated with the multiple gauge origins used in the IGLO method are discussed in their relationship to the bond contribution analysis.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560310106
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  • 2
    Electronic Resource
    Electronic Resource
    Structure determination of a new saponin from the plant Alphitonia zizyphoides by NMR spectroscopy (1993)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 31 (1993), S. 472-480 
    Details
    ISSN: 0749-1581
    Keywords: Alphitonia zizyphoides ; Saponin ; 2D NMR ; INADEQUATE ; Molecular structure ; Computerized spectral analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: High-field NMR experiments, including the 2D INADEQUATE technique coupled with a computerized spectral analysis, were used to determine the full structure of a new saponin extracted from a plant (Alphitonia zizyphoides) found in the Samoan rain forests. The saponin, which shows significant pharmacological activity, consists of an aglycone framework of six rings (three saturated six-membered rings, two oxygen-containing five-membered rings and a five-membered carbon ring) to which are attached four sugar units and a six-carbon side-chain. The INADEQUATE experiment, which was carried out on 60 mg of sample, provided absolute confirmation of the assignments for 35 of the possible 53 C—C bonds from the 13C-13C connectivities.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260310511
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  • 3
    Electronic Resource
    Electronic Resource
    Computerized analysis of 2D INADEQUATE spectra to assign chemical shifts in aromatic compounds (1995)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 33 (1995), S. 803-811 
    Details
    ISSN: 0749-1581
    Keywords: NMR ; 13C NMR ; 2D INADEQUATE ; polycyclic benzenoid aromatics ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A computerized analysis of a single 2D INADEQUATE spectra assigns all of the 13C chemical shifts in fairly complex aromatic systems. Without the aid of the computer this information is often difficult, if not impossible, to retrieve owing to overlap of the signals in the double quantum dimension. In addition, the use of the computerized analysis allows for the interpretation of INADEQUATE spectra with much lower signal-to-noise ratios than are practical if the analysis were to be done visually. Finally, narrowing the spectral window to a subset of the entire spectrum and the companion advantages are demonstrated. The assignments of the aromatic chemical shifts in 2-methoxydibenzofuran, 6-methylchrysene, 1-decylpyrene, and 7-methylbenzo[a]pyrene illustrate the power of automated pattern recognition methods while supplying previously unavailable chemical shift assignments on these complex fused polycyclic aromatic systems.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260331007
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  • 4
    Electronic Resource
    Electronic Resource
    Solid-state 13C NMR study of drugs: Aspirin (1986)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 24 (1986), S. 768-771 
    Details
    ISSN: 0749-1581
    Keywords: Solid-state ; 13C NMR ; Aspirin ; Drugs ; Polymorphism ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Natural abundance 13C NMR spectra of different crystal habits of pure aspirin and several aspirin tablets in the solid state have been measured by using the combined techniques of high-power decoupling, cross-polarization and magic angle spinning. Solid-state NMR of aspirin had excellent sensitivity compared with liquid-state NMR, and the carbon signals were assigned using a modified pulse sequence to detect non-protonated carbons. The solid-state 13C NMR spectra of two crystalline forms of aspirin were identical, suggesting that the origin of their difference is not polymorphic.The solid-state 13C NMR spectra of several commercial aspirin tablets, some of them containing buffer components, indicated that there were no interactions among the aspirin and the buffer components; only after dissolving the tablets and lyophilization did the 13C NMR spectra of the dry lyophilized powders show strong interactions between aspirin and the buffer components.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260240907
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  • 5
    Electronic Resource
    Electronic Resource
    Conformational analysis of DL-, L- and D-methionine by solid-state 13C NMR spectroscopy (1986)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 24 (1986), S. 167-170 
    Details
    ISSN: 0749-1581
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The conformational analysis of DL-, L- and D-methionine was studied by solid-state 13C NMR with the help of cross-polarization and magic-angle spinning techniques. The spectrum of commercial crystalline DL-methionine showed two chemical shifts (18.7 and 15.8 ppm) for the methyl carbon. Crystallization from water or water-ethanol (95 : 5) allowed the separation of two crystalline forms (α and β), of which one had δ (CH3) 18.7 ppm and the other δ (CH3) 15.8 ppm. Therefore, each crystalline form of DL-methionine consists of a single conformer, a result in agreement with x-ray diffraction data. This conformational difference of the two crystalline forms was also reflected in the carbon resonances of C-β and C-γ. When L- and D-methionine were crystallized from water-ethanol (3 : 2), the solid-state 13C NMR spectra showed that each isomer displayed two methyl carbon peaks at 18.1 and 16.2 ppm of equal intensities, while the α-carbon resonances showed a broad peak due to two unresolved doublets. These results suggest that the L- or D-methionine crystal contains two different conformers in one unit cell, a conclusion that is also supported by the x-ray data.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260240213
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  • 6
    Electronic Resource
    Electronic Resource
    The use of high-field carbon-13 NMR spectroscopy to characterize chiral centers in isopranes (1986)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 24 (1986), S. 191-198 
    Details
    ISSN: 0749-1581
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 13C nuclear magnetic resonance spectra of four diastereomeric, acyclic isoprenoids [farnesane (C15), pristane (C19), phytane (C20), and squalane (C30)] have been obtained as a means for interpreting hydrocarbon mixtures common in some fossil fuels and biosynthesized organic compounds. Multiple resonance environments were detected for carbons influenced by two or three chiral centers. Samples of farnesane and squalane were found to exhibit random stereochemistry, whereas the phytane sample was demonstrated to be a mixture of two isomers, probably the 6(R), 10(S), 14(R,S) compound. The sample of pristane consisted of a single diastereomer and was probably obtained from a natural product. It is shown that general chemical shift assignments can be made in this class of molecules by considering the number of carbons located at positions one, two and three bonds distant, while assignment of closely spaced lines may be made on the basis of diastereomerically induced chemical shifts. Using these principles, the structural features of two fossil fuels were analysed.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260240303
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  • 7
    Electronic Resource
    Electronic Resource
    A comparison of the IGLO and LORG methods for the calculations of nuclear magnetic shieldings (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 11 (1990), S. 32-44 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The individual gauge for localized orbitals (IGLO) and localized orbital/local origin (LORG) methods for the calculation of chemical shieldings are compared from their theoretical and computational viewpoints. A detailed analysis of the fluorine α-substituent effect in a series of fluoromethanes is given in terms of the IGLO and LORG bond contributions. The performance of both methods is discussed for molecular systems of fairly different sizes.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540110104
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  • 8
    Electronic Resource
    Electronic Resource
    Structural study of phenol-formaldehyde polymers with proton magnetic resonancePresented in part at the Conference on Analytical Chemistry and Applied Spectroscopy in Pittsburgh, Pa., March, 1962. (1965)
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A: General Papers 3 (1965), S. 2091-2105 
    Details
    ISSN: 0449-2951
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Proton magnetic resonance spectra were obtained for a number of representative phenol-formaldehyde dimers and trimers of known structure and for related compounds having methyl or chloro substituents on the aromatic ring. The data thus obtained, particularly for the methylene protons, were used in the interpretation of the structure of well characterized, linear phenol-formaldehyde polymers and the corresponding halogenated polymers prepared by the condensation of o- and p-chlorophenol with formaldehyde. In all cases there was a shift to lower field as the methylene linkage was varied from para-para to ortho-para to ortho-ortho, although in certain instances the ortho-para and ortho-ortho peaks moved very close together. The spectra obtained indicated that the condensation of o-chlorophenol with formaldehyde proceeds in an essentially random manner, since the ratio of ortho-ortho to ortho-para to para-para methylene linkages was found to be 1:2:1, within the limits of experimental error. The preliminary results obtained in this work clearly demonstrate the potential utility of PMR as a valuable tool in the characterization of the highly complex products obtained from phenol-formaldehyde systems.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1965.100030602
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  • 9
    Electronic Resource
    Electronic Resource
    Development of recombinant viral insecticides by expression of an insect-specific toxin and insect-specific enzyme in nuclear polyhedrosis viruses (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Archives of Insect Biochemistry and Physiology 22 (1993), S. 315-344 
    Details
    ISSN: 0739-4462
    Keywords: Chemistry ; Food Science, Agricultural, Medicinal and Pharmaceutical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: As supplements to classical chemical insecticides, two approaches to develop recombinant baculovirus insecticides are described. In one approach an insect-specific toxin is expressed leading to a dramatic reduction in time to death. In the second approach an insect juvenile hormone esterase is expressed which leads to a reduction in feeding. Modifications of the wildtype esterase led to viruses which reduced the time to death as efffectively as did the toxin-expressing virus. In both cases existing recombinant viruses are viewed as leads, and approaches to further improvement in the engineered viruses are suggested. Many of these approaches are based on analogy with the development of classical synthetic insecticides. Using these viruses as examples, the potential utility and limitations of recombinant viruses and other biological insecticides are discussed. © 1993 Wiley-Liss, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/arch.940220303
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  • 10
    Electronic Resource
    Electronic Resource
    α,ω-Disubstituted polymethylpolyphosphonates and polyphenylpolyphosphonates from condensation polymerization (1967)
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-1: Polymer Chemistry 5 (1967), S. 57-75 
    Details
    ISSN: 0449-296X
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Condensation polymerization of phosphonates through formation of P—O—P linkages has been achieved by (1) volatilization of methyl chloride from mixtures of CH3P(O)Cl2 with CH3P(O)(OCH3)2; (2) volatilization or chemical removal of water from CH3P(O)(OH)2; and (3) volatilization of HCl from mixtures of CH3P(O)Cl2 with CH3P(O)(OH)2 or C6H5P(O)Cl2 with C6H5P(O)(OH)2. Depending on the proportions of the reagents, the polymerization products consist of various mixtures of chain molecules of the type \documentclass{article}\pagestyle{empty}\begin{document}${\rm X \hbox{--} P}({\rm O})({\rm R})\rlap{--}[{\rm O \hbox{--} P}({\rm O})({\rm R})\rlap{--}]_n {\rm X}$\end{document} for R = CH3 and X = OCH3, Cl, or OH, or for R = C6H5, x = Cl or OH. 31P nuclear magnetic resonance (NMR) was used to investigate both the polymethylpolyphosphonates and the polyphenylpolyphosphonates; and 1H NMR of the CH3P and CH3O moieties was also used to study the polymethylpolyphosphonates. In the methoxyl-terminated polymethylpolyphosphonates, which was the system studied most extensively, no detectable amounts of cyclic molecules were found at equilibrium, but a crystalline methylphosphonic anhydride, CH3PO2, exhibited some ring structures. The equilibrium size distributions gave evidence that the sorting of the mono- and difunctional phosphorus-based units making up the oligomeric chains is affected by neighboring units. Kinetic measurements demonstrated that the condensation polymerization is a complicated process involving considerable scrambling of terminal groups with bridging oxygen atoms.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1967.150050106
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