CHEMICAL AND REACTION METRICS FOR GRAPH-THEORETICAL MODEL OF ORGANIC-CHEMISTRY

Two different metrices for families of isomeric molecular graphs are determined. The chemical distance between a pair of molecular graphs corresponds to the number of edges that should be created and/or annihilated in the course of chemical transformation of the given graph into another one. The reaction distance is determined as the minimal number of so-called elementary transformations (simple heterolytic dissociations and associations) that are necesary for the transformation of the initial molecular graph into the product molecular graph. The chemical transformations are formally expressed by the reaction graphs. Two approaches for the construction of reaction networks are suggested. The first approach consists of successive applications of prototype reaction graphs into the initial molecular graph. The second approach is based on the decomposition of the reaction graph into prototype reaction graphs. Both these approaches are substantially accelerated by heuristic rules which manifest the well-known organic chemistry principle of minimal structural change.