http://www.ck12.org Chapter 9. Chemistry of Carbon
Aromatic Hydrocarbons
Unsaturated cyclic hydrocarbons are calledaromatic hydrocarbons. That’s because they have a strong aroma, or
scent. Their molecules consist of six carbon atoms in a ring shape, connected by alternating single and double
bonds. Aromatic hydrocarbons may have a single ring or multiple rings joined together by bonds between their
carbon atoms.
Benzene is the smallest aromatic hydrocarbon. It has just one ring. You can see its structural formula inFigure9.14.
Benzene has many uses. For example, it is used in air fresheners and mothballs because of its strong scent.
FIGURE 9.14
Benzene is an aromatic hydrocarbon. Does each carbon atom in benzene
have a total of four bonds? Count them to find out.You can learn more about benzene and other aromatic hydrocarbons at this URL: http://www.youtube.com/watch
?v=8gW7H0ReN5g (4:54).
MEDIA
Click image to the left for use the URL below.
URL: http://www.ck12.org/flx/render/embeddedobject/5091Uses and Sources of Hydrocarbons
It is hard to overstate the importance of hydrocarbons to modern life. Hydrocarbons have even been called the driving
force of western civilization. You saw some ways they are used inFigure9.6. Several other ways are illustrated in
Figure9.15. Their most important use is as fuels. Gasoline, natural gas, fuel oil, diesel fuel, jet fuel, coal, kerosene,
and propane are just some of the hydrocarbon compounds that are burned for fuel. Hydrocarbons are also used to
manufacture many products, including plastics and synthetic fabrics such as polyester.
The main source of hydrocarbons is fossil fuels —coal, petroleum, and natural gas. Fossil fuels form over hundreds
of millions of years when dead organisms are covered with sediments and put under great pressure. Giant ferns in
ancient swamps turned into coal deposits. Dead organisms in ancient seas gradually formed deposits of petroleum
and natural gas. You can read more about these sources of hydrocarbons in the chapterIntroduction to Energyand
at the URL below.