Polycyclic aromatic hydrocarbon isomers

Wise SA, Deissler A, and Sander LC (1993b) Liquid chromatographic determination of polycyclic aromatic hydrocarbon isomers of molecular weight 278 and 302 in environmental reference materials. Polycyclic Aromat Compd 3 169-184. 

Wise, S. A. and Sander, L. C. 1985. Factors affecting the reversed-phase liquid chromatographic separation of polycyclic aromatic hydrocarbon isomers. J. High Resolut. Chromatogr. Commun. 8 248-255. 

Wise, S. A., A. Deissler, and L. C. Sander, Liquid Chromatographic Determination of Polycyclic Aromatic Hydrocarbon Isomers of Molecular Weight 278 and 302 in Environmental Standard Reference Materials, Polycyclic Aromat. Compd., 3, 169-184(1993). 

Dias, J.R. 1982. A Periodic Table of Polycyclic Aromatic Hydrocarbons. Isomer Enumeration of Fused Polycyclic Aromatic Hydrocarbons. Journal of Chemical Information and Computer Sciences 22 15-22. 

A Periodic Table for Polycyclic Aromatic Hydrocarbons - Isomer 1 Polycyclic Aromatic Hydrocarbons — 1. J Chem Inf Comput Sd 22 ... 

Wise SA, Benner Jr BA, Liu H, Byrd GD, Colmsjo A. Separation and identification of polycyclic aromatic hydrocarbon isomers of molecular weight 302 in complex mixtures. Anal Chem 1988 60(7) 630—7. 

In fused ring systems, the positions are not equivalent and there is usually a preferred orientation even in the unsubstituted hydrocarbon. The preferred positions may often by predicted as for benzene rings. Thus it is possible to draw more canonical forms for the arenium ion when naphthalene is attacked at the a position than when it is attacked at the p position, and the a position is the preferred site of attack,though, as previously mentioned (p. 682), the isomer formed by substitution at the p position is thermodynamically more stable and is the product if the reaction is reversible and equilibrium is reached. Because of the more extensive delocalization of charges in the corresponding arenium ions, naphthalene is more reactive than benzene and substitution is faster at both positions. Similarly, anthracene, phenanthrene, and other fused polycyclic aromatic hydrocarbons are also substituted faster than benzene. 

This chemistry becomes synthetically useful when one of the isomeric palladium intermediates can react with a neighboring substituent and the other isomer cannot. Thus, we have taken advantage of this effect to synthesize a range of polycyclic aromatic hydrocarbons by Pd migration and subsequent arylation (Scheme 24).21 This provides a unique way to form new carbon-carbon bonds in a location remote from the original functionality. 

The first scientists to investigate the coastal atmospheric presence of APs were Van Ry and Dachs, in a study conducted in the Hudson river estuary. GC-MS analyses showed that atmospheric NP isomer mixtures have a similar composition to technical mixtures, with relatively high total concentrations in the range of 0.0002—0.069 xg m-3 in the gas phase, and 0.0001-0.051 p,gm-3 in the aerosol phase. These concentrations are higher than those of polycyclic aromatic hydrocarbons and up to two orders of magnitude higher than polychlorinated biphenyl concentrations in impacted urban-industrial areas [32]. 

Thermochemical data are available (Ref 2) on the heats of combustion and formation for all five isomers, on the heats of nitration from various Dinitrotoluenes for the 23,4-, 2,4,5-, and 2,3,6-isomers, and on the heats of crystn for the 2,3,4- and 2,4,5-isomers. Data are also available (Ref 1) on the shock sensitivities of all of the isomers except 2,3,6-, and on the rates of decompn at 140° of the 23,4-, 2,4,5-, and 23,5-isomers. The detonation pressure and the temp coefficient of decompn between 140 and 180° have been measured for the 2,4,5-isomer 2,3,4- and 2,4,5-TNT form addition compds ( 7r-complexes ) at 1 1 molar ratio with several polycyclic aromatic hydrocarbons (naphthalene, acenaphthene, fluorene, phenanthrene and anthracene) (Ref 2). 2,4,5-TNT forms complexes with 4-aminozaobenzene, 4-aminoacetophenone, bis (2 hydroxy ethyl) amine, and tris (2-hydroxy-ethyl) amine (Ref 1). The first two have a 1 1 molar ratio, the third 1 2, and the fourth 2 1. Upon heating, the two 4-amino compds react with replacement of the 5-nitro group, as discussed below... 

Hubert et al. [101] state that accelerated solvent extraction compared to alternatives such as Soxhlet extraction, steam distillation, microwave extraction, ultrasonic extraction and, in some cases, supercritical fluid extraction is an exceptionally effective extraction technique. Hubert et al. [ 101 ] studied the effect of operating variables such as choice of solvent and temperature on the solvent extraction of a range of accelerated persistent organic pollutants in soil, including chlorobenzenes, HCH isomers, DDX, polychlorobiphenyl cogeners and polycyclic aromatic hydrocarbons. Temperatures ofbetween 20 and 180 °C were studied. The optimum extraction conditions use two extraction steps at 80 and 140 °C with static cycles (extraction time 35 minutes) using toluene as a solvent and at a pressure of 15 MPa. 

Analytical Properties Separation of three- and four-member methylated polycyclic aromatic hydrocarbons (PAHs) on basis of length-to-breadth ratio (l/b) as l/b increases, retention time decreases cross-linking increases retention times, separation of methylcrypene isomers Reference 18... 

Table 15.1 Polycyclic aromatic hydrocarbon (PAH) isomer ratios for major emisson...

In the light of these long traditions, extensive enumerations of the isomers of benzenoid hydrocarbons is a very new area. A systematic investigation can be dated to 1982 with the first paper of Dias [7] (but see also below). He published an article series in ten parts [7-16] entitled A Periodic Table for Polycyclic Aromatic Hydrocarbons and more recent works [17, 18]. With the invention of the periodic table, Dias created orderness in the chaotic myriads of chemical formulas for benzenoid hydrocarbons, which may be written. He has also written a monograph [19] with relevance to this topic and some other reviews [20-22], Two years before Dias, Elk [23] published a paper on benzenoids, which contains explicitly the enumeration of isomers up to h = 5. It seems that the work of Elk has largely been overlooked in the context of benzenoid isomer enumeration. 

---