Ozonides structural characterization

Secondary ozonides are significantly more stable than primary ozonides, since the former contain only one O—O bond while the latter contain two. Some have been isolated and structurally characterized. However, they should be considered compounds that are explosive and dangerous. Therefore, secondary ozonides must be reduced to compounds without O—O bonds prior to reaction workup, too. Figures 17.27 and 17.28 show how this is accomplished. 

The ozonides, MO3, have historically been prepared by the reaction of the metal hydroxide with ozone. They may also be prepared from the respective superoxide (for M = K, Rb, Cs) . They are isolated from the superoxide by filtration in liquid ammonia followed by slow removal of the ammonia through evaporation. The CsOs can then be used to form the Li and Na derivatives by ion exchange in situ. NaOs cannot be isolated in the solid but can, along with the heavier congeners, be isolated (and structurally characterized) as a cryptand complex ([M-cryptJ Os-) . ... 

One of the most important features of the ozonolysis reaction of alkenes is one in which ozone adds to the C=C bond to form a primary ozonide (1,2,3-trioxolane). The Criegee mechanism suggests that this unstable intermediate decomposes into a carbonyl compound and a carbonyl oxide that recombine to form a final isomeric ozonide (1,2,4-trioxolane). Direct spectroscopic evidence for a substituted carbonyl oxide has only recently been reported by Sander and coworkers for the NMR characterization of dimesityl carbonyl oxide. Kraka and coworkers have theoretically modeled dimesityl carbonyl oxide and confirmed the structural aspects reported by Sander and coworkers on the basis of NMR data. 

The structural elucidation of the ozonide function is not always an easy task. For example, compounds 282 and 283, carrying stiff substituents on the double bond, each yield on ozonization a stable derivative containing three O atoms, that is hard to characterize as POZ or FOZ by the usual chemical and spectroscopic methods ... 

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