Photolytic oxidation

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. 

Organotellurium tri- and dihaUdes undergo a-elimination by oxidative, photolytic or thermal routes, giving the corresponding halides with a selective transference of the halogen at the position where the tellurium moiety was originally attached (/pxo-substitution). 

Mechanistic work on the aforementioned ruthenium and vanadium systems has been more limited. Katsuki has proposed a possible mechanism for the (nitro-so)Ru-salen catalyzed oxidation. Photolytic dissociation of NO enables coordination of alcohol. Presumably, 02 then performs two sequential one-electron oxidations to yield the ketone and hydrogen peroxide. This sequence is based primarily on the performance of certain alcohols in the oxidation [10]. 

The temperature/humidity conditions used may be more severe than the typical accelerated stability testing conditions in order to generate potential degradation products in a reasonable time. The typical forced degradation conditions include thermolytic, hydrolytic, oxidative, photolytic (in excess of ICH conditions), high pH (alkaline conditions), and low pH (acidic conditions). Outlined in Table 9-25 and Table 9-26 are some solid-state and solution forced degradation studies, respectively, that could be conducted. In the following... 

Histidine may undergo either photo-catalyzed or metal-catalyzed oxidation. Photolytic oxidation results in the formation of 2-oxohistidine, also known as 2-oxoimidazoline, as shown in Scheme 3. Because His is an effective chelating agent, it is highly sensitive to metal-catalyzed oxidation. Additional oxidation products may be observed through metal-catalyzed oxidation of His, including the formation of Asp or Asn, but the mechanism for the formation of these products is not understood. ... 

O-demethylsalutaridine (43e), and sinoacutine (43a) have been synthesized (480). Kametani et al. (455, 481-487) synthesized them either by oxidation with potassium ferricyanide, Ag2C03, electrolytic oxidation, photolytic synthesis, or by the benzyne reaction. All these reactions (yield 1-5%) and... 

Low-molecular, non-polar substances are relatively volatile. They therefore occur as air-borne pollutants, can be dispersed dilfusively and with movements of the air and may undergo oxidative, photolytic degradation. 

Heterocycles which provide the NOC or CNO component synthon Isoxazoles can be prepared by the thermal or photolytic cleavage of a number of heterocycles, such as 1,3,5-dioxazolidone, furazans, furoxans and 1,3,2,4-dioxathiazole 2-oxides, in the presence of a reactive alkene or alkyne. 

The thermal or photolytic fragmentation of furazans to nitriles and nitrile Af-oxides has been reported (73JOC1054, 75JOC2880). The irradiation of dimethylfurazan (419) in the presence of cyclopentene, and benzofurazan (420) in the presence of dimethyl acety-lenedicarboxylate, gave isoxazoline (421) and isoxazole (422), respectively, in good yields. The thermolysis of acenaphtho[l,2-c]furazan (423) in the presence of phenylacetylene gave isoxazole (424) in 55% yield. 

Not all DMS released reaches the atmosphere. As can be seen from the summarizing Figure 5, some undergoes photolytic oxidation within the sea through the reaction... 

Amine oxides, prepared to protect tertiary amines during methylation and to prevent their protonation in diazotized aminopyridines, can be cleaved by reduction (e.g., SO2/H2O, 1 h, 22°, 63% yield H2/Pd-C, AcOH, AC2O, 7 h, 91% yield Zn/HCl, 30% yield). Photolytic reduction of an aromatic amine oxide has been reported [i.e., 4-nitropyridine A-oxide, 300 nm, (MeO)3PO/CH2Cl2, 15 min, 85-95% yieldl. ... 

Because of the possibility of focusing laser beams, tlrin films can be produced at precisely defined locations. Using a microscope train of lenses to focus a laser beam makes possible tire production of microregions suitable for application in computer chip production. The photolytic process produces islands of product nuclei, which act as preferential nucleation sites for further deposition, and tlrus to some unevenness in tire product film. This is because the subsuate is relatively cool, and therefore tire surface mobility of the deposited atoms is low. In pyrolytic decomposition, the region over which deposition occurs depends on the drermal conductivity of the substrate, being wider the lower the thermal conductivity. For example, the surface area of a deposit of silicon on silicon is nanower dran the deposition of silicon on silica, or on a surface-oxidized silicon sample, using the same beam geomeU y. 

The coordination chemistry of NO is often compared to that of CO but, whereas carbonyls are frequently prepared by reactions involving CO at high pressures and temperatures, this route is less viable for nitrosyls because of the thermodynamic instability of NO and its propensity to disproportionate or decompose under such conditions (p. 446). Nitrosyl complexes can sometimes be made by transformations involving pre-existing NO complexes, e.g. by ligand replacement, oxidative addition, reductive elimination or condensation reactions (reductive, thermal or photolytic). Typical examples are ... 

Anhydrous HX are versatile and vigorous reagents for the halogenation of metals, non-metals, hydrides, oxides and many other classes of compound, though reactions that are thermodynamically permissible do not always occur in the absence of catalysts, thermal initiation or photolytic encouragement, because... 

Expansions of cyclic sulfones to cyclic sulfinates are known124, and a similar mechanistic pathway of the expansion of the three-membered ring to a four-membered ring has been suggested for the photolytic fragmentation of the 2,3-diphenylthiirene oxide 18a22. 

Thiazepinones, as photolytic products 883 Thiazine 1-oxides, synthesis of 323, 352 Thiene dioxides formula of 382 synthesis of 469 Thiene oxides formula of 382 synthesis of 469... 

Square brackets around a molecular species indicate atmospheric concentration. The rate constants k times the reactant concentration product refers to the rates of the chemical reactions of the indicated number. The photolytic flux term /l4 refers to the photodissociation rate of N02 in Reaction R14, its value is proportional to solar intensity.]. RO2 stands for an organic peroxyl radical (R is an organic group) that is capable of oxidizing NO to NO2. Hydrocarbons oxidize to form a very large number of different RO2 species the simplest of the family is methylperoxyl radical involved in R5, R6 and R8. 

Stilbenes that are used as fluorescent whitening agents are photolytically degraded by reactions involving cis-trans isomerization followed by hydration of the double bond, or oxidative fission of the double bond to yield aldehydes (Kramer et al. 1996). 

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