Ionization energies of some amines and enamines and an estimation of their relative basicity in gaseous phase

The ionization energy (i.e.) values for electrons in the π MOs of some tertiary amines and enemines derived from morpholine, piperidine and pyrrolidine have been determined by u.v. photoelectron spectroscopy. The effects of structural changes are discussed. The nitrogen lone pair i.e. value is taken as a measure of basicity of amines and enamines in the gas phase. The relative order of basicity is secondary amines < tertiary amines < enamines. This order differs from that found in aqueous solution probably because of solvation effects in the latter.