Chapter 10 - Molecular Structure and Symmetry

Abstract

Although the molecular orbital approach for the description of bonding is used more often, the valence bond approach has several advantages. The geometric arrangement of hybrid orbitals is often useful when describing structures. After illustrating the valence bond method, molecular symmetry is discussed in terms of the rotation axes and mirror planes that a molecule possesses. The symmetry characteristics are then applied to the description of a molecule in terms of group theory. For some molecules, there are too few electrons for all bonds to involve shared pairs of electrons. In such cases, an orbital on one atom serves as a bridge between two other atoms to generate a three-center bond. The symmetry properties of orbitals can affect the way in which molecules interact, and this is illustrated by considering conrotation and disrotation in the 1,3-butadiene molecule.