Polynuclear aromatic hydrocarbons. See

Fig. 8. Stmctures of fused-ring polynuclear aromatic hydrocarbons. See Table 4.

In addition to the exhaust gas components legislated for, the diesel oxidation catalyst also reduces the emissions of exhaust gas components such as aldehydes and polynuclear aromatic hydrocarbons, see Fig. Ill [70]. 

Polynoxylin. See Urea-formaldehyde resin Polynuclear aromatic hydrocarbon. See Petroleum distillates, heavy thermal cracked Polyoctadecylmethylsiloxane. See Stearyl methicone Polyoctenamer... 

Outside of carbon monoxide for which the toxicity is already well-known, five types of organic chemical compounds capable of being emitted by vehicles will be the focus of our particular attention these are benzene, 1-3 butadiene, formaldehyde, acetaldehyde and polynuclear aromatic hydrocarbons, PNA, taken as a whole. Among the latter, two, like benzo [a] pyrene, are viewed as carcinogens. Benzene is considered here not as a motor fuel component emitted by evaporation, but because of its presence in exhaust gas (see Figure 5.25). 

The fused 3+ ring aromatics in petroleum include both cata- and peri-condensed stmctures (see Table 4, Fig. 8). The cata-condensed species are those stmctures where only one face is shared between rings, the peri-condensed molecules are those that share more than one face. The fused ring aromatics form the class of compounds known as polynuclear aromatic hydrocarbons (PAH) which includes a number of recognized carcinogens in the 4+ ring family (33). Because of the potential health and environmental impact of PAH, these compounds have been studied extensively in petroleum. 

After a plate has been exposed to the mobile-phase solvent for the required time, the compounds present can be viewed by several methods. Polynuclear aromatic hydrocarbons, other compounds with conjugated systems, and compounds containing heteroatoms (nitrogen, oxygen, or sulfur) can be viewed with long-and short-wave ultraviolet light. The unaided eye can see other material, or the plates can be developed in iodine. Iodine has an affinity for most petroleum compounds, including the saturated hydrocarbons, and stains the compounds a reddish-brown color. 

Since much of the theoretical and experimental work in the field of organic semiconductors has been concerned with polynuclear aromatic hydrocarbon crystals, the theories advanced apply mainly to this particular group of compounds. It then remains to see how well the ideas developed may be extended to other more complex systems, particularly polymers. In order to extend the hypotheses to more complicated systems, not only will it be necessary to perform more meaningful... 

Some halogen derivatives of polynuclear aromatic hydrocarbons form picrates (for experimental details, see under Aromatic hydrocarbons, Section 9.6.3, p. 1240), for example, 1-chloronaphthalene (m.p. 137°C), 1-bromonaphthalene (m.p. 134°C) and 2-bromonaphthalene (m.p. 86 °C). 

See also Chapter 4, Polynuclear Aromatic Hydrocarbons [PAHs] and Related Aromatic Hydrocarbons)... 

Odd-Alternate Polynuclear Aromatic Hydrocarbon Radicals. Substantial evidence supports the contention that the stable free radicals formed during the pyrolysis of polynuclear aromatic compounds are odd-alternate hydrocarbon radicals. As an example, the phenalenyl radical (5) is formed during pyrolysis of a number of organic compounds including acenaphthylene (3) and dihydronaphthalene (4) (24) (see Scheme III). The... 

Dobbins, J.T. Jr Discussion of methods for determination of polynuclear aromatic hydrocarbons (with Celanese research persoimel) RDM, 1968, No. 62, October 10, see www.ijrtdocs.com 500604311 4 314. 

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