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Saturday, 5 April 2014

J-HMBC / Broadband XLOC

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
  • tau 1 = ( 2×(Jmin + 0.070(Jmax - Jmin)))-1
  • tau 2 = ( Jmax + Jmin)-1
  • tau 3 = ( 2×(Jmax - 0.070(Jmax - Jmin)))-1
  • sum tau i: duration of low-pass J filter (LPJF)
  • kappa : scaling factor for apparent upscaling of nJ(X,H)
  • Delta = kappa × t1max
  • tA = 0.5 × ( Delta - sum tau i + t1max) - delta
  • tB = 0.5 × ( Delta + t1max - (1 + kappa )×t1)
  • tC = 0.5 × ( kappa ×t1 + sum tau i) + delta
  • delta = 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
  • tau 1 = ( 2×(Jmin + 0.070(Jmax - Jmin)))-1
  • tau 2 = ( Jmax + Jmin)-1
  • tau 3 = ( 2×(Jmax - 0.070(Jmax - Jmin)))-1
  • sum tau i: duration of low-pass J filter (LPJF)
  • Delta : Excitation delay
  • delta = 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. Delta = 500 ms, kappa = 22;
F1 sections from J-HMBC spectra of 15 µl of ethyl trans-cinnamate in 600 µl CDCl3 at 25° C. Delta = 500 ms and kappa = 22 which results in an apparent splitting of the doublet components by kappa 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

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