An Ab Initio SCF-MO Study of Conformational Properties of Cyclodeca-1,2,3-triene

Abstract

Ab initio calculation at HF/6-31G* level of theory for geometry optimization and MP2/6-<br />31G*//HF/6-31G* for a single point total energy calculation are reported for the important energyminimum<br />conformations and transition-state geometries of of cyclodeca-1,2,3-triene (1). The most<br />favorable conformation of 1 is a unsymmetrical twist-chair (1-TC) structure. Degenerate<br />interconversion of 1-TC with itself can take place via Cs symmetric half-chair (1-HC, Cs). The<br />calculated energy barrier for this processes is 30.3 kJ mol-1, respectively. The twist (1-Twist)<br />conformation of the 1, with C2 symmetry, is calculated to be more unstable than the twist-chair<br />(1-TC, C1) geometry by 12.4 kJ mol-1. Interconversion between 1-TC and 1-Twist conformations<br />takes place via the unsymmetrical transition state, which is 50.3 kJ mol-1 above 1-TC form. The<br />boat (C1) geometry of 1 is higher in energy by 19.1 kJ mol-1, respectively. Ring inversion in twistchair<br />and boat conformations takes place via C2 symmetric 1-TB (1-HC, C2) form and requires<br />65.6 kJ mol-1.