Pyrene, ozonolysis

Chemical/Physical. Ozonolysis to benzo[a]pyrene-l,6-quinone or benzo [a] pyrene-3,6-quinone followed by additional oxidation to benzanthrone dicarboxylic anhydride was reported (lARC, 1983). 

Kormniiller et al., 1997 b). For example, in the ozonation of the five ring condensed benzo(e)pyrene this was confirmed by the oxidation products being formed a secondary ozonide and oxepinone (hydroxytriphenylenol[4,5-cde]oxepin-6(4H)-one), which are specific for an ozonolysis (Kornmuller and Wiesmann, 1999). 

An attempted synthesis of 9-methylnaphtho[crf]oxepine-2-one 494 by heterocyclization of 8-acetyl-1-naphthoic acid 491 (R = Me, R = H) has failed. In acidic medium or on heating acid 491 to 150°C, as well as under formation conditions for the acid chloride or ester from acid 491, 2-acetylacenaphthene-l-one 495 is obtained (79ZOR1562). A synthesis of tribenzo[c]oxepine derivatives 499 and 501 has been described as resulting from heterocyclization of the products of reduction (498) or oxidation (500) of 4-formyl-5-carboxyphenanthrene 497. The latter compound was obtained on ozonolysis of pyrene 496 [71JCS(C)729]. 

In the case of pyrene, there are two sextets and two fixed double bonds similar to the phenanthrenic double bond. In agreement with this argument and with the result for phenanthrene, co-ozonolysis of pyrene with formaldehyde or acetyl cyanide afforded the expected normal ozonide 114 and the cross-ozonide 115 with an aldehydic group. In a separate co-ozonolysis of 115 with vinyl acetate, diozonides 116 were prepared. No cross-ozonide was obtained in the presence of benzoyl cyanide, which afforded only the normal mono-ozonide 114 (Scheme 36 and Table 15). 

The World Health Organization recommends that the total concentration of PAHs in drinking water should not exceed 10ngL 1. The ozonation of the above two PAHs, plus benzo[ ]pyrene, in water solution was examined experimentally as a function of pH and concentration of radical scavenger (tert-butanol). Acidic pH values accelerate the disappearance of the PAHs. At pH 2, the direct ozonolysis rates were approximately 33000M-1 s-1 for benzopyrene, 11 000 M-1 s 1 for chrysene, and 45 M 1 s 1 for fluorene <2004MI453>. 

The direct mutagenicity of the reaction mixture was shown to be caused by the presence of the benzo(a)pyrene-4,5-epoxide in small yield (Pitts et al. (70)). This compound is a photosensitive intermediate of the ozonolysis and is known as a DNA-binding metabolite in biological systems (Grover and Sims (95a). 

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