NMR Spectral Properties

Nuclear magnetic resonance (NMR) is probably the most widely applied spectroscopic technique in modem chemical research. Its high sensitivity and the mild conditions required for its application render it peerless for sttucture determination and kinetics measurements in many instances. As an experimental technique, its use is extraordinarily widespread. 

Until quite recently, however, theoretical prediction of NMR spectral properties significantly lagged experimental work. The ultimate factor slowing theoretical work has been simply that it is more difficult to model the interactions of a wave function with a magnetic field than it is to model interactions with an electric field. Nevertheless, great progress has been made over the last decade, particularly with respect to DFT, and calculation of chemical shifts is becoming much more routine than had previously been true. 

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Quin L D and Verkade J G (eds) 1994 Phosphorus-31 NMR Spectral Properties in Compound Characterization and Structural Analysis (New York VCH)... 

The NMR spectral properties of the parent heterocycles are summarized in Table 12. The signal for the pyrrole a-carbon is broadened as a result of coupling with the adjacent nitrogen-14 atom (c/. Section 3.01.4.3). While the frequencies observed for the /3-carbon atoms show a fairly systematic upheld shift with increasing electronegativity of the heteroatom, the shifts for the a-carbon atoms vary irregularly. The shifts are comparable with that for benzene, S 128.7. 

IR and H-NMR Spectral Properties for Titanocene Monocarbonyl-Phosphine Complexes... 

Annulenones containing 15 carbon-atoms may be expected to be diatropic. Since the [13]annulenones were paratropic it was of interest to determine the NMR spectral properties of the next higher members. 

Recent work in our laboratories has confirmed the existence of a similar pathway in the oxidation of vindoline in mammals (777). The availability of compounds such as 59 as analytical standards, along with published mass spectral and NMR spectral properties of this compound, served to facilitate identification of metabolites formed in mammalian liver microsome incubations. Two compounds are produced during incubations with mouse liver microsome preparations 17-deacetylvindoline, and the dihydrovindoline ether dimer 59. Both compounds were isolated and completely characterized by spectral comparison to authentic standards. This work emphasizes the prospective value of microbial and enzymatic transformation studies in predicting pathways of metabolism in mammalian systems. This work would also suggest the involvement of cytochrome P-450 enzyme system(s) in the oxidation process. Whether the first steps involve direct introduction of molecular oxygen at position 3 of vindoline or an initial abstraction of electrons, as in Scheme 15, remains unknown. The establishment of a metabolic pathway in mammals, identical to those found in Strep-tomycetes, with copper oxidases and peroxidases again confirms the prospective value of the microbial models of mammalian metabolism concept. 

Carbon-13 NMR was utilized to study different aspects of the reactivity of the metal complexes as a function of certain structural features in the selected oxocyano complexes of Mo(IV), W(IV), Tc(V), Re(V), and Os(VI) as depicted in Scheme 1 and illustrated in Figs. 1-4. The NMR spectral properties were similar to those obtained from 13C NMR in general, i.e., very sharp lines indicative of fairly long relaxation times in the order of a few seconds. The large quadrupolar moment ofTc-99 (7 = 9/2, 100% abundance) led to a very broad bound 13C signal (Fig. 5), thus excluding the quantitative study of the cyanide exchange by 13C NMR. However, 16N NMR was successfully used instead. 

Early CE-NMR experiments were aimed at understanding the effects of eleetro-phoresis on NMR spectral properties and determining physicochemical properties such as electrophoretic mobilities and diffusion coefficients. Since then, CE-NMR has garnered attention as an effective hyphenated technique with a variety of applications... 

Majoral, J. -P., Caminade, A. -M., and Igau, A. (1994). Elucidation of small ring and macrocycle structures using 31P NMR. In L. D. Quin and J. G. Verkade, Eds., Phosphorus-31 NMR Spectral Properties in Compound Characterization and Structural Analysis. New York VCH pp. 57-68. 

The 13C- and H-NMR spectral data of a set of 2-acyl-2-nitroenamines are collected in Tables 31 and 32. The stereochemistry around C(1)=C(2) has been assigned by correlation with the NMR spectral properties of the corresponding enamines with a single electron-withdrawing group at C(2), or by comparison with compounds of fixed configuration, as those in Table 32. In the case of 3-amino-2-nitroacrylic esters (554... 

NMR Spectral Properties in Compound Characterisation and Structural Analysis VCH New York 1994. (c) Verkade, J. G Quin, L. D. Phosphorus-31 NMR Spectroscopy in Stereochemical Analysis VCH Publishers Deerfield Beach, FL 1987. (d) Gorenstein, D. G Phosphorus-31 NMR Principles and Applications Academic Press Orlando, FL 1984. (e) NMR Spectra of Phosphorus Compounds, Topics in Phosphorus Chemistry Interscience Publishers New York 1967, Vol. 5. 

The database is updated on an annual basis with new data extracted from the literature. This database is also the foundation of data supporting the prediction algorithms that are required to predict NMR spectral properties for chemical structures not contained within the database. 

The NMR spectral properties of a number of the oxygenated tetra-hydroisoquinolines have been published.846... 

The kinetic properties of the parent benzenium ion [295] were first studied by Olah et al. (1970b, 1972d). The nmr-spectral properties ( H and C) of [295] were in excellent agreement with values calculated from model substances, assuming [295] to be a set of rapidly rearranging ions. The activation energy... 

The structure and aromatic nature of 4.115 was deduced from an analysis of its H NMR and C NMR spectral properties, and from a single crystal X-ray diffraction study. For instance, in the NMR spectrum both upheld shifts for the internal (NH) protons and downfield shifts for the external meso-protons were observed. This led to the conclusion that 4.115 can indeed sustain an induced diamagnetic ring current. The NMR spectrum confirmed the cumulenic nature of... 

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