Nuclear Magnetic Resonance Characterizing species

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. 

GC and GC-MS (see Chapter 2), are ideal for the separation and characterization of individual molecular species. Characterization generally relies on the principle of chemotaxonomy, where the presence of a specific compound or distribution of compounds in the ancient sample is matched with its presence in a contemporary authentic substance. The use of such 6molecular markers is not without its problems, since many compounds are widely distributed in a range of materials, and the composition of ancient samples may have been altered significantly during preparation, use and subsequent burial. Other spectroscopic techniques offer valuable complementary information. For example, infrared (IR) spectroscopy and 13C nuclear magnetic resonance (NMR) spectroscopy have also been applied. 

Nuclear magnetic resonance (NMR) spectroscopy has been used to directly observe varied persistent superelectrophilic species. Although H and 13C NMR have been the most often used techniques, there have also been applications of 15N, 170, and 19F NMR in their structural characterization. Coupled with theoretical computational methods capable of estimating NMR chemical shifts, these studies have been very useful in the study of superelectrophiles. 

In gas-phase reactions catalyzed by a solid surface, characterization of the chemisorbed species that are principally covering the surface can nowadays be made relatively easily by means of techniques such as IR and Raman spectroscopy, EELS, radioisotope labeling of reagents, and in some cases by nuclear magnetic resonance (NMR), electron spin resonance (ESR), and ESCA spectroscopies. In many cases, thermal desorption spectroscopy can be usefully applied to deduce indirectly the nature of species, and their distribution of energies of adsorption, that may have been strongly chemisorbed on the catalyst originally. 

T.M. Duncan, P. Winslow, and A.T. Bell, The Characterization of Carbonaceous Species on Ruthenium Catalysts with C Nuclear Magnetic Resonance Spectroscopy, J. Catal. 93 (1985) 1. 

The catalysts were also characterized with P magic angle spinning nuclear magnetic resonance (MAS-NMR) spectra (Fig. 17.2) which showed that they were all mixtures of several heteropolyphosphotungstate species. 

The ubiquitous nature and broad importance of phosphates demands exacting analytical methods for their characterization. Phosphorus-31 nuclear magnetic resonance ( P NMR) has been used as a method for the quantitative analysis of small inorganic phosphates (1-4). Several potential advantages are offered by "P NMR including observation of only the phosphorus-containing species, structural information which may complement or aid Retired... 

Ferrocene is an attractive and convenient organometallic species to incorporate into conjugated polymers—it is stable, easy to functionalize, has reversible electrochemistry, and its derivatives (both monomeric and polymeric) can be easily characterized [e.g., by nuclear magnetic resonance (NMR) spectroscopy]. Ferrocene has been incorporated into the backbone and side chains of polythiophene 45 In 1999, both Higgins and Wolf independently reported the synthesis of polythiophenes with ferrocene in the backbone.46,47 Electropolymerization of ferrocene substituted... 

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