Ab initio study of conformational properties of (Z,Z,Z)-cyclonona-1,3,5-triene

Ab initio HF/6-31G* and MP2/6-31G*//HF/6-31G* methods were employed to calc ulate the relative energies of the important energy-minimum conformations a nd transition-state geometries of (Z,Z,Z)-cyclonona-1,3,5-triene (1). The t wist-boat (TB) conformation of 1, with C-2 symmetry, is calculated to be 7. 1 kJ mol(-1) which is more stable than the plane-symmetrical boat-chair (BC ) conformer. The plane-symmetrical boat-boat (BB) geometry of 1 is calculat ed to be a transition state, separating the unsymmetrical twist-boat-boat ( TBB) conformers. Pseudorotation of the chiral twist-boat conformation with its mirror image takes place via BB geometry and requires 35.5 U mol(-1). T he calculated energy barrier for ring inversion of TB conformation is 60.9 kJ mol(-1). (C) 2001 Elsevier Science B.V. All rights reserved.