Influence of remote substituents on ionization potential. Part II. Enamines

Electronic interactions in vinylamines can be divided into nN − π conjugation, and effects arising as a consequence of the electron-withdrawing abilities (−I) of both the nitrogen and π-system. Dehydroquinuclidine represents an ideal model which minimizes nN − π conjugation, and exhibits a pe spectrum which indicates that both the nN and π-orbitals are stabilized by about 0.4 eV relative to quinuclidine and bicyclooctene respectively. This stabilization is proposed to be a consequence of −I effects of each group and/or rehybridization of the nitrogen. Similar inductive effects are assumed to operate in enamines which do not prohibit nN − π interaction. In these cases, strong conjugative effects are operative in addition to the −I effects.