WHY IS THE TOPOLOGICAL APPROACH IN CHEMISTRY SO SUCCESSFUL

Graph theory has been used in chemistry to describe molecular structur es, chemical reactions, and it has been particularly widely used in st udies of the structure property relationship. On the other hand, the q uantum mechanical approach to the molecular structure also leads to ex pressions that offer descriptions of molecular properties. Little effo rt was made in the past to combine the two approaches and investigate how an approximate description of molecular properties relates to the electronic structure of chemical compounds as computed from the quantu m chemical stand point. We present a graph theoretical scheme for calc ulation of the heat of formation of saturated compounds, based on quan tum mechanically calculated atomic charges.