Polyaromatic hydrocarbons structures

Chemicals that possess a common structural feature are called congeners. Some common examples are polychlorinated biphenyls (PCBs), polyaromatic hydrocarbons (PAHs), poly-brominated diphenylethers (PBDE) and chlorofluorocarbons (CFC). The common features... 

Hydrogen donors are, however, not the only important components of solvents in short contact time reactions. We have shown (4,7,16) that condensed aromatic hydrocarbons also promote coal conversion. Figure 18 shows the results of a series of conversions of West Kentucky 9,14 coal in a variety of process-derived solvents, all of which contained only small amounts of hydroaromatic hydrocarbons. The concentration of di- and polyaromatic ring structures were obtained by a liquid chromatographic technique (4c). It is interesting to note that a number of these process-derived solvents were as effective or were more effective than a synthetic solvent which contained 40% tetralin. The balance between the concentration of H-donors and condensed aromatic hydrocarbons may be an important criterion in adjusting solvent effectiveness at short times. 

Polyaromatic hydrocarbons (PAH) are those which exists as combined aromatic ring structures represented by naphthalene (C10Hg) ... 

Figure 16.4 Structural formulae of polyaromatic hydrocarbons—brightness organic ECL luminophores blue emissive 9,10-diphenylanthracene, green emissive 5,12-diphenylnaphtha-cene, orange emissive 5,6,11,12-tetraphenylnaphtacene (RUB), and red emissive bis-4,4 -(7,12-dipheny l)-benzo [k] fluoranthene.

Anthracene is a three-ring polyaromatic hydrocarbon (PAH) with the following structure. 

In addition to preserving structure, a soft ionization technique such as chemical ionization (Cl) has a further advantage in ms /ms. By minimizing the number of ions generated from each molecular species the complexity of the (ionic) mixture which has to be separated is minimized. It is for this reason that electron impact ionization is seldom a good choice for ms/ms, although for compounds such as the polyaromatic hydrocarbons which give predominantly one ion in their electron impact spectra this complication is minimized. 

The ring-number tabulations in Tables II, III, IV, and V are satisfactory for a simplified summary of composition and comparison. The typical Co-Mo or Ni-Mo catalyst commonly used for upgrading will saturate many of the multiple aromatic rings, depending upon severity and activity, but frequently not the last ring of a condensed-ring polyaromatic. Thus, the total number of rings is a measure of the complexity of the hydrocarbon structure. As noted earlier, more detailed data on the distribution of hydrocarbon types in these liquids are available when needed. 

M. Yuan and P. C. Jurs, Toxicol. Appl. Pharmacol., 52, 294 (1980). Computer-Assisted Structure-Activity Studies of Chemical Carcinogens A Polyaromatic Hydrocarbon Data Set. 

D. F. V. Lew s, Xenobiotica, 17,1351 (1987). Molecular Orbital Calculations and Quantitative Structure-Activity Relationships for Some Polyaromatic Hydrocarbons. 

In addition to the biochemistry introduced in this chapter, a great deal of emphasis is placed on the determination of the activity of a compound by an analysis of its structure. Quantitative structure-activity relationships (QSAR), used judiciously, have the ability to help set testing priorities and identify potentially toxic materials in mixtures. Heavily reliant upon the quality of the toxicity data discussed in Chapter 4, these methods use sophisticated statistical techniques or analysis of interaction of a toxicant with the receptor to estimate toxicity. A method that uses structure-activity relationships coupled with availability and an assumed additive model for toxicity is presented to estimate the risk due to polyaromatic hydrocarbons (PAHs). 

Another important and well-known aspect in structure/response correlation studies is the concept of congenericity. Congenericity is a fuzzy concept related to the structures of molecules in a data set. With respect to some molecular structural characteristics, chemical analogues can be considered congeneric if their structural differences are the interesting part of the study. Monosubstituted benzenes, polychlorobiphenyls, triazines, and polyaromatic hydrocarbons are all examples of the families of congeneric compounds. 

Attention in fundamental and applied research on shape-selective catalysis has been largely focused on open-chain and monocyclic compounds. However, we have observed the rapid developments in polymer materials containing multi-ring aromatic units and the need to develop the monomers and other specialty chemicals from polyaromatic hydrocarbons that are rich in coal-derived liquids [Song and Schobert, 1993, 1996]. Scheme 1 shows the structures of some advanced polymer materials containing aromatic ring in the main-chain. 

The current information on size, structure and chemistry of diamond nuclei is primarily speculative, with a small number of conclusive results. It has been proposed that diamond nuclei may be multiple twinned particles, likely containing some of the structures related to the boat-boat conformer of bicyclodecane (10 carbon atoms) or boat-chair-chair-boat tetracyclo octadecane (18 carbon atoms) within higher molecular weight compounds formed by the partial hydrogenation of graphitic or polyaromatic hydrocarbons. The diameter of a critical nucleus of diamond is presumably around 3 nm. 

Helicenes are extended fused polyaromatic hydrocarbons that have a helical or screw-shaped structure. 

It s been recognized for a long time that certain structural features can predispose a compound to mutagenicity. Think mutagen, and the words nitroso and polyaromatic hydrocarbons (PAHs) will likely come to mind. In the mid 1980s Dr. John Ashby introduced alerts to structural features associated with carcinogens. More recently a nice structural analysis of over 4000 compounds for which Ames test data were available was... 

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