Ozonolysis ozonides

The dipolar ion can react in several ways according to the solvent and the stmcture of the olefin. In inert solvents, if the carbonyl compound is highly reactive (eg, an aldehyde), the dipolar ion can be added to the carbonyl fragment to give the normal ozonide or 1,2,4-trioxolane (7) for example, 1,1-and 1,2-dialkylethylenes react in this manner. Tri- or tetraalkyl-substituted olefins produce a smaH, if any, yield of an ozonide when the ozonolysis is... 

Most ozonolysis reaction products are postulated to form by the reaction of the 1,3-zwitterion with the extmded carbonyl compound in a 1,3-dipolar cycloaddition reaction to produce stable 1,2,4-trioxanes (ozonides) (17) as shown with itself (dimerization) to form cycHc diperoxides (4) or with protic solvents, such as alcohols, carboxyUc acids, etc, to form a-substituted alkyl hydroperoxides. The latter can form other peroxidic products, depending on reactants, reaction conditions, and solvent. 

By-products include ozonides (17). Other peroxidic products including polymeric peroxides and polymeric ozonides can form, depending on reaction conditions, solvent, and olefin used. A variety of cycHc diperoxides (4) have been obtained by ozonolysis of olefins. Both cis- and... 

Other methods have been described to produce dodecanedioic acid. Cyclododecene is prepared from cyclododecatriene by partial hydrogenation. Ozonolysis of the cyclododecene followed by oxidation of the intermediate ozonides gives dodecanedioic acid (72). Hydrogenation of riciaoleic acid gives 12-hydroxystearic acid, which upon treatment with caustic at high temperatures, 325—330°C, gives a mixture of undecanedioic and dodecanedioic acids. 

Low -molecular-weight ozonides are explosive and are theretore not isolated. Instead, the ozonide is immediately treated with a reducing agent such as zinc metal in acetic acid to convert it to carbonyl compounds. The net result of the ozonolysis/reduction sequence is that the C=C bond is cleaved and oxygen becomes doubly bonded to each of the original alkene carbons. If an alkene with a letrasubstituted double bond is ozonized, two ketone fragments result if an alkene with a trisubstituted double bond is ozonized, one ketone and one aldehyde result and so on. 

But their instability makes it difficult to prepare them in good yields and to use them safely in reactions. Ozonides or ozonolysis products have at times expld on standing. Ozonolysis products are also thermally unstable. One must maintain the reaction at a certain temp in order to prepare and react these compds. Moreover, since the ozone addition reaction is highly exothermic, reactors must be cooled to maintain the desired temp (Ref 4)... 

Griesbaum K, V Miclaus, IC Jung (1998) Isolation of ozonides from gas-phase ozonolysis of terpenes. Environ Sci Technol 32 647-649. 

The location of the position of double bonds in alkenes or similar compounds is a difficult process when only very small amounts of sample are available [712,713]. Hass spectrometry is often unsuited for this purpose unless the position of the double bond is fixed by derivatization. Oxidation of the double bond to either an ozonide or cis-diol, or formation of a methoxy or epoxide derivative, can be carried out on micrograms to nanograms of sample [713-716]. Single peaks can be trapped in a cooled section of a capillary tube and derivatized within the trap for reinjection. Ozonolysis is simple to carry out and occurs sufficiently rapidly that reaction temperatures of -70 C are common [436,705,707,713-717]. Several micro-ozonolysis. apparatuses are commercially available or can be readily assembled in the laboratory using standard equipment and a Tesla coil (vacuum tester) to generate the ozone. Reaction yields of ozonolysis products are typically 70 to 95t, although structures such as... 

Several procedures that intercept the intermediates have been developed. When ozonolysis is done in alcoholic solvents, the carbonyl oxide fragmentation product can be trapped as an a-hydroperoxy ether.202 Recombination to the ozonide is then prevented, and the carbonyl compound formed in the fragmentation step can also be... 

A number of the bicyclic ozonides 12 were prepared in good yield (45-65 %) by diimide reduction of furan singlet oxygenates (Eq. 9) 23>. Again, low temperature were essential because the furan endoperoxides readily transform into 1,2-diacyl-ethylenes. Of course, the bicyclic ozonides 12 can alternatively be prepared via ozonolysis of the appropriate 1,2-disubstituted cyclobutene 24). 

The suggested fragments from (54a) are a carbonyl compound (58) and a peroxy zwitterion (59), the latter then effecting a 1,3-dipolar addition on the former to yield the ozonide (57a). Alternative reactions of the zwitterion (59), including its polymerisation, lead to the formation of the abnormal products that are sometimes observed in addition to the ozonide, If ozonolysis is carried out in MeOH as solvent then (59) is trapped , as it is formed, by its conversion into the relatively stable a-hydroperoxy ether (60) ... 

The zwitterion (59) is thereby prevented from reacting with the ketone (58) to form the ozonide in the normal way, and both (58) and (60) may now be isolated and identified. In preparative ozonolysis it is important to decompose the ozonide (57a) by a suitable reductive process, as otherwise H202 is produced (on decomposition of the ozonide with H20, for example) which can further oxidise sensitive carbonyl compounds, e.g. aldehydes— carboxylic acids. 

The above pathway accounts satisfactorily for the main features of ozonolysis but requires modification in detail to account for the observed stereochemistry of the reaction. Thus while a trans- (or cis-) alkene is often found to lead to a mixture of cis- and trans-ozonides as might have been expected, the trans-alkene (55) leads only to the trans-ozonide (57). The latter example demands a high degree of stereoselectivity in both the decomposition of (54) to aldehyde + peroxyzwitterion and in their subsequent recombination to (57) a demand that is not implicit in the pathway as we have written it. 

During ozonolysis of vinyl fluoride an explosive solid residue is produced, and the volatile ozonide, trapped at —63°C, may explode spontaneously or dining removal by syringe [1]. During the cryogenic distillation of the ozonide (formulated as a trioxolane), several explosions occurred, and the explosive reaction residue was destroyed by digestion with 5% potassium iodide solution for 24 h [2],... 

When a sufficient amount of sample is available (ca. 1 pg), monoenyl compounds can be analyzed by micro-ozonolysis with and without a solvent [146, 165]. Ozonides, directly injected into GC-MS, are reductively decomposed into two aldehydes by heat. Besides this chemical reaction, the double-bond position is easily and high-sensitively confirmed by making an adduct with DMDS, which... 

The use of both ozonation and ozonolysis is reviewed32. Ozonation leads to ozonide and ozonolysis leads to oxidized fragments, showing the use of both oxidative (AgN03) or reductive [(CH3)2S or PI13P] methods to produce the FAME (fatty acids methyl esters) that by subsequent GC analysis enabled determination of the position of the double bonds in the original molecule (equations 2-4). 

Reaction of ozone with a double bond is not surprisingly a function of the nucleophilicity or electron density of the double bond. Therefore, in ozonolysis of octamethylsemibullvalene208 (122) as well as for hexamethylbicyclo[2.2.0]-2,5-hexadiene209 and octamethyltricyclo-octadiene210 the diozonides, e.g. 123, are formed as the major product (equation 33). On the other hand, for hexachlorobicyclopentadiene211 (124), hexachlorobicycloheptadiene212 and 2-chloro-3-methyl-l,3-butadiene213 attack takes place at the nonchlorinated double bond only to form the ozonide 125 (equation 34). 

Ozonolysis has been a very important reaction in locating the position of the double bonds in the molecule. From the nature of products obtained after decomposing the ozonide, it becomes possible to locate the double bonds. If the molecule contains more than one double bond, generally ozone adds at all the bonds and so all the bonds are cleaved. 

These are only the suggested mechanisms. Less is known about how the ozonides are decomposed, at least in case of triple bonds. The knowledge about ozonolysis at present available is largely due to the work of R.C. Criegee (in Peroxide Reaction Mechanisms, interscience, New York, 1962, p. 29.). 

Cyclic enones can be oxidatively cleaved by a range of reagents to yield keto acids. As ozonolysis can be quite hazardous for large-scale preparations with the build up of ozonides, the procedure has been modified using quaternary ammonium salts to catalyse the transfer of peroxide anion for a rapid oxidative work-up [32]. Two methods are available but, in the safer procedure (10.7.15.A), there is no effective build-up of the ozonide. 

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