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.

Fig. 31 : The dibenzofuran (D.B.F.)
Table 2  : Chemical shifts of the protons from the DBF

1H

Shift

(ppm)

A

8.15

B

7.4

C

7.5

D

7.7

Table 3 : Chemical shifts of the carbons from the DBF

13C

Shift (ppm)

a

156.2

b

111.6

c

127.0

d

122.6

e

120.6

f

124.2

Spectrum 11 : XHCORR of the DBF.

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.

Fig. 25 : The XHCORR pulse sequence
  1. G. E. Reeman et Morris

    J. Chem.Soc, Chem.Comm, 684 (1978)

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