Chemical shift correlation, 2D NMR

The two-dimensional H- H chemical shift correlated (2D NMR, COSY-45) data for isomeric 5P-cholestane-3a,7a,12a, 25-tetrol and 5P-cholestane-3a,7P, 12a,25-tetrol were acquired at a sweep width of 3200 Hz using a standard pulse sequence (collection of 256 free induction decays, FlDs) as described previously (28-30). A transform size of 2K x 2K data points was obtained after zerofilling. 

Like their H C counterparts, inverse-detected F C experiments are preferred to direct-detected C F experiments. In principle, H C correlated experiments can be readily adapted to collect F C chemical shift correlated 2D-NMR spectra by taking into account the differences between the C—F and C—H couplings when setting the coherence transfer delays and the different resonance frequencies of F and H. However, their application to the study of fluoropolymers is not widespread. In practice, many other factors must be considered in order to obtain good quality correlated 2D-NMR spectra from fluoropolymers. The high... 

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