Polycyclic aromatic compounds naphthalene

The Huckel rule is strictly applicable only to monocyclic compounds, but the genera] concept of aromaticity can be extended beyond simple monocyclic compounds to include polycyclic aromatic compounds. Naphthalene, with two... 

The Hiickel rule is strictly applicable only to monocyclic compounds, but the general concept of aromaticity can be extended beyond simple mono-cyclic compounds to include polycyclic aromatic compounds. Naphthalene, with two benzene-like rings fused together, anthracene, 1,2-benzpyrene, and coronene are all well-known compounds. Benzolalpyrene is particularly interesting because it is one of the cancer-causing substances that has been isolated from tobacco smoke,... 

Comparison of data in Tables 1 and 2 shows that the addition of 0.05% Bi to Pt-Re catalysts leads to an increase of n-hexane conversion and benzene yield from 82 to 93%, and from 47 to 68%, respectively. Maximum toluene yield decreases under these conditions from 29 to 21%. Ci-Cs hydrocarbons were not found in the products, but there were polycyclic aromatic compounds (naphthalene, anthracene, etc.). Their amounts were observed to increase with the increase in reaction temperature up to 650°C. The appearance of these products has been confirmed by ER-spectroscopy and chromatomassspectroscopy methods. 

Carbonaceous materials are obtained via heat treatment from various sources, including coal, liquefied coal, coke, petroleum, resins, carbon blacks, paraffins, olefins, pitch, tar, polycyclic aromatic compounds (naphthalene, biphenyl, naphthalene sulfonic acid, anthracene sulfonic acid, phenanthrene sulfonic acid, etc.), polymers (polyethylene, polymethylacrylale, polyvinyl chloride, phenol resin, polyacrylonitrile, etc.) [99-101J. This kind of fluids is claimed to. show a strong ER effect, low electric power consumption and excellent durability [101]. Several publications addressed the ER effect and physical properties of carbonaceous ER fluids [102-104]. 

Dewar and his co-workers, as mentioned above, investigated the reactivities of a number of polycyclic aromatic compounds because such compounds could provide data especially suitable for comparison with theoretical predictions ( 7.2.3). This work was extended to include some compounds related to biphenyl. The results were obtained by successively compounding pairs of results from competitive nitrations to obtain a scale of reactivities relative to that of benzene. Because the compounds studied were very reactive, the concentrations of nitric acid used were relatively small, being o-i8 mol 1 in the comparison of benzene with naphthalene, 5 x io mol 1 when naphthalene and anthanthrene were compared, and 3 x io mol 1 in the experiments with diphenylamine and carbazole. The observed partial rate factors are collected in table 5.3. Use of the competitive method in these experiments makes them of little value as sources of information about the mechanisms of the substitutions which occurred this shortcoming is important because in the experiments fuming nitric acid was used, rather than nitric acid free of nitrous acid, and with the most reactive compounds this leads to a... 

Hiickel 4n -r 2 rule and, 523-524 imidazole and, 529 Indole and. 533 ions and,525-527 isoquinoline and, 533 naphthalene and, 532 polycyclic aromatic compounds and,531-532 purine and, 533... 

The reactions of the tetrahalogenobenzynes with polycyclic aromatic compounds follow the expected paths. Thus with naphthalenes 54,57) cyclo-addition at the 1,4-positions occurs even with 1,4,5,8-tetramethyl-naphthalene 64>. Thus the tetrahalogenobenzynes are only able to destroy the aromaticity of one ring to form example the compound (46). 

Polycyclic aromatic compounds, namely naphthalene, anthracene and pyrene derivatives are widely used as fluorescent probes in relevant biomolecules. 

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. 

The study of vapour-deposited organic films has been applied to a large number of molecular systems. However, most of the work has concentrated on the study of the growth and optoelectronic characteristics of planar stacking molecules such as the Pc and polycyclic aromatic compounds based on naphthalene, and perylene. In particular, PTCDA has become extensively studied. 

Lane, D. A., and H. Tang, Photochemical Degradation of Polycyclic Aromatic Compounds. I. Naphthalene, Polycyclic Aromat. Compd., 5, 131-138 (1994). 

However, it should be noted that even where kerosene heaters do not contribute significantly to particle mass concentrations, they may still be important in terms of health effects. This is because of the composition of the particles emitted, which include polycyclic aromatic compounds and other mutagenic species, as well as sulfate (Leaderer et al., 1990 Traynor et al., 1990). For example, Traynor et al. (1990) studied the emissions from unvented kerosene space heaters and identified a number of PAHs (naphthalene, phenanthrene, fluoranthene, anthracene, chrysene, and indeno[c,rf]pyrene) and nitro-PAHs (1-nitronaphtha-lene, 9-nitroanthracene, 3-nitrofluoranthene, and 1-nit-ropyrene), in addition to a host of other gaseous species. Baek et al. (1997) also reported increased levels of a number of gases indoors in homes and offices in Korea due to the use of kerosene heaters. 

INDENES, NAPHTHALENES, AND OTHER POLYCYCLIC AROMATIC COMPOUNDS... 

Two or more benzene rings fused together form a number of polycyclic benzenoid aromatic compounds, naphthalene, anthracene and phenanthrene, and their derivatives. All these hydrocarbons are obtained from coal tar. Naphthalene is the most abundant (5%) of all constituents of coal tar. 

The intercalation of polycyclic aromatic compounds into duplex DNA structures was used to develop nucleic acid-based electrochemical sensors.66 For example, the bis-ferrocene-tethered naphthalene diimide (16) was used as a redox-active intercalator to probe DNA hybridization.67 The thiolated probe was assembled on a Au electrode, and the formation of the duplex DNA with the complementary analyte nucleic acid was probed by the intercalation of (16) into the double-stranded nucleic acid structure and by following the voltammetric response of the ferrocene units (Fig. 12.17a). The method enabled the analysis of the target DNA with a sensitivity that corresponded to ca. 1 x 10-20mol. 

Isoprenoid structures for carotenoids, phytol, and other terpenes start biosynthetically from acetyl coenzyme A (89) with successive additions giving mevalonate, isopentyl pyrophosphate, geranyl pyrophosphate, farnesyl pyrophosphate (from which squalene and steroids arise), with further build-up to geranyl geranyl pyrophosphate, ultimately to a- and /3-carotenes, lutein, and violaxanthin and related compounds. Aromatic hydrocarbon nuclei are biosynthesized in many instances by the shikimic acid pathway (90). More complex polycyclic aromatic compounds are synthesized by other pathways in which naphthalene dimerization is an important step (91). 

As shown in Figure 1.14, some aromatic compounds, such as naphthalene and the polycyclic aromatic compound, benzo(a)pyrene, contain fused rings. 

Polycyclic aromatic compounds also undergo electrophilic aromatic substitution reactions. Because the aromatic resonance energy that is lost in forming the arenium ion is lower, these compounds tend to be more reactive than benzene. For example, the brotni-nation of naphthalene, like that of other reactive aromatic compounds, does not require a Lewis acid catalyst ... 

All possible interactions between the K and L groups were taken into account and Akk = 0. The definition contains a minimum number of groups and is satisfactory for most of the binary systems studied. However, it cannot take into account the structural differences which exist between position isomers. This is the case of polycyclic aromatic compounds presenting cycle position isomers or substitute position isomers. Structural differences of this type determine the gaps between the values of certain thermophysical properties of isomers, such as, for example, the fusion temperature or sublimation enthalpy. The further the temperature falls, the more these differences are accentuated. The representation of the solid-fluid (low temperature) equilibria is consequently more difficult and the model must take into account the existing structural differences. We came across this problem in the compounds such as anthracene, phenanthrene, pyrene, methylated naphthalenes, hexamethylbenzene and triphenylmethane. As it was out of the question to increase the number of groups because... 

The binuclear reagents are effective at shifting the spectra of fused ring polycyclic aromatic compounds. Compounds with no substituent groups on the rings such as naphthalene, anthracene, phenanthrene and pyrene did not exhibit specific bonding to the... 

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