Chrysene, structure

The phenanthrene and chrysene structures could be derived from cyclic terpenoids such as abietic acid, sterols, and hopanes (34). Although tri-phenylene, which has the highest resonance energy among the four-ring catacondensed PAHs (35), was not present in the SRC II HD at a significant level, this compound was found in the coal tar which is a higher temperature... 

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bond, such as o-naphthoquinone, since an analogous reaction of the latter provides a product of undetermined structure (unpublished result).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. 

Benzo[c]phenanthridine alkaloids are widespread in Papaveraceae, Fumariaceae, and Rutaceae. Fagaridine (118), the structure of which had to be revised, is a derivative of the unknown 5-methyl-benzo[c]phenan-thridine-8-olate (119) which is isoconjugate with the 2-methyl-chrysene anion (Scheme 43). Thus, Fagaridine is a member of class 1 of conjugated heterocyclic mesomeric betaines, which are isoconjugate with odd alternant hydrocarbon anions. 

Figure 4. Views of DMBA, BP, 5,6-dimethylchrysene, 5,12-dimethyl-chrysene and 5-methyl chrysene. These illustrate the distortions that occur as a result of steric effects. These and many subsequent representations of molecular structure are stereoviews and may be viewed with stereoglasses alternatively the reader can focus his eyes on the two images until an image between them begins to form and then allow his eyes to relax until the central image becomes three-dimensional. This process calls for patience and may take a minute or so. The reader who does not wish to do this may simply inspect one of the two diagrams for each structure.

Figure 1. Structures and numbering of benzo[h]quinoline (BhQ), benzoff)quinoline (BfQ), Benzofc]phenanthridine (BcPhen) and their carbon analogues phenanthrene (Phe) and Chrysene (Chry). Adapted from Reference 26.

A set of n = 209 polycyclic aromatic compounds (PAC) was used in this example. The chemical structures have been drawn manually by a structure editor software approximate 3D-structures including all H-atoms have been made by software Corina (Corina 2004), and software Dragon, version 5.3 (Dragon 2004), has been applied to compute 1630 molecular descriptors. These descriptors cover a great diversity of chemical structures and therefore many descriptors are irrelevant for a selected class of compounds as the PACs in this example. By a simple variable selection, descriptors which are constant or almost constant (all but a maximum of five values constant), and descriptors with a correlation coefficient >0.95 to another descriptor have been eliminated. The resulting m = 467 descriptors have been used as x-variables. The y-variable to be modeled is the Lee retention index (Lee et al. 1979) which is based on the reference values 200, 300, 400, and 500 for the compounds naphthalene, phenanthrene, chrysene, and picene, respectively. 

Photolytic. Based on structurally related compounds, chrysene may undergo photolysis to yield quinones (U.S. EPA, 1985) and/or hydroxy derivatives (Nielsen et al, 1983). The atmospheric half-life was estimated to range from 0.802 to 8.02 h (Atkinson, 1987). Behymer and Hites (1985) determined the effect of different substrates on the rate of photooxidation of chrysene using a rotary photoreactor. The photolytic half-lives of chrysene using silica gel, alumina, and fly ash were 100, 78, and 38 h, respectively. 

Diindeno[l,2,3,4-de l, 2, 3, 4 - tn(7p]chrysene (116a) can be considered as a symmetrical cap that was cut out of the fullerene Cgo molecule. This compound and its alkylated derivative (116b) react with Li to yield dianions and tetraanions in solution. The standard two-dimensional NMR techniques are insufficient for the structural assignment of the spectra. A special carbon edited NOESY approach was developed for total assignment of the spectra of the neutral species and the dianion. DFT calculations aided in the assignment of the tetraanion spectra ... 

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. 

Chia and Simmons388 calculated the resonance energies (ER)20 of four mono- and dibenzotetraazapentalenes (Scheme 24). Values are comparable with those of o-condensed aromatic systems (naphthacene, ER = 110 kcal mol-1 chrysene, ER = 116.5 kcal mol-1), and, like these carbocyclic systems, angularly-shaped molecules are more stable than linear ones. HMO calculations of delocalization energies (DE) show that the tetraazapentalene structure 15 is more stable than the tetra-azacyclooctatetraene valence isomer 324 (Scheme 14, Section IV,B,2) whether 324 is planar or tub-shaped. Calculations of electrophilic reactivity (Section IV,C,4,d), electronic spectra (by the PPP method employing all singly excited configurations), and bond orders have been carried out, and they confirm the aromatic nature of these systems. 

Chrysene is an aromatic hydrocarbon found in coal tar. Convert the molecular model to a Lewis structure in which all of the rings correspond to Kekule formulas of benzene. 

Compounds such as phenanthrene, chrysene, and pyrene, in which the aromatic rings are fused in an angular manner, have complex electronic spectra with considerable fine structure. The Xmax values normally are at shorter wavelengths than those of their linear isomers. 

The benzo[ a Jphenanthridine ring system resembles the structure of chrysene, another carcinogen. It is intriguing to note that the carcinogenicity of chrysene is drastically increased by the addition of a methyl group at position 5 of that molecule [86-90]. The position of this methyl group (see structure 9) corresponds to that in the aforementioned benzophenanthridine alkaloids. 

The crystal structure of chrysene has been accurately analysed by Bums and Iball (1960). The coordinates of the carbon and hydrogen atoms and the anisotropic thermal vibrations of the carbon atoms were determined by three-dimensional least-squares refinement, as well as by three-dimensional Fourier and difference Fourier syntheses, a total of 1037 planes being employed. The value of the residual, R, is 0-076. 

The most stable resonance form is the one that has the greatest number of rings that correspond to Kekule formulations of benzene. For chrysene, electrons are moved in pairs from the structure given to generate a more stable one ... 

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