Ozonide decomposition

Fajgar, R. Roithova, J. Pola, J. Trimethylsilyl Group Migrations in Cryogenic Ozonolysis of Trimethylsilylethene Evidence for Nonconcerted Primary Ozonide Decomposition Pathway. . Org. Chem. 2001, 66, 6977-6981. 

Diazene, furan ozonide decomposition, 730 Diazo compounds, ozone adducts, 734 Diazonium salts, TEARS assay, 667 Dibenzoyl peroxide, determination, 698 Z-Dibenzoylstilbene, tetracyclone bleaching, 734-5... 

An application of the regiocontrol for ozonide decomposition by an allylic methoxy group (donor) is a macrolide synthesis [247]. 

The hydrogenolysis of 0-0 linkages is involved in the hydrogenation of peroxides, hydroperoxides, and ozonides. Decomposition may occur catalytically in the absence of hydrogen, as was observed in as early as 1818 by Thenard with hydrogen peroxide in the presence of platinum. 

The rate coefficients of limonene ozonolysis, evaluated at the BH and HLYP/cc-pvdz level, and the theoretical Arrhenius expression were in reasonable agreement with the experimental values and correctly described the initial steps of ozonolysis. The ozonide formation was highly exothermic, and the decomposition channels had similar free energies of activation, AG, indicating that there was no primary pathway for ozonide decomposition. ... 

The linear character and the absence of induction periods in the curves of OZ, CHP and DMPC formation are an indication that these products are obtained in parallel reactions. The pattern of the kinetic curves is typical for the formation of intermediate products. In the case of DMPC the curve reaches a plateau in 10 min, and that of OZ, which at the beginning is identical to the latter after 15 min begins to go down. This fact is apparently related to the ozonides decomposition and polymerization and from this part of the curve its rate of decomposition was calculated as 3x10 s. ... 

A 38.63-mg sample of potassium ozonide, KO3, was heated to 70 °C for 1 h, undergoing a weight loss of 7.10 mg. Write a balanced chemical reaction describing this decomposition reaction. A 29.6-mg sample of impure KO3 experiences a 4.86-mg weight loss when treated under similar condition. What is the %w/w KO3 in the sample ... 

The procedures for the decomposition of the ozonide and separation of the reaction products will vary according to the nature of the compounds and must be designed and selected accordingly. 

Ozone cracking is a physicochemical phenomenon. Ozone attack on olefinic double bonds causes chain scission and the formation of decomposition products. The first step in the reaction is the formation of a relatively unstable primary ozonide, which cleaves to an aldehyde or ketone and a carbonyl. Subsequent recombination of the aldehyde and the carbonyl groups produces a second ozonide [58]. Cross-linking products may also be formed, especially with rubbers containing disubstituted carbon-carbon double bonds (e.g. butyl rubber, styrene-butadiene rubber), due to the attack of the carbonyl groups (produced by cleavage of primary ozonides) on the rubber carbon-carbon double bonds. 

Few kinetic studies of the decompositions of higher oxides have been reported one probable reason is that the preparation of pure samples of these highly reactive compounds is difficult. Accordingly, interest has been largely restricted to the most readily available substances which are the alkali and alkaline earth peroxides (02-), superoxides (02) and ozonides (03). Some of these may be hydrated. E values reported [656] for the dehydrations of M02 8 H20 (288—313 K) were 96, 163 and 63 kJ mole-1 for the Ca, Sr and Ba compounds, respectively. 

The hydroperoxide (POOH) concentration was determined iodometri-cally after decomposition of the ozonides with excess of alcoholic sodium hydroxide. 

The addition of ozone to alkenes to form ozonides, and the subsequent decomposition of the latter to yield carbonyl compounds, has long been known ... 

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. 

Interaction of alkenes with ozonised oxygen tends to give several types of products or their polymers, some of which show more pronounced explosive tendencies than others [1]. The cyclic ge/n-diperoxides are more explosive than the true ozonides [2], It has been calculated that ozonisation of the endothermic /rara-stilbene (AH°f +135.4 kJ/mol, 0.78 kJ/g) would give, in the event of decomposition of the unstable ozonide, an exothermic release of 1.41 kJ/g which would attain an adiabatic decomposition temperature approaching 750°C with a 27-fold pressure increase in a closed vessel [3],... 

The preparation, properties and uses of ozonides have been reviewed comprehensively [1]. Many pure ozonides (trioxolanes) are generally stable to storage some may be distilled under reduced pressure. The presence of other peroxidic impurities is thought to cause the violently explosive decomposition often observed in this group [2], Use of ozone is not essential for their formation, as they are also produced by dehydration of c cF-dihydroxy peroxides [3], A very few isomeric linear trioxides (ROOOR) are known, they are also explosively unstable. Inorganic ozonides, salts of the radical C>3 anion, are also hazardous. 

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