Polycyclic aromatics alkylation

On the basis of the reaction of alkyl radicals with a number of polycyclic aromatics, Szwarc and Binks calculated the relative selectivities of several radicals methyl, 1 (by definition) ethyl, 1.0 n-propyl, 1.0 trichloromethyl, 1.8. The relative reactivities of the three alkyl radicals toward aromatics therefore appears to be the same. On the other hand, quinoline (the only heterocyclic compound so far examined in reactions with alkyl radicals other than methyl) shows a steady increase in its reactivity toward methyl, ethyl, and n-propyl radicals. This would suggest that the nucleophilic character of the alkyl radicals increases in the order Me < Et < n-Pr, and that the selectivity of the radical as defined by Szwarc is not necessarily a measure of its polar character. 

One example of normal-phase liquid chromatography coupled to gas chromatography is the determination of alkylated, oxygenated and nitrated polycyclic aromatic compounds (PACs) in urban air particulate extracts (97). Since such extracts are very complex, LC-GC is the best possible separation technique. A quartz microfibre filter retains the particulate material and supercritical fluid extraction (SPE) with CO2 and a toluene modifier extracts the organic components from the dust particles. The final extract is then dissolved in -hexane and analysed by NPLC. The transfer at 100 p.1 min of different fractions to the GC system by an on-column interface enabled many PACs to be detected by an ion-trap detector. A flame ionization detector (PID) and a 350 p.1 loop interface was used to quantify the identified compounds. The experimental conditions employed are shown in Table 13.2. 

Alkylated, oxygenated and nitrated polycyclic aromatic compounds... 

Figure 13.16 LC separation of urban air particulate exrtact (a), along with the GC/FID cliro-matogram (b) of an oxy-PAC fraction (transfeired via a loop-type interface). Reprinted from Environmental Science and Technology, 29, A. C. Lewis et al., On-line coupled LC-GC-ITD/MS for the identification of alkylated, oxygenated and nirtated polycyclic aromatic compounds in urban air particulate exti acts , pp. 1977-1981, copyright 1995, with permission from the American Chemical Society.

A. C. Eewis, R. E. Robinson, K. D. Bartle and M. J. Pilling, On-line coupled EC-GC-ITD/MS for the identification of alkylated, oxygenated and nitr-ated polycyclic aromatic compounds in urban ah particulate extr acts . Environ. Sci. Technol. 29 1977-1981 (1995). 

In contrast to the dihalogens, there are only a few spectral studies of complex formation of halocarbon acceptors in solution. Indeed, the appearance of new absorption bands is observed in the tetrabromomethane solutions with diazabicyclooctene [49,50] and with halide anions [5]. The formation of tetrachloromethane complexes with aromatic donors has been suggested without definitive spectral characterization [51,52]. Moreover, recent spectral measurements of the intermolecular interactions of CBr4 or CHBr3 with alkyl-, amino- and methoxy-substituted benzenes and polycyclic aromatic donors reveal the appearance of new absorption bands only in the case of the strongest donors, viz. Act = 380 nm with tetramethyl-p-phenylendiamine (TMPD) and Act = 300 nm with 9,10-dimethoxy-l,4 5,8-... 

Alkyl radicals generated efficiently from allylsulfones in 80% aqueous formic acid induced a cyclization reaction on aromatic and heteroaromatic compounds to provide polycyclic aromatic and heteroaromatic derivatives (Eq. 7.17).37... 

Consequently, Europe has historically been a hotspot of environmental pressures because of the contamination caused by agricultural, municipal, and industrial activities and high population densities [5, 6], Such contamination has led to poor water quality in many European river basins [7-12], In addition, this pollution can cause the accumulation in river sediments of toxic compounds such as pesticides [13], surfactants [14], and alkyl polycyclic aromatic hydrocarbons (PAHs) [15], These can in turn act as a source to biota [16] and as a potential risk for entire ecosystems [17] if the compounds bioaccumulate, and thereby enter the food chain [18],... 

In LB films [1], the arrangement of the various functional moieties is considered to be controlled spatially across the films at molecular dimensions as described above. As one of functional moieties, various polycyclic aromatic hydrocarbons were used [55,56]. Some of the compounds were mixed with arachidic acid to form stable monolayers [37], because the amphiphilc derivatives of aromatic hydrocarbons themselves often form unstable monolayers on the subphase [40], For preparation of stable monolayers of polycyclic aromatic amphiphiles, Steven et al. investigated the effects of the length of alkyl chain and the composition and pH of the subphase [57],... 

Polycyclic aromatic hydrocarbons (PAHs, sometimes also called polynuclear aromatics, PNA) are a hazardous class of widespread pollutants. The parent structures of the common PAHs are shown in Fig. 4 and the alkylated homologs are generally minor in combustion emissions. PAHs are produced by all natural combustion processes (e.g., wild fires) and from anthropogenic activity such as fossil fuels combustion, biomass burning, chemical manufacturing, petroleum refining, metallurgical processes, coal utilization, tar production, etc. [6,9,15,18, 20,24,131-139]. 

As above, the log k values of the different types of compounds [alkanols (ROH), polycyclic aromatic hydrocarbons (PAH), alkyl benzenes (RB), and alkyl benzoates (ROB)] each demonstrated a linear relationship with their log P values and this relationship was observed with different ratios of acetonitrile and water. The experiment was then performed in eluents containing different organic modifiers and it was found that the behaviour of analytes containing different functional groups differed and the effect depended on the log P of the analyte. 

Example 2 Separation of a polycyclic aromatic hydrocarbon and an alkyl benzoate. The logP values of fluorene and butyl benzoate are 3.91 and 3.74, respectively, from Table 4.1. The separation is poor in 50% aqueous aceto-... 

Figure 6.8 Relationship of enthalpy to log k values. Column, ODS silica, ERC-ODS, 15 cm x 6.0 mm i.d. eluent, 80% aqueous acetonitrile at 30 °C. Numbers beside symbols see Table 6.4. O, Polycyclic aromatic hydrocarbons x, alkyl-benzenes, O, halogenated benzenes A, alkanols and , alkanes.

White P. M., Wolf D. C., Thoma G. J., and Reynolds C. M., 2006, Phytoremediation of alkylated polycyclic aromatic hydrocarbons in a crude oil-contaminated soil, Water Air SoilPollut. 160 207-220. 

Carr, J.W. and Harris, J.M., In situ fluorescence detection of polycyclic aromatic hydrocarbons following pre-concentration on alkylated silica adsorbents. Anal. Chem., 60, 698, 1988. 

The toxicities of nine alkyl aromatics (4) are appreciably less than those of the polycyclic aromatics. No signihcant retardation is observed in benzene-deuterium oxide exchange reactions at 30° even when the poisons are present in benzene in concentrations of 3.6 mole %. The high temperature exchange rate (Table II) of sterieally unhindered ring positions in the alkylbenzenes indicates that adsorption strength... 

Hawthorne, S.B., Grabanski, C.B., and Miller, D.J. Measured partitioning coefficients for parent and alkyl polycyclic aromatic hydrocarbons in 114 historically contaminated sediments Part 1. iCc values, Environ. Toxicol Chem., 25(11) 2901-2911, 2006,... 

With stringent precautions to avoid the presence of water, polycyclic aromatic hydrocarbons show two one-electron reversible waves on cyclic voltammetry in dimethylformamide (Table 7.1). These are due to sequential one-electron additions to the lowest unoccupied molecular n-orbital [1]. Hydrocarbons with a single benzene ring are reduced at very negative potentials outside the accessible range in this solvent. Radical-anions of polycyclic aromatic hydrocarbons [2] and also alkyl benzenes [3] were first obtained by the action of alkali metals on a solution of the hydrocarbon in tetrahydrofuran. They have been well characterised by esr spectroscopy. The radical-anions form coloured solutions with absorption bands at longer wavelength than the parent hydrocarbon [4,5]. 

Fraction 12 as shown in Figure 5-9 has overlapping from two types of aromatics - alkylated aromatics and polycyclic aromatics. 

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