Formation of Ozonides

The mechanism of the reaction of ozone with double bonds (equation 68) is very complex and still subject to arguments. An alkene and ozone may first form a it complex (a), which forms a a complex (b), a molo-zonide (c), or both. The molozonide may change to a dipolar ion (d), which breaks down with the fission of the carbon-carbon bond to a carbonyl compound and another dipolar ion (e). The two species recombine to give the ultimate product, ozonide (f) (1,3,4-trioxolane, also known as 1,3,4-trioxacyclopentane) [76], The temporary presence of the carbonyl com- 

The reaction is even more complicated when cis-trans isomerism is involved. Whereas tra 5-2,2,5,5-tetramethyl-3-hexene gives trans-di-tert-butylethylene ozonide, the cis isomer gives a mixture of 70% of cis ozonide and 30% of trans ozonide [79]. The ratios of cis and trans isomers may vary over a wide range depending mainly on the bulkiness of the alkyl groups at the double bonds. Whereas both cis- and tram-2-butene yield cis and trans ozonides in the ratio 2 3, cw-ethyl-tert-butylethylene gives cis and trans ozonides in the ratio 2 1. With the trans alkene, the ratio is 3 7 [76], 

In the majority of cases, the ozonide structure is unimportant, because the purpose of the ozonation of double bonds is to prove structures by cleaving the chain or ring to form alcohols, aldehydes, ketones, or acids after reductive or oxidative workup of the ozonides. 

When ozonides are to be isolated, a stream of 2-6% ozone in oxygen is passed through a solution of an alkene or a cycloalkene in low-boiling solvents, such as methyl chloride, pentane, hexane, chloroform, or carbon tetrachloride, at low temperatures (-78 to 5 °C) until the solution acquires a blue tinge (the color of ozone). The solvent is then evaporated at reduced 

Isobutylene gives a liquid ozonide, which is isolated in 40% yield by distillation at 43-43.5 °C at 143 mm of Hg (equation 69) [75]. 

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Formation of Ozonides. Although the patent compound, HO3, is too unstable to be isolated, metal and nonmetal ozonides have been... 

An important reaetion of ozone is the formation of ozonides MO3. The formation of a red eoloration when O3 is passed into eoneentrated aqueous alkali was first noted by C. F. Sehdnbein in 1866, but the presenee... 

Structure and mechanism of formation of ozonides (1,2,3- and 1,2,4-trioxolanes) 92CSR79. 

If terminally bifunctional prepolymers are to be formed by ozono-lytic degradation, several restrictions are immediately apparent. Ozonization is best carried out in aliphatic hydrocarbons because they are inert to ozone, they dissolve the original elastomer easily, and they are inexpensive. Formation of ozonides and peroxides should be prevented because they are difficult to convert to useful terminal functionality. The best way to prevent their formation is the reaction of the zwitterion with a nucleophile as in Path a of Figure 2. 

The formation of ozonides in this manner is of considerable value to... 

Griffin s group [105], demonstrated the formation of ozonides by electron-transfer photooxidation of small-ring cycloalkenes, a further significant achievement to the mechanistic pathways involved in these processes. 

In a reversal of the formation of ozonides without ozone, Rieche ef al.23 obtained dihydroxydialkyl peroxides (2) as the first isolable products by acid hydrolysis of ozonides. 

The action of oxygen on furan and furan derivatives in light leads to 1,4 addition with formation of ozonides.197 However, the only case in which the ozonide has been isolated is that of 1,4-diphenylisobenzo-furan this gives the crystalline ozonide (176), which explodes at 18°.198 In most cases only the decomposition products of the ozonides (carbonyl compounds, acids, and their derivatives) are isolated. 

In the gas phase formation of ozonide would be unlikely, and the intermediates should live long enough to react with NO2 as in Equations 11 and 12, with CgHe as in 13, 14, 15, and 16, and with O2 as in 17 and 18. However preliminary calculations using Equation 51 indicate that reactions 13, 14, 15, and 16 are too slow to be important in this process. Reactions of intermediates, as in 17 and 18, explain the non-stoichiometric ratio of olefin to O3 in the presence of O2 as observed by Cvetanovic (3) and others. Ozone may also be formed upon reacting with peroxyacyl radicals such as in Equation 31. 

Oxidation with potassium permanganate in acetic acid [231], resulting in extensive oxidation, and with a milder potassium permanganate—potassium periodate mixture [232], have recently been displaced by ozonolysis, first proposed by Bon [233]. The method is based on the formation of ozonides, their degradation and GC identification of the products. 

An efficient method for converting an epoxide to an ozonide has been reported1. Photooxygenation of tetraphenyloxirane (191) in dry 0-saturated MeCN sensitised by 9,10-dicyanoanthracene (DCA) led to the formation of ozonide (192) (64 ) and (193) (25 ) after 40h. This reaction is dramatically affected by the presence of biphenyl which can reduce reaction time to 10 minutes and affords (192) (93 ) together with (193)... 

The mechanism of the reaction is as follows ozone is passed through the alkene which causes the formation of ozonides the ozonides, which are explosive, are converted into aldehydes and ketones in the presence of zinc dust and acid. 

When appreciable concentrations of carbonyl compounds are present before complete formation of ozonide, crossed ozonides are formed. This occurs when the added carbonyl compound traps the zwitterion formed in the cleavage step. When c -stilbene is subjected to ozonolysis in the presence of 0-labeled benzal-dehyde, the label is incorporated into the ether rather than the peroxide portion of the ozonide ... 

Kuezkowski, R. L. The Structure and Mechanism of Formation of Ozonides, Chem. 

The oxidation of double bonds in polymers in a non-aqueous solvent leads to the formation of ozonides which, when acted upon by water, are hydrolysed to carbonyl compounds ... 

Futamura, S., Kusunose, S., Ohta, H., and Kamiya, Y, Formation of ozonides via 9,10-dicyanoan-thracene-sensitized photo-oxidation of epoxides,/. Chem. Soc., Chem. Commun., 1223, 1982. 

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