Polynuclear aromatic hydrocarbons hydrogenation

The most commonplace substrates in energy-transfer analytical CL methods are aryl oxalates such as to(2,4,6-trichlorophenyl) oxalate (TCPO) and z s(2,4-dinitrophenyl) oxalate (DNPO), which are oxidized with hydrogen peroxide [7, 8], In this process, which is known as the peroxyoxalate-CL (PO-CL) reaction, the fluorophore analyte is a native or derivatized fluorescent organic substance such as a polynuclear aromatic hydrocarbon, dansylamino acid, carboxylic acid, phenothiazine, or catecholamines, for example. The mechanism of the reaction between aryl oxalates and hydrogen peroxide is believed to generate dioxetane-l,2-dione, which may itself decompose to yield an excited-state species. Its interaction with a suitable fluorophore results in energy transfer to the fluorophore, and the subsequent emission can be exploited to develop analytical CL-based determinations. 

The complex [Rh(MeOH)2(diphos)]+ (diphos = l,2-bis(diphenylphosphino)eth-ane) has been reported to hydrogenate polynuclear aromatic hydrocarbons under mild conditions (60 °C, 1 bar H2) [17]. A kinetic study of the hydrogenation of 9-CF3CO-anthracene to the corresponding 1,2,3,4-tetrahydroanthracene was consistent with a rapid conversion of the precursor to [Rh( 76-anthracene)(diphos)]+ and a rate-determining step involving the reaction of the latter complex with H2... 

Chemical/Physical. Incomplete combustion of propane in the presence of excess hydrogen chloride resulted in a high number of different chlorinated compounds including, but not limited to alkanes, alkenes, monoaromatics, alicyclic hydrocarbons, and polynuclear aromatic hydrocarbons. Without hydrogen chloride, 13 nonchlorinated polynuclear aromatic hydrocarbons were formed (Eklund et al, 1987). 

Polynuclear aromatic hydrocarbons (PAH), of widespread occurrence in the environment, result from incomplete combustion of carbon- and hydrogen-containing substances. Many PAHs are well-recognized carcinogens and mutagens. Several industrial processes, such as fossil fuel conversion and production of aluminium and ferroalloys, can produce PAHs and result in their occurence in the working environment. 

Photolysis, in the presence of oxygen, of alkenes containing an ally lie hydrogen atom leads to the formation of hydroperoxides. The sensitized process is more efficient, and often yields photoproducts different in structure from those obtained by nonsensitized photooxidation. Cyclohexadiene and related dienes on photolysis in the presence of oxygen yield the transannular peroxides. Thus, on photosensitized oxidation, a-terpinene (410) is converted into ascaridole (411).435 The equivalent process is not, in general, observed in acyclic dienes. Certain polynuclear aromatic hydrocarbons, such as anthracene and naphthacene and including the heterocycles 5,10-diphenyl-1-... 

Beltran FJ, Ovejero G, Rivas J. Oxidation of polynuclear aromatic hydrocarbons in water. 3. UV radiation combined with hydrogen peroxide. Ind Eng Chem Res 1996 35 883-890. 

Table HI. The Pathways and Kinetics of Hydrogenation of Polynuclear Aromatic Hydrocarbons...

TABLE 11.25 Hydrogenation of Polynuclear Aromatic Hydrocarbons over Pd and Pt... 

Scheme I is a generalized scheme for the transformation of a polynuclear aromatic hydrocarbon to carbon and graphite. Heat treatment at about 350-500 °C leads to a complex reaction product mixture designated as pitch. Further reaction at temperatures near 500 °C results in an infusible polymeric hydrocarbon mixture designated as coke. As the heat-treatment process continues, the remaining hydrogen is removed, and a two-dimensional carbon polymer is formed. Finally, at temperatures near 3000 °C, three-dimensionally ordered graphite is produced.

The PET-generated arene radical cations also undergo nucleophilic substitution via the a-complex. Photocyanation of arenes may be cited in this context as a very early example [139], where hydrogen served as the group undergoing displacement. This concept is further extended [140] for the direct amination of polynuclear aromatic hydrocarbons with ammonia or primary amines via the arene radical cation produced by irradiating arenes in die presence of DCNB. Another potentially useful application of this methodology is... 

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