CL-35/CL-37 ONE-BOND ISOTOPE EFFECTS ON C-13 CHEMICAL-SHIFTS IN A SERIES OF PARASUBSTITUTED CHLOROBENZENES

One-bond isotope shifts of Cl-35/Cl-37 natural abundance chlorine isotopomers were measured in the 75.4 MHz C-13 NMR spectra of a series of para-substituted chlorobenzenes. The high-field isotope shift effect (1) Delta(13)C(Cl-37) was established from the relationship between the chlorine isotopomeric ratio and the carbon peak intensities. It was found that the (1) Delta(13)C(Cl-37) values are in the range of - 4.0 to - 5.2 ppb. The isotope shifts tend to decrease as the electron-attracting character of the substituent increases, providing a linear correlation between the isotope shift and the chemical shift of the chlorine-bearing carbon.