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Multinuclear Magnetic Resonance (multinuclear + magnetic_resonance)
Selected AbstractsMultinuclear magnetic resonance, electrospray ionization time-of-flight mass spectral and molecular modelling characterization of lithocholic acid amide esters with various nitrogen heterocyclesMAGNETIC RESONANCE IN CHEMISTRY, Issue 8 2003Elina Virtanen Abstract 1H, 13C and 15N NMR and electrospray ionization time-of-flight mass spectrometric characterizations of five lithocholate esters of piperazine diamides are described. Two of them are cholaphane-type cyclic structures esterified with 2,2,-bipyridine-4,4 , - and pyridine-2,6-dicarboxylic acid and the other three esters are open structures comprising two or four lithocholyl residues. The conformational preferences of the dimeric congeners were examined by using molecular modelling and variable-temperature 1H NMR techniques. Copyright © 2003 John Wiley & Sons, Ltd. [source] Multinuclear magnetic resonance, electrospray ionization,mass spectroscopy, and parametric method 5 studies of a new derivative of gossypol with 2-thiophenecarbohydrazide as well as its complexes with LI+, Na+, K+, RB+, and Cs+ cationsBIOPOLYMERS, Issue 3 2006Piotr Przybylski Abstract A new derivative of racemic gossypol with 2-thiophenecarbohydrazide (GHHT) and its complexes with monovalent cations have been synthesized and studied by electrospray ionization,mass spectroscopy (ESI-MS), multinuclear nuclear magnetic resonance (NMR), as well as by the Parametric Method 5 (PM5) methods. It is demonstrated that GHHT forms stable complexes of 1:1 stoichiometry with monovalent metal cations. The structures of the complexes are stabilized by three types of intramolecular hydrogen bonds. The spectroscopic methods have provided clear evidence that GHHT and its complexes exist in the DMSO-d6 solution in the N-imine,N-imine tautomeric forms. The structures of the GHHT and its complexes with Li+, Na+, K+, Rb+, and Cs+ cations are visualized and discussed in detail. © 2006 Wiley Periodicals, Inc. Biopolymers 83: 213,225, 2006 This article was originally published online as an accepted preprint. The "Published Online" date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com [source] Conformational and structural analysis of exocyclic olefins and ketimines by multinuclear magnetic resonanceMAGNETIC RESONANCE IN CHEMISTRY, Issue 10 2008Rubén Montalvo-González Abstract The 1H, 13C, and 15N NMR spectra of 5 exocyclic alkenes and 15 different ketimines obtained from cyclohexanone and derivatives using benzyl bromide and primary amines,are analyzed. Relative stereochemical and preferential conformations are determined by analyzing both the homonuclear coupling and the chemical shifts of the protons and carbon atoms in the aliphatic rings, which are directly related to the geometry of the double bond and the steric and electronic effects of the exocyclic group. In addition, the racemic mixture of the N -(4-methylcyclohexylidene)pyridine-3-amine derivative is resolved. Copyright © 2008 John Wiley & Sons, Ltd. [source] Synthesis and reactivity of some diselenasila cycles containing an annelated dicarba- closo -dodecaborane(12) unitAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 1 2010Bernd Wrackmeyer Abstract The use of 1,2-diselenolato-1,2-dicarba- closo -dodecaborane(12) dianions [1,2-(1,2-C2B10H10)Se2]2, prepared in situ as the dilithium salt may lead to irreproducible results. This is shown by the straightforward synthesis of silanes using the purified and isolated dianions, in contrast with previous less successful attempts. Thus, the reactions of the dianions with dichlorosilanes afford the five-membered diselenasila cycles containing the SiMe2 or the SiPh2 units, and with 1,2-dichloro-tetramethyldisilane the six-membered cycle containing the Si2Me4 unit. The latter was studied by X-ray diffraction, and all products were characterized by multinuclear magnetic resonance (1H, 13C, 29Si, 77Se NMR) in solution. Novel isotope effects were detected in 13C and 77Se NMR spectra. Exchange reactions of the five- and six-membered diselanasila cycles with chlorosilanes were studied. Copyright © 2009 John Wiley & Sons, Ltd. [source] | ||||||||||