Results 271 to 280 of about 220,097 (316)

A Laboratory Assignment in 1H NMR Spectroscopy: A Comparative Analysis of Calculated and Experimental 1H NMR Chemical Shifts

Journal of Chemical Education, 2006
A computer program is used to determine the proton NMR chemical shifts of endo- and exo-norbornenyl ketones and these values are compared to the experimental values. As part of an undergraduate spectroscopy course, the differences in chemical shifts between the actual and the calculated values serve to underscore the importance of through-space ...
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The conformational analysis of oligosaccharides by 1H-NMR and HSEA calculation

Archives of Biochemistry and Biophysics, 1983
The application of 1H-nuclear Overhauser enhancement, 1H-spin-lattice-relaxation-time and 1H-chemical shift measurements for the assessment of the conformational preferences of oligosaccharides are briefly reviewed. It is demonstrated that additivity rules, for the correlation of the chemical shifts of similar hydrogen atoms in different ...
Raymond U. Lemieux, Klaus Bock
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1H NMR Spectroscopy and Conformational Analysis of N-Benzylimidazolidines

HETEROCYCLES, 2003
1H NMR spectra of a series of 1-benzyl- and 1,3-dibenzylimidazolidines are analyzed and correlated with their conformational features. The spectra are assigned on the basis of chemical shifts and proton coupling constant values, and confirmed by NOESY spectra. C 2 -Unsubstituted imidazolidines (1, 9) show a fast inversion of the nitrogen atoms.
Isabel A. Perillo, Carlos de los Santos, Alejandra Salerno   +2 more
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1H NMR analysis of sporopollenin from Typha Angustifolia

Phytochemistry, 1999
Abstract The first analysis of sporopollenin using 1H NMR-techniques revealed the presence of four phenolic compounds in different amounts. The phenolic compounds are tri- or tetrasubstituted. The sporopollenin was isolated and purified from Typha angustifolia by an enzymatic procedure, followed by extraction with organic solvents.
Friedhelm Ahlers, Ina Thom, Jörg Lambert, Rüdiger Kuckuk, null Rolf Wiermann   +4 more
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The analysis of the high-resolution 1H NMR spectrum of indene

Journal of Magnetic Resonance (1969), 1982
The long-range coupling constants in unsaturated systems are still a subject of interest because of their sensitivity to conformational and other structural changes (1). Proton magnetic resonance studies in this field, however, usually do not enter into a complete analysis of the spectra avoiding the tedious work necessary to measure extremely high ...
Hartmut Nies, Dieter Rewicki
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Preliminary analysis of the 1H-NMR and 13C-NMR spectra of poly(2-vinylpyrazine)

Polymer Bulletin, 1995
The title polymer was synthesized by free radical initiation. The 1H-NMR and 13C-NMR spectra revealed several resonances that were sensitive to polymer stereosequence distribution. Analysis of these resonances showed that free radical initiated poly (2-vinyl pyrazine) is an atactic polymer, a result consistent with data accumulated for other poly ...
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Quantitative 1H NMR analysis of alkaline polysulfide solutions

Holzforschung, 2005
Abstract A novel analytical protocol for the absolute determination of the various polysulfide species present in alkaline aqueous media was developed. The method is comprised of alkylating polysulfide ions with dimethyl sulfate, followed by quantitative proton NMR spectroscopy using 1,3,5-tributyl benzene as the internal standard. In order
Dimitris S. Argyropoulos, Yihua Hou, Ramana Ganesaratnam, David N. Harpp, Keiichi Koda   +4 more
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1H and 13c nmr analysis of lycorine and α-dihydrolycorine

Phytochemistry, 1983
Abstract -The 1 H and 13 C NMR spectra of lycorine and its α-dihydro derivative have been studied. The employment of nuclear magnetic double resonance, nuclear Overhauser effect and acetylated derivatives, allows the assignment of all proton resonances.
EVIDENTE, ANTONIO, Maria Rosaria Cicala, Italo Giudicianni, Giacomino Randazzo, Rodolfo Riccio   +4 more
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1H NMR analysis of fibril-forming peptide fragments of transthyretin.

International journal of peptide and protein research, 1994
Peptide fragments of the protein transthyretin, previously shown to form cross beta-sheet amyloid-like fibrils in vitro, were investigated using 1H 1D and 2D NMR techniques. TTR 10-20, TTR 105-115 as well as a substituted analogue, (TTR 105-115Met111) all formed amyloid-like fibrils readily in 20-30% acetonitrile/water at room temperature. It was found
Jarvis, J. A., Kirkpatrick, A., Craik, D. J.   +2 more
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Quantitative analysis of fluoroquinolones by 1H- and 19F-NMR spectroscopy

International Journal of Pharmaceutics, 1995
Abstract 1H- and 19F-NMR assay of pefloxacin (I), norfloxacin (II) and ofloxacin (III) in some pharmaceutical forms has been developed. The method, based on the integration of appropriate signals of both analytes and internal standards, is simple, rapid, precise, and accurate, and can be used for quality control of these drugs.
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