Nuclear magnetic resonance spectroscopic data

VIII. Appendix I Nuclear Magnetic Resonance Spectroscopic Data and... 

APPENDIX I NUCLEAR MAGNETIC RESONANCE SPECTROSCOPIC DATA AND AVAILABILITY OF STRUCTURAL DATA FOR METALLOBORANE CLUSTERS WITH A RATIO OF M AND B ATOMS OF AT LEAST 1 1... 

Tormena and co-workers have explored the conformational preferences of 3-hydroxytetrahydropyran (Fig. 3c) using infrared and nuclear magnetic resonance spectroscopic data in solvents of different polarities and theoretical methods. The authors concluded that the axial conformation was more stable in the isolated phase and a nonpolar solvent, while the equatorial conformation was more stable than the axial in polar media. The oecurrence of intramolecular hydrogen-bonded O-H- O in the axial conformer was detected from infrared spectra in a non-polar solvent at different coneentrations. In this work, the authors computed y(H,H) applying the SOPPA(CCSD)/EPR-III method. 

Specinfo, from Chemical Concepts, is a factual database information system for spectroscopic data with more than 660000 digital spectra of 150000 associated structures [24], The database covers nuclear magnetic resonance spectra ( H-, C-, N-, O-, F-, P-NMR), infrared spectra (IR), and mass spectra (MS). In addition, experimental conditions (instrument, solvent, temperature), coupling constants, relaxation time, and bibliographic data are included. The data is cross-linked to CAS Registry, Beilstein, and NUMERIGUIDE. 

Beryllium(II) is the smallest metal ion, r = 27 pm (2), and as a consequence forms predominantly tetrahedral complexes. Solution NMR (nuclear magnetic resonance) (59-61) and x-ray diffraction studies (62) show [Be(H20)4]2+ to be the solvated species in water. In the solid state, x-ray diffraction studies show [Be(H20)4]2+ to be tetrahedral (63), as do neutron diffraction (64), infrared, and Raman scattering spectroscopic studies (65). Beryllium(II) is the only tetrahedral metal ion for which a significant quantity of both solvent-exchange and ligand-substitution data are available, and accordingly it occupies a... 

Aside from the direct techniques of X-ray or electron diffraction, the major possible routes to knowledge of three-dimensional protein structure are prediction from the amino acid sequence and analysis of spectroscopic measurements such as circular dichroism, laser Raman spectroscopy, and nuclear magnetic resonance. With the large data base now available of known three-dimensional protein structures, all of these approaches are making considerable progress, and it seems possible that within a few years some combination of noncrystallo-graphic techniques may be capable of correctly determining new protein structures. Because the problem is inherently quite difficult, it will undoubtedly be essential to make the best possible use of all hints available from the known structures. 

As part of a mechanistic and synthetic study of nucleophihc carbenes the spirocyclic 4(5/l)-oxazolone 18 has been obtained from benzoyl isocyanate (Scheme 6.1) Thermal extrusion of nitrogen from the 1,3,4-oxadiazoline 14 produced the carbonyl ylide 15 that fragmented via loss of acetone to the aminooxycarbene 16. Spectroscopic data [gas chromatography-mass spectrometry (GC-MS), infrared (IR), proton and C-13 nuclear magnetic resonance ( H and NMR)] of the crude thermolysate was consistent with 18. The formation of 18 was rationalized to result from nucleophihc addition of 16 to benzoyl isocyanate followed by cyclization of the dipolar intermediate 17. Thermolysis of 19 and 21 under similar reaction conditions afforded 20 and 22 respectively, also identified spectroscopically as the major products in the thermolysate. 

Nuclear magnetic resonance (NMR) spectroscopic data have been reported by Takeda et al.32 for silylene-isocyanide complexes 28-30, which are stable at room temperature due to the bulky substituents. The Aic coupling constants of 38.6 Hz (28), 22.1 Hz (29), and 1.0 Hz (30) are considerably smaller than that of a Si-C single bond and indicate a weak Si-C interaction as expected for a dative bond. 

The 111 NMR, 13C NMR (NMR - nuclear magnetic resonance), infrared (IR), ultraviolet (UV), and mass spectrometry (MS) data have been reported for the first example 5 of a 2/7-azepin-2-one (2-azatropone). The carbonyl group stretching frequency appeared at 1682 cm 1 in the IR spectrum of the neat material <2000JOC6093>. Further H and 13C NMR spectroscopic data on azepine derivatives have been summarized by Smalley <1997HOU(E9d)108>. 

Spectroscopic techniques, such as ultra-violet (9), Infrared (25), Nuclear Magnetic Resonance (24), and Fluorescence spectroscopies (5-8), constitute direct probes of specific events occurring at the molecular scale. When a quantitative interpretation is possible, spectroscopy provides very detailed microscopic information. Unfortunately however, the interpretation of spectra in terms of molecular events is often complex. Yet another approach that probes events at the molecular scale involves the use of tracers, such as chromophores (1-225). Again, the complexity of the tracer imposes limitations on the extent to which the data can be interpreted quantitatively. 

Some of the new spectroscopic data are taken from the collections of the School of Chemistry, Thames Polytechnic, and we wish to acknowledge particularly the assistance of Dr E. Vidgeon for specifically recording the majority of the 13C-n.m.r. spectra. We acknowledge the inclusion of other spectroscopic data from the Sadtler Collections, Standard Infrared Spectra, Standard Ultraviolet Spectra and Standard Nuclear Magnetic Resonance Spectra, Sadtler Research Laboratories, Philadelphia, USA, and from Compilation of Mass Spectral Data, A. Cornu and R. Massot (1966-1971), Heyden and Son Ltd in collaboration with Presses Universitaires de France. 

Several spectroscopic techniques, namely, Ultraviolet-Visible Spectroscopy (UV-Vis), Infrared (IR), Nuclear Magnetic Resonance (NMR), etc., have been used for understanding the mechanism of solvent-extraction processes and identification of extracted species. Berthon et al. reviewed the use of NMR techniques in solvent-extraction studies for monoamides, malonamides, picolinamides, and TBP (116, 117). NMR spectroscopy was used as a tool to identify the structural parameters that control selectivity and efficiency of extraction of metal ions. 13C NMR relaxation-time data were used to determine the distances between the carbon atoms of the monoamide ligands and the actinides centers. The II, 2H, and 13C NMR spectra analysis of the solvent organic phases indicated malonamide dimer formation at low concentrations. However, at higher ligand concentrations, micelle formation was observed. NMR studies were also used to understand nitric acid extraction mechanisms. Before obtaining conformational information from 13C relaxation times, the stoichiometries of the... 

---