EDGE ADJACENCY RELATIONSHIPS IN MOLECULAR GRAPHS CONTAINING HETEROATOMS - A NEW TOPOLOGICAL INDEX RELATED TO MOLAR VOLUME

Adjacency between edges in molecular graphs containing heteroatoms is considered by using weights in the nondiagonal entries of the edge adjacency matrix. Values of k(C-X) parameters used in HMO calculation for molecules containing heteroatoms are used as edges weights. One index is derived using the Randic-type graph theoretical invariant. This index is well correlated (r > 0.99) with the molar volume of 112 aliphatic organic compounds, including aldehydes, ketones, ethers, thioethers, tertiary amines, and alkyl halides. A parametrization methods is proposed in order to obtain the values of k(C-X) parameters, based on correlation found between the proposed index and molar volumes.