Ozonides peroxide formation

Final ozonides (FOZ), 716, 717, 718 cis and trans isomers, 719, 720 dialkyl peroxide formation, 706 IR spectroscopy, 719 mass spectrometry, 690 microwave spectroscopy, 721-3 molecular model, 750 NMR spectroscopy, 724-5 ozone water disinfection, 606 X-ray crystallography, 726-30 Fireflies... 

The products depend on the reaction conditions. In the presence of reactive solvent, such as methanol, Path a dominates. Ozonization in an inert medium leads to ozonide (Path b) and peroxide formation (Path c) the relative yield of ozonide and peroxide depends upon the olefin, solvent, and other reaction conditions. 

Due to the retractive forces in stretched mbber, the aldehyde and zwitterion fragments are separated at the molecular-relaxation rate. Therefore, the ozonides and peroxides form at sites remote from the initial cleavage, and underlying mbber chains are exposed to ozone. These unstable ozonides and polymeric peroxides cleave to a variety of oxygenated products, such as acids, esters, ketones, and aldehydes, and also expose new mbber chains to the effects of ozone. The net result is that when mbber chains are cleaved, they retract in the direction of the stress and expose underlying unsaturation. Continuation of this process results in the formation of the characteristic ozone cracks. It should be noted that in the case of butadiene mbbers a small amount of cross-linking occurs during ozonation. This is considered to be due to the reaction between the biradical of the carbonyl oxide and the double bonds of the butadiene mbber [47]. 

This discussion of the structures of diene polymers would be incomplete without reference to the important contributions which have accrued from applications of the ozone degradation method. An important feature of the structure which lies beyond the province of spectral measurements, namely, the orientation of successive units in the chain, is amenable to elucidation by identification of the products of ozone cleavage. The early experiments of Harries on the determination of the structures of natural rubber, gutta-percha, and synthetic diene polymers through the use of this method are classics in polymer structure determination. On hydrolysis of the ozonide of natural rubber, perferably in the presence of hydrogen peroxide, carbon atoms which were doubly bonded prior to formation of the ozonide... 

For analysis of dienes and polyenes via oxidations one has to distinguish between the formation of an oxidized product of the target molecule (epoxide, peroxide, ozonide etc.) and the oxidative fragmentation of the molecule as in the case of ozonolysis30. Both... 

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. 

Dichloroaluminium hydride in ether or sodium borohydride in TEA can lead to formation of ethers from ozonides by reductive cleavage of the two C—O bonds of the peroxide bridge (Equation (19)) <85JOC275>. 

Acid-catalyzed condensation of bicyclic ozonides with aldehydes and ketones, in the presence of hydrogen peroxide, leads to the formation of bicyclic peroxide analogs of acetals in low yields, as shown in equation 91 for the condensation of the ozonide of 1-phenylcyclopentene (266) with benzaldehyde. The structure of compound 267, with the preferred ring conformation as shown, was determined by XRD analysis . The same method served to demonstrate that the condensation compound 16c is unique, with structure 254 . 

Synthetic operations involving ozonolysis lead to formation of aldehydes, ketones or carboxylic acids, as shown in Scheme 16, or to various peroxide compounds, as depicted in Scheme 7 (Section V.B.5), depending on the nature of the R to R substituents and the prevalent conditions of reaction no effort is usually made to isolate either type of ozonide, but only the final products. This notwithstanding, intermediates 276 and 278 are prone to qualitative, quantitative and structural analysis. The appearance of a red-brown discoloration during ozonization of an olefin below — 180°C was postulated as due to formation of an olefin-ozone complex, in analogy to the jr-complexes formed with aromatic compounds however, this contention was contested (see also Section V1I.C.2). 

Cyclic hydrocarbons, diastereoselective allylic hydroperoxide formation, 861-3, 864 Cyclic olefins, final ozonides, 718 Cyclic peroxides... 

Risk labels, lATA/ICAO, 751-3 Risk phrases, 621, 748, 749 River water, peroxide determination, 642 RNA, ozone disinfection, 616 ROS see Reactive oxygen species Rose Bengal sensitized photooxidation, 890 Rotational barriers, regioselective allylic hydroperoxide formation, 836, 847-9 Rotational isomers, peroxynitrous add, 8-9 Rotational spectra, ozonides, 721, 722-3 RP-HPLC, hydrogen peroxide determination, 627... 

Why do some of the alkali metals form oxides, while others form peroxides when they burn in the air How does the stability of the alkali metal oxides and peroxides change (from lithium to cesium) when heated Why is the formation of peroxides and also of ozonides the most characteristic of the alkali metals ... 

Cyclo-addition (Criegee mechanism) — As a result of its dipolar structure, an ozone molecule may lead to three dipolar cyclo-additions on unsaturated bonds, with the formation of primary ozonide (I) corresponding to the reaction shown in Figure 4.8. In a protonic solvent such as water, this primary ozonide decomposes into a carbonyl compound (aldehyde or ketone) and a zwitterion (II) that quickly leads to a hydroxy-hyperoxide (III) stage that, in turn, decomposes into a carbonyl compound and hydrogen peroxide (see Figure 4.9). 

Ozonolysis of alkenes in the presence of amine A-oxides resulted in reductive ozonolysis, i.e, the direct formation of aldehydes in high yields, avoiding the generation and isolation of ozonides or other peroxide products. Use of DMSO and tertiary amines improved the yield of aldehydes but some amount of ozonides remained. This... 

Hydrogen atoms in allylic position are favorite sites for hydroperoxidation of chains. So, this mechanism proceeds in the formation of lateral hydroperoxides, and not like for other polymers, in intramolecular peroxides. Rearrangement of chemical structures coming from ozonides are rapidly observed (Scheme 33). 

The principles underlying alternative formation of 1,2,4-trioxolanes by cyclodehydration of a,a -dihydroxydialkyl peroxides (Rieche s ozonide synthesis without ozone ), or by photooxidation of diazo compounds in the presence of aldehydes, are outlined in Table 10. 

If terminally bifunctional prepolymers are to be formed by ozono-lytic degradation, several restrictions are immediately apparent. Ozonization is best carried out in aliphatic hydrocarbons because they are inert to ozone, they dissolve the original elastomer easily, and they are inexpensive. Formation of ozonides and peroxides should be prevented because they are difficult to convert to useful terminal functionality. The best way to prevent their formation is the reaction of the zwitterion with a nucleophile as in Path a of Figure 2. 

This chapter deals with the formation and behavior of peroxides in which the 0—0 group forms part of a ring. The most important of these heterocycles are peroxides of carbonyl compounds, which may also contain two or three peroxy groups in the same ring ozonides, which are also peroxides of carbonyl compounds, i.e., peroxidic acetals and endoperoxides, as cyclic dialkyl peroxides. 

The ozonization of olefins yields not only the ozonides (which were first isolated by Harries,82 and whose structures were subsequently elucidated by Staudinger83 and Rieche),2,23 but also other cyclic peroxides. The formation of these products is explained by the ozonization mechanism proposed by R. Criegee64 In 1958, Bailey8 published a review of ozonization reactions in general. 

Whereas ozonides are stable to methanol even at room temperature, the primary ozonide (94) reacts with methanol to give methoxyhydro-peroxide (96). This indicates the formation of a peroxidic zwitterion [Eq. (4)]. 

According to Huisgen,84 the formation of the ozonide by addition of the peroxidic zwitterion to a carbonyl group is a 1,3-dipolar addition. This explains the fact that, in the ozonization of open-chain olefins, ozonides are obtained as the principal products only when the carbonyl fragment has a sufficiently high dipolarophilic activity. This is so in the case of aldehydes, particularly formaldehyde simple ketones, on the other hand, are less reactive. For this reason, aliphatic tetrasubstituted ethylenes do not normally form ozonides.86... 

In a reversal of the formation of ozonides without ozone, Rieche ef al.23 obtained dihydroxydialkyl peroxides (2) as the first isolable products by acid hydrolysis of ozonides. 

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