Conformations of Acyclic Alkanes—Ethane

Let s now take a closer look at the three-dimensional structure of alkanes. The study of three-dimensional structure is called stereochemistry. In Chapter 4 we examine the effect of rotation around single bonds. In Chapter 5, we will learn about other aspects of stereochemistry. 

Recall from Section 1.9A that rotation occurs around carbon-carbon a bonds. Thus, the two CH3 groups of ethane rotate, allowing the hydrogens on one to adopt different orientations relative to the hydrogens on the other. These arrangements are called conformations. 

The location of the indicated atom changes with rotation. 

Conformations are different arrangements of atoms that are interconverted by rotation about single bonds. 

Alkanes have low bp s compared to more polar compounds of comparable size. 

Refining crude petroleum Into usable fuel and other petroleum products 

The mutual insolubility of nonpolar oil and very polar water leads to the common expression, Oil and water don t mix.  

Energy from petroleum is nonrenewable, and the remaining known oil reserves are limited. Given our dependence on petroleum, not only for fuel, but also for the many necessities of modem society, it becomes clear that we must both conserve what we have and find alternate energy sources. 

AlkS i oiS j polSsJ S C- IEonds, and as a result they exhibit only weak van der Waals forces. Table 4.2 summarizes how these intermolecular forces affect the physical 

Because nonpolar alkanes are not water soluble, crude petroleum that leaks into the sea from an oil tanker creates an insoluble oil slick on the surface. The insoluble hydrocarbon oil poses a special threat to birds whose feathers are coated with natural nonpolar oils for insulation. Because these hydrophobic oils dissolve in the crude petroleum, birds lose their layer of natural protection and many die. 

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