Reactive species singlet oxygen atom

Although this mechanism could explain the inertness of di-t-butyl sulphide towards oxidation due to the absence of a-hydrogen atoms, it was later ruled out by Tezuka and coworkers They found that diphenyl sulphoxide was also formed when diphenyl sulphide was photolyzed in the presence of oxygen in methylene chloride or in benzene as a solvent. This implies that a-hydrogen is not necessary for the formation of the sulphoxide. It was proposed that a possible reactive intermediate arising from the excited complex 64 would be either a singlet oxygen, a pair of superoxide anion radical and the cation radical of sulphide 68 or zwitterionic and/or biradical species such as 69 or 70 (equation 35). 

H-atom abstraction has been demonstrated to be the mechanism of action of excited uranyl ions, and in this case negligible base oxidation is found. Nucleo-base (especially guanine) oxidation is the principal reaction caused by singlet oxygen and this reactive species can be generated by a number of the complexes (e.g. many Ru(II)polypyridyls and porphyrins). It is worth pointing out, however, that the yield of may be lower when the sensitiser is bound to DNA, and it is the authors view that some of the reactions claimed to proceed via 62 may be caused by direct reaction of the photo-oxidised sensitiser with the DNA. 

The photochemical smog contains several oxygen species such as atomic oxygen (0), ozone (0 ) and singlet oxygen ( O2) which are highly reactive with several polymers. The concentration of 0 and 0 is low and their effect is considered to be less important in the total corrosion of polymers than the effects of ozone, nitric and sulfuric acids. 

Other oxygen species are also reactive with double bonds. Detailed sp ctroscopical studies show hat all oxygen species, i.e. singlet ( O2) and molecular oxygen ( atomic oxygen (0) and ozone (0 ) react with cis-l,4-polybutadiene forming different... 

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