Ozone examples

The best opportunities for predicting redox transformations come from engineered systems where a known oxidant is added to achieve contaminant remediation. Well-documented examples include the use of ozone (Example 2.2.1.1) and chlorine dioxide (e.g., 41, 42) in... 

A complete description of the rate of a photolytic reaction should include the electronic states of the product molecules. / contains contributions from photons of all wavelengths that lead to a reaction. The flux of photons and the likelihood that photon absorption will lead to a reaction depend on the wavelength of the radiation. In the ozone example, / is sensitive to the flux of ultraviolet [A (wavelength) < 320 nm] radiation and thus / increases with height in the atmosphere, varies with time of day, and becomes zero at night. 

Several forms of aging of SOA vapors have been observed. One clear form is oxidation of multiply unsaturated alkenes. Many terpenes have multiple unsaturations, and in some cases different double bonds have very different rate constants for reaction with ozone. Examples include terpinolene, myrcene, hmo-nene, a-humulene, and p-caryophyllene [149, 150]. In these systems, ozone will react with one double bond in the terpene and produce some SOA. However, after the precursor is completely removed, SOA levels can continue to rise as the first-generation semi-volatile products continue to react with ozone to produce less volatile second-generation products [149]. 

R class elastomers have backbones consisting exclusively of carbon atoms, some of which are connected by double bonds (reactive sections). These double bonds enable crosslinking with sulfur, but are simultaneously sensitive to attack by oxygen and ozone. Examples natural rubber (NR), nitrile rubber (NBR), styrene-butadiene rubber (SBR)... 

To estimate the effect of automobile traffic and motor fuels on ozone formation, it is necessary to know the composition of exhaust gas in detail. Figure 5.26 gives an example of a gas phase chromatographic analysis of a conventional unleaded motor fuel. 

Example of an analysis of exhaust gas by gas phase chromatography and j relative reactivity of effluents with respect to tropospheric ozone formation. I... 

Another approach is to use the LB film as a template to limit the size of growing colloids such as the Q-state semiconductors that have applications in nonlinear optical devices. Furlong and co-workers have successfully synthesized CdSe [186] and CdS [187] nanoparticles (<5 nm in radius) in Cd arachidate LB films. Finally, as a low-temperature ceramic process, LB films can be converted to oxide layers by UV and ozone treatment examples are polydimethylsiloxane films to make SiO [188] and Cd arachidate to make CdOjt [189]. 

It decomposes exothermically to oxygen, a reaction which can be explosive. Even dilute ozone decomposes slowly at room temperature the decomposition is catalysed by various substances (for example manganese(IV) oxide and soda-lime) and occurs more rapidly on heating. 

Ozone is very much more reactive than oxygen and is a powerful oxidising agent especially in acid solution (the redox potential varies with conditions but can be as high as + 2.0 V). Some examples are 1. the conversion of black lead(ll) sulphide to white lead(II) sulphate (an example of oxidation by addition of oxygen) ... 

When writing a Lewis structure we restrict a molecule s electrons to certain well defined locations either linking two atoms by a covalent bond or as unshared electrons on a sm gle atom Sometimes more than one Lewis structure can be written for a molecule espe cially those that contain multiple bonds An example often cited m introductory chem istry courses is ozone (O3) Ozone occurs naturally m large quantities m the upper atmosphere where it screens the surface of the earth from much of the sun s ultraviolet rays Were it not for this ozone layer most forms of surface life on earth would be dam aged or even destroyed by the rays of the sun The following Lewis structure for ozone satisfies fhe ocfef rule all fhree oxygens have eighf elecfrons m fheir valence shell... 

If IS imporfanf fo remember fhaf fhe double headed resonance arrow does not mdi cate a process m which fhe fwo Lewis sfrucfures mferconvert Ozone for example has... 

The importance of ozone in the stratosphere has been stressed in Section 9.3.8. The fact that ozone can be decomposed by the halogen monoxides CIO, BrO and 10 means that their presence in the stratosphere contributes to the depletion of the ozone layer. For example, iodine, in the form of methyl iodide, is released into the atmosphere by marine algae and is readily photolysed, by radiation from the sun, to produce iodine atoms which can react with ozone to produce 10 ... 

Fig. 2. Examples of ozone isopleths generated using four different chemical mechanisms (a) EPA (b) ESM (c) CBII (d) ELSTAR NMOC = nonmethane...

Most chlorofluorocarbons are hydrolytically stable, CCI2F2 being considerably more stable than either CCl F or CHCI2F. Chlorofluoromethanes and ethanes disproportionate in the presence of aluminum chloride. For example, CCl F and CCI2F2 give CCIF and CCl CHCIF2 disproportionates to CHF and CHCl. The carbon—chlorine bond in most chlorofluorocarbons can be homolyticaHy cleaved under photolytic conditions (185—225 nm) to give chlorine radicals. This photochemical decomposition is the basis of the prediction that chlorofluorocarbons that reach the upper atmosphere deplete the earth s ozone shield. 

Ttinitroparaffins can be prepared from 1,1-dinitroparaffins by electrolytic nitration, ie, electrolysis in aqueous caustic sodium nitrate solution (57). Secondary nitroparaffins dimerize on electrolytic oxidation (58) for example, 2-nitropropane yields 2,3-dimethyl-2,3-dinitrobutane, as well as some 2,2-dinitropropane. Addition of sodium nitrate to the anolyte favors formation of the former. The oxidation of salts of i7k-2-nitropropane with either cationic or anionic oxidants generally gives both 2,2-dinitropropane and acetone (59) with ammonium peroxysulfate, for example, these products are formed in 53 and 14% yields, respectively. Ozone oxidation of nitroso groups gives nitro compounds 2-nitroso-2-nitropropane [5275-46-7] (propylpseudonitrole), for example, yields 2,2-dinitropropane (60). 

Depletion of the Ozone Layer. As a constituent of the atmosphere, ozone forms a protective screen by absorbing radiation of wavelengths between 200 and 300 nm, which can damage DNA and be harmful to life. Consequently, a decrease in the stratospheric ozone concentration results in an increase in the uv radiation reaching the earth s surfaces, thus adversely affecting the climate as well as plant and animal life. Pot example, the incidence of skin cancer is related to the amount of exposure to uv radiation. 

Environmental Impact of Ambient Ozone. Ozone can be toxic to plants, animals, and fish. The lethal dose, LD q, for albino mice is 3.8 ppmv for a 4-h exposure (156) the 96-h LC q for striped bass, channel catfish, and rainbow trout is 80, 30, and 9.3 ppb, respectively. Small, natural, and anthropogenic atmospheric ozone concentrations can increase the weathering and aging of materials such as plastics, paint, textiles, and mbber. For example, mbber is degraded by reaction of ozone with carbon—carbon double bonds of the mbber polymer, requiring the addition of aromatic amines as ozone scavengers (see Antioxidants Antiozonants). An ozone decomposing polymer (noXon) has been developed that destroys ozone in air or water (157). 

Type Example (trade name) Staining Oxyge n Heat Resistance to Flexing Metal catalysis Ozon e... 

Ozonc-rcsjstant elastomers which have no unsaturation are an exceUent choice when their physical properties suit the appHcation, for example, polyacrylates, polysulfides, siHcones, polyesters, and chlorosulfonated polyethylene (38). Such polymers are also used where high ozone concentrations are encountered. Elastomers with pendant, but not backbone, unsaturation are likewise ozone-resistant. Elastomers of this type are the ethylene—propylene—diene (EPDM) mbbers, which possess a weathering resistance that is not dependent on environmentally sensitive stabilizers. Other elastomers, such as butyl mbber (HR) with low double-bond content, are fairly resistant to ozone. As unsaturation increases, ozone resistance decreases. Chloroprene mbber (CR) is also quite ozone-resistant. 

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