Carbon-hydrogen bonds ozonization

The unsaturated structure of the diene hydrocarbon rubbers makes them susceptible to attack by both oxygen and ozone. Oxidative degradation of all rubbers, irrespective of their structures, is inevitable as the energy associated with incident natural light is approximately three times that of a typical carbon-carbon or carbon-hydrogen bond. 

The problem then is the route to hydrogen peroxide in the present case. Insertion of ozone into a carbon—hydrogen bond has been postulated by White and Bailey (14) to explain the ozonation of benzaldehydes, by Price and Tumolo (15) in the ozonation studies of ethers, and by Batter-bee and Bailey (16) in their studies on the ozonation of anthrone. We postulate a similar intermediate to explain the formation of hydrogen peroxide and subsequently the diaminoperoxide VII. 

Whiting, M. C. , A. Bolt, J. N. Parish, J. H. The Reaction between Ozone and Saturated Compounds. Int. Symp. Oxidation Preprints, San Rrancisco 1967, 2, 267-287 Giamalva, D. H. Church, D. R. Pryor, W. A. Kinetics of ozonation. 5. Reactions of ozone with carbon-hydrogen bonds. Journal of the American Chemical Society, 1986, 108(24), 7678-7681. 

Ozonation ofAlkenes. The most common ozone reaction involves the cleavage of olefinic carbon—carbon double bonds. Electrophilic attack by ozone on carbon—carbon double bonds is concerted and stereospecific (54). The modified three-step Criegee mechanism involves a 1,3-dipolar cycloaddition of ozone to an olefinic double bond via a transitory TT-complex (3) to form an initial unstable ozonide, a 1,2,3-trioxolane or molozonide (4), where R is hydrogen or alkyl. The molozonide rearranges via a 1,3-cycloreversion to a carbonyl fragment (5) and a peroxidic dipolar ion or zwitterion (6). 

Further chemistry of alkenes and alkynes is described in this chapter, with emphasis on addition reactions that lead to reduction and oxidation of carbon-carbon multiple bonds. First we explain what is meant by the terms reduction and oxidation as applied to carbon compounds. Then we emphasize hydrogenation, which is reduction through addition of hydrogen, and oxidative addition reactions with reagents such as ozone, peroxides, permanganate, and osmium tetroxide. We conclude with a section on the special nature of 1-alkynes— their acidic behavior and how the conjugate bases of alkynes can be used in synthesis to form carbon-carbon bonds. 

More powerful oxidants are almost always needed. Those commonly used for cleavage of olefins — and for other degradations — include nitric acid, hydrogen peroxide, permanganate, chromic acid, very concentrated alkali hydroxides, and in particular ozone. The products to be expected from oxidative fission of an ethylenic carbon-carbon double bond are carbonyl compounds — an aldehyde or a ketone or both according as the doubly bonded carbon atoms do or do not carry a hydrogen atom — but it often happens that 1,2-glycols are obtained as intermediates. 

In addition to hydrogen halides, water is the most studied HBD in the gas phase. The structures of the complexes with water, dinitrogen, carbon monoxide, ozone, benzene, ethane, formaldehyde, formamide, 1,4-dioxane, ethylene oxide, tetrahydropyran, difluo-romethane, pyrazine, pyrimidine, pyridazine, benzonitrile, quinuclidine, ammonia, methy-lamine, trimethylamine and so on can be found in the Mogadoc database [29]. In the water-morpholine complex [30], water is hydrogen bonded to the nitrogen and not to the oxygen, as predicted by the higher HB basicity of amines than that of ethers. 

This discussion of the structures of diene polymers would be incomplete without reference to the important contributions which have accrued from applications of the ozone degradation method. An important feature of the structure which lies beyond the province of spectral measurements, namely, the orientation of successive units in the chain, is amenable to elucidation by identification of the products of ozone cleavage. The early experiments of Harries on the determination of the structures of natural rubber, gutta-percha, and synthetic diene polymers through the use of this method are classics in polymer structure determination. On hydrolysis of the ozonide of natural rubber, perferably in the presence of hydrogen peroxide, carbon atoms which were doubly bonded prior to formation of the ozonide... 

The analysis of published data on reactions of ozone with low molecular hydrocarbons shows that double bonds react with ozone more quickly than saturated bonds (12). Ozone reacts with saturated hydrocarbons in reactions in which hydrogen abstraction s followed by re-hydridization of the carbon atom form sp to sp state (43,44) ... 

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