Nuclear magnetic resonance model compounds

The presence of iminium salts can be detected by chemical means or by spectroscopic methods. The chemical means of detecting iminium salts are reactions with nucleophiles and are the subject of this review. The spectroscopic methods are more useful for rapid identification because with the large number of model compounds available now the spectroscopic methods are fast and reliable. The two methods that are used primarily are infrared and nuclear magnetic resonance spectroscopy. Some attempts have been made to determine the presence of iminium salts by ultraviolet spectroscopy, but these are not definitive as yet (14,25). 

The formation of compound (1) has been established under well-defined laboratory conditions in such reaction mixtures [15,26-35]. Comparison of nuclear magnetic resonance (NMR) spectra of model compounds prepared by Bakker and Cerfontain [29] with those of the reaction mixture has also clearly shown the presence of (1). p-Sultones (1) have also been identified in commercial scale equipment under less well-defined conditions [21-24]. 

In a study being conducted at Case Western Reserve University under the direction of Dr. Lawrence Sayre, trifluoromethyl-substituted analogs of 2,5-hexanedione will be synthesized, compared with the parent compound in chemical model studies, and evaluated for neurotoxicity in rats. This is part of an effort to address how gamma-diketone-induced pyrrole formation at neurofilament-based lysine epsilon-amino groups leads to neurofilament accumulations. Nuclear magnetic resonance (NMR) studies will provide direct visualization of the nature of chemical modification. 

Abstract This chapter describes the experimentai compiement of theoretical models of the microscopic mechanism of ferroelectric transitions. We use the hydrogen-bonded compounds as examples, and attempt to show that the new experimental data obtained via recently developed high resolution nuclear magnetic resonance techniques for solids clearly support the hypothesis that the transition mechanism must involve lattice polarizability (i.e. a displacive component), in addition to the order/disorder behaviour of the lattices. 

In an attempt to relate calculated results to experimental findings for monomeric, lignin model compounds, preliminary work has compared theoretically determined electron densities and chemical shifts reported from carbon-13 nuclear magnetic resonance spectroscopy (62). Although chemical shifts are a function of numerous factors, of which electron density is only one, both theoretical and empirical relationships of this nature have been explored for a variety of compound classes, and are reviewed by Ebra-heem and Webb (63), Martin et al. (64), Nelson and Williams (65), and Farnum (66). 

Abstract—The nature of the product of the reaction between an aminated silane and carbon dioxide was re-examined with the aid of simple model compounds, several amines, and several aminosilanes. Since the reaction products previously proposed include the amine bicarbonate and a carbamate derived from the amine, ammonium bicarbonate and ammonium carbamate were studied as models for the anions. Carbon dioxide adducts of neat model amines were prepared and studied. Results from a variety of techniques are summarized. Among the most useful was Fourier transform infrared (FTIR) spectroscopy of fluorolube mulls. FTIR spectra were distinctive and assignments characteristic of the two species were extracted from the spectral data. Comparisons of these assignments with the products of the reaction between carbon dioxide and various amines were made. The results indicate that alkylammonium carbamates are the principal product. Nuclear magnetic resonance (NMR) spectra in D20 indicated much dissociation and were not helpful in defining the products. 

There have been recent attempts to identify the reaction products of glutaraldehyde with the model compounds 6-aminohexanoic acid and a-A-acetyllysine. The ultraviolet, infrared, and nuclear magnetic resonance spectra of a purified product from the reaction of glutaraldehyde with 6-aminohexanoic acid has led to the postulate that compounds of the type illustrated below that have a polymeric quaternary pyridinium structure are a major type of product seen in proteins. More work will be needed to identify with certainty all the various reaction products that occur in proteins. 

Marchessault, R.H. Nuclear magnetic resonance and conformational studies on amylose and model compounds in dimethyl sulfoxide solution. J. Am. Chem. Soc. 1976, 37. 

With the development of polymer structural characterizations using spectroscopy, there has been a considerable effort directed to measurements of tacticity, sequence distributions and number average sequence lengths (59 65). Two methods have been traditionally used for microstructure analysis from polymer solutions. Vibrational spectroscopy (infrared) and Nuclear Magnetic Resonance (NMR). Neither of these techniques is absolute. The assignment of absorption bands requires the use of model compounds or standards of known structure. 

Noroxycodeine, synthesis of 1275, 1276 Novolac resins 367, 1457-1460 model compounds of 1463-1469 reactions with HMTA 1470-1475 structure of 1469 synthesis of 1460-1463 Nuclear magnetic resonance spectroscopy 335-367... 

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