Aromatic Hydrocarbons and Petroleum

By the middle of the nineteenth century, chemists had a basic understanding of the structures of hydrocarbons with single, double, and triple covalent bonds. However, a fourth class of hydrocarbon compounds remained a mystery. The simplest example of this class of hydrocarbon is benzene, which the English physicist Michael Faraday (1791-1867) had first isolated in 1825 from the gases given off when either whale oil or coal was heated. 

Although chemists had determined that benzene s molecular formula was CgHg, it was hard for them to determine what sort of hydrocarbon structure would give such a formula. After all, the formula of the saturated hydrocarbon with six carbon atoms, hexane, was Because the benzene mole- 

Although this structure has a molecular formula of CgHg, such a hydrocarbon should be unstable and extremely reactive because of its many double bonds. However, benzene was fairly unreactive and, when it did react, it was not in the ways that alkenes and alkynes usually react. For that reason, chemists reasoned that structures such as the one shown above must be incorrect. 

Kekule s dream In 1865, the German chemist Friedrich August Kekul6 (1829-1896) proposed a different kind of structure for benzene—a hexagon of carbon atoms with alternating single and double bonds. How does the molecular formula of this structure compare with that of benzene  

A modern model of benzene Since the time of Kekul6 s proposal, research has confirmed that benzene s molecular structure is indeed hexagonal. However, an explanation of benzene s unreactivity had to wait until the 1930s when Linus Pauling proposed the theory of hybrid orbitals. When applied to benzene, this theory predicts that the pairs of electrons that form the second bond of each 

The hydrocarbon known as benzene consists of a ring of six carbon atoms with six attached hydrogen atoms. The benzene ring has a system of delocalized electrons that are shared evenly over the carbon atoms in the ring. The sharing of electrons makes benzene a fairly stable and unreactive compound. The pictorial representation of benzene usually omits the hydrogen atoms. 

230 chemistry Matter and Change Solving Problems A Chemistry Handbook 

Organic compounds that contain benzene rings as part of their molecular structure are called aromatic compounds. Nonaromatic hydrocarbons such as alkanes, alkenes, and alkynes are called aliphatic compounds. Some aromatic compounds contain two or more benzene rings fused together. Examples include naphthalene and anthracene. In these compounds, electrons are shared over all of the carbon atoms in the fused ring system. 

The —CH3 group is attached to the ring in place of a hydrogen atom. You can verify that the molecular formula of toluene is C- Hg. The rules for naming substituted benzene compounds are the same as those for naming cycloalkanes. 

Draw the structural formula and determine the molecular formula for these aromatic hydrocarbons. 

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Richardson, B.J. Zheng, G.J. Tse, E.S.C. De Luca-Abbott, S.B. Siu, S.Y.M, Lam, P.K.S. 2003, A comparison of polycyclic aromatic hydrocarbon and petroleum hydrocarbon uptake by mussels (Pema viridis) and semi-permeable membrane devices (SPMDs) in Hong Kong Coastal Waters. Environ. Pollut. 122 223-227. 

M.C. Pelletier, R.M. Burgess, K.T. Ho, A. Kuhn, R.A. McKinney, S.A. Ryba (1997). Phototoxicity of individual polycyclic aromatic hydrocarbons and petroleum to marine invertebrate larvae and juveniles. Environ. Toxicol. Chem., 16,2190-2199. 

Huntley SL, Bonnevie NL, Wenning RJ. 1995. Polycyclic aromatic hydrocarbon and petroleum hydrocarbon contamination in sediment from the Newark Bay Estuary, New Jersey. Arch Environ Contain Toxicol 28 93-107. 

Edeleanu process An extraction process utilizing liquid sulphur dioxide for the removal of aromatic hydrocarbons and polar molecules from petroleum fractions. 

Acetyl chlotide reacts with aromatic hydrocarbons and olefins in suitably inert solvents, such as carbon disulfide or petroleum ether, to furnish ketones (16). These reactions ate catalyzed by anhydrous aluminum chlotide and by other inorganic chlotides (17). The order of catalytic activity increases in the order... 

Benzene is the simplest and most important member of the aromatic hydrocarbons and should not be confused with benzine, a low boiling petroleum fraction composed chiefly of aUphatic hydrocarbons. The term benzole, which denotes commercial products that are largely benzene, is not common in the United States, but is stiU used in Europe. 

Coates JD, J Woodward, J Allen, P Philip, DR Lovley (1997) Anaerobic degradation of polycyclic aromatic hydrocarbons and alkanes in petroleum-contaminated marine harbor sediments. Appl Environ Microbiol 63 3589-3593. 

Parathion is very slightly soluble in water (20 parts per million), but is completely miscible in many organic solvents including esters, alcohols, ketones, ethers, aromatic and alkylated aromatic hydrocarbons, and animal and vegetable oils. It is practically insoluble in such paraffinic hydrocarbons as petroleum ether, kerosene, and refined spray oils (about 2%) unless a mutual solvent is used (1). 

Petroleum products contain many fluorescing compounds, e.g., aromatic hydrocarbons, polycyclic aromatic hydrocarbons, and various heterocyclic... 

Aroflning A process for removing aromatic hydrocarbons from petroleum fractions by catalytic hydrogenation to naphthenes. Developed by Labofina, France, and licensed by Howe-Baker Engineers. 

Arosolvan A solvent extrachon process for removing aromatic hydrocarbons from petroleum mixtures, using N-methyl pynolidone (NMP) containing 12 to 14 percent water at 20 to 40°C. Developed by Luigi, and first used commercially in Japan in 1961. 

Catarole Also spelled Catarol. A process for making aromatic hydrocarbons and olefins by cracking petroleum fractions over copper turnings. Invented by C. Weizmann in England in... 

OCTENAR [Octane enhancement by removing aromatics] A process for removing aromatic hydrocarbons from petroleum reformate by extractive distillation with N-formyl mor-phylane. The product can be blended with gasoline to increase its octane number — hence the name. A paraffin mixture is obtained as a side-product. Developed by Krupp Koppers from its MORPHYLANE and MORPHYLEX processes. 

Sulfolane A process for removing aromatic hydrocarbons from petroleum fractions by liquid-liquid extraction using sulfolane (tetramethylene sulfone tetrahydrothiophene-1,1-dioxide) at approximately 190°C. Developed by Shell Development Company in 1959 and first commercialized in 1962 now licensed through UOP. It replaced the Udex process. Sulfolane is used for another purpose in the Sulfinol process. 

The petroleum-based oils contain hundreds to thousands of hydrocarbon compounds, including a substantial fraction of nitrogen- and sulfur-containing compounds. The hydrocarbons are mainly mixtures of snaight- and branched-chain hydrocarbons (alkanes), cycloalkanes, and aromatic hydrocarbons. Polynuclear aromatic hydrocarbons, alkyl polynuclear aromatic hydrocarbons, and metals are important components of motor oils and crankcase oils, with the used oils... 

Residua are the dark-colored nearly solid or solid products of petroleum refining that are produced by atmospheric and vacuum distillation (Figure 11.1 Chapter 3). Asphalt is usually produced from a residuum and is a dark brown to black cementitious material obtained from petroleum processing that contains very high-molecular-weight molecular polar species called asphaltenes that are soluble in carbon disulfide, pyridine, aromatic hydrocarbons, and chlorinated hydrocarbons (Chapter 3) (Gruse and Stevens, 1960 Guthrie, 1967 Broome and Wadelin, 1973 Weissermel and Arpe, 1978 Hoffman, 1983 Austin, 1984 Chenier, 1992 Hoffman and McKetta, 1993). 

The application of biomarker research in the geologic record has dealt with the derivative hydrocarbons as found in petroleum, coals, and sedimentary rocks. Reports on biomarkers in discrete fossils compared to the host rocks are sparse because (1) previous studies focused on the highly degraded geoterpenoids, i.e. saturated and aromatic hydrocarbons, and (2) the preservation potential of polar compounds (natural product bioterpenoids ) was believed to be low. Flowever, recent investigations of conifer fossils demonstrated that unaltered natural product terpenoids can be preserved in resin material.This will be illustrated here with an example. 

Pentagone is an aqueous-based surface decontamination product developed for the cleanup of pentachlorophenols, creosote, petroleum hydrocarbons, chlorinated hydrocarbons, polynuclear aromatic hydrocarbons, and selected pesticide and herbicide spills. It can be used on concrete, asphalt, or metal and is capable of being applied as a foam, allowing treatment of overhead, vertical, and horizontal surfaces. It has been commercially available since 1993 and has been used in multiple applications. 

Another significant trend is the current program to increase the production of benzene from petroleum 16). Increasing requirements for the production of styrene, phenol, and other intermediates have made it essential that new sources be found to supplement current supplies of this aromatic hydrocarbon, and the only apparent source is from petroleum processes. To meet current needs of the military and civilian program the United States Petroleum Administration for Defense has been asked to increase petroleum benzene from the current rate of 12,000,000 gallons to 100,000,000 gallons per year 84). Present production from petroleum is small in comparison with that from other sources, but these proposed expansions may add materially to the output of petroleum-derived intermediates that will ultimately go to the manufacture of plastics and synthetic rubber. 

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