The Quantum Mechanics of Unsaturated and Aromatic Molecules: A Comparison of Two Methods of Treatment

A comparison is made of two quantum-mechanical methods of treatment of unsaturated and aromatic organic molecules. The HLSP treatment, which is based upon the use of Slater valence-bond eigenfunctions, seems to give results in somewhat better general agreement with experiment than the HMH, which is based upon the use of molecular orbitals of the Hund-Mulliken type. The latter, however, can be extended to a wider variety of problems. The problems considered include the energy relations among hydrocarbons, the dissociation of aryl substituted ethanes, the electron-affinity of free radicals and the acid strength of hydrocarbons.