Natural abundance 15N NMR

With improvements in instrument sensitivity and the use of techniques such as enhancement by polarization transfer (INEPT), it can be expected that natural abundance 15N NMR spectra will become increasingly important in heterocyclic chemistry. The chemical shifts given in Table 10 illustrate the large dispersion available in 1SN NMR, without the line broadening associated with 14N NMR spectra. 

The resolutions and signal to noise ratios of natural abundance 15N NMR spectra of nylons are sufficient to detect individual absorptions arising from morphologically different phases in nylons. In addition, the NMR data, which give immediate qualitative identification of the type of crystallinity, do not depend as much on size and perfection of the crystalline regions as X-ray analysis [56, 57], However, the broad unresolved peaks and shoulders on sharp... 

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