Bond Correlation (bond + correlation)

Distribution by Scientific Domains
Chemistry66%

Kinds of Bond Correlation

  • heteronuclear multiple bond correlation
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  • multiple bond correlation
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    Selected Abstracts

    Direction of Isomerization of 5-Hydroxy-3-propargylthio-1,2,4-triazines According to 1H/15N Heteronuclear Multiple Bond Correlation (HMBC) Spectra.

    CHEMINFORM, Issue 48 2006
    V. Yu.
    Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source]

    Preparation of carbonated natural rubber

    JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 4 2006
    Seiichi Kawahara
    Carbonated natural rubber was prepared from deproteinized natural rubber with supercritical carbon dioxide, in which the deproteinization of natural rubber was performed in the latex stage with urea in the presence of a surfactant. The deproteinized natural rubber was epoxidized with peracetic acid in the latex stage, and this was followed by depolymerization with peroxide to prepare liquid epoxidized natural rubber. The liquid epoxidized rubber was incubated with supercritical carbon dioxide with lithium bromide as a catalyst at various temperatures and pressures. The product was proved to be carbonated natural rubber by means of Fourier transform infrared, 1H NMR, 13C NMR, two-dimensional 1H,1H correlation, two-dimensional 1H,13C correlation, and two-dimensional heteronuclear multiple bond correlation. [source]

    Synthesis of rhodium(III) complexes with tris/tetrakis-benzimidazoles and benzothiazoles,quick identification of cyclometallation by nuclear magnetic resonance spectroscopy

    MAGNETIC RESONANCE IN CHEMISTRY, Issue 8 2009
    N. Chandrashekhar
    Abstract Reactions of rhodium(III) halides with multidentate N,S -heterocycles, (LH3) 1,3,5-tris(benzimidazolyl)benzene (L1H3; 1), 1,3,5-tris(N -methylbenzimidazolyl) benzene (L2H3; 2) and 1,3,5-tris(benzothiazolyl)benzene (L3H3; 3), in the molar ratio 1:1 in methanol,chloroform produced mononuclear cyclometallated products of the composition [RhX2(LH2)(H2O)] (X = Cl, Br, I; LH2 = L1H2, L2H2, L3H2). When the metal to ligand (1,3 or 1,2,4,5-tetrakis(benzothiazolyl)benzene [L4H2; 4]) molar ratio was 2:1, the reactions yielded binuclear complexes of the compositions [Rh2Cl5(LH2)(H2O)3] (LH2 = L1H2, L2H2, L3H2) and [Rh2X4(L4)(H2O)2] (X = Cl, Br, I). Elemental analysis, IR and 1H nuclear magnetic resonance (NMR) chemical shifts supported the binuclear nature of the complexes. Cyclometallation was detected by conventional 13C NMR spectra that showed a doublet around ,190 ppm. Cyclometallation was also detected by gradient-enhanced heteronuclear multiple bond correlation (g-HMBC) experiment that showed cross-peaks between the cyclometallated carbon and the central benzene ring protons of 1,3. Cyclometallation was substantiated by two-dimensional 1H1H correlated experiments (gradiant-correlation spectroscopy and rotating frame Overhauser effect spectroscopy) and 1H13C single bond correlated two-dimensional NMR experiments (gradient-enhanced heteronuclear single quantum coherence). The 1H15N g-HMBC experiment suggested the coordination of the heterocycles to the metal ion via tertiary nitrogen. Copyright © 2009 John Wiley & Sons, Ltd. [source]

    Assignments of 1H and 13C NMR spectral data for ondansetron and its two novel metabolites, 1-hydroxy-ondansetron diastereoisomers

    MAGNETIC RESONANCE IN CHEMISTRY, Issue 10 2006
    Mingyu Duan
    Abstract Assignments of 1H and 13C NMR chemical shifts were made by means of heteronuclear single quantum coherence (HSQC) and heteronuclear multiple bond correlation (HMBC) experiments for ondansetron, and by means of 1H- 1H correlation spectroscopy (1H- 1H COSY) and two-dimensional nuclear Overhauser effect spectroscopy (NOESY) experiments for two novel metabolites (M1 and M2) of ondansetron. These two metabolites were isolated for the first time from Mucor circinelloides. Copyright © 2006 John Wiley & Sons, Ltd. [source]

    Regime-switching in stock index and Treasury futures returns and measures of stock market stress

    THE JOURNAL OF FUTURES MARKETS, Issue 8 2010
    Naresh Bansal
    We investigate bivariate regime-switching in daily futures-contract returns for the US stock index and ten-year Treasury notes over the crisis-rich 1997,2005 period. We allow the return means, volatilities, and correlation to all vary across regimes. We document a striking contrast between regimes, with a high-stress regime that exhibits a much higher stock volatility, a much lower stock,bond correlation, and a higher mean bond return. The high-stress regime is associated with higher average values of stock-implied volatility, stock illiquidity, and stock and bond futures trading volume. The lagged implied volatility from equity-index options is useful in modeling the time-varying transition probabilities of the regime-switching process. Our findings support the notions that: (1) stock market stress can have a material influence on Treasury bond pricing, and (2) the diversification benefits of combined stock,bond holdings tend to be greater during times with relatively high stock market stress. © 2009 Wiley Periodicals, Inc. Jrl Fut Mark 30:753,779, 2010 [source]

    A robust method for determining 1H,15N long-range correlations: 15N optimized CIGAR-HMBC experiments,

    MAGNETIC RESONANCE IN CHEMISTRY, Issue 5 2003
    Mike Kline
    Abstract An examination of a variety of common nitrogen-containing systems was undertaken to optimize parameters for observation of 1H,15N long-range correlations. Because of the diversity of coupling constants encountered with 1H,15N correlations, a modified accordion-based sequence was used to provide the best results. Optimization of the values for the accordion delay revealed that a range between 3 and 10 Hz provided the best compromise between detection of weak correlations and loss of signal to T2 processes. Multiple bond correlations were readily detected for each class of compound with the exception of anilines. Correlations within heterocyclic systems revealed some general patterns. In general, stronger correlations were observed from protons to ,pyrrole-like' nitrogens than to the ,pyridine-type' nitrogens of imidazoles and pyrazoles. Very long-range (four- and five-bond) correlations were routinely observed between methyl groups and the nitrogens of aromatic heterocycles. Copyright © 2003 John Wiley & Sons, Ltd. [source]