CONFORMATIONS OF METHOXY(HYDROXY)-SUBSTITUTED BENZENES AND BENZALDEHYDES IN THE GAS-PHASE

The electronic structure of o-methoxy(hydroxy)-substituted benzenes ha s been investigated by the combined use of photoelectron spectroscopy and molecular orbital calculations by means of the semi-empirical AM1 method. Absorption bands in the PE spectra have been assigned, the dep endence of some pi-orbital energies on the molecular conformation has found, and the estimation of the mean torsion angle of the OCH3-group with the plane of the benzene ring has been carried out. The results o btained show that the conformations of the heavy-atom framework of gua iacol and vanillin molecules are planar. For veratrole and veratraldeh yde, nonplanar conformations with mean torsion angles phi almost-equal -to 80-degrees and 55-degrees, respectively, have been observed.