Conformation primary ozonides

An ab initio study of the ozonolysis of (E)- and (Z)-butene-2 <1999PCP3981> revealed slightly twisted O-envelope conformations for the primary ozonides. The ( )-butene-2 ozonide has a distorted geometry, with its two 0-0 bonds... 

A detailed structural and conformational study by DFT and ab initio methods has been reported for the ozonolysis of isoprene <2002JA2692>. The O-envelope conformers of the primary ozonides have the lowest energy. 

According to the results of ab initio calculations <2003PCA7574>, the two O-envelope conformers of the bicyclic primary ozonide of benzene are nearly equally stable. The product of ozone addition in the immediate vicinity of the hydroxyl group of phenol prefers an exo-O-conformation. The carbon rings in the primary ozonides of benzene and phenol are found to retain their planarity. 

While both the primary and secondary ozonides have been isolated and characterized, the pair formed by the carbonyl oxide (CO) and the carbonyl compound (CC) has never been directly put into evidence. This elusive intermediate, called also Criegee intermediate zwitterion (CZ), according to this AMI study which did not take into account solvent effects, forms a tight pair or a dipolar complex (DC). The primary ozonide has an O-envelope halfchair conformation and as such two conformers are possible from a rfr-alkene 11 and 12 and only one 13 from the trans-alkene. The splitting of the primary ozonide can lead either to an anti 14 or syn 15 CO and has a determining role for the stereochemical outcome of the reaction <1997JOC2757>. 

The CBS-QB3, MCG3, RRKM/master equation, and transition-state theory (TST) calculations were made for a detailed analysis of cyclopropene ozonolysis, treating all possible conformers of all intermediates and transition structures (TSs). The TST rate constant indicated that approximately 90% of the reaction proceeded through the endo-TS. It was predicted that approximately one-third of activated syn Criegee intermediates (Cls) would cyclize to dioxiranes despite the fact that the barriers to dioxirane formation were higher than the barriers to the 1,4-hydrogen shift that would lead to vinyl hydroperoxides and "OH. This helped to reduce the predicted OH yield for cyclopropene ozonolysis to 44%. It was also predicted that approximately 20% of either the endo-primary ozonide (PO) or its syn Cl derivatives would isomerize to the exo-PO or anti Cls. ... 

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