The XHCORR sequence
This sequence allows to correlate the signals of the
and of the
bound to
each other[1].
The spectrum 11 (XHCORR), shows the correlations for the dihydrofuran (Fig. 31) between bound carbons and protons.
The chemical shifts of the protons of this molecules are in the table 2, those of the carbon are in the table 3.
1H | Shift (ppm) |
|---|---|
A | 8.15 |
B | 7.4 |
C | 7.5 |
D | 7.7 |
13C | Shift (ppm) |
|---|---|
a | 156.2 |
b | 111.6 |
c | 127.0 |
d | 122.6 |
e | 120.6 |
f | 124.2 |
Within the XHCORR pulse sequence (Fig. 25), transverse magnetization is caused by a
impulsion which is evolving during the
period. The
impulsion
, located in the middle of this period refocuses the heteronuclear couplings.
The optimization of the
and
delays allows the selection of the long range heteronuclear couplings, this means that instead of seeing the correlation between
and protons directly bound
, we favour the appearance of the correlations spots between
and non bound protons
.
For example, for a coupling constant J=10 Hz then
=50ms and
=33ms.
