PARTIAL-LEAST-SQUARES MODELS FOR THE OCTANE NUMBER OF ALKANES BASED ON SUBGRAPH DESCRIPTORS

A new multivariate topological descriptor, the subgraph count set (SCS) is described. Chemically, the SCS is a count of all (or some of) the radicals obtained by breaking one bond in a molecule. The SCS is applied in modelling the octane number of heptane and octane isomers by using the multivariate partial-least-squares method. Results are discussed with reference to the meaning of the subgraphs (radicals) found to be relevant in establishing the predictive ability of the models. Most of the important radicals are simple and the algebraic signs of their regression coefficients in the final PLS (validated) models are consistent with their contribution to the degree of branching of the molecules. © 1990.