ELUCIDATION OF 11BORON NUCLEAR MAGNETIC RESONANCE SPECTRA BY HETERONUCLEAR SPIN DECOUPLING.

Abstract : It is indicated that heteronuclear spin decoupling does aid the evaluation of 11boron spectra in that the information obtained is compatible with the information obtained from the 64.2 Mc/sec. spectra. It is noted that these spectral evaluations might suggest an unexpected consideration pertaining to spectral assignments. Both the ortho and meta isomers have one pair of equivalent boron nuclei more intimately neighbored to carbon than the four equivalent boron nuclei, and two pair of equivalent boron nuclei further removed from carbon than the four equivalent boron nuclei. This suggests that the spectra should have one doublet on one side of the resonance of the four equivalent boron nuclei and two doublets on the other side. In both cases, the doublet is at higher field than the resonance of the four equivalent boron nuclei, and the pair of doublets is at lower field. This seems to suggest that carbon could be imparting a diamagnetic shift to its neighboring boron nuclei. A paramagnetic shift would be expected if only relative electronegativities were considered.