Extension of edge connectivity index. Relationships to line graph indices and QSPR applications

The concept of edge connectivity index is extended to a series of indices based on adjacency between edges in various fragments of the molecular graph. The analogous concept of vertex adjacency indices of the line graph of the molecular graph is also introduced. Some mathematical relations between both series of indices are found, showing that line-graph-based connectivity indices are linear combinations of edge-based descriptors. The study of eight representative physical properties of alkanes was used to compare the ability of both series of indices to produce significant quantitative structure-property relationship (QSPR) models.