Ozone adducts with aromatic compounds

B. Primary Ozonides and Adducts of Ozone with Aromatic Compounds... 

Solid styrene was exposed at — 196°C to ozone, in an attempt to discern whether the behavior of the system is similar to that of olefinic compounds, yielding an ozonide, or to that of aromatic compounds, yielding a 7r-complex. On heating to about — 100°C, an adduct is formed that is stable until about —55 °C, when benzaldehyde and a peroxidic polymer are slowly obtained. The structure of the adduct is probably that of a POZ, based on the similarity of the IR spectrum with the ozone adduct of vinyl chloride described in the preceding paragraph . 

Such a process can produce 02( Ag) with 80% efficiency and similar reactions involving peroxide decomposition have been documented [21]. Of particular interest is the use of the decomposition of the endoperoxides of aromatic compounds, which, when appropriately substituted can be used in water [22] and of water soluble phosphite/ozone adducts [23]. Such chemical methods can provide a critical control for reactions in which photoexcitation of a sensitizer is suspected of doing more than just produce 02(1Ag). A prime example involves the rose bengal sensitized photooxidation of relatively unreactive alkenes [24],... 

Studies of the oxidation of aromatic compounds have established that the reaction of the initial adduct, formed by attack by OH, reacts with O2 to produce HO2 on a short timescale. This observation, together with the fast reaction rate for the OH reaction with substituted aromatic compounds, accounts for their efficient ozone production. 

Additionally in the case of ozone reaction with electron-rich compounds, such as phenols (phenolates) and akoxylated aromatics in aqueous phase again OH radicals are formed, most probably via the mechanism of formation of the respective ozone adduct [88,89]. For example it has been established that as a result of the electron transfer from phenol to ozone (reaction 11) at neutral pH the radical anion O3 " is obtained with an 5deld of 22% [90]. 

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