N-14 NMR-STUDIES ON CYCLIC NITRAMINES - CORRELATIONS OF CHEMICAL-SHIFTS WITH NITROGEN PARTIAL ATOMIC CHARGE AND PI-ORBITAL OVERLAP

The N-14 chemical shifts of nitro groups in the NMR spectra of cyclic nitramines have been correlated with their electronic environment in t he minimium energy conformers determined using AM1 semiempirical molec ular orbital calculations. Both the Mulliken population-derived atomic charge at the nitro nitrogen and the extent of pi-orbital overlap inf luence the observed shifts. Equations useful for predicting the shifts of nitro groups bonded to either the imino group of cyclic guanidines or secondary amines and ureas in heterocycles have been derived and a re discussed.