LCAO - MO-STUDIES ON INTRAMOLECULAR HYDROGEN BONDING . LCAO-MO STUDIES OF MOLECULAR STRUCTURE .4.

CNDO/2-calculations on energy surfaces, which describe the motion of the proton in intramolecular hydrogen bonds, were performed for two examples - β-hydroxypropionaldehyde and the enol of malondialdehyde. Intramolecular hydrogen bonds in systems without conjugation of acceptor and donator group and intermolecular hydrogen bonds don't differ very much in stability and electronic structure. On the other hand hydrogen bonds become much stronger, if there is a conjugated π-electron system connecting both functional groups. In this case the frequency of the proton transfer along the hydrogen bond has a distinct influence on the electronic structure and the stability of the hydrogen bond. © 1969 Springer-Verlag.