Characterization by Nuclear Magnetic Resonance

The cyclopentane cyclitols have been characterized by nuclear magnetic resonance. The conformational analysis of cyclopentene and of poly-substituted cyclopentanes has been discussed. 

The application of nuclear magnetic resonance to organic compounds is discussed in a number of excellent books its application to carbohydrates has been reviewed in this Series.  

The usual solvents are deuterium oxide for free cyclitols, and cliloro-form-d for their nonpolar derivatives, such as acetates. The use of methyl sulfoxide may be advantageous. When necessary, samples of one milligram or less may be examined, using special micro-cells or micro-tubes 

Changes in solvent or concentration sometimes improve resolution, or yield helpful information regarding, for example, hydrogen bonding.  

For proving identity or nonidentity of two samples, nuclear magnetic resonance is often superior to older techniques, especially with diastereo-meric samples.  

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The azoniaspirocycles described in this chapter have mostly been synthesised in situ, and thus were not isolated. As a result, complete characterization by nuclear magnetic resonance (NMR) spectroscopy is not always available. However, in many cases, the azoniaspiro species has been detected by H NMR analysis of the reaction mixture. In addition, the formation of the ammonium salts can sometimes lead to stable solids which can be kept for significant periods without decomposition. 

Most of the attempted asymmetric reductions have used sodium borohydride in conjunction with quaternary ammonium catalysts. Recently, the solution structures of ion pairs formed by quaternary ammonium ions derived from quinine with borohydride ion have been characterized by nuclear magnetic resonance methods in CDC13.1741... 

In this Sect, we describe the starting material impurities and their effect on the processing and cure reactions of TGDDM-DDS epoxies. The cure reactions are characterized by differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR) studies. The BF3 amine catalysts used to accelerate the cure of TGDDM-DDS epoxies are characterized by nuclear magnetic resonance (NMR) spectroscopy studies. 

To the best of the present authors knowledge, correlations between the catalyst s structure and activity have been demonstrated only for tin catalysts [41]. A series of di-n-butyl tin(IV) compounds have been synthesized, characterized by nuclear magnetic resonance (NMR) and infrared (IR) spectroscopies, and screened for methyl carbamate methanolysis at 463 K. The key reactions proposed are depicted in Scheme 7.3. 

Structural characterization by nuclear magnetic resonance (NMR) methods is routine and, in general, mention of the results has been deferred to the sections dealing with the synthesis of particular heterocycles. This section includes results where sufficient work has been performed to suggest patterns and where more unusual techniques have been discussed. 

A solution of 5 mmol of olefins, 15 mmol of acetaldehyde, and 0.5 mmol of NHPI in 10 ml of acetonitrile was stirred at room temperature (RT) in atmospheric pressure of O2 for 14—24 h the known epoxides were isolated by flash chromatography (hexaneiethyl acetate, 9 1) and characterized by nuclear magnetic resonance (NMR) and mass spectrometry (MS) (by comparison with authentic samples). 

However, other perspectives suggest that there are likely to be as yet unidentified protein folds. As of 2004, the Pfam database (version 10.0) contained 6190 domains only about a third were associated with a protein of known structure. Some of these may be cases in which highly divergent or completely unrelated sequences adopt an already discovered fold. Some may not be amenable to structural characterization, either because they are too large for characterization by nuclear magnetic resonance spectroscopy (NMR), or contain disordered regions that interfere with crystallization. However, there may indeed be unidentified protein domain structures remaining to be discovered. 

A new ONO-type tridentate dianionic chelating ligand, binuclear aluminum complex 99 was synthesized by the reaction of 2,4-pentanedionewith (lS,2R)-(-)-cis-amino-2-indanol and then reacting with AlMe (Scheme 6.23), which was characterized by nuclear magnetic resonance (NMR) spectroscopy, mass spectrometry, and elemental analysis [74],... 

These and other copolymers have been extensively characterized by nuclear magnetic resonance (NMR) spectroscopy. ... 

Many of these nanocomposites have been characterized by nuclear magnetic resonance (NMR) spectroscopy, single-molecule spectroscopy, and small-angle scattering. - Some applications require other measurements, such as permeability or ionic conductivity. In the case of permeability, the presence of the filler can substantially reduce flux by blocking low-resistance pathways and by modification of the elastomer in the vicinity of the filler (figure 9.1). 

The chemical structures of D-A alternating copolymers are routinely characterized by nuclear magnetic resonance (NMR) spectroscopy. Again, since the polymer chains need to be properly solvated and dispersed to expose all of the characteristic protons, higher temperatures near 100 °C are necessary. Therefore, deuterated solvents with high boiling points, such as 1,1,2,2-tetra-chloroethane-D2 (C2D2CI4), are typically used. 

Carotenoids have also been characterized by nuclear magnetic resonance (NMR), infrared (IR), and Raman spectroscopy as well as by x-ray analysis and mass spectrometry (6). Because of their low volatility and relatively high molecular weight, the C-40 carotenoids have not as yet been separated by gas chromatography. Currently, carotenoids are primarily isolated by liquid chromatography on solid supports. 

The oils and the biodiesel products of the transesterification procedures are mainly characterized by nuclear magnetic resonance ( H-NMR) and gas chromatography (GC) techniques. The H-NMR technique provides chemical characteristics of the oils, fats, and products and the conversion degrees of the transesterification procedures. GC allows a more accurate characterization of the molecular species involved in the transesterification procedure. Additionally, the Analysis Biodiesel Protocol for the characterization of the methyl or ethyl biodiesel must include information of the following physicochemical techniques kinematic viscosity, density, flash point, cloud point, pour point, cold filter plugging point, free and total glycerol, ethanol residue, sulfur content, acid number, oxidative stability, and refractive index. 

The phosphonated polymer was prepared via a neutral precursor polymer, which was soluble in organic solvents, enabhng the material to be characterized by nuclear magnetic resonance (NMR) and gel permeation chromatog-... 

To benzo[A]quinolinyl palladium(II) pyridine-sulfonamido complex (12.8 mg, 0.0200 mmol) in acetonitrile-c/i (0.6 mL) at 23 °C was added l-chloromethyl-4-fluoro-l,4-diazoniabicyclo [2.2.2]octane bis(tetrafluoroborate) (7.1 mg, 0.020 mmol). After stirring for 10 min at 23 °C, the colorless suspension formed a dark purple solution. The complex was characterized by nuclear magnetic resonance (NMR spectroscopy) in acetonitrile solution without purification. ... 

A keen interest in microemulsions of fluorocarbons in water was kindled by the need for synthetic oxygen earners in blood (see Section 10.4). Gerbacia and Rosano [121] prepared a stable fluorocarbon emulsion using a mixture of fluorinated and hydrocarbon-type nonionic surfactants. The droplet size was not determined, however, and the emulsions were not characterized. Oliveros et al. [122] prepared perfluorinated microemulsions consisting of four components (1) sodium perfluorooctanoate, an anionic fluorinated surfactant (2) 2,2,3,3,4,4,4-heptafluoro-1-butanol (3) perfluorohexane (4) water. The pseudoternary-phase diagram (Fig. 4.40) shows two regions. Mi and Mi, of respective W/0 and OAV microemulsions [122]. These optically transparent microemulsions were characterized by nuclear magnetic resonance spectroscopy. 

Some of these compounds have been isolated in sufficient quantities for partial characterization by nuclear magnetic resonance spectroscopy. These include three trace compounds designated I, II and III which were isolated from extracts of some 3200 skins of Dendrobates histrionicus (86). All three compounds were bicyclic and based on the mass spectra and proton resonance spectra were proposed to be members of the pumiliotoxin-C class (cw-decahydroquinolines) of alkaloids. 

T. Jiang, G. Hirasaki, C. Miller, K. Moran and M. Fleury. Diluted bitumen water-in-oil emulsion stability and characterization by nuclear magnetic resonance (NMR) measurements. Energy Fuels 21, 2007, 1325-1336. 

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