Bond-Bond Interactions in Linear and Angular Molecules

Abstract

The vibration potential function of several molecules is studied with special emphasis on the bond‐bond interaction terms. It is shown that in the case of molecules with localized bonds a satisfactory correlation of the results cannot be obtained without assuming the existence of a maximum in the bond‐bond energy curve. This maximum presumably arises from the electrostatic interactions between the bond orbitals. As a result, the bond‐bond interaction terms may be either positive or negative, according to the position of the point which represents the equilibrium position of the molecule on the curve. However, this sign seems generally positive, except for molecules with hydrogenated bonds. On the other hand, for molecules with delocalized bonds (resonance), a general law may be formulated for the behavior of these terms when they refer to nonadjacent as well as to adjacent bonds. In those cases, the part played by the electrostatic interactions seems to be dominated by the resonance effects.