The COLOC sequence (COrrelation via LOng range Coupling)

The sequence which is used (Fig 26) allows generally a good correlation between the quaternary carbons and the neighbouring protons.

On the spectrum 12 (COLOC), the correlation between the quaternary carbon (13C=a=156.2) and its vicinal proton (D=7.7) is named Cq. However, it does not give good results for long range correlations involving protonated carbons[1].

This observation led to write a pulse sequence named XC ORFE (X nucleus proton CORrelation with Fixed Evolution time). This one is very closed to the COLOC sequence.

Fig. 26 : The COLOC pulse sequence
Spectrum 12 : COLOC of DBF
  1. H. Kessler, W. Bernel et C. Giresinger

    J. Am. Chem. Soc. 107, 1083 (1985)