Polycyclic heteroaromatic hydrocarbons

The flash evaporation pyrolysis gas chromatography method [16] as described in section 11.1.4 for the determination of polycyclic aromatic hydrocarbons, haloorganics, aliphatic hydrocarbons, heteroaromatics, elemental sulphur and pyrolysis products of synthetic polymers in soils has also been applied to non-saline sediments. 

Dewar MJS, Rogers H (1962) Pi-complexes. 2. Charge transfer spectra of pi-complexes formed by tetracyanoethylene with polycyclic aromatic hydrocarbons and with heteroaromatic boron compounds. J Am Chem Soc 84 395... 

The rate of success falls whenever these conditions are not met. For example, condition (1) is not always satisfied in aromatic substitution reactions. The FOs of polycyclic aromatic hydrocarbons are not well separated from the other MOs,66 so subjacent orbital control may intervene. Particular care should be taken with non-alternant hydrocarbons because they tend to react under charge control. This is even truer in heteroaromatic systems (cf. Exercise 15, p. 119, and Exercise 16, p. 121), where Hiickel... 

Mercury. - Cadmium. - Polycyclic Aromatic and Heteroaromatic Hydrocarbons. - Fluorocarbons. -Chlorinated Paraffins. - Chloroaromatic Compounds Containing Oxygen. - Organic Dyes and Pigments. - Inorganic Pigments. - Radioactive Substances. - Subject Index. 

Cyclic Polyenes This group of chromogens are represented by polycyclic aromatic and heteroaromatic hydrocarbons. One such example isThermoplast Brilliant Yellow 10G (9) which is a green fluorescent dye. 

As was true for the hydrogens attached to heteroaromatic rings and polycyclic aromatic hydrocarbons (Section 6.5), the carbons of such rings also appear in the aromatic region. Some examples are given below,1 and these can be used as base values when calculating chemical shifts for substituted derivatives of these compounds ... 

Such polycyclic aromatic hydrocarbons as anthracene or heteroaromatics as acridine, phenazine and 2,4,5-triphenyl oxazole act as Jt-donors for the Jt-acceptors AN and alkyl methacrylates [50-53]. Again, the interaction of the donor excited states with vinyl monomers leads to exciplex formation. But, the rate constants (k ) of these quenching processess are low compared to other quenching reactions (see Table 1). The assumed electron transfer character is supported by the influence of the donor reduction potential on the k value (see Table 1), and the detection of the monomer cation radicals with the anthracene-MMA system. Then, the ion radicals initiate the polymerization, the detailed mechanism of which is unsolved,... 

Figure 4. Relationship between force constants (Fee) and intemuclear carbon-carbon distance (toc. Our results, aromatic polymers heteroaromatic polymers, inter-ring x, and intra-iing . Polyacetylene o (Ref. 2S) Polycyclic aromatic hydrocarbons A (Ref. 26).

Zander, M. Polycyclic Aromatic and Heteroaromatic Hydrocarbons In Hutzinger, O., Ed. The Handbook of Environm. Chem., 3/A, Springer-Verlag, Berlin/Heidelberg (1980)... 

In 1997, Bird studied the absolute hardness as a criterion for heteroaromaticity. In this study, it was found that good correlations existed between the Zhou and Parr hardness values and the REPE values for polycyclic benzenoid hydrocarbons but that the correlation was not good when heterocyclic compounds were included. This was also confirmed in a 1998 study by Bean, where only a very low correlation between the HOMO—LUMO gap, on one hand, and geometric, energetic, and other delocalization measures was found for a series of five-membered heteroaromatic compounds. However, Bird suggested using the reformulation of the hardness in terms of molar refractivity as suggested in the work of Komorowski ... 

Bioremediation is the reversing of pollution with the aid of microorganisms. In the marine environment, the two main types of pollutants are petroleum products, especially polycyclic aromatic hydrocarbons (PAHs), and heavy metals (Juhasz and Naidu, 2000 Vidali, 2001). For petroleum derivatives must be found bacteria that are capable of gradually degrading aromatic and heteroaromatic systems... 

Flash-vacuum pyrolysis has been utilized to synthesize complex thiophene-containing polycyclic hydrocarbons from alkynyl-substituted thiophenes and chlorovinyl-substituted thiophenes <99TL2789>. For example, the bowl-shaped heteroaromatic thiophene 92 was prepared by flash-vacuum pyrolysis of benzotrithiophene 91 <99CC1859>. 

The trend observed with the polycyclic hydrocarbons (see preceding section), namely that the product radical anions (ArNu ) are more stable than those derived from the simple benzene analogs, is even more evident with the heteroaromatic substrates and, as a consequence, fragmentation processes are minimized.41 For example, 2-chloroquinoline is the only substrate of many studied to undergo a substitution reaction with PhCH2S- ion without fragmentation of the benzyl-S bond,103 and to react with diphenyl-arsenide ion without scrambling of the aryl moieties.25... 

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