High-resolution INADEQUATE experiments

This section highlights the typical applications of 13C- and 1H-detected INADEQUATE and details a selection of examples from different areas of chemistry. These include primary structure determination of small molecules, the use of partially 13C-enriched compounds in biosynthetic studies, the recent structural analysis of fullerenes and the latest development in NMR hardware that promises to advance the use of high-resolution INADEQUATE experiments for polymers. 

A number of two-dimensional NMR experiments have been introduced in high-resolution solid-state NMR studies, designed, for example, to investigate chemical exchange processes [64], to retrieve chemical shift anisotropies [65] and dipolar couplings [66], and to probe spin-diffusion proces.ses 67j. Opella has proposed an intemuclear distance-determined, spin-diffusion mechanism in molecular crystals [68], and Benn and coworkers have demonstrated C/ C connectivities using the INADEQUATE sequence for the plastic crystal camphor and have used the COSY sequence for Si/ Si connectivities in the reference molecule Q Ms [691. 

For these high-resolution solid state spectra, many techniques analogous to those used in solution NMR can be applied. For exanple, 2D HETCOR experiments have been achieved using several pulse sequences (138). 2D double quantum correlation NMR (equivalent to 2D inadequate in solution and requiring C-labelled spin pairs) has been found to be a good technique to study chain conformations in the sohd state (139). Homonuclear double... 

When enough sample is available, the concentration is chosen depending on the information desired. Thus, high concentrations are desired for good signal-to-noise ratios e.g., nuclei with low natural abundance), for short recording times and for some two dimensional experiments e.g., H,C-COSY, COLOC, INADEQUATE). On the other hand, dilute solutions are preferred for higher resolution spectra, NOE experiments and other two dimensional experiments e.g., H,H-COSY). 

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