Polycyclic aromatic hydrocarbons cation

Rodgers et al. [85] identified soil surface-bound polycyclic aromatic hydrocarbons through the use of real-time aerosol mass spectrometry in two NIST standard research material soils (Montana SRM 2710 and Peruvian SRM 4355), each contaminated separately with three common petroleum hydrocarbons (diesel fuel, gasoline and kerosene). This method required no sample preparation. Direct laser desorption/ionisation mass spectrometric analysis of individual soil particles contaminated with each of the petroleum hydrocarbons at three different contamination levels (0.8,8, and 80 ppth (wt/wt)) yielded detectable polycyclic aromatic hydrocarbon cation distributions that ranged from m/z 128 to 234, depending on the fuel contaminant. The same analysis... 

Polycyclic aromatic hydrocarbons Silica gel G Monovalent oxidation of the iodine complexes via radical cations yields dimeric or tetrameric aromatics [16]... 

In complex organic molecules calculations of the geometry of excited states and hence predictions of chemiluminescent reactions are very difficult however, as is well known, in polycyclic aromatic hydrocarbons there are relatively small differences in the configurations of the ground state and the excited state. Moreover, the chemiluminescence produced by the reaction of aromatic hydrocarbon radical anions and radical cations is due to simple one-electron transfer reactions, especially in cases where both radical ions are derived from the same aromatic hydrocarbon, as in the reaction between 9.10-diphenyl anthracene radical cation and anion. More complex are radical ion chemiluminescence reactions involving radical ions of different parent compounds, such as the couple naphthalene radical anion/Wurster s blue (see Section VIII. B.). 

Kinetic characteristics are obtained for the reaction between several polycyclic aromatic hydrocarbons with nitrogen dioxide in dichloromethane at 25°C. They are in accord with the intermediate formation of the cation-radicals (Pryor et al 1984). 

Miller, J. L., Khaledi, M. G., and Shea, D., Separation of polycyclic aromatic hydrocarbons by nonaqueous capillary electrophoresis using charge-transfer complexation with planar organic cations, Anal. Chem., 69,1223-1229,1997. 

Central Role of Radical Cations in Metabolic Activation of Polycyclic Aromatic Hydrocarbons ... 

The most widespread environmental carcinogens are the polycyclic aromatic hydrocarbons (PAHs), which are found, among other places, in automobile exhaust, cigarette smoke, and broiled meats. PAHs undergo two main pathways of bioactivation one-electron oxidation and oxygenation. The former yields cation radicals the latter produces hydroxyl derivatives. 

The reason that one-electron oxidation is suggested as playing a central role in the metabolic activation of polycyclic aromatic hydrocarbons derives from certain features of the radical cations that are common to the most potent carcinogens of the family ... 

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,... 

Creed, 1978a). It was found that as the charge-transfer character in the transition state increased the rate constant for cycloaddition decreased. The oxidation of crystal violet to its cation radical can be initiated by reaction of the dye with the excited singlet states of many polycyclic aromatic hydrocarbons. This reaction was found to be far less efficient for polymer-bound pyrene than for free pyrene and this was attributed to excimer formation occurring in the polymer system which ultimately led to energy wastage (Tazuke et al., 1979). 

Irradiation of styrene in the presence of oxygen leads to polymerisation (Kodaira et ai, 1978). Although radical cations may well be intermediates in such reactions it has proved impossible to detect them in the reactions of polycyclic aromatic hydrocarbons with oxygen in acetonitrile solution (Watkins, 1979a). 

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