THEORETICAL DETERMINATION OF MOLECULAR-STRUCTURE AND CONFORMATION .3. PSEUDO-ROTATION SURFACE OF 1,2,3-TRIOXOLANE AND 1,2,4-TRIOXOLANE

The potential surfaces of 1,2,3-trioxolane (primary ozonide) and 1,2,4-trioxolane (final ozonide) have been explored by ab initio MO theory using large augmented basis sets. Extensive optimization of geometry has been performed with and without polarization functions. Results indicate that the latter are necessary in order to obtain reliable theoretical predictions with regard to the degree and mode of puckering of the two five-membered rings and with regard to their conformational barriers. Contrary to previous quantum chemical calculations the envelope form (Cs symmetry) of the primary ozonide is found to be the most stable conformation. Pseudorotation is hindered by a barrier of 3.5 kcal/mole which is about half as high as the barrier to planarity (7.7 kcal/mole). Similar barrier heights are calculated for the final ozonide (3 kcal/mole vs 6 kcal/mole), but in this case the twist conformation (C2 symmetry) corresponds to the conformational minimum. The electronic features determining the conformational tendencies of the trioxolanes are analysed in detail using hydrogen trioxide and hydrogen peroxide as alicyclic model compounds. © 1979 American Institute of Physics.