Aromatic Hydrocarbons. Benzene

Aromatic hydrocarbons are unsaturated cyclic compounds that are resistant to addition reactions. The aromatic hydrocarbons derive their name from the distinctive odors they exhibited when discovered. Benzene is the most important aromatic compound. Because many other aromatic compounds are derived from benzene, it can be considered the parent of other aromatic compounds. Benzene molecular formula is 

Benzene was discovered in 1825 by Michael Faraday who identified it from a liquid residue of heated whale oil. Faraday called the compound bicarburet of hydrogen and its name was later changed to benzin by Eilhardt Mitscherlich (1794—1863) who isolated the compound from benzoin. Benzene s formula indicates it is highly unsaturated. This would suggest benzene 

Alkane, alkenes, and alkynes can fold themselves to form cyclic compounds. Those represented above are cycloalkanes. 

A true picture of benzene s structure was not determined until the 1930s when Linus Pauling produced his work on the chemical bond. Benzene does not exist as either of its resonance structures, and its structure should not be considered as either one or the other. A more appropriate model is to consider the 

Kekul6 proposed that the structure for benzene resonated between two alternate structures in which the position of the double and single bonds switched positions. 

Acetylene is a colorless gas (b.p. —84 C), with a characteristic garliclike odor. It is liable to explode when compressed in a pure state, and is usually kept in solution under pressure in acetone. It is used as a fuel, in the oxyacetylene torch and the acetylene lamp, and is also used as the starting material for making other chemicals. 

Acetylene is most easily made from calcium carbide (calcium acetylide, CaCa). Calcium carbide is made by heating lime (calcium oxide, CaO) and coke in an electric furnace  

Calcium carbide is a gray solid that reacts vigorously with water to produce calcium hydroxide and acetylene  

The existence of calcium carbide and other carbides with similar formulas and properties shows that acetylene is an acid, with two replaceable hydrogen atoms. It is an extremely weak acid, however, and its solution in water does not taste acidic. 

Acetylene and other substances containing a carbon-carbon triple bond are very reactive. They readily undergo addition reactions with chlorine and other reagents, and they are classed as unsaturated substances. 

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Concentrated sulphuric acid. The paraffin hydrocarbons, cych-paraffins, the less readily sulphonated aromatic hydrocarbons (benzene, toluene, xylenes, etc.) and their halogen derivatives, and the diaryl ethers are generally insoluble in cold concentrated sulphuric acid. Unsaturated hydrocarbons, certain polyalkylated aromatic hydrocarbons (such as mesitylene) and most oxygen-containing compounds are soluble in the cold acid. 

Divide the heats of combustion by the number of carbons The two aromatic hydrocarbons (benzene and [18]annulene) have heats of combustion per carbon that are less than those of the nonaromatic hydrocarbons (cyclooctatetraene and [16]annulene) On a per carbon basis the aromatic hydrocarbons have lower potential energy (are more stable) than the nonaromatic hydrocarbons... 

Of the top ten most frequently reported toxic chemicals on the TRI list, the prevalence of volatile chemicals explains the air intensive toxic chemical loading of the refining industry. Nine of the ten most commonly reported toxic chemicals are highly volatile. Seven of the ten are aromatic hydrocarbons (benzene, toluene, xylene, cyclohexane, 1,2,4-trimethylbenzene, and ethylbenzene). 

A strain of Rhodococcus sp. was capable of degrading a number of chlorinated aliphatic hydrocarbons including vinyl chloride and trichloroethene, as well as the aromatic hydrocarbons benzene, naphthalene, and biphenyl (Malachowsky et al. 1994). 

The method by whieh erude oils are expelled from souree kerogen also influences oil group eomposition. In the case of hydrothermal oils or hydrothermal bitumens, hot water ean enhanee the content of lighter aliphatie and aromatic hydrocarbons (benzene, toluene, ethylbenzene, and xylenes). Typieal hydrothermal oils have a... 

Monomeric aromatic hydrocarbons Benzene, toluene, ethylbenzene, xylene (BTEX) Oil industry (P,D) Gasoline stations (P) Manufactured gas plants (P,D) 6 [43]... 

So-called green petrol is a preferred alternative to leaded petrol it contains about 3 per cent of the aromatic hydrocarbon benzene (C6H6, IV) as an additive, the benzene acting as a lead-free alternative to PbEt4 as an anti-knocking compound. 

Similarly, benzene and hydrazoic acid in the presence of a mixture of fluorosulphonic and trifluoromethanesulphonic acid give aniline quantitatively. From toluene 100% of a mixture of o-, m- and p-toluidines is obtained and bromobenzene yields 42% o-bromoaniline and 47% p-bromoaniline, Butyl azide gives iV-butylarylamines under these conditions89. Photolysis of 1-aminoquinolinium perchlorate (76) in aromatic hydrocarbons (benzene, toluene, ethylbenzene or mesitylene) in the presence of 18-crown-6 affords arylamines, e.g. aniline and p-toluidine, by way of the nitrenium ion90 cf Reference 91. 

Aromatic hydrocarbons Benzene systems Condensed aromatic systems Condensed aromatic-cycloalkyl systems Alkyl side chains on ring systems... 

Soluble in alcohol, ether (Weast, 1986), and many aliphatic hydrocarbons (hexane, pentane), and aromatic hydrocarbons (benzene)... 

It was suggested that the chlorination of naphthalene in tap water accounted for the presence of chloro- and dichloronaphthalenes (Shiraishi et ah, 1985). Kanno et al. (1982) studied the aqueous reaction of naphthalene and other aromatic hydrocarbons (benzene, toluene, o-, m-, and p-xylene) with hypochlorous acid in the presence of ammonium ion. They reported that the aromatic ring was not chlorinated as expected but was cleaved by chloramine forming cyanogen chloride. The amount of cyanogen chloride increased at lower pHs (Kanno et ah, 1982). 

Aquaplant is not suitable for the remediation of aromatic hydrocarbons benzene, toluene, ethylene, and xylene (BTEX), polychlorinated biphenyls, volatile chlorinated hydrocarbons, pesticides, dioxins, and furans. 

In early measurements the solubility of [C2CiIm][PFg] in aromatic hydrocarbons (benzene, toluene, ethylbenzene, o-xylene, m-xylene, and p-xylene) and that of [C4QIm][PFg] in the same aromatic hydrocarbons, and in n-alkanes (pentane, hexane, heptane, and octane), and in cyclohydrocarbons (cyclopentane and cyclohexane) has been presented [96]. 

The LLE of twenty binary systems containing [CglTj30ClT2-Cilm][BFJ with aliphatic hydrocarbons (n-pentane, n-hexane, n-heptane, or n-octane) and aromatic hydrocarbons (benzene, toluene, ethylbenzene, o-xylene, m-xylene, or p-xylene) were presented [78]. Also, the mixtures of [CglTj30ClT2-Qlm][Tf2N]... 

The separation of aromatic hydrocarbons (benzene, toluene, ethyl benzene, and xylenes) from mefhane to n-decane aliphatic hydrocarbon mixtures is challenging since the boiling points of fhese hydrocarbons are in a close... 

Based on their chemical structure, the organic chemicals were divided into a number of categories alkanes, alkenes, amines, aromatic hydrocarbons, benzenes, carboxylic acids, halides, phenols, and sulfonic acid. Linear regression analysis has been applied using the method of least-squares fit. Each correlation required at least three datapoints, and the parameters chosen were important to ensure comparable experimental conditions. Most vital parameters in normalizing oxidation rate constants for QSAR analysis are the overall liquid volume used in the treatment system, the source of UV light, reactor type, specific data on substrate concentration, temperature, and pH of the solution during the experiment. 

Aromatic Hydrocarbons. Benzene is probably the one of greatest concern, but others, such as toluene, are also used. 

Aromatic hydrocarbons Benzene, toluene, ethylbenzene, propylbenzene, 1,3,5-trimethylbenzene, 1,2,4-trimethylbenzene, 1,2,3-trimethylbenzene, tert-butylbenzene, o,m,p-xylene, p-cymene, styrene, alpha-methylstyrene, naphthalene, methylnaphthalene... 

Aromatic Compounds. Forms solid complexes with aniline, pyridine, toluene, benzene, and many other aromatic hydrocarbons benzene complex explodes violently on crushing in a mortar.2... 

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