Some new theorems and methods for establishing the relationship between the symmetry of a molecular orbital and its energy

Abstract

Some theorems are derived connecting the symmetry properties of molecular orbitals with their relative energies, for particular types of system. For example, when two identical fragments are joined by a single atomic orbital, or by two identical orbitals, the energies of the symmetrical m.o.s. alternate with those of the antisymmetrical m.o.s.

The theorems are used in the construction of correlation diagrams in which chosen interactions within a system are varied. By this purely diagrammatical procedure it is possible to estimate the relative m.o. energies in systems for which the m.o. parameters are not specified exactly.