J-HMBC / Broadband XLOC

Measurement of long-range J(X,H) and J(H,H) coupling constants.

Sequences

J-HMBC and constant-time J-HMBC for measurement of long-range J(X,H) coupling constants

•  1 = ( 2×(Jmin + 0.070(Jmax - Jmin)))-1
•  2 = ( Jmax + Jmin)-1
•  3 = ( 2×(Jmax - 0.070(Jmax - Jmin)))-1
•   i: duration of low-pass J filter (LPJF)
•  : scaling factor for apparent upscaling of nJ(X,H)
•  =  × t1max
• tA = 0.5 × (  -   i + t1max) - 
• tB = 0.5 × (  + t1max - (1 +  )×t1)
• tC = 0.5 × (  ×t1 +   i) + 
•  = gradient delay
• Gradient ratios:
  • LPJF: +7, -4, -2, -1
  • Echo: +5.0 : -3.0
  • Antiecho: -3.0 : +5.0

Broadband XLOC for measurement of J(H,H) coupling constants

•  1 = ( 2×(Jmin + 0.070(Jmax - Jmin)))-1
•  2 = ( Jmax + Jmin)-1
•  3 = ( 2×(Jmax - 0.070(Jmax - Jmin)))-1
•   i: duration of low-pass J filter (LPJF)
•  : Excitation delay
•  = gradient delay
• Gradient ratios:
  • LPJF: +7, -4, -2, -1
  • Echo: +5.0 : -3.0
  • Antiecho: -3.0 : +5.0

Results

Expansion of a constant-time J-HMBC spectrum of 15 µl of ethyl trans-cinnamate in 600 µl CDCl3 at 25° C.  = 500 ms,  = 22;
F1 sections from J-HMBC spectra of 15 µl of ethyl trans-cinnamate in 600 µl CDCl3 at 25° C.  = 500 ms and  = 22 which results in an apparent splitting of the doublet components by  J relative to the 13C chemical shifts.
Expansion from a Broadband XLOC spectrum of 15 µl of ethyl trans-cinnamate in 600 µl CDCl3 at 25° C. with F2traces suitable for measurement of J(H,H) coupling constants.

References

• Meissner, A. and Sorensen, O.W. Measurement of J(H,H) and long-range J(X,H) coupling constants in small molecules. Broadband XLOC and J-HMBC Magn.Reson.Chem. 39 49-522001