Reaction with double bonds, Criegee

There have been numerous theoretical and experimental efforts to explain the mechanism by which ozone reacts with double bonds of unsaturated substances (11,12,35). Perhaps the more widely accepted reaction is the Criegee mechanism which produces the two groups A and B (as shown below) ( 36-42) ... 

The reaction of ozone with alkenes proceeds via addition to the double bond giving a short lived energy-rich ozonide, which decomposes via C - C bond scission to give carbonyl compounds and biradical species known as Criegee biradicals ... 

In summary, the reaction of ozone with alkenes is important in the atmospheric degradation of alkenes. In all cases the reaction leads to rupture of the > C = C < double bond. The double bond is replaced by a carbonyl group on one side and a Criegee biradical on the other. The Criegee biradical is formed energetically excited and decomposes by a variety of different routes to give a complex mixture of oxygenated products (mainly carbonyls). 

Ozonolysis of pinenes contributes to OH radical and SOA formation. The latter has been speculated to be responsible for the formation of "blue haze". Hence, it is of vital importance to quantitatively understand the roles of ozonolysis of a- and jS-pinenes on both OH and SOA formation in the troposphere. The O3 reaction with both pinenes follows the Criegee mechanism, similar to that of iso-prene. The initial step proceeds through cycloaddition of O3 to the C=C double bond of each pinene, forming a primary ozonide (POZ). The available reaction energy is retained as the internal energy of the product, resulting in formation... 

The use of ozone in organic synthesis has been reviewed by Haines, Below, Razumovskii and Zai-kov, Bailey, Kuczkowski, Criegee and Camithers." Although the details of the reaction of ozone with carbon-carbon double bonds are not all completely understood, there is good evidence that the mechanism proposed by Criegee " is fundamentally correct. 

In accordance with Criegee s mechanism as applied to abnormal ozonizations (4), an unsaturated substance which contains electron-donating groups attached to a carbon atom adjacent to a double bond will produce zwitterions which will rearrange in such a manner as to produce abnormal products. This can be illustrated by the following sequence of reactions, in which R contains an electron-donating atom attached to a carbon adjacent to the double bond ... 

As for the reactions of O3 with olefins, the reaction of O3 with ROCH=CH2 proceeds by initial addition of O3 to the carbon-carbon double bond, followed by decomposition of the ozonide to form formaldehyde and a formate as stable eompoxmds in addition to two Criegee intermediates ... 

Ethene, like other alkenes, reacts also with ozone in the atmosphere. The older work on ozone reactions has been reviewed by Leighton (1961) and by Bufalini and Altshuller (1965). More recent work has done much to clarify the principal reaction mechanisms involved. Criegee (1957, 1962, 1975), who had studied the ozonolysis of alkenes in solution, suggested that ozone adds to the C=C double bond, forming an unstable intermediate, which then decomposes toward a carbonyl compound and a zwitterion fragment, for example ... 

The interest in the reaction of ozone with polydienes is mainly due to the problems of ozone degradation of mbber materials [1-4] and the application of this reaction to the elucidation of the stmctures of elastomers [5-8], It is also associated with the possibilities of preparing bifunctional oligomers by partial ozonolysis of some unsaturated pol5miers [9-12], Usually, the interpretation of experimental results are based on a simplified scheme of Criegee s mechanism of C=C-double bond ozonolysis, explaining only the formation of the basic product, ozonides [13, 14],... 

Criegee and co-workers (30,31) first reported the reaction of tetramethyl-cyclobutadienenickel chloride (XIV) with excess sodium cyclopentadienide. The original formulation of the product was later shown to be inconsistent with its H NMR spectrum (56) and a full X-ray structure determination (81) showed it to have the structure (LXXXI) with the cyclopentadienyl group exo to the metal. The positions of the double bonds in the cyclo-pentadiene ring of (LXXXI) are still in doubt and Criegee et al, (30) have suggested that two isomers may be present. The mechanism of the formation of (LXXXI) can most easily be understood in terms of a two-stage reaction modeled on those described as... 

Current ideas about the mechanism of C=C double bond ozonolysis in solution are summarized in Schemes 1 and 2 [19, 21, 34], As a result of the decomposition of the initial reaction product, primary ozonide (PO), zwitterionic species is formed, termed as Criegee s intermediates or carbonyl oxides (hereafter referred to as Cl) (Scheme 1, reactions 2 and 2 ). Two intermediates are formed from asymmetric olefins monosubstituted Cl (MCI) and disubstituted Cl (DCI), if their syn and anti stereoisomers are not taken into account. It is known that carbonyl oxides are predominantly formed at carbon atoms with electron-donating substituents [19], Excellent correlations of the regioselectivities of MO fragmentation with electron donation by substituents (as measured by Hammett and Taft... 

The reaction of ozone with allyl alcohol is expected to involve, as for other unsaturated alcohols and olefins, electrophilic addition at the carbon-carbon double bond leading to the formation of a trioxide followed by its unimolecular decomposition into two carbonyls and two biradicals (Criegee intermediates) ... 

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