Aromatics from coal, isolation polycyclic

In the 1930s, polycyclic aromatic hydrocarbon was isolated from coal tar and demonstrated to be carcinogenic. Despite this evidence, millions of people continue to expose themselves to the soot from tobacco and suffer from the resulting lung cancer. 

Marvin CH, Lundrigan JA, McCarry BE, et al. 1995. Determination and genotoxicity of high molecular mass polycyclic aromatic hydrocarbons isolated from coal-tar-contaminated sediment. Environ Toxicol Chem 14(12) 2059-2066. 

Triphenylene (TP) derivatives have been described as the work horses in the field of DLCs [11]. It is the most studied discotic core system [20, 21]. TP (1), see Scheme 4.1, belongs to the polycyclic aromatic hydrocarbon (PAH) group and has been known in the chemical literature for more than a century. This trimer of benzene was isolated from the pyrolytic products of benzene by Schultz who named it as triphenylene [22]. It can also be isolated from coal tar. Trimerization of cyclohexanone followed by dehydrogenation has been used to generate TP in the early twentieth century and its various chemical and physical properties were studied [22]. 

Many sulfur-containing organic compounds can be isolated from natural sources such as crude oil, petroleum, gas condensates, and coals <2004MI1>. By chromatographic methods <1999MI58> various polycyclic aromatic sulfur heterocycles (PASHs) (1-7) have been identified from standard samples of coal tar, petroleum crude oil and decant oil. 

The best evidence for the occurrence of polycyclic aromatic ring reduction is the comparison of the aqueous Na2Cr20y oxidation products of the hydrolytic product with those of the original coal. This procedure has been used in this laboratory to identify many of the important aromatic and heteroaromatic units in coals (4). It has been shown to be very selective for these molecules. Equation 1 is an example of the pathway by which polycyclic aromatics are isolated from the raw coal. 

Ultrasonic LSE is most applicable to the isolation of semivolatile and nonvolatile organic compounds from solid matrices such as soil, sediment, clays, sand, coal tar, and other related solid wastes. U-LSE is also very useful for the disruption of biological material such as serum or tissue. U-LSE can be coupled with solid-phase extraction (SPE) to give a very robust sample preparation method at relatively low cost in comparison to MAE and ASE approaches. The author has utilized U-LSE/SPE to isolate and recover 9,10-dimethyl-l,2-benzanthracene from animal bedding. A 89% recovery was obtained for bedding that was spiked with this polycyclic aromatic hydrocarbon (PAH) of interest to toxicologists (20). An ultrasonic horn and tip are immersed into a mixture of liquid extractant and solid sample and sonicated at some percent of full power for a finite length of time, either continuously or pulsed. 

Nitro-PAHs are polycyclic aromatic hydrocarbon derivatives that contain one or more nitro groups covalently bound at chemically reactive positions on the aromatic ring. Mixtures of nitrated PAHs are generated either by reactions of PAHs with nitrogen oxides or as byproducts of the incomplete combustion of fossil fuels (65). A wide variety of nitro-PAHs have been isolated from environmental sources, such as coal fly ash, diesel emission particulates, cigarette smoke and carbon black photocopier toners (29, 52, 63, 74, 75, 86, 87, 88). Structures of representative nitro-PAHs isolated from the environment are shown in Figure 1. 

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