Ozone, and

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. 

Tribromine octoxide, Br30g, is a white solid obtained when ozone and bromine react together at 273 K at low pressure. It is unstable above 200 K in the absence of ozone. It is known to exist in two forms, both soluble in water. 

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)... 

Silicone rubbers have excellent ozone and weathering resistance, good electrical properties, and good adhesion to metal. 

Perfluorinated ethers and perfluorinated tertiary amines do not contribute to the formation of ground level ozone and are exempt from VOC regulations (32). The commercial compounds discussed above have an ozone depletion potential of zero because they do not contain either chlorine or bromine which take part in catalytic cycles that destroy stratospheric ozone (33). 

The aromatic ring of a phenoxy anion is the site of electrophilic addition, eg, in methylolation with formaldehyde (qv). The phenoxy anion is highly reactive to many oxidants such as oxygen, hydrogen peroxide, ozone, and peroxyacetic acid. Many of the chemical modification reactions of lignin utilizing its aromatic and phenoHc nature have been reviewed elsewhere (53). 

The rate of aqueous ozonation reactions is affected by various factors such as the pH, temperature, and concentration of ozone, substrate, and radical scavengers. Kinetic measurements have been carried out in dilute aqueous solution on a large number of organic compounds from different classes (56,57). Some of the chemistry discussed in the foUowing sections occurs more readily at high ozone and high substrate concentrations. 

Most ozone is formed near the equator, where solar radiation is greatest, and transported toward the poles by normal circulation patterns in the stratosphere. Consequendy, the concentration is minimum at the equator and maximum for most of the year at the north pole and about 60°S latitude. The equihbrium ozone concentration also varies with altitude the maximum occurs at about 25 km at the equator and 15—20 km at or near the poles. It also varies seasonally, daily, as well as interaimuaHy. Absorption of solar radiation (200—300 nm) by ozone and heat Hberated in ozone formation and destmction together create a warm layer in the upper atmosphere at 40—50 km, which helps to maintain thermal equihbrium on earth. 

The common oxidants are ozone, hydrogen peroxide, H2O, catalyzed usually with ferrous iron, Fe , and ia some cases chlorine dioxide and uv light. Advanced oxidation systems iaclude H2O2 + uv ozone + uv and H2O2, ozone, and uv. Depending on the appHcation, the oxidation can be complete to end products as in a contaminated groundwater or partial to degradable intermediate products as in a process wastewater. 

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