Ozone reaction with olefins

The reaction of ozone with olefinic compounds is very rapid. Substiments on the double bond, which donate electrons, increase the rate of reaction, while electron-withdrawing substituents slow the reaction down. Thus, the rate of reaction with ozone decreases as follows polyisoprene > polybutadiene > polychloroprene [48]. The effect of substiments on the double bond is clearly demonstrated in Tables 15.2 and 15.3. Rubbers that contain only pendant double bonds such as EPDM do not cleave since the double bond is not in the polymer backbone. 

TS-1 is a material that perfectly fits the definition of single-site catalyst discussed in the previous Section. It is an active and selective catalyst in a number of low-temperature oxidation reactions with aqueous H2O2 as the oxidant. Such reactions include phenol hydroxylation [9,17], olefin epoxida-tion [9,10,14,17,40], alkane oxidation [11,17,20], oxidation of ammonia to hydroxylamine [14,17,18], cyclohexanone ammoximation [8,17,18,41], conversion of secondary amines to dialkylhydroxylamines [8,17], and conversion of secondary alcohols to ketones [9,17], (see Fig. 1). Few oxidation reactions with ozone and oxygen as oxidants have been investigated. 

The secondary component results from atmospheric chemical reactions that produce inorganic ionic species of which the most important are NH. and NOJ. Organic vapors also react in the atmosphere to form condensable products. For example, cyclic olefins react with ozone to form less volatile dicarboxyiic acids. The secondary chemical species nomially reported in studies ofaliiiospheric aerosol composition are relatively stable reaction products they have usually survived in the atmosphere and on filter or impactor... 

The impact of ozone on MTBE has been studied intensively in literature. For the reaction of ozone with MTBE two major reaction mechanisms have to be considered firstly the direct reaction of ozone with MTBE and secondly the elimination via so-called AOP (advanced oxidation processes), where the reaction is induced by OH radicals as oxidants. The mechanism is strongly dependent on the pH. At low pH values, direct reaction with ozone prevails, especially if functional groups with high electron density are present (e.g., olefinic double bounds). As the milieu is getting more alkaline, radical mechanisms gain importance since ozone is decomposing into OH radicals in the presence of hydroxyl ions. Erom pH 11 only radical reactions are taking place [64]. 

Reactions with ozone are competitive with the daytime OH radical reactions and the nighttime NO-, radial reactions as a tropospheric loss process for the alkenes. These reactions have been shown to proceed via initial O, addition to the olefinic double bond, followed by rapid decomposition of the resulting molozonide (Atkinson, 1990) ... 

These reactions proceed by initial ozone attack on the C = C bond of the olefin. An intermediate ozonide is formed, which rapidly decomposes to a carbonyl and a biradical. The biradical can be stabilized, or it can decompose. Paulson et al. (1991b) found the products methacrolein, methyl vinyl ketone, and propene, in yields of 68%, 25%, and 7%, respectively. Based on the presence of epoxides in the ozone/isoprene system, Paulson et al. concluded that 0(3P) was being formed. Calculations indicated that 0.45 0(3P) radicals were formed for every ozone/isoprene reaction. However, Atkinson et al. (1993) recently showed that the epoxides were formed directly from the reaction with ozone rather than the reaction with 0(3P). The epoxides formed were l,2-epoxy-2-methy 1-3-butene and l,2-epoxy-3-methyl-3-butene, in yields of 0.028 and 0.011, respectively. There was also definite evidence for the formation of OH radicals in the ozone system, thus causing difficulties in product analyses. Each ozone/isoprene reaction yielded 0.68 OH radicals (Paulson et al., 1991b). 

The stabilization of products of decomposition of primary ozonide, and as a consequence secondary reactions with ozone and olefines existence. One can underline that corpuscular chlorine plays role in such reactions with olefines [21]. This fact has been taken into account in Ref [21] by inducing of radical scavengers. Experimental rate constant is should be considered as an upper edge of rate constant of elementary act, which is an object of present work. 

Differences between Polymers. The degree of required ozone protection varies with the type of rubber. Saturated elastomers need no antiozonant protection, because they have no sites for reaction with ozone. Rubbers such as EPDM, which have a low olefin concentration, need essentially no protection against the effects of ozone. St5rene-butadiene rubber (SBR) requires antiozonant, while NR and synthetic pol5dsoprene (IR) may require somewhat increased dosages of antiozonant. Nitrile rubber (NBR) is very difficult to protect against ozone attack. 

The stereoselective synthesis of vinyl ethers is accomplished by N -(arylidene (or alkylidene) amino) - 2-azetidinones reaction with ozone and NaBH treatment resulting in di- and trisubstituted olefins derivatives [78],... 

P. S. Bailey, Ozonation in Organic Chemistry, Vol. 1, Olefinic Compounds, Academic Press, New York, 1978, 272 pp. Vol. 2, Nonolefinic Compounds, 1982, 496 pp. S. D. Razumovski and G. E. Zaikov, Ozone and Its Reactions with Organic Compounds, Elsevier, Amsterdam, 1984, 404 pp. 

A well-known example for a 1,3-dipolar compound is ozone. The reaction of ozone with an olefin is a 1,3-dipolar cycloaddition (see ozonolysis). 

A cursory inspection of key intermediate 8 (see Scheme 1) reveals that it possesses both vicinal and remote stereochemical relationships. To cope with the stereochemical challenge posed by this intermediate and to enhance overall efficiency, a convergent approach featuring the union of optically active intermediates 18 and 19 was adopted. Scheme 5a illustrates the synthesis of intermediate 18. Thus, oxidative cleavage of the trisubstituted olefin of (/ )-citronellic acid benzyl ester (28) with ozone, followed by oxidative workup with Jones reagent, affords a carboxylic acid which can be oxidatively decarboxylated to 29 with lead tetraacetate and copper(n) acetate. Saponification of the benzyl ester in 29 with potassium hydroxide provides an unsaturated carboxylic acid which undergoes smooth conversion to trans iodolactone 30 on treatment with iodine in acetonitrile at -15 °C (89% yield from 29).24 The diastereoselectivity of the thermodynamically controlled iodolacto-nization reaction is approximately 20 1 in favor of the more stable trans iodolactone 30. 

As inert as the C-25 lactone carbonyl has been during the course of this synthesis, it can serve the role of electrophile in a reaction with a nucleophile. For example, addition of benzyloxymethyl-lithium29 to a cold (-78 °C) solution of 41 in THF, followed by treatment of the intermediate hemiketal with methyl orthoformate under acidic conditions, provides intermediate 42 in 80% overall yield. Reduction of the carbon-bromine bond in 42 with concomitant -elimination of the C-9 ether oxygen is achieved with Zn-Cu couple and sodium iodide at 60 °C in DMF. Under these reaction conditions, it is conceivable that the bromine substituent in 42 is replaced by iodine, after which event reductive elimination occurs. Silylation of the newly formed tertiary hydroxyl group at C-12 with triethylsilyl perchlorate, followed by oxidative cleavage of the olefin with ozone, results in the formation of key intermediate 3 in 85 % yield from 42. 

The reaction of ozone with an unsaturated organic compd was reported more than a century ago (Schonbein, JPraktChem 66, 282 (1855)), however, complete explanation of this reaction has not been made until recent times. In 1905, Harries (Ref 1) postulated that the addition of ozone to an olefin resulted in the formation of an ozonide according to the formula ... 

Although the cracking of mbbers is related to the reaction of ozone on the double bond, it must be mentioned that ozone reacts also with sulfur cross-links. These reactions, however, are much slower. The reaction of ozone with di- and polysulfides is at least 50 times slower than the corresponding reaction with olefins [49]. 

Grosjean, D., Grosjean, E., Williams, II, E.L. (1994) Atmospheric chemistry of olefins A product study of the ozone — alkene reaction with cyclohexane added to scavenge OH. Environ. Sci. Technol. 26, 186-196. 

Huie, R.E., Herron, J.T. (1975) Temperature dependence of the rate constants for reaction of ozone with some olefins. Int l. J. Chem. Kinet. SI, 165. 

Stedman, D.H., Wu, C.H., Niki, H. (1973) Kinetics of gas-phase reactions of ozone with some olefins../. Phys. Chem. 77, 2511-2514. 

The most widely used gas-phase chemiluminescence reagent is ozone. Analytically useful chemiluminescence signals are obtained in the reactions of ozone with NO, SO, and olefins such as ethylene and isoprene, but many other compounds also chemiluminesce with ozone. Ozone is conveniently generated online at mixing ratios of =1-5% by electrical discharge of air or 02 at atmospheric pressure [14]. 

As the reaction temperature is increased, chemiluminescence is observed in the reactions of ozone with aromatic hydrocarbons and even alkanes. Variation of temperature has been used to control the selectivity in a gas chromatography (GC) detector [35], At room temperature, only olefins are detected at a temperature of 150°C, aromatic compounds begin to exhibit a chemiluminescent response and at 250°C alkanes respond, giving the detector a nearly universal response similar to a flame ionization detector (FID). The mechanisms of these reactions are complex and unknown. However, it seems likely that oxygen atoms produced in the thermal decomposition of ozone may play a significant role, as may surface reactions with 03 and O atoms. 

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