Molecular modeling of the physical properties of alkanes

Abstract

Eight physical properties (boiling points, molar volumes, molar refractions, heats of vaporization, surface tensions, melting points, critical temperatures, and critical pressures) of 74 normal and branched alkanes were examined by molecular modeling techniques. Structural parameters employed include Wiener indices, connectivity indices, ad hoc descriptors, information indices, and molecular volumes and surface areas. Most of the properties were well modeled (r/sup 2/ > 0.97) by the Wiener indices, connectivity indices, and ad hoc descriptors. An exception was the melting points, which were not well modeled by any of the available indices. Factor analysis (principal component analysis) was used to examine the intrinsic dimensionalities of the data and parameter sets. A single factor accounts for about 82% of the variance in the eight physical properties, two factors account for 94%, and three factors account for 99%. The melting points load strongly on a factor independent of the other properties. Of the examined parameter sets, the connectivity indices exhibited the highest dimensionality.