Study of Dynamic Effects by NMR Spectroscopy

The position of an equilibrium, A B, between two states A and B in equilibrium is determined by the free energy, AG, of the process, and it may be described by the equation 

The rate, k, of the interconversion between the states A and B is determined by the free energy of activation, AG as given by the equation 

The position at which the peaks of the methyl groups A and B of dimethylformamide just merge into each other is called the coalescence 

One can broadly distinguish three rate types in exchange processes  

In the following sections the equilibria which can be studied by NMR spectroscopy are categorized. 

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Kessler, H., Gehrke, M., Lautz, J., Kock, M., Seebach, D., Thaler, A. Complexation and medium effects on the conformation of cyclosporin A studied by NMR spectroscopy and molecular dynamics... 

The methods available to determine reaction rates by NMR spectroscopy include line broadening, spin saturation transfer and exchange spectroscopy (EXSY). The latter approach can be completed by both 1 and 2 D procedures. Several studies in the literature have served to illustrate that the dynamic behaviom of complexes detected through the parahydrogen effect can be examined. A general feature of this approach has involved the refocusing of the initial antiphase magnetisation. 

The principal techniques for determining the microstmcture of phenoHc resins include mass spectroscopy, proton, and C-nmr spectroscopy, as well as gc, Ic, and gpc. The softening and curing processes of phenoHc resins are effectively studied by using thermal and mechanical techniques, such as tga, dsc, and dynamic mechanical analysis (dma). Infrared (ir) and electron spectroscopy are also employed. 

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