Polycyclic aromatic compounds chemical classes

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. 

Considerable research effort has been directed towards the generation, detection, and isolation of oxirenes, a highly strained class of antiaromatic heterocycles <83CRV519>. Although the unsaturated oxiranes are called oxirenes, much confusion is generated by the fact that Chemical Abstracts denotes oxiranes fused onto a polycyclic aromatic compound as oxirenes also (e.g., compound (16), Figure 9 <91JHC473 . 

There are several chemical compounds found in the waste waters of a wide variety of industries that must be removed because of the danger they represent to human health. Among the major classes of contaminants, several aromatic molecules, including phenols and aromatic amines, have been reported. Enzymatic treatment has been proposed by many researchers as an alternative to conventional methods. In this respect, PX has the ability to coprecipitate certain difficult-to-remove contaminants by inducing the formation of mixed polymers that behave similarly to the polymeric products of easily removable contaminants. Thus, several types of PX, including HRP C, LiP, and a number of other PXs from different sources, have been used for treatment of aqueous aromatic contaminants and decolorization of dyes. Thus, LiP was shown to mineralize a variety of recalcitrant aromatic compounds and to oxidize a number of polycyclic aromatic and phenolic compounds. Furthermore, MnP and a microbial PX from Coprinus macrorhizus have also been observed to catalyze the oxidation of several monoaromatic phenols and aromatic dyes (Hamid and Khalil-ur-Rehman 2009). 

The NO + 03 chemiluminescent reaction [Reactions (1-3)] is utilized in two commercially available GC detectors, the TEA detector, manufactured by Thermal Electric Corporation (Saddle Brook, NJ), and two nitrogen-selective detectors, manufactured by Thermal Electric Corporation and Antek Instruments, respectively. The TEA detector provides a highly sensitive and selective means of analyzing samples for A-nitrosamines, many of which are known carcinogens. These compounds can be found in such diverse matrices as foods, cosmetics, tobacco products, and environmental samples of soil and water. The TEA detector can also be used to quantify nitroaromatics. This class of compounds includes many explosives and various reactive intermediates used in the chemical industry [121]. Several nitroaromatics are known carcinogens, and are found as environmental contaminants. They have been repeatedly identified in organic aerosol particles, formed from the reaction of polycyclic aromatic hydrocarbons with atmospheric nitric acid at the particle surface [122-124], The TEA detector is extremely selective, which aids analyses in complex matrices, but also severely limits the number of potential applications for the detector [125-127],... 

Air quality is important from both a health and a safety perspective. In the USA, the National Institute for Occupational Safety and Health (NIOSH) and the Occupational Safety and Health Administration set limits of exposure to over 2000 different chemicals or classes of respiratory irritants [11, 12], Many of the compounds that are monitored indoors are of similar interest to outdoor assessment, such as in the atmosphere and stratosphere. VOCs emitted from industrial operations are continuously monitored as required by US and local Environmental Protection Agencies. Power plants and waste incinerators are required to follow emission guidelines for harmful combustion gases, including CO and NO, as well as other combustion by-products, including polycyclic aromatic hydrocarbons, phenols, and hy-... 

Such a molecule can be stabilized by a system of delocalized Ji-electrons, which is closed into a toroid of 10 aromatic rings. Reactive sites are four CH groups, which are at the ends of this molecular tube. Such substances belong apparently to a new class of organic compounds, which is intermediate between planar polycyclic aromatic hydrocarbons and three-dimensional fullerenes, nanotubes. Quantum-chemical calculations of the electronic and spatial structure of C32H8 and some other molecules indicate that they have an increased reactivity and semiconductor properties. 

Index Chemical Chemical selected as the basis for standardization of toxicity of components in a chemical class (e.g., 2,3,7,8-tetrachlorodibenzo-p-dioxin [TCDD] for the assessment of dioxin-like compounds benzo[a]pyrene for the assessment of carcinogenic polycyclic aromatic hydrocarbons [PAHs]). 

This test uses specially constructed bacteria to detect reverse mutations. Each tester strain has enhanced sensitivity and selectivity for the classes of compounds it will pick up. Therefore, several tester strains are generally used to maximize the possibility of detecting a mutagenic compound. It is well known now that many compounds, for example polycyclic aromatic hydrocarbons, must undergo some kind of enzymatic or chemical modification before becoming reactive. Therefore, in many cases an enzyme preparation (commonly called S9) is added to the chemical in order to ensure conversion to a chemically-reactive species. 

Each particulate extract was separated into four chemical compound classes using open-bed silica gel column chromatography (1) aliphatic hydrocarbons—hexane elution, (2) polycyclic aromatic hydrocarbons—hexane benzene (1 1 v/v) elution,... 

Using this approach, methods were established for the degradation of selected compounds in the following seven classes of chemical carcinogens aflatoxins, nitrosamines, nitrosamides, polycyclic aromatic hydrocarbons, hydrazines, haloethers and aromatic amines. A first study was also set up to investigate methods of degradation of some antineoplastic agents,... 

FIGURE 32.8 Chemical class separation scheme for synthetic fuel products. HCs, hydrocarbons PACs, polycychc aromatic compounds N-PACs, nitrogen polycychc aromatic compounds 2 -PANHs, secondary nitrogen polycyclic aromatic heterocycles APAHs, amino polycyclic aromatic hydrocarbons 3 -PANHs, tertiary nitrogen polycyclic aromatic heterocycles. 

Polycyclic aromatic hydrocarbons refer to a group of over 200 chemicals (made up of varying numbers of carbon and hydrogen atoms connected in ring-like forms) that have been cited as carcinogenic and environmentally hazardous substances. They result predominantly from the incomplete combustion of organic compounds and materials (http //envirocancer.cornell.edu) [41,42]. Naphthalene is the most volatile member of this class of pollutants and is typically considered as a model compound of these molecules. 

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