Stereoselectivity ozonide formation

This indicates no evidence of stereorandomization about the carbon—carbon double bond. It means that 74 cleaves in a concerted fashion to yield syn and anti zwitter-ions produced in different amounts depending on the alkene geometry. The stereo-isomeric zwitterions remain attached to each other like an ion pair and recombine stereoselectively with aldehydes. The subtle nature of ozonation, however, may be illustrated by the observation that ozonide formation may be nonconcerted under... 

Ah initio calculations suggest that in ozonolysis, as the two fragments formed by dissociation of the primary ozonide start to move apart, a strong electrostatic attraction builds up between newly formed dipoles.157 The torque created causes a flip of one relative to the other, with formation of a dipolar complex which converts to the secondary ozonide. Thus, the authors suggest that the carbonyl oxide and carbonyl are never actually separated to a van der Waals distance. This argument goes some way to explaining some observed experimental stereoselectivities. 

Schaap, A.P., Siddiqui, S., Prasad, G., Rahman, A.F.M.N., and Oliver, J.P., Stereoselective formation of ds-ozonides by electron transfer photooxygenation of naphthyl-substituted epoxides. Stereochemical assignment of ozonides by x-ray crystallography and chromatographic resolution,/. Am. Chem. Soc., 106, 6087, 1984. 

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