Octane numbers (ONs) of hydrocarbons: a QSPR study using optimal topological indices for the topological equivalents of the ONs

A new method proposed for solving QSPR tasks is based on transition from numerical values to topological equivalents (TEs) of physicochemical properties of chemical compounds. The TEs are unambiguously related to corresponding properties; for n-alkanes, they are linear functions of the number, n, of carbon atoms. Since the TE depends only on the corresponding physicochemical parameter, it can be calculated for any hydrocarbon using the same relationships as those known for n-alkanes. The optimal topological index (OTI) constructed using the chemical structure matrix for TEs usually has a much smaller basis compared to the topological index obtained by analogous procedure for the physicochemical property. An algorithm for modeling of physicochemical properties using the TEs was developed and evaluated taking the octane numbers of alkanes and cycloalkanes as examples.