Ozone reaction with ethene

Hydrocarbons emitted into the atmosphere react with OH and other transient oxidants (NO3 radicals, O3, Cl-atoms) to form oxygenates. Hydrocarbons have a wide variety of atmospheric lifetimes. Methane is the least reactive hydrocarbon and has an atmospheric lifetime with respect to OH radicals of about 10 years. The lifetimes (days) of ethane, propane, n-butane, and n-decane are about 47, 11, 4.9, and 1, respectively. Alkenes are more reactive than alkanes of the same carbon number and are transformed into oxygenates much more quickly by reactions with OH and O3. For example, the lifetimes for reaction with OH for ethene, propene, and trans-2-butene are about 1.3 days, 10 h, 4.3 h, respectively. In addition, the alkenes react rapidly with ozone to form oxygenates. In the presence of 60 ppb of O3, the lifetimes of ethene, propene, and trans-2-butene with repect to reaction with ozone are 4.9 days, 18 h, and 1.0 h, respectively. Of course, the nature of the products formed by reactions of the hydrocarbons with... 

HO2 addition to CH2O. In the atmosphere it can also be formed through the reaction of the Criegee biradical (CH2OO) with water vapor (Neeb et al., 1997). Ethene and all alkenes of the structure, CH2=CR2, form the CH2OO biradical on reaction with ozone. Hellpointner and Gab (1989) have reported the detection of this compound and other peroxides in the atmosphere. 

Another chemiluminescence method for monitoring ozone involves the production of electronically excited formaldehyde in the 03 reaction with ethene ... 

Detection techniques. Detection techniques for surface-based measurements of ozone include (1) UV absorption at 254 nm (2) chemiluminescence on reaction with NO (or ethene) (3) DOAS (4) TDLS and (5) wet chemical methods, mainly those involving the oxidation of I to 12 and measurement of the I2 colori-metrically or coulometrically. The wet chemical method and the principles behind DOAS and TDLS were discussed earlier and are not treated further here. 

The formation of 1,2,3-trioxolane 1 (the primary ozonide) and of 1,2,4-trioxolane (the secondary ozonide) in the reaction of ozone with ethene in a cryogenic matrix was observed by IR spectroscopy at much lower temperatures than previously reported as low as 25 K in the amorphous CO2 matrix < 1996JA3687>. There was no indication of Criegee intermediates -carbonyl oxide and formaldehyde. No reaction was found in an argon matrix at temperatures up to 35 K. The identification of the ozonides was supported by ab initio calculation of the IR spectmm <1996JA3687, 1996SAA1479>. 

Dowideit P, VonSonntag C. Reaction of ozone with ethene and its methyl-and chlorine-substituted derivatives in aqueous solution. Environ Sci Technol 1998 32 1112-1119. 

Photolysis of atmospheric pollutants by solar radiation results in an increase of ozone concentration in certain urban areas and is the cause of a sequence of oxidation reactions with polymers. Ozone reacts with practically all organic materials especially with alkenes. The rate of its reaction with alkene is several orders of magnitude higher than that with alkane. The ratio of the rate constants of ozone with ethene/ethane is 1.5 x 105, with propene/propane 1.6 x 106, and with butene- 1/butane 1.1 x 106, at room temperature [5],... 

Another potential dark source of in the atmosphere, more particularly in the boundary layer, is from the reactions between ozone and alkenes. The ozonolysis of alkenes can lead to the direct production of the OH radical at varying yields (between 7 and 100%) depending on the structure of the alkene, normally accompanied by the co-production of an (organic) peroxy radical. As compared to both the reactions of OH and NO3 with alkenes the initial rate of the reaction of ozone with an alkene is relatively slow, this can be olfset under regimes where there are high concentrations of alkenes and/or ozone. For example, under typical rural conditions the atmospheric lifetimes for the reaction of ethene with OH, O3 and NO3 are 20 h, 9.7 days and 5.2 months, respectively in contrast, for the same reactants with 2-methyl-2-butene the atmospheric lifetimes are 2.0 h, 0.9 h and 0.09 h. 

Ethene, like other alkenes, reacts also with ozone in the atmosphere. The older work on ozone reactions has been reviewed by Leighton (1961) and by Bufalini and Altshuller (1965). More recent work has done much to clarify the principal reaction mechanisms involved. Criegee (1957, 1962, 1975), who had studied the ozonolysis of alkenes in solution, suggested that ozone adds to the C=C double bond, forming an unstable intermediate, which then decomposes toward a carbonyl compound and a zwitterion fragment, for example ... 

In contrast to the reaction of ethene with ozone, which is very fast, the reaction with an allyl anion itself is not observed, even though the reaction does meet the symmetry requirement. 

Figure 11.21. Frontier orbital interactions of ozone and ethene. [Reprinted with permission from Fleming, i. Frontier Molecular Orbitals and Organic Chemical Reactions, Wiley, London, 1976, pp. 93. Copyright 1976 by John Wiley and Sons, Inc.]...

The observed pressure independence of the product distribution in the ozone-ethene reaction between 100 and 1030 mbar indicates that the branching ratio may not be pressure dependent, in this pressure region. The pressure independence of the H2 yield has been shown, even down to 1 mbar (Becker). These findings are not in agreement with reaction step (3) by which excited Criegee intermediates are stabilised. 

This is carried out by operating a chemiluminescent NOj analyzer (cf. NO, analysis) at a NO excess condition. As the reaction of ozone with NO is faster and gives more intense CL than that with ethene, this method is preferred for some purposes in which a fast response is required (i.e., aircraft flux measurements). However, this CL method is subject to interference from water vapor and may contaminate the environment with NO. The ozone-NO reaction is also known as a gas-phase titration reaction, in which sample gas is mixed with a low-concentration standard NO gas and the NO2 formed in quantities equivalent to ozone is determined by an appropriate method. While CL reactions of ozone with other alkenes, alkyl sulfides, phosphine, arsine, and stibine... 

Olzmann, M., Kiaka, E., Cremer, D., Gutbrod, R., Anderssproduct distributions of the reactions of ozone with ethene and 2,3-dimethyl-2-butene. J. Phys. Chem. A 101, 9421-9429 (1997)... 

Since then, there have been a number of studies of this reaction, which have been summarized by Hatakeyama and Akimoto (1994). The mechanism appears to involve formation of an adduct that can either decompose to S02 and an isomerization product of the Criegee intermediate or, alternatively, react with a second S02 molecule to generate other products. For the Criegee intermediate formed in the ethene-ozone reaction, for example, the proposed reaction sequence is the following ... 

In studies of the reactions of 1.1 -difluoroethene, trifluoroethene, and perfluoroethene, the mechanism of ozonide, epoxide, and cyclopropane formation have been studied.84 Unusually stable ozonides 46A and B are prepared by treating mono- and bis(fluoroalkyl)cthenes with ozone85 at room temperature or on heating the substrate to which ozone is introduced. The rates are approximately 1()10 slower than that for the nonfluorinated analogs. Mono-perfluoroalkylated ethene seems to react several times more rapidly than the bis-perfluoroalkylated ethene.85... 

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