Aromatic hydrocarbons directing groups

Jung, H., A. U. Shaikh, R. H. Heflich, and P. P. Fu, Nitro Group Orientation, Reduction Potential, and Direct-Acting Mutagenicity of Nitro-Polycyclic Aromatic Hydrocarbons, Environ. Mol. Mutagen., 17, 169-180 (1991). 

In the EU Directive on Drinking Water Quality [35], 23 individual chemical parameters have specific limits together with two group limits for polycyclic aromatic hydrocarbons and pesticides. In the case of pesticides, no individual pesticide is permitted to exceed 0.1 pgL , and pesticides in total should not exceed 0.5 xgL" . These limits were a compromise, the original demand having been for a zero limit for pesticides in drinking water, and these standards were set, in 1998, as the effective analytical detection limit. The revision of this directive and its application to pharmaceuticals is currently under discussion, although it seems unlikely that specific limits will be set for individual pharmaceuticals [36]. 

Analytical Properties Resolution of several enantiomers of polycyclic aromatic hydrocarbons, for example, chrysene 5,6-epoxide, dibenz[a,h]anthracene 5,6-epoxide, 7-methyl benz[a]anthracene 5,6-epoxide resolution of barbiturates, mephenytoin, benzodiazepinones, and succinimides direct separation of some mono-ol and diol enantiomers of phenanthrene, benz[a]anthrene, and chrysene ionically bonded to silica gel, this phase provides resolution of enantiomers of c/s-dihydroidiols of unsubstituted and methyl- and bromo-substituted benz[a]anthracene derivatives having hydroxyl groups that adopt quasiequatorial-quasiaxial and quasiaxial-quasiequatorial conformation Reference 31-35... 

Mobile phases are usually binary or ternary mixtures of solvents. Selectivity is affected mostly by mobile phase composition rather than strength, and peak shape and retention are both influenced by the addition of organic modifiers.101 Some compounds naturally have 77-donor or 77-acceptor groups and can be resolved directly. In many cases, however, introduction of 77-donating groups by derivatization steps is necessary. Figure 2.20 shows the proposed three-point interaction of 3-aminobenzo[a]pyrene, a polycyclic aromatic hydrocarbon (PAH), with a Pirkle-type stationary phase.111 Two possible interactions are illustrated, showing the best orientations for maximum interaction. 

Direct photolysis processes on the surface of airborne particulate matter can be important sinks of sunlight-absorbing compounds (see [28] for a recent review by our group on this subject), and in particular of polycyclic aromatic hydrocarbons (PAHs) [11]. The particles can protect adsorbed substrates against reaction with species such as OH and N03 from the gas phase, and enhance the relative role of direct photolysis. However, it should be considered that black carbonaceous... 

Nitro-polycyclic aromatic hydrocarbons, referred to as nitro-aromatic compounds hereafter, constitute one of the most troubling classes of environmental pollutants. They are derivatives of polycyclic aromatic hydrocarbons (PAHs) that contain two or more fused aromatic rings made of carbon and hydrogen atoms and at least one nitro group (Fig. 10.1). Concern about these compounds arises partly from their ubiquity nitro-aromatic compounds are released to the environment directly from a variety of incomplete combustion processes [1] and are also formed in situ by atmospheric reactions of PAHs [2]. Nitro-aromatic compounds have been found in grilled food in diesel, gasoline, and wood-smoke emissions and are commonly found in atmospheric particulate matter, natural waters, and sediment [3-8],... 

Exposure of cells to carcinogens may result in the formation of DNA adducts varying in size from methyl groups to bulky structures, such as metabolites of polycyclic aromatic hydrocarbons and aromatic amines. In vivo, these adducts usually are removed enzymatically and at different rates from the DNA. Because the liver is the main site of activation of chemical carcinogens, the DNA of this organ usually forms more adducts. Direct detection and measurement of DNA damage are thus possible, in principle, by detection and measurement of the bound adduct. Because the number of adducts is usually extremely small, very sensitive methods cure required for their measurement. 

On the other hand, the indirect type of ozonation is due to the reactions of free radical species, especially the hydroxyl radical, with the organic matter present in water. These free radicals come from reaction mechanisms of ozone decomposition in water that can be initiated by the hydroxyl ion or, to be more precise, by the hydroperoxide ion as shown in reactions (4) and (5). Ozone reacts very selectively through direct reactions with compounds with specific functional groups in their molecules. Examples are unsaturated and aromatic hydrocarbons with substituents such as hydroxyl, methyl, amine groups, etc. [45,46],... 

Metal alkyl. A compound of a metal with directly linked aliphatic or aromatic hydrocarbon radicals, as in zinc dimethyl, Zn(CHs)2, or mercury diphenyl, Hg(C6H5)2. A normal alkyl has sufficient organic groups to satisfy the normal valence of the metal and therefore contains no halogen or other substituent in place of organic radicals. 

Although this obituary is primarily concerned with Hirst s achievements in carbohydrate chemistry, it must be emphasized that the Edinburgh laboratories contained research groups active in other branches of organic chemistry. The largest of these dealt with polycyclic, aromatic hydrocarbons, and was directed by Dr. (later Professor) Neil Campbell, who, throughout the period, was an effective lieutenant in... 

An apolar aprotic solvent is characterized by a low relative permittivity (sr < 15), a low dipole moment [ju < 8.3 10 Cm = 2.5 D), a low value ca. 0.0... 0.3) cf. Table A-1, Appendix), and the inability to act as a hydrogen-bond donor. Such solvents interact only slightly with the solute since only the non-specific directional, induction, and dispersion forces can operate. To this group belong aliphatic and aromatic hydrocarbons, their halogen derivatives, tertiary amines, and carbon disulfide. 

The direct reaction between a metal carbonyl and an aromatic hydrocarbon often leads to the replacement of 2 or 3 carbonyl groups yielding arene complexes. Complexes of the type [(arene)V(CO)4][V(CO)g] 50), (arene)Cr(CO)g 327), and (arene)Fe(CO)3 281) have been prepared in this manner. Carbonyl metal halide complexes have also been observed to react with aromatic hydrocarbons in the presence of AlClg yielding cationic arene derivatives, e.g. 71, 104, 448),... 

The effect of crown ethers on the selectivity of nitration of aromatic hydrocarbons and anisole has been studied with a mixture of trifluoroacetic anhydride and tetrabutylammonium nitrate as nitration agent. The largest effects on selectivity have been observed with 21-crown-7, which causes ortho-para-directing groups to act essentially as para-directing groups. ... 

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