THEORETICAL-ANALYSIS OF THE STEREOSELECTIVITY IN THE OZONOLYSIS OF OLEFINS - EVIDENCE FOR A MODIFIED CRIEGEE MECHANISM

The Criegee mechanism of the ozonolysis of cis and trans symmetric alk enes of the type RCH=CHR is investigated by semiempirical AM1 calculat ions. The observed stereoselectivity trends are qualitatively explaine d in terms of the original Criegee mechanism. However, it is shown tha t in order to elucidate some subtle stereochemical effects as well as to account for the vain attempts to detect the carbonyloxide intermedi ate, a modification is required. This is done by adopting a proposal m ade by Cremer et al. (Chem. Phys. Lett. 1991, 187, 491) for the specif ic case of ethylene and applying it to all systems. The carbonyl oxide and aldehyde formed upon dissociation of the primary ozonide are not separated but forma strongly bound complex that subsequently transform s to the secondary ozonide.