Nuclear magnetic resonance spectroscopy solved problems

Vargha was very progressive as far as the application of new techniques was concerned. He aided the introduction of the various chromatographic methods and the use of infrared (i.r.) and nuclear magnetic resonance spectroscopy and mass spectrometry in solving the various problems of structure determination. Despite the fact... 

In spite of the difficulties discussed above, the spectra of the cyclo-carbosilanes may be used in solving structural problems such as those associated with position isomerism in unsymmetrical methyl-substituted rings. This type of analytical application of nuclear magnetic resonance spectroscopy is particularly valuable for the carbosilanes, as the possibilities of establishing structures by chemical means are very restricted. The carbosilanes are not reactive and, unlike carbon compounds, undergo few reactions which yield information concerning their structures. In fact the structures of a number of compounds were first established with the aid of nuclear resonance. 

Computational chemistry is a new multidisciplinary area of research that transcends boundaries traditionally separating biology, chemistry, and physics. Computational chemistry is, de facto, a direct consequence of the computer. The computer serves as an instrument to solve real-world research problems, much like a diffractometer is the tool of X-ray crystallography or a spectrometer is the tool of nuclear magnetic resonance spectroscopy. 

Nuclear magnetic resonance (NMR) spectroscopy in pharmaceutical research has been used primarily in a classical, organic chemistry framework. Typical studies have included (1) the structure elucidation of compounds [1,2], (2) investigating chirality of drug substances [3,4], (3) the determination of cellular metabolism [5,6], and (4) protein studies [7-9], to name but a few. From the development perspective, NMR is traditionally used again for structure elucidation, but also for analytical applications [10]. In each case, solution-phase NMR has been utilized. It seems ironic that although —90% of the pharmaceutical products on the market exist in the solid form, solid state NMR is in its infancy as applied to pharmaceutical problem solving and methods development. 

The widespread use of synthetic polymers has led to the development of a considerable number of analytical tools for polymer characterization and analysis. Analytical pyrolysis, consisting of pyrolysis coupled with an analytical technique, is one of these tools. The technique can be invaluable in solving many practical problems in polymer analysis. It can be used alone or can provide complementary information to other techniques such as thermal analysis, infrared spectroscopy, or even nuclear magnetic resonance. 

We introduced nuclear magnetic resonance (NMR) in Chapter 3 as part of a three-pronged attack on the problem of determining molecular structure. We showed that mass spectrometry weighs the molecules, Infrared spectroscopy tells us about functional groups, and and Iff NMR tell us about the hydrocarbon skeleton. We concentrated on NMR because it s simpler, and we were forced to admit that we were leaving the details of the most important technique of all—proton ( H) NMR—until a later chapter because it is more complicated than NMR. This is that chapter and we must now tackle those complications. We hope you will see NMR for the beautiful and powerful technique that it surely is. The difficulties are worth mastering for this is the chemist s primary weapon in the battle to solve structures. 

Due to the complexity of food matrices several advanced spectroscopic techniques have recently been successfully employed to solve authenticity problems, including near infrared spectroscopy (NIR), mid infrared spectroscopy (MIR), low- and high-field nuclear magnetic resonance (NMR), site-specific natural isotopic fiactionation (SNIF-NMR) and... 

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