Oxygen and singlet

Decomposition of adducts such as triphenyl phosphite—ozone provides a convenient method for accomplishing chemical oxidations involving singlet oxygen and making it a useful oxygenating agent for synthetic and mechanistic appHcations. 

The endoperoxides of polynuclear aromatic compounds are crystalline soHds that extmde singlet oxygen when heated, thus forming the patent aromatic hydrocarbon (44,66,80,81). Thus 9,10-diphenyl-9,10-epidioxyanthrancene [15257-17-7] yields singlet oxygen and 9,10-diphenylanthracene. 

The primary interaction of singlet oxygen, produced by energy transfer from the excited sensitizer, with the diene can give rise to an exciplet that then collapses to peroxide, to a 1,4-biradical or to a 1,4-zwitterion alternatively, the adduct is the result of a concerted action without the involvement of an intermediate. Detailed kinetic Diels-Alder investigations of singlet oxygen and furans indicate that the reactions proceed concertedly but are asynchronous with the involvement of an exciplex as the primary reaction intermediate [63]. 

There is a continuing interest in the use of phosphite-ozone adducts as sources of singlet oxygen and as reagents for mimicking the reactions of this species. The commercially available phosphite (54) forms an ozone adduct of striking stability. Decomposition of the adduct only becomes appreciable at temperatures > 0 °C the decomposition exhibits first-order kinetics, so that at 10 °C= 9.10 x 10 min and= 76.2 min. These... 

Carotenoid chemical structure is usually not affected by the physical quenching. Another mechanism can occur in which a carotenoid chemically quenches singlet oxygen and is thus transformed in derived products. ... 

Fukuzawa, K. et ah. Rate constants for quenching singlet oxygen and activities for inhibiting lipid peroxidation of carotenoids and alpha-tocopherol in liposomes. Lipids, 33, 751, 1998. 

Bilirubin (normal plasma concentration < 20 iM) is able to scavenge singlet oxygen and peroxyl radicals. It has been proposed that bilirubin bound to human albumin contributes significantly to the non-enzymic antioxidant defences in human plasma (Stocker and Ames, 1987). 

Vandeplassche, G., Bernier, M., Thone, F., Borgers, M., Kusama, Y. and Hearse, D.J. (1990). Singlet oxygen and myocardial injury ultrastructural, cytochemical and electrocardiographic consequences of photoactivation of rose bengal. J. Mol. Cell. Cardiol. 22, 287-301. 

At room and higher temperatures the pattern of interaction between the singlet oxygen and anthracene changes. Changes in the mass of weighed sample of anthracene being acted upon by C>2( ) at room... 

Again, the bicyclic valence isomer coexists in sufficient concentration, that the bicyclic peroxide 19 was readily accessible in ca. 20% yield. Alternatively, the thermally labile bicyclic valence isomer of cyclooctatetraene, namely bicyclo[4.2.0]-octa-2,4,7-triene, was converted into the corresponding endoperoxide on low temperature singlet oxygenation and reduced with diimide to yield 19. 

Foote, C. S., Y. C. Chang, and R. W. Denny. 1970. Chemistry of singlet oxygen. XI. Cis-trans isomerization of carotenoids by singlet oxygen and a probable quenching mechanism. J. Am. Chem. Soc. 92 5218-5219. 

Antioxidant and Photoprotection Functions and Reactions Involving Singlet Oxygen and Reactive Oxygen Species... 

Bohm, F, R Edge, M Burke, and TG Truscott. 2001. Dietary uptake of lycopene protects human cells from singlet oxygen and ntirogen dioxide—ROS components from cigarette smoke. J Photochem Photobiol B 64 176-178. 

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