multiple region selective HMQC

  • Summary

NM050016E

In 2D NMR measurements involving 19F, unlike those for 1H and 13C only, wide  chemical shifts of 19F make it difficult to detect correlation peaks. RF pulses should  manipulate magnetizations as designed, and otherwise signal intensities become  considerably low. In multiple region selective (mrs) HMQC,1) 19F pulses are  replaced by a selective excitation E-BURP1 pulse and a selective refocusing RE-  BURP pulse, and several frequency regions are simultaneously excited/refocused  using shifted laminar pulses, permitting all the correlation peaks to be detected.


Fig. 1  Pulse diagram of mrs-HMQC

Fig. 2  mrs-HMQC spectra of CF3CHFCF2OCH2CH3
Spectrometer: JNM-ECA500
 

Conventional HMQC method, where the offset of 19F rectangular pulses is fixed at -80ppm, does not give a correlation peak at -210ppm, but all the correlation peaks  are detected in the mrs-HMQC spectrum.

Reference

1) S. Cheatham and J. Groce, J. Fluorine Chem. 125, 1111(2004).

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