Hydroperoxides ozonide decomposition

The hydrogenolysis of 0-0 linkages is involved in the hydrogenation of peroxides, hydroperoxides, and ozonides. Decomposition may occur catalytically in the absence of hydrogen, as was observed in as early as 1818 by Thenard with hydrogen peroxide in the presence of platinum. 

The hydroperoxide (POOH) concentration was determined iodometri-cally after decomposition of the ozonides with excess of alcoholic sodium hydroxide. 

Temperature-programmed thermal desorption particle beam MS of collected secondary aerosol particles shows that the major ozonization products of normal alkenes in an environmental chamber include organic hydroperoxides, peroxides, final ozonides and monocarboxylic acids. Attempts to analyze these compounds by GC result in their decomposition to simpler molecules". 

IR spectrophotometry, 661, 662 TEARS assay, 667 hydroperoxide oxidation, 692 Upid hydroperoxides, 977-8 decomposition, 669 DNA adducts, 978-84 protein adducts, 984-5 ozone adducts, 734 ozonide reduction, 726 ozonization characterization, 737, 739 peroxydisulfate reactions, 1013, 1018 Alkali metal ozonides, 735-7 Alkaline peroxide process, pulp and paper bleaching, 623... 

No cross ozonide was formed from unsymmetrical alkenes. The authors theorized628 that the carbonyl oxide zwitterionic species formed on wet silica gel immediately adds water followed by rapid decomposition of the intermediate hydroxyalkyl hydroperoxide to carboxylic acid and water. It means that water on silica gel acts as participating solvent. In the absence of adsorbed water, rapid recombination of the adsorbed aldehyde and carbonyl oxide due to a favorable proximity effect gives normal ozonide. The low mobility of adsorbed species on the silica surface accounts for the absence of cross ozonides. 

Fig. 15.47. Solvent dependence of the decomposition of the symmetric primary ozonide formed in the ozonolysis of tetramethylethene (2,3-di-methyl-2-butene). The initially formed carbonyl oxide forms a hydroperoxide in methanol, while it dimerizes to give a 1,2,4,5-tetroxane in CH2C12.

Fig. 15.48. Decomposition of the asymmetric primary ozonide formed in the ozonolysis of oleic acid. Two different aldehydes and two different carbonyl oxides are formed. In CH2Cl2 these molecules react with each other to form three secondary ozonides. In methanol, on the other hand, the carbonyl oxides react with the solvent to form hydroperoxides.

In the Criegee proposals the initial product is stipulated to have a 1,2,3-trioxolane structure (I) which is also known as a molozonide structure. This undergoes a concerted decomposition to give a zwit-terion (II) and a carbonyl compound (III). The decomposition products (II) and (III) in most cases recombine to give the normal ozonide (IV). Other possible reactions include dimerization of the zwitterion to yield a diperoxide (V) or a higher peroxide (VI) whilst in the presence of methanol as a reactive solvent a methoxy-hydroperoxide (VII) may be produced. 

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