Ozone Ozonides

The formation of addition products such as ozonates, ozonides, and oxozonides, in which the ozone molecule as a whole is attached to the final product. 

A varying and much more complex mechanistic situation exists in heterogeneous photocatalysis (Fig. 5-13). With respect to the transient oxygen species, comparable overall oxidation reactions are usually observed, but the set of primary reactive oxygen species is slightly different. It is commonly assumed, that superoxide radical anions and hydroxyl radicals are the primary species formed after photogeneration of the electron-hole pair of a semiconductor catalyst in the presence of water and air (Serpone, 1996). In the presence of ozone, ozonide radical anions or are formed by fast electron transfer reaction of superoxide radical anions with O3 molecules. The combination Ti02-03-UV/VIS is called photocatalytic ozonation (Kopf et al., 2000). For example, it was applied for the decomposition of tri-chloroethene in the gas phase (Shen and Kub, 2002). 

Ozone / ozonides Os (VI) / Os(VIII) (Ipc)2BCl, other boron reagents... 

BQDI 53 is the principal product of both sacrificial and depleting transformations of PD in model hydrocarbons, PO and rubbers and is formed via oxidation with ROO , oxygen, ozone, ozonides, organic peroxides or ions of transition metals. BQDI have therefore been found in PD doped polymers degraded under various conditions [3-5,58]. They are formed in high preparative yield by oxidation with femcyanide and also result in interactions of PD with some rubber chemicals, e.g, with benzothiazolyl-2-sulfenemorpholide. 

Addition compounds called ozonides are produced when alkenes react with ozone and reductive cleavage of these compounds is used extensively in preparative and diagnostic organic chemistry. 

How would you obtain a sample of pure ozone Account for the conditions used in your method of preparation. What is the arrangement of oxygen atoms in an ozonide and what evidence would you cite in support of the structure you suggest ... 

Excess of ozone should be avoided since further oxidation may occur to oxozonides or perozonides. ) The ozonides are usually not isolated since they are generally viscid oils or glasses, sometimes with violently explosive properties particularly on warming. They can, however, be completely... 

Aldehydes are easily oxidized to carboxylic acids under conditions of ozonide hydroly SIS When one wishes to isolate the aldehyde itself a reducing agent such as zinc is included during the hydrolysis step Zinc reduces the ozonide and reacts with any oxi dants present (excess ozone and hydrogen peroxide) to prevent them from oxidizing any aldehyde formed An alternative more modem technique follows ozone treatment of the alkene m methanol with reduction by dimethyl sulfide (CH3SCH3)... 

The relevant properties of peroxide and superoxide salts are given in Table 4 (see Peroxides and peroxide compounds, inorganic). Potassium peroxide is difficult to prepare and lithium superoxide is very unstable. The ozonides, MO3, of the alkah metals contain a very high percentage of oxygen, but are only stable below room temperature (see Ozone). 

Oxygen Compounds. Although hydrogen peroxide is unreactive toward ozone at room temperature, hydroperoxyl ion reacts rapidly (39). The ozonide ion, after protonation, decomposes to hydroxyl radicals and oxygen. Hydroxyl ions react at a moderate rate with ozone (k = 70). 

The unstable ammonium ozonide [12161 -20-5] NH O, prepared at low temperatures by reaction of ozone withHquid ammonia, decomposes rapidly at room temperature to NH NO, oxygen, and water (51). Tetrametbylammonium ozonide [78657-29-1] also has been prepared. 

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). 

The ozonides are characterized by the presence of the ozonide ion, O - They are generally produced by the reaction of the inorganic oxide and ozone (qv). Two reviews of ozonide chemistry are available (1,117). Sodium ozonide [12058-54-7] NaO potassium ozonide [12030-89-6] 35 rubidium ozonide [12060-04-7] RbO and cesium ozonide [12053-67-7] CsO, have all been reported (1). Ammonium ozonide [12161 -20-5] NH O, and tetramethylammonium ozonide [78657-29-1/, (CH ) NO, have been prepared at low temperatures (118). 

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). 

H. Ozonizalion of organic compounds. The ozonization of each unsaturated organic compound is more or less an individual problem, but some general comments may be made. Organic ozonides are highly explosive, and hence it is safest to carry out the ozonization in a solvent which dissolves both the original compound and the ozonide. In all cases, a shatterproof screen of laminated safety glass should be placed between the operator and the tubes H, I, and J. A second screen should be placed back of the tubes to protect other pieces of the apparatus. 

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. 

CIS- And trans-1,2-difluoroethylene are oxidized by ozone stereoselectively to a mixture of the corresponding epoxides and ozonides with formyl fluoride The composition of the mixture depends on the solvent used [25] (equation 16)... 

Unusually stable ozonides are prepared by treating mono- and bisffluroal-kyl)ethylenes with ozone [26] (equation 17)... 

Bubbling ozone into a pentane solubon ot hexakjs(trifluoromethyl)benzvalene gives a pale yellow ozonide, which is stable at room temperatures [27] (equation 18)... 

An important reaetion of ozone is the formation of ozonides MO3. The formation of a red eoloration when O3 is passed into eoneentrated aqueous alkali was first noted by C. F. Sehdnbein in 1866, but the presenee... 

Ozone adds readily to unsaturated organie eompounds and ean eause unwanted eross-linking in rubbers and other polymers with residual unsaturation, thereby leading to brittleness and fraeture. Addition to alkenes yields ozonides whieh ean be reduetively eleaved by Zn/H20 (or I /MeOH, ete.) to yield aldehydes or ketones. This smooth reaetion, diseovered by C. D. Harries in 1903, has long been used to determine the position of double bonds in organie moleeules, e.g. ... 

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