| Popis: |
A simple approach to estimating properties of branched molecules is suggested: A property of any nonlinear molecule is considered as a sum of the property of the corresponding linear molecule and correction "for branching,"] determined by the interaction of atoms of the substituting group with atoms of the main chain. The potential of this approach is demonstrated by the calculation of the melting points, heat capacities, entropies, and enthalpies and free energies of formation for 117 saturated hydrocarbon molecules, including all the linear C1-C20 molecules and branched C4-C10 molecules with methyl substituents; also the heats of vaporization are calculated for 72 molecules including all linear C1-C20 molecules and branched C4-C9 molecules with methyl substituents. The accuracy of all the estimates is high. When the linear contribution is taken into account more accurately, with correction for nonlinear variation of properties of linear molecules, it becomes possible to highly accurately in estimate various properties of both linear and branched molecules, using the molecular connectivity indices. |
