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Molozonides

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). [Pg.493]

Unsaturated compounds undergo ozonization to initially produce highly unstable primary ozonides (15), ie, 1,2,3-trioxolanes, also known as molozonides, which rapidly spHt into carbonyl compounds (aldehydes and ketones) and 1,3-zwitterion (16) intermediates. The carbonyl compound-zwitterion pair then recombines to produce a thermally stable secondary ozonide (17), also known as a 1,2,4-trioxolane (44,64,125,161,162). [Pg.117]

Molozonide (Seclion 7.9) The initial addition product of ozone with an alkene. [Pg.1246]

The molozonide was unstable and would either rearrange into the isozonide or form polymers. While Staudinger s theory explained the formation of the major products, some of the by-products could not be accounted for. The greatest step toward complete elucidation of the ozonolysis reaction was made by Criegee (Ref 3) In the 1950s. From a study of ozonolysis in various solvents and the constitution of the products, Criegee proposed these reactions ... [Pg.469]

The primary ozone-olefin addition product splits into a molozonide zwitterion (3). The zwitterion (3) then stabilizes by splitting into a carbonyl compd (4) and another zwitterion (5). [Pg.469]

Compare this step to the mechanisms we saw in the previous section syn dihydroxy-lation), and you should see striking similarities. The initial product (shown above) is called a molozonide, and it subsequently undergoes further rearrangements, before ultimately giving the product upon treatment with dimethyl sulfide (DMS). The structure of DMS is ... [Pg.299]

Dipolar addition to alkenes also occurs with species other than ozone, often to give products much more stable than the labile molozonides (54), e.g. addition of azides (61) to give dihydrotriazoles (62) ... [Pg.194]

The initial addition of ozone to alkenes to form molozonides (p. 193) can be regarded as a 1,3-dipolar addition, and many other such additions are of great importance in the preparation of five-membered heterocyclic systems. Thus we have already seen the... [Pg.351]

Ozone reacts vigorously with alkenes to form unstable initial ozonides (molozonides) which rearrange spontaneously to form ozonides. [Pg.349]

The very low yield of radicals by the reaction of ozone with cumene was found to be the result of the intensive ozone reaction with the benzene ring of cumene with molozonide formation. The values of the parameter e in other reactions are typical of the cage effect of radical pairs in solutions. The rate constants of ozone reactions with various compounds are presented in Table 3.7 and Table 3.8. [Pg.132]

Another reaction in which an oxygen cation is plausible as an intermediate is in the ozonization of olefins. Ozonides are now known to have many structures, but the molozonide precursor of the classical" or most common ozonide is believed to have a four-membered, cyclic structure. Criegee and the author have independently proposed a mechanism in which heterolytic fission of the cyclic peroxide bond leads to an intermediate that can rearrange either to the classical ozonide or to an "abnormal ozonide 816 328... [Pg.171]

A mechanism has been proposed recently by O Neal and Blumstein for the gas-phase ozone-olefin reaction. This mechanism postulates that molozonide-biradical equilibrium is reached fast and postulates a competition between a-, 8-, and y-hydrogen abstraction reactions and the classical mechanism proposed by Criegee for the liquid-phase reaction. The main features of the Criegee mechanism (Figure 3-9) are the formation, from the initial molozonide, of the major carbonyl products and a second biradical intermediate, the zwitterion. The decomposition pathways of the zwitterion comprise unimolecular re-... [Pg.72]

Direct calorimetric measurements of two ozonides have been reported. Both the enthalpy of combustion of the ozonides and the direct enthalpies of ozonation of the precursor olefin were measured. The first species to be studied was the purported ozonide of A °octalin (l,2,3,4,5,6,7,8-octahydronaphthalene) . It is doubtful that the product of the octalin ozonation reaction would be the molozonide formed by direct addition with no subsequent rearrangement (i.e. ll,12,13-trioxabicyclo[4.4.3]tridecane) but perhaps even less likely is the rearranged and hence normal ozonide, the ll,12,13-trioxa[4.4.2.1]paddlane. From the published enthalpy of combustion of —5628 kJmoU, we derive an enthalpy of formation of this species, whatever it is, of —593.7 kJmoU. ... [Pg.165]

Molozonides see Primary ozonides Molybdenum(VI) complexes bimetallic complexes, 428 hydrogen peroxide determination, 635-6, 640... [Pg.1474]

It is well known that the initial step in the reaction is the addition of O-, across the double bond to form what is known as a primary ozonide, or molozonide ... [Pg.196]


See other pages where Molozonides is mentioned: [Pg.236]    [Pg.703]    [Pg.175]    [Pg.218]    [Pg.237]    [Pg.237]    [Pg.1307]    [Pg.469]    [Pg.193]    [Pg.240]    [Pg.193]    [Pg.74]    [Pg.74]    [Pg.75]    [Pg.109]    [Pg.333]    [Pg.610]    [Pg.218]    [Pg.716]    [Pg.197]    [Pg.311]    [Pg.716]   
See also in sourсe #XX -- [ Pg.193 ]

See also in sourсe #XX -- [ Pg.193 ]

See also in sourсe #XX -- [ Pg.193 ]

See also in sourсe #XX -- [ Pg.193 ]

See also in sourсe #XX -- [ Pg.441 ]

See also in sourсe #XX -- [ Pg.218 ]

See also in sourсe #XX -- [ Pg.218 ]

See also in sourсe #XX -- [ Pg.373 ]

See also in sourсe #XX -- [ Pg.437 ]

See also in sourсe #XX -- [ Pg.367 ]

See also in sourсe #XX -- [ Pg.263 ]




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Molozonide

Molozonide

Molozonide intermediate

Molozonide, atmosphere

Ozonolysis molozonide

Rearrangement reactions molozonide

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