ANISOTROPY OF THE H-1 AND C-13 SHIELDING TENSORS IN CHLOROFORM

The anisotropies, Delta sigma, of the H-1 and C-13 nuclear shielding t ensors of chloroform were determined experimentally and theoretically. The liquid crystal NMR ENEMIX method gives Delta sigma(C) = -51.8 to -51.4 ppm in excellent agreement with ab initio GIAO SCF/MCSCF calcula tions resulting in -51 ppm, preferring the ENEMIX results for C to the ones based on spin-lattice relaxation. A theoretical model and furthe r experiments imply that the deviation of the ENEMIX Delta sigma(H) va lue from the calculated 7 ppm is caused by hydrogen bonding between CH Cl3 and the C=N groups of the liquid crystal ZLI 1167, which is usuall y considered an inert solvent.