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CYCLOALKANE NOMENCLATURECycloalkanesare alkanes that contain a ring of three or more carbons.They are frequently encountered in organic chemistry and arecharacterized by the molecular formulaCnH2n. Some examples include:As you can see, cycloalkanes are named, under the IUPAC system, byadding theprefixcyclo-to the name of the unbranched alkane with thesame number of carbons as the ring. Substituent groups are identified inthe usual way. Their positions are specified by numbering the carbonatoms of the ring in the direction that gives the lowest number to thesubstituents at the first point of difference.When the ring contains fewer carbon atoms than an alkyl group attachedto it, the compound is named as an alkane, and the ring is treated as acycloalkyl substituent:
SOURCES OF ALKANES AND CYCLOALKANESAs noted earlier, natural gas is especially rich in methane and alsocontains ethane and propane, along with smaller amounts of other low-molecular-weight alkanes. Natural gas is often found associated withpetroleum deposits. Petroleum is a liquid mixture containing hundreds ofsubstances,including approximately150hydrocarbons,roughly halfofwhich are alkanes or cycloalkanes. Distillation of crude oil gives anumber of fractions, which by custom are described by the names givenin(Figure1). High-boilingfractions such as kerosene and gas oil findwide use as fuels for diesel engines and furnaces, and the nonvolatileresidue can be processed to give lubricating oil, greases, petroleumjelly,paraffin wax, and asphalt.Although both are closely linked in our mindsand by our own experience, the petroleumindustry predated theautomobile industry by half a century. The first oil well, drilled inTitusville, Pennsylvania, by Edwin Drakein1859,providedrock oil,as it was then called, on a large scale. This was quickly followed by thedevelopmentof a process torefineit so as to produce kerosene. As afuel for oil lamps, kerosene burned with a bright, clean flame and soonreplacedthe more expensive whale oil then in use. Other oil fields werediscovered, and uses for other petroleum products werefoundilluminating gas lit city streets, and oil heated homes and poweredlocomotives.There were oil refineries longbefore there wereautomobiles. By the time the first Model T rolled off Henry Fordsassembly line in1908,John D.Rockefellers Standard Oil holdings hadalready made him one of the half-dozen wealthiest peoplein the world.Modern petroleum refining involves more than distillation, however, andincludestwo major additional operations:
1.Cracking.Itisthemorevolatile,lower-molecular-weighthydrocarbons that are useful as automotive fuels and as a source ofpetrochemicals. Cracking increases the proportion of these hydrocarbonsat the expense of higher molecular-weightones by processes that involvethe cleavage of carboncarbon bonds induced byheat(thermal cracking)or with the aid of certain catalysts(catalytic cracking).2.Reforming.The physical properties of

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Term
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