Ozone reaction with ethylene

Chemiluminescence. Chemiluminescence (262—265) is the emission of light duting an exothermic chemical reaction, generaUy as fluorescence. It often occurs ia oxidation processes, and enzyme-mediated bioluminescence has important analytical appHcations (241,262). Chemiluminescence analysis is highly specific and can reach ppb detection limits with relatively simple iastmmentation. Nitric oxide has been so analyzed from reaction with ozone (266—268), and ozone can be detected by the emission at 585 nm from reaction with ethylene. 

Anticipated products from the reaction of ethylene dibromide with ozone or OH radicals in the atmosphere are bromoacetaldehyde, formaldehyde, bromoformaldehyde, and bromide radicals (Cupitt, 1980). 

Onsager inverted snowball theory (Com.) relation to Smoluchowski equation in, 35 relaxation time by, 34 rotational diffusion and, 36 Ozone in the atmosphere, 108 alkene reactions with, 108 Crigee intermediate from, 108 molozonide from, 108 ethylene reaction with, 109 acetaldehyde effect on, 113 formic anhydride from, 110 sulfur dioxide effect on, 113 sulfuric acid aerosols from, 114 infrared detection of, 108 tetramethylethylene (TME) reaction with, 117... 

Anticipated products from the reaction of ethylene dibromide with ozone or hydroxyl radicals in the atmosphere include bromoacetaldehyde, formaldehyde, bromoformalde-hyde and bromide radicals (Cupitt, 1980). In the atmosphere, ethylene dibromide is slowly oxidized by peroxides and ozone. The half-life for these reactions is generally >100 days (Leinster et al., 1978). 

O ne. Air pollution (qv) levels are commonly estimated by determining ozone through its chemiluminescent reaction with ethylene. A relatively simple photoelectric device is used for rapid routine measurements. The device is caHbrated with ozone from an ozone generator, which in turn is caHbrated by the reaction of ozone with potassium iodide (308). Detection limits are 6—9 ppb with commercially available instmmentation (309). 

Chemiluminescent analyzers are based on the light (chemiluminescence) emitted in the gas-phase reaction of ozone with ethylene, which is measured with a photomultipHer tube. The resulting current is proportional to the ozone concentration (see Luminescent materials, chemiluminescence). 

Ozonuies (1,2,4-trioxolanes) are generally obtained by the reaction of fluoroalkenes with ozone Thus, vmyl fluonde is oxidized to monofluoroozomde and formyl fluonde [23] (equation 15) The same ozomde is formed by ozonolysis of a mixture of cis 1,2-difluoroethylene with ethylene [24]... 

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]. 

In 1965, a gas-phase chemiluminescent reaction between ozone and ethylene was reported by Nederbragt et and the sensitivity of this technique was later improved by Warren and Babcock.The reaction between ozone and ethylene yields chemiluminescent emission in the 300- to 600-nm region, with maximal intensity at 435 nm. The intensity of this emission is directly proportional to the ozone concentration. 

Slight improvements in sensitivity can be achieved by cooling the phototubes used to detect the emitted light or by increasing the ethylene flow rate. Chemiluminescence produced by the reaction of ozone with ethylene has been designated by the epa as the reference method for monitoring ozone. Several different commercially produced instru< ments are available. 

Chemical/Physical. Gaseous products formed from the reaction of cyclohexene with ozone were (% yield) formic acid (12), carbon monoxide (18), carbon dioxide (42), ethylene (1), and valeraldehyde (17) (Hatakeyama et al., 1987). In a smog chamber experiment conducted in the dark at 25 °C, cyclohexane reacted with ozone. The following products and their respective molar yields were oxalic acid (6.16%), malonic acid (6.88%), succinic acid (0.63%), glutaric acid (5.89%), adipic acid (2.20%), 4-hydroxybutanal (2.60%), hydroxypentanoic acid (1.02%), hydroxyglutaric acid (2.33%), hydroxyadipic acid (1.19%), 4-oxobutanoic acid (6.90%), 4-oxopentanoic acid (4.52%), 6-oxohexanoic acid (4.16%), 1,4-butandial (0.53%), 1,5-pentanedial (0.44%), 1,6-hexanedial (1.64%), and pentanal (17.05%). 

Chemical/Physical. Gaseous products formed from the reaction of cyclopentene with ozone were (% yield) formic acid (11), carbon monoxide (35), carbon dioxide (42), ethylene (12), formaldehyde (13), and butanal (11). Particulate products identified include succinic acid, glutaraldehyde, 5-oxopentanoic acid, and glutaric acid (Hatakeyama et al., 1987). 

However, of all the methods used to measure ozone, the chemiluminescence reaction with ethylene is the one most often used. 

The reaction between olefins and ozone produces light that can be measured and related to the concentration of the reactants. One of the preferred methods for measuring ambient ozone concentrations utilizes the chemiluminescence generated in the ozone-ethylene reaction for detection. Recently, Hills and Zimmerman (16) described the use of this detection principle for determining hydrocarbon concentrations. They utilized the chemiluminescence created when ozone reacts with isoprene for development of a continuous, fast-response isoprene analyzer. This real-time isoprene system is reported to be linear over three orders of magnitude and to have a detection limit of about 1 ppbv. Because the system doesn t include a preseparation of hydrocarbons, interferences from other olefins (ethylene, propylene, and so forth) could occur. Thus far the chemiluminescent detector has been used to monitor isoprene emissions under conditions in which the concentrations of olefins that could interfere are negligible compared to those of the biogenic hydrocarbon. 

The effects contributed by alkyl groups to the relative rate constants, kreh for the reaction of ozone with cis- and trans-1,2-disubstituted ethylenes are adequately described by Taft s equation = k °reX -f pSo-, where So- is the sum of Taft s polar substituent constants. The positive p values (3.75 for trans- and 2.60 for cis-l,2-disubstituted ethylenes) indicate that for these olefins the rate-determining step is a nucleophilic process. The results are interpreted by assuming that the electrophilic attack of ozone on the carbon-carbon double bond can result either in a 1,3-dipolar cycloaddition (in which case the over-all process appears to be electrophilic) or in the reversible formation of a complex (for which the ring closure to give the 1,2,3-trioxolane is the nucleophilic rate-determining step). 

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