Criegee’s mechanism

SCHEME 16. Criegee s mechanism of ozonide formation and ozonolys... 

Criegee s mechanism, ozonolysis, 606, 685, 716-17, 721, 726, 729 Criminals, dialkyl peroxide explosives, 708 Cross-hnking... 

Ozonolysis of (E) and (Z)-l,2-dimethoxyethene at —41 °C in the presence of acetaldehyde produced mixtures of (E)- and (Z)-3-methyl-5-methoxy-l,2,4-trioxolane, and in the presence of isobutyraldehyde mixtures of (/, )- and (Z)-3-isopropyl-5-methoxy-l,2,4-trioxolane. Ozonolysis of vinyl acetate affords 3-acetoxy-l,2,4-trioxolane and 3-acetoxy-1,2-dioxolane in 34% and 51% yields, respectively, in agreement with Criegee s mechanism <1990JOC1120>. 

A recent publication from this laboratory (5) presented evidence in favor of a mechanism of ozonization of unsaturated substances differing somewhat from that previously proposed by Criegee and Werner (1). Inasmuch as the results of abnormal ozonization reactions (3, 8, 10,11) were used in partial support of Criegee s mechanism, it was thought advisable to reinvestigate some of these ozonizations from the recent point of view. 

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 ... 

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],... 

The primary step of acetylene ozonation has been studied by BILYP, PBEO, CASSCF, MRMP2, and CCSD methods using the 6-31-l-G, aug-cc-p VDZ, cc-pVTZ, and aug-cc-p VTZ basis sets. The study confirms that the intermediate complex, the transition states of the concerted addition (Criegee s mechanism) and unconcerted addition (DeMore s mechanism) are involved in this reaction. Although Criegee s mechanism is dominant, the DeMore mechanism also contributes. ... 

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