Theoretical justification of empirical additivity schemes for conformational energies

Additivity of conformational energy of saturated molecules has been studied using the perturbation theory for density matrix. Analytical expressions for both total and conformational energies have been obtained and analyzed up to the third-order members. It is shown that the conformational energy of compounds under investigation can be presented as a sum of transferable increments corresponding to the energies of separate conformational segments and their sequences. The role of end groups in determination of energies of conformational segments is revealed. The influence of substitution has been investigated. The dependence of subtle conformational effects on common structural peculiarities of Hamiltonians of saturated molecules has been concluded. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2003