Benz anthracene structure

PAHs also generally have well-structured emission spectra (see Figs. 10.6-10.10) and relatively large fluorescence quantum yields. For example, in degassed n-heptane at room temperature, the fluorescence quantum yields are as follows fluoranthene, 0.35 benz[ ]anthracene, 0.23 chrysene, 0.18 BaP, 0.60 BeP, 0.11 and benzo[g/zi]perylene, 0.29 (Heinrich and Giisten,1980). Cyclopenta[crf]pyrene, however, does not fluoresce. 

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 synthetic procedure described is based on that reported earlier for the synthesis on a smaller scale of anthracene, benz[a]anthracene, chrysene, dibenz[a,c]anthracene, and phenanthrene in excellent yields from the corresponding quinones. Although reduction of quinones with HI and phosphorus was described in the older literature, relatively drastic conditions were employed and mixtures of polyhydrogenated derivatives were the principal products. The relatively milder experimental procedure employed herein appears generally applicable to the reduction of both ortho- and para-quinones directly to the fully aromatic polycyclic arenes. The method is apparently inapplicable to quinones having an olefinic bond, such as o-naphthoquinone, since an analogous reaction of the latter provides a product of undetermined structure (unpublished result). As shown previously, phenols and hydro-quinones, implicated as intermediates in the reduction of quinones by HI, can also be smoothly deoxygenated to fully aromatic polycyclic arenes under conditions similar to those described herein. 

Danishefsky et al. succeeded in preparing the benz[a] anthracene core structure 111 of angucycline antibiotics by performing a benzannulation reaction with the cycloalkynone 109 [69]. Deprotonation of the naphthoquinone 110 with DBU yields the desired anthraquinone 111 (Scheme 49). 

Scheme 49 Synthesis of the benz[a] anthracene core structure...

A second vital observation was made when Mayneord, a physicist, joined in the research effort and decided to examine the conspicuous fluorescence of the many carcinogenic distillates present in Kennaway s laboratory. He found that most of the carcinogenic tars exhibited a common fluorescence spectrum (X 400, 418 and 440 nm) but, in subsequent studies with Hieger, none of the hydrocarbons available at that time exhibited these spectral characteristics (7 ). The spectrum of benz[a]anthracene was found to be similar to, but of longer wavelength than, that of the carcinogenic preparations but this similarity directed Kennaway s attention to Clar s report of the synthesis of dibenz[a hjanthracene (10). Tumors were obtained when this hydrocarbon was repeatedly painted on to mice and thus it was established that the properties necessary to elicit tumors in animals were contained within the structure of a single pure chemical compound (11). 

Our understanding of the importance of steric factors was initiated by structure determinations by X-ray diffraction techniques of two trans-diols of benz[a]anthracene (89), XVI and XVII, shown in Figure 12. The crystal structures showed diequatorial... 

Figure 12. The structures of two trans diols of benz[a]anthracene showing the diequatorial conformation of the unhindered 10,11-diol and the diaxial conformation of the hindered 1,2-diol. These trends persist in solution where the 10,11-diol exists as an equilibrium of 30% axial and 70% equatorial conformers (that is, the ring is flexible) on the other hand the 1,2-diol is 100% diaxial even in solution. If the 1-hydroxyl group were equatorial it would "bump" into the hydrogen atom on Cl2.

The sample sizes collected by our PMj 5 sampling systems are insufficient to conduct detailed chemical analyses. However, available data for size-fractionated fine particulate matter indicates that PAH quinones, including 1,4-naphthoquinone, 5,12-naphthacenequinone, benz[a]anthracene-7,12-dione, and anthracene-9,10-dione, are important organic components (41, 42). The detection of these molecular species that are similar in structure to semiquinone-type radicals supports the assignment of our EPR signals. 

Anthracene and certain other polynuclear hydrocarbons have long been known to dimerize readily on photolysis the formation of such dimers [Eq. (68)] is also the result of 1,4-addition, and is believed to involve a singlet excited state. With substituted anthracenes, the head-to-head dimer is generally formed, although there are exceptions to this rule. Dimerizations probably of a similar nature, have been reported for a number of azaanthracenes including 1-azaanthra-cene,270,271 2-azaanthracene,271 and benz[6]acridine.272 The precise structure of these dimers in uncertain. 

In practice, we have utilized it for the analysis of molecular systems comprised of 3 to 5 fused benzene rings. Our discussion in this document is limited to the following compounds phenanthrene, anthracene, fluoranthene, pyrene, benz(a)anthracene, chrysene, benzo(e)pyrene, benzo(a)pyrene, and dibenz(a,h)anthracene. The structures for these compounds are presented in Table I. It is important to note that the method has also been adapted to the determination of several other PAH compounds (e.g., benzo(c)phenanthrene, perylene, 3-methylcholanthrene, carbazole, 7H-dibenzo(c,g)carbazole, and indeno(l,2,3-cd)pyrene). 

Figure 22.16. Structures of the dihydrodiol epoxides of several polycyclic aromatic hydrocarbons. (A) Benzo[a]pyrene-fnms-7,8-dihydrodiol-9,10-epoxide (BPDE) (B) benz[a]anthracene-frara-8,9-dihydrodiol-10,11-epoxide (BADE) (C) benzo[fe]fluoranthene-fnms-9,10-dihydrodiol-ll, 12-epoxide (BFDE) (D) chrysene-fnms-l,2-dihydrodiol-3,4-epoxide (CDE) and (E)dibenzo[a,/]pyrene-fra ,s-ll,12-dihydrodiol-13,14-epoxide (DBPDE). Only one enantiomer for each dihydrodiol epoxide is shown.

Some models may appear very different from the objects they represent-Such "abstract" models may be rewarding because they are likely to reveal qualities of a system that may not even be suspected- There are numerous worthy models and modeling in chemistry relating to structures, reactions, transition states, spectra, bulk or local properties of large molecules, etc- Fig- 1 shows how a standard organic chemistry text [l] "models" the molecule of benz[a]anthracene and various other modelings of this benzenoid system at various levels of abstaction-... 

Figure 2 Structures of polycyclic aromatic hydrocarbons. Symbols used in this figure and text Na (naphthalene). Ay (acetonaphthylene), Ae (acenaphthene), FI (fluorene). Pa (phenanthrene), A (anthracene), MPa (methyl phenanthrene), F (fluoranthene), Py (pyrene), BaA (benz(a)anthracene), Chy (chrysene), BlcF (benzo(k)fluoranthene), BbF (benzo(b)fluoranthene), BaP (benzo(a)pyrene), IP (indenopyrene), B(ghi)Pe (benzo(ghi)perylene), and Db(ah)A...

Klein, C. L., Stevens, E. D., Zacharias, D. E., and Glusker, J. P. 7,12-dimethyl-benz[ a [anthracene refined structure, electron density distribution, and endo-peroxide structure. Carcinogenesis 8, 5-18 (1987). 

Foster, R., Iball, J., Scrimgeour, S. N., and Williams, B. C. Crystal structure and nuclear magnetic resonance spectra of a 1 1 complex of benz[ a ]anthracene and pyromellitic dianhydride (benzene-1,2,4,5-tetracarboxylic dianhydride). J. Chem. Soc., Perkin Trans. II, 682-685 (1976). 

In the laboratory of S.J. Danishefsky, the synthesis of antibiotics containing the benz[a]anthracene core structure was... 

Animal studies with structurally related polynuclear aromatic hydrocarbons (PAHs), such as benzo(d )py-rene, benz(it)anthracene, and 3-MC, confirmed that intestinal transport readily occurs primarily by passive diffusion after oral dosing. From the partitioning parameters, the rate-limiting step involves solvation of transfer species in the interfacial water at the phospholipid surface. 

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