Aromatic ring hydrocarbons

Several methods, involving solvent extraction or destructive hydrogenation, can accomplish the removal of aromatic hydrocarbons from naphtha. By destructive hydrodegation methods, aromatic hydrocarbon rings are first ruptured and then saturated with hydrogen, which converts aromatic hydrocarbons into the odorless, straight-chain paraffinic hydrocarbons required in aliphatic solvents. 

Polymers with aromatic hydrocarbon backbone include polymers containing in their chain aromatic hydrocarbon rings, or alternating aromatic rings and aliphatic carbon groups. Thermosetting phenolic resins can be included in this class. 

Photolysis of indole with naphthalene or phenanthrene in either the solid state or when dissolved in polar solvents leads to the formation of products of addition of the indole nitrogen to the aromatic hydrocarbon ring, as shown in Scheme 34 [71],... 

In contrast to the poly(enamine-ketones) prepared by Imai e al. the methyl substituted poly(enamine ketones), J 2, prepared from the condensation of diamines and bis-acetylacetylarenes, were found to be hydrolytically stable and thermally stable from 257 to 340 C, When a linear and rigid aromatic bis(1,3-diketone) was condensed with alkaline dieamines with ten or more carbons or with rigid aromatic diamines, thermotropic liquid crystalline materials were obtained. The monomers and polymers have much higher solubilities and lower transition temperatures as compared with liquid crystals containing only aromatic hydrocarbon rings of similar structures. 

The free radical mechanism is confirmed by the fact that if a substituted aromatic hydrocarbon is used in this reaction, the incoming group (derived from the diazotate) may not necessarily occupy the position in the benzene ring normally determined by the substituent present—a characteristic of free radical reactions. 

Members of a class of arenes called polycyclic aromatic hydrocarbons possess subslanlial resonance energies because each is a colleclion of benzene rings fused logelher... 

Polycyclic aromatic hydrocarbons, of which anthracene is an example contain two or more benzene rings fused together... 

Polyamine (Section 22 4) A compound that contains many ammo groups The term is usually applied to a group of nat urally occurring substances including spermine spermi dine and putrescme that are believed to be involved in cell differentiation and proliferation Polycyclic aromatic hydrocarbon (Section 118) An aromatic hydrocarbon charactenzed by the presence of two or more fused benzene rings... 

Radicals derived from monocyclic substituted aromatic hydrocarbons and having the free valence at a ring atom (numbered 1) are named phenyl (for benzene as parent, since benzyl is used for the radical C5H5CH2—), cumenyl, mesityl, tolyl, and xylyl. All other radicals are named as substituted phenyl radicals. For radicals having a single free valence in the side chain, these trivial names are retained ... 

Aromatic hydrocarbons with an unsaturated side chain undergo ring closure when heated with Lewis acids (56). 

Pig. 6. Typical stmctures in lube oil (a) / -paraffin, (b) isoparaffin, (c) cycloparaffin, (d) aromatic hydrocarbon, and (e) mixed aUphatic and aromatic ring... 

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. 

Table 4. Fused-Ring Polynuclear Aromatic Hydrocarbons Found in Petroleum ...

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

Coal tar is the condensation product obtained by cooling to approximately ambient temperature, the gas evolved in the destmctive distillation of coal. It is a black viscous Hquid denser than water and composed primarily of a complex mixture of condensed ring aromatic hydrocarbons. It may contain phenoHc compounds, aromatic nitrogen bases and their alkyl derivatives, and paraffinic and olefinic hydrocarbons. Coal-tar pitch is the residue from the distillation of coal tar. It is a black soHd having a softening point of 30—180°C (86—359°F). 

Coke-oven tar is an extremely complex mixture, the main components of which are aromatic hydrocarbons ranging from the monocyclics benzene and alkylbenzenes to polycycHc compounds containing as many as twenty or more rings. HeterocycHc compounds containing oxygen, nitrogen, and sulfur, but usually only one heteroatom per ring system are present. Small amounts of paraffinic, olefinic, and partly saturated aromatic compounds also occur. 

The bromination of aromatic hydrocarbons can occur either in a side chain or on the ring, depending on conditions. In the presence of sunlight aLkylben2enes are brominated predominately in the side chain (24). 

In the presence of halogen Lewis acids, such as metal haUdes or iodine, aromatic hydrocarbons are halogenated on the ring (24). 

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