Photooxidation peroxides

Photooxidation of tetrafluoroethylene (TFE) and hexafluoropropylene (HEP) yield peroxides that can be decomposed to esters and ultimately long-chain ether-containing carboxyUc acids. Equation 6 shows a simplified version of what occurs during photooxidation and workup (TFE R = F,... 

Ho PC (1986) Photooxidation of 2,4-dinitrotoluene in aqueous solution in the presence of hydrogen peroxide. 

Xanthophylls can further inhibit the peroxidation of membrane phospholipids (Lim et al. 1992) and reduce photooxidation of lipofuscin fluorophores (Kim et al. 2006), which are implicated in the pathogenesis of AMD (Sparrow and Boulton 2005). Furthermore, it was shown that light-induced damage to photoreceptors was reduced in quails fed zeaxanthin, with the number of apoptotic photoreceptor cells being inversely related to the concentration of zeaxanthin in the retina (Thomson et al. 2002). 

The next step was therefore to study the interaction of TMP derivatives with peroxides and with the products arising from them during photooxidation. A direct hydroperoxide decomposing effect of the HALS derivatives studied was not observed. 

Polynuclear aromatic hydrocarbons can be oxidized photolytically with the formation of cyclic peroxide. For example, anthracene is photooxidized to peroxide with the quantum yield 0 = 1.0 [205], The introduction of quenchers lowers the peroxide yield. 

Dienic hydrocarbons are photooxidized to cyclic peroxides. For example, terpinene is photooxidized to ascaridole peroxide [217] ... 

Photooxidation reactions of fluoroolefins in the presence of oxygen is one commercial method used in the production of PFPEs, generally employing either TFE or HFP. Fluorolefin concentration, oxygen level, light intensity, and temperature are all variables that have substantial impact on reaction rates, product distributions, polymer microstructure, peroxide content, and molecular weight. While HFP photooxidations are often carried out in bulk at low temperatures, TFE photooxidation must be carried out in an inert solvent, historically chlorofluor-ocarbons. 

Besides these external processes, formation of ROS may also take place intrac-ellularly. Photooxidative stress, including UVB, stimulates various cellular processes leading to the production of superoxide radicals and hydrogen peroxide, as well as singlet-oxygen and hydroxyl radicals. The sources and production sites of ROS are mainly related to photosynthetic activities such as the pseudocyclic photophosphorylation and the Mehler reaction, which stimulate the accumulation of hydrogen peroxide (Asada 1994 Elstner 1990). 

Draper WM, Crosby DG. 1984. Solar photooxidation of pesticides in dilute hydrogen peroxide. J Agric Food Chem 32 231-237. 

Anticipated products from the reaction of formaldehyde with ozone or OH radicals in the atmosphere are carbon monoxide and carbon dioxide (Cupitt, 1980). Major products reported from the photooxidation of formaldehyde with nitrogen oxides are carbon monoxide, carbon dioxide, and hydrogen peroxide (Altshuller, 1983). 

The photooxidation of fuel oil no. 2 in water is quite rapid in sunlight. The rate is four times that of coal liquids, producing two photooxidant pools with reaction rate constants of 0.58/minute and 0.037/minute. The faster reacting photooxidant was tentatively identified as hydrogen peroxide and the slower reacting... 

---