Quantum mechanical study of additivity of conformational energy in chloroalkanes

In order to prove the possibility to work out the quantum mechanically based additivity schemes for conformational energies the analytically predicted [D. Å atkovskienė, Int. J. Quantum Chem., 91 (2003) 5.] “additivity rule” as well as quantum mechanical calculations of chloro-substituted saturated hydrocarbons have been used. Notwithstanding that the evaluated magnitudes of additivity increments are sensitive to the method and the basis set used, the obtained results demonstrate the possibility to reach the optimal concert at the same level of calculations for all increments. The results showed independence of additivity increments on the size of the molecule, the location of the conformational segment in the molecule and the number of substitutes involved. The transferability of additivity increments was proved by good coincidence of relative arrangement of conformational energies obtained using the additivity rule with direct quantum mechanical calculations as well as with experimental findings available for various conformers in series of polysubstituted chloroalkanes. The possibility to limit series in the additivity rule by reasonable number of most important increments for chloroalkanes has been examined.