Introduction to H NMR Spectroscopy

This book does not intend to explain NMR spectroscopy in full. It does not even intend to explain enough theory to enable the reader to understand P-NMR spectroscopy without prior knowledge of H- or C-NMR spectroscopy. There are many books that give a detailed explanation of H- and C-NMR spectroscopy. It is expected that the reader of this book is familiar with these nuclei in an NMR spectroscopic sense. However, a brief reminder of the basic concepts of NMR spectroscopy is given in this chapter as a way of introduction. 

H-NMR analysis allows the elucidation of GSL structures, without the use of destructive methods and requires small amounts (nmole) of material. In addition to one dimensional 1 H-NMR, other methods such as two-dimensional 1H-NMR shift correlations spectroscopy (COSY), two-dimensional nuclear Overhauser 1 H-NMR spectroscopy (NOESY) and homonuclear two-dimensional spin-echo J-resolved 1 H-NMR spectroscopy. The introduction of1 C-NMR into the field of glycosphingolipid research should give useful information on the stereochemical conformation of molecules. This is of coniderable interest, as they most probably contribute to the immunological specificity of glycosphingolipids (37). 

An example of the selective introduction of a deuterium probe into the ligand of a transition metal catalyst (followed by in situ H-NMR spectroscopy) was earher apphed to ejq)lain the activation of the square planar Nislightly acidic chloroaluminate ionic hquids [72], The D-labeled ligand was prepared according to Scheme 5.3-6 by reacting l,5-diphenyl-2,4-pentadione with NaH foUowed by hydrolysis with D2O. 

Apart from chiral HPLC methods, H NMR spectroscopy has often been used to determine the enantiomeric excess (ee[%] = [(R-S)/(R+S) x 100) of an asymmetric synthesis by derivatization with chiral (enantiomerically pure) reagents, e.g. Mosher s reagent, a-methoxy-a-trifluoromethyl-phenylacetic acid (MTPA) [1], Recently, international authorities, e.g. the European Pharmacopoeia Commission, have encouraged for the introduction of NMR spectroscopy for chiral analysis. 

Now that we have had an introduction to key aspects of H NMR spectra (chemicai shift, peak area, and signai spiitting), we can start to appiy NMR spectroscopy to eiucidating the structure of unknown compounds. The foiiowing steps summarize the process ... 

The metabolic profiling of tomato using H NMR spectroscopy has been applied in order to detect the unintended effects of the introduction of two maize transcription factors (LC and Cl) inducing the accumulation of flavonols (Le Gall et al, 2003) and in another study to identify the effects on tomato fruits engineered to accumulate spermine and spermidine (Mattoo et al, 2006). 

The standard monograph for those seeking an introduction to EPR spectroscopy. Frieboiin H 1993 Basic One- and Two-Dimensional NMR Spectroscopy (New York VCH) A basic introduction to NMR spectrai anaiysis. 

It is useful to compare the spectroscopic data of 1,2,4-triazine mono-A-oxides with the data for the corresponding 1,2,4-triazines. Introduction of an A-oxide group in the 1,2,4-triazine ring changes its physicochemical properties dramatically, and the analysis of these changes allows one to determine which of three nitrogens is oxidized. The most useful method in this case is NMR spectroscopy, including H, C, and N NMR. 

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