NMR STUDIES OF RATE PROCESSES AND CONFORMATIONS .9. CONFORMATIONAL RATE PROCESSES IN BRIDGED BICYCLIC TETRAHYDROPYRIDAZINE AND PIPERIDAZINE SYSTEMS

The NMR spectra of compounds of the bicyclo [2.2.1] heptane and bicyclo [2.2.2] octane types and containing the N(COOR)N(COOR) fragment have been studied. These spectra are temperature dependent. Free enthalpies of activation have been obtained from the observed spectral changes. These changes have been related to conformational changes in the molecules studied. The nitrogen sites are probably nearly planar and none of the boserved processes is hindered nitrogen inversion. Hindered rotation about the NCOOR bonds is present in both systems. In addition, a bridge-flipping" process has been found in the derivatives of the bicyclo [2.2.2] octane type. The origin of the potential barriers for these processes is discussed. © 1977."