Reinvestigation of the formaldehyde–aniline condensation. Part 4. Ultraviolet photoelectron and electron transmission spectra of N-methyleneaniline and its symmetric dimethyl ring-substituted homologues and semiempirical theoretical evaluations

Abstract

A study of the vapours over heated 1,3,5-triphenylhexahydrotriazine (III) has been made by u.v. photoelectron and electron transmission spectral techniques. Complementary data are also reported for the homologous derivatives 2,2′,2″,6,6′,6″- and 3,3′,3″,5,5′,5″-hexamethyl-1,3,5-triphenylhexahy-drotriazines. The vapours over these compounds are found to be made up mostly of monomeric N-methyleneaniline (I) and of its dimethyl derivatives, respectively. The ionization and electron affinity data are compared with those of reference molecules. Theoretical MO energies obtained by means of an MNDO program for optimized geometries of (I), its dimer 1,3-diphenyldiazetidine (II), and of the references molecules are compared with the experimental data. It appears that, in the gas phase (ca. 100 °C and 0.0001 Torr)(I) and its dimethyl derivatives adopt a conformation characterized by a strong π(ring)–π(NC) mixing, that is, a nearly coplanar conformation.