Nuclear magnetic resonance examination

In the case of the less volatile alcohols, such as 2-ethylhexanol and higher alcohols, the alcohol can be recovered by extraction of the alkaline saponification mixture with diethyl ether, followed by carefiil evaporation of the solvent. Subsequent infrared (or nuclear magnetic resonance) examination of the residue usually suffices for the identification of the alcohol. Of course, if more than one alcohol is present, the gas -liquid chromatographic examination is called for. 

If required, the free acid, usually thioglycollic, or thiol can be obtained in a purer state by acidifying the silver complex with hydrochloric acid and extracting the liberated acid and thiol with diethyl ether. The infrared and nuclear magnetic resonance examinations can then be repeated on the thioacid or thiol itself. 

For bulk structural detemiination (see chapter B 1.9). the main teclmique used has been x-ray diffraction (XRD). Several other teclmiques are also available for more specialized applications, including electron diffraction (ED) for thin film structures and gas-phase molecules neutron diffraction (ND) and nuclear magnetic resonance (NMR) for magnetic studies (see chapter B1.12 and chapter B1.13) x-ray absorption fine structure (XAFS) for local structures in small or unstable samples and other spectroscopies to examine local structures in molecules. Electron microscopy also plays an important role, primarily tlirough unaging (see chapter B1.17). 

Physical Methods of Examination. Physical methods used to examine coals can be divided into two classes which, in the one case, yield information of a stmctural nature such as the size of the aromatic nuclei, ie, methods such as x-ray diffraction, molar refraction, and calorific value as a function of composition and in the other case indicate the fraction of carbon present in aromatic form, ie, methods such as ir and nuclear magnetic resonance spectroscopies, and density as a function of composition. Some methods used and types of information obtained from them are (41) ... 

The spectroscopic techniques that have been most frequently used to investigate biomolecular dynamics are those that are commonly available in laboratories, such as nuclear magnetic resonance (NMR), fluorescence, and Mossbauer spectroscopy. In a later chapter the use of NMR, a powerful probe of local motions in macromolecules, is described. Here we examine scattering of X-ray and neutron radiation. Neutrons and X-rays share the property of being found in expensive sources not commonly available in the laboratory. Neutrons are produced by a nuclear reactor or spallation source. X-ray experiments are routinely performed using intense synclirotron radiation, although in favorable cases laboratory sources may also be used. 

C NMR (Section 13.14) Nuclear magnetic resonance spectroscopy in which the environments of individual carbon atoms are examined via their mass 13 isotope. 

Enamino ketones can protonate not only on nitrogen or carbon but also on oxygen to give 12,13, and 14, respectively. Enamino ketones form stable perchlorates, chlorides, bromides, and iodides, and examination of their infrared (21,22), ultraviolet (23), and nuclear magnetic resonance (24,25) spectra show these salts to be O protonated. The salts of 4-dialkylamino-... 

The 9ai7-quinolizine structure (82) for the labile adduct from 3,5-dimethylpyridine was clearly established by the nuclear magnetic resonance studies of Richards and Higham, and subsequent work showed the labile adduct from 3-methylpyridine was analogous. As the labile adducts from all the pyridines and benzopyridines so far examined have very similar infrared absorption spectra in the 5-7 yn. (carbonyl and aromatic) region and within quite close limits very similar ultraviolet absorption spectra, it can be concluded that all are derivatives of 9aH-quinolizine,... 

As a prelude to the discussion it is necessary to consider the definition of orientation in terms of the Euler angles, and the definition ofan orientation distribution function in terms ofan expansion ofLegendre functions. These definitions set the scene for examining the information which can be obtained from different spectroscopic techniques. In this review, infra-red and Raman spectroscopy and nuclear magnetic resonance, will be considered. 

Nuclear magnetic resonance (NMR) spectroscopy is a powerful tool that can provide the binding sites of Ugand-DNA interactions at the molecular level. A prerequisite for the examination of ligand-DNA complexes is assignment of all resonances in the NMR spectra of the free DNA and the ligand and of both components in the complex. 

Robins, D., A. Alstin, and D. Fletton (1987), The examination of organic components in historical non-metallic seals with C-13 Fourier transform nuclear magnetic resonance spectroscopy, in Grimstad, K. (ed.), 8th Triennial Mtg., Int. Council of Museums Committee for Conservation, Sidney, pp. 82-87. 

SEM and transmission electron microscopy (TEM) are employed to examine materials for the presence and distribution of impact modifiers such as polybutadiene rubber in high impact polystyrene (HIPS) and methacrylate butadiene styrene terpolymer in PVC. Quantification is either by transmission IR spectroscopy against standards or nuclear magnetic resonance (NMR) spectroscopy. 

Because of the grandiose scale of the apparatus involved, SANS facilities are few in number worldwide access to them is limited and expensive. We have attempted to devise an experiment which employs solid state nuclear magnetic resonance to examine some aspects of affine deformation. 

Nuclear magnetic resonance spectroscopy was investigated as a method to screen for organic substances (and metabolites) in patients with indications of a drug overdose [17]. Urine specimens containing valproic acid were examined by H-NMR spectroscopy at 300 MHz and the results compared with GC MS. 

The objectives of this review are to discuss the fundamental and more recently discovered properties of water alone and to critically examine the system properties and measurement methods used to measure the mobility of water and solids in foods—specifically water activity, nuclear magnetic resonance (NMR), and the glass transition. 

Throughout this review, the concept of mobility has been highlighted as a key parameter for understanding and predicting the processability and stability of food systems. Mobility is the common denominator of the three methods examined in this review—water activity, nuclear magnetic resonance, and glass transition. An emerging aspect of the picture for food... 

Examines hyphenated chromatographic techniques with nuclear magnetic resonance spectroscopy... 

Morrow et al. also examined the effects of pressure and temperature on DPPC and DMPC choline headgroup conformation using deuterium nuclear magnetic resonance. The electric dipole resulting from charge separation in... 

This is the first attempt to examine family-held ginseng landraces that have been in cultivation for several decades. Clearly, there is evidence of variation between these landraces. Although HPLC-DAD analysis clearly quantified ginsenoside levels and showed variability, it did not present unique characteristics that would rapidly identify each landrace. Currenfiy, Nuclear Magnetic Resonance (NMR) methods are... 

Until recently it was thought that mono-substituted hydrazines invariably reacted with 5-methylisothiouronium salts to give compounds of type (XVII) [129, 192, 193] however, examples have now come to light in which the alternative isomer (XVI) has been isolated from this reaction [21, 131, 194, 195). This formulation is based on (a) the failure of the products to react with benzaldehyde, [21, 129, 131, 194], (b) the unambiguous synthesis of the two possible alternative structures [21, 129, 194], and (c) an examination of the nuclear magnetic resonance spectra of the mono- and di-protonated forms of some... 

In an attempt to delineate the degree of preservation of lignin in pre-Tertiary coal, we examined numerous coalified wood samples ranging in age from Carboniferous to Cretaceous. The samples were initially screened by solid-state l C nuclear magnetic resonance to detect the possible presence of methoxyl carbon. Once such carbons were detected, the samples were subjected to analytical pyrolysis to determine the relative yields of methoxyphenols which would provide an indication of the state of preservation of the lignin-derived structu units. We report here on the identification of lignin-derived methoxyphenols in the coalified wood samples selected for analytical pyrolysis. 

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