Chrysene Subject

Boeda et al. (1996) identified bitumen on a flint scraper and a Levallois flake, discovered in Mousterian levels (about 40 000 BP) at the site of Umm el Tlel in Syria. The occurrence of polyaromatic hydrocarbons such as fluoranthene, pyrene, phenanthrenes and chrysenes suggested that the raw bitumen had been subjected to high temperature. The distribution of the sterane and terpane biomarkers in the bitumen did not correspond to the well-known bitumen occurrences in these areas. In other studies of bitumen associated with a wide variety of artefacts of later date, especially from the 6th Millennium BC onwards, molecular and isotopic methods have proved successful in recognizing different sources of bitumen enabling trade routes to be determined through time (Connan et al., 1992 Connan and Deschesne, 1996 Connan, 1999 Harrell and Lewan, 2002). 

Chrysene (5.0 mg/L) in a methanol-water solution (1 1 v/v) was subjected to a high pressure mercury lamp or sunlight. Based on a rate constant of 7.07 x 10 Vmin, the corresponding half-life is 1.63 h (Wang et al, 1991). 

Intramolecular cyclisation of a 4-arylbutanoic acid system is also an important step in a convenient synthesis of the polycyclic system, chrysene, which is formulated and described in Expt 6.12. Here, methyl cinnamate is first subjected to reductive dimerisation to give methyl meso-ft,y-diphenyladipate, which is accompanied by some of the ( + )-form. The meso isomer (16) is the most easily isolable and cyclisation occurs smoothly in sulphuric acid to yield the diketone 2,1 l-dioxo-l,2,9,10,ll,18-hexahydrochrysene, which is obtained as the trans form (17) as shown in the following formulation. Clemmensen reduction of this ketone followed by dehydrogenation (in this case using selenium) completes the synthesis of chrysene. 

Direct irradiation at 254 nm of 1-phenylpropene 93a in cyclohexane affords a Z/E mixture in a ratio of 65 35 [223], whilst photosensitized isomerization of 93a gives (Z/E)pss ratios of 55 45 and 88 12 upon benzophenone and chrysene sensitization, respectively (Sch. 37). Similarly, a variety of P-alkylstyrenes has been subjected to triplet sensitization [224,225]. Upon direct irradiation of ( )-P-bromo-P-nitro-styrenes, the (Z)-isomers are obtained in 40-50% yield, but the major... 

Being interested here in the volatile components of coffee aroma, we shall arbitrarily limit the list of the aromatic hydrocarbons to tricyclic structures. The higher fused polycyclic hydrocarbons (fluoranthene [206-44-0], pyrene [129-00-0], chrysene [218-01-9], benz[ ]anthracene (1,2-benzanthracene) [56-55-3], benz[< ]acephenanthrylene (3,4-benzofluoranthene) [205-99-2], benzo[ ]pyrene (3,4-benzopyrene, 3,4-BP) [50-32-8], benzo[e]pyrene (1,2-benzopyrene) [192-97-2], perylene [198-55-0], benzo[g,/i,/]perylene (1,12-benzopyrene) [191-24-2], and dibenz[ ,//]anthracene (1,2,5,6-dibenzanthracene) [53-70-3]) cannot be considered as a part of the aroma. However, as some of these, specially benzo[o pyrene, are known for carcinogenic properties, they have been particularly analyzed in food subject to roasting or smoke-curing. 

The tobacco smoke PAH references cited in Table I.E-6 are not necessarily all that are available, particularly for those PAHs such as B[a]P and DB[fl,ft]A that have been the subject of much research and discussion for over half a century. In most cases, included is a reference to the publication or presentation by the investigator(s) who hrst reported a particular PAH in MSS. References of articles and/or presentations on specihc PAHs that contained evidence later criticized are included plus references to the misinterpretations or errors. The criticism by Fieser (1181) in 1957 of the shortcomings of the evidence (55-57, 592-594, 820) supposedly indicating the presence of B[fl]P in cigarette smoke has already been mentioned. Two other notable situations involved l,2-dihydrobenz[/] aceanthrylene (cholanthrene) and dibenzo[ /e/p]chrysene (formerly named dibenzo[fl,/]pyrene, initially 1,2,3,4-dibenzopyrene). These two PAH identihcahons, based solely on UV spectral data, were found to be incorrect. In their study, Rodgman and Cook (3273) incorrectly dehned a PAH as 1,2-dihydrobenz[/]aceanthrylene (cholanthrene). In the massive study by USDA personnel on the identihcation of MSS PAHs,... 

PROBABLE FATE photolysis very little specific data, but photolysis may claim some of the dissolved compound, atmospheric and aquatic photolytic half-life 4.4-13 hrs, subject to near surface, direct photolysis with a half-life of 4.4 hrs, if released to air, it will be subject to direct photolysis, although adsorption may affect the rate, reaction with photochemically produced hydroxyl radicals gives an estimated half-life of gas phase crysene of 1.25 hrs oxidation chlonne and/or ozone in sufficient quantities may oxidize chrysene, photooxidation half-life in air 0.802-8.02 hrs hydrolysis not an important process volatilization probably too slow to compete with adsorption as a transport process, will not appreciably evaporate sorption adsorption onto suspended solids and sediment is the dominant transport process if released to soil or to water, expected to adsorb very strongly to the soil biological processes short-term bioaccumulation, metabolization and biodegradation are the principal fates... 

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