ISSN:
0749-1581
Keywords:
Long-range CH correlation
;
2D NMR
;
Response intensities
;
Optimal delays
;
Chemistry
;
Analytical Chemistry and Spectroscopy
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
In long-range heteronuclear chemical shift correlation experiments, modulation of the response intensities of cross-peaks due to other long-range couplings to the carbon, although slower than that by direct couplings, must be taken into consideration in optimizing the polarization transfer (Δ1) and refocusing (Δ2) delays. The long-range modulation is experimentally confirmed using the standard CH correlation pulse sequence with a BIRD pulse midway through the refocusing delay. Analysis of aromatic correlations using hypothetical coupling constants shows that, in general, a choice of Δ2 = 0.667Δ1 is better than Δ2 = Δ1 for C—CH correlations, particularly when other interfering long-range couplings are involved. Guidelines for choosing optimal delays are given by response intensity and attenuation factor contours as a function of J and Δ1 values.
Additional Material:
8 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/mrc.1260260505
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