Proton nuclear magnetic resonance spectrum analysis

Use of an integrated system incorporating CCC separation, PDA detector, and LC-MS proved to be a valuable tool in the rapid identification of known compounds from microbial extracts.6 This collection of analytical data has enabled us to make exploratory use of advanced data analysis methods to enhance the identification process. For example, from the UV absorbance maxima and molecular weight for the active compound(s) present in a fraction, a list of potential structural matches from a natural products database (e.g., Berdy Bioactive Natural Products Database, Dictionary of Natural Products by Chapman and Hall, etc.) can be generated. Subsequently, the identity of metabolite(s) was ascertained by acquiring a proton nuclear magnetic resonance ( H-NMR) spectrum. 

Nuclear magnetic resonance analysis with double and triple resonance was used to elucidate the structure as 3, 4 -dideoxykanamycin B 2"-adenylate. The spectrum of the inactivated 3, 4 -dideoxykanamycin B in deuterium oxide at pH 8.0, with tetramethylsilane as the external reference standard (8 =0), showed signals at 8 8.63 and 8.85 attributable to the adenine-ring protons, and at 8 6.53, 5.28, 4.98, 4.83 and 4.6 (H-2) the latter were assigned to the D-ribose-ring protons by successive doubleresonance experiments, and by comparison with disodium 5 -adenylate in deuterium oxide. Therefore, these observations confirmed the presence of one molecular proportion of 5 -adenylic acid in the molecule. Irradiation at 8 5.45 (7 3.6, H-1") caused the complex signal at 8 4.3 (H-2")... 

Nuclear magnetic resonance (NMR) is a physical process in which nuclei in a magnetic field absorb and reemit electromagnetic radiation. Analysis of NMR spectra allows the determination of polymer composition, and the distribution of monomer units can be deduced from the diad and triad sequences by NMR spectral analysis. For characterization of polymer, the extracted polymer wiU be dissolved in CDCI3 followed by NMR analysis. The NMR spectrum for PHB shows three characteristic signals. A doublet at 1.53 ppm represented the methyl group (CH3) coupled to one proton while a doublet of... 

Nuclear magnetic resonance spectroscopy CTC detection tool, 208-211 Diels-Alder structure proof, 117 ene reaction mechanism study, 168 MA copolymer studies, 281, 290 MA-ene adduct structure proof, 153 MA grafted polyisoprene, 466 for maleate isomerization analysis, 484 MA monomer spectrum, 8, 10 MA polymer analyses, 241, 245, 249, 256, 259 MA protonation study, 211 polyester structural analysis, 484 Nylons, MA grafted, 477... 

In this chapter, you will employ jointly all of the spectroscopic methods we have discussed so far to solve stractural problems in organic chemistry. Forty-five problems are provided to give you practice in applying the principles learned in earlier chapters. The problems involve analysis of the mass spectrum (MS), the infrared (IR) spectrum, and proton and carbon ( H and nuclear magnetic resonance (NMR). Ultraviolet (UV) spectral data, if provided in the problem, appear in a tabular form rather than as a spectrum. You will notice as you proceed through this chapter that the problems use different mixes of spectral information. Thus, you may be provided with a mass spectrum, an infrared spectrum, and a proton NMR spectrum in one problem, and in another you may have available the infrared spectrum and both proton and carbon NMR. 

Apart from giving information about solvent participation, the nuclear magnetic resonance (n.m.r.) spectrum can reveal other features of the reaction mechanism as well. The reason for this is that the spectrum often consists of several resonances the independent analysis of which gives different and complementary kinetic information. Thus, for asymmetrically substituted amines, it is possible to measure the rate of Walden inversion as well as the rate of proton exchange [11,12]. In other cases it is possible to compare the rate of proton exchange (as measured by n.m.r.) with that of proton transfer (as measured by relaxation spectrometry), thus evaluating statistical factors in proton exchange [13]. 

Nuclear magnetic resonance analysis of Rosa glauca araban has provided additional evidence that the arabinosyl residues are a-5-linked and in the furanose configuration. The C-1 resonance expected of a-arabinofuranosyl residues, but not the C-1 resonances expected of the P-arabinofuranosyl or a- and P-arabinopyranosyl residues, was detected by C-NMR analysis 68b). The proton NMR spectrum is consistent with a- or P-furanosyl residues and P-pyranosyl residues, but not with a-pyranosyl residues 68b). The a-anomeric nature of these linkages is confirmed by the negative optical rotations, from —181 to —108, exhibited by such arabans 11, 68b). 

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