ELECTRONIC-STRUCTURE OF MONOSUBSTITUTED BENZENES AND X-RAY-EMISSION SPECTROSCOPY .1. BENZALDEHYDE

The electronic structure of the benzaldehyde molecule has been studied by X-ray emission spectroscopy. The gas-phase O-K alpha- and C-K alph a-spectra of this compound have been obtained. MNDO quantum-chemical c alculations have been carried out. The structure of the MO's of benzal dehyde has been compared with those of benzene and formaldehyde molecu les. The character of the p pi-p pi interaction of the phenyl and form yl fragments has been considered. The contribution of the latter to th e highest occupied molecular orbitals of the pi-system has been shown to be small.