Aromatic compounds derive their names from the fact that many of these compounds in the early days of discovery were grouped because they were oils with fragrant odors, hence the name aromatic. The current definition of aromatic compounds includes only those with a benzene ring, which is a special six carbon ring compound with three alternating double bonds. This structure imparts unique properties to benzene which are different from other ring compounds. See the benzene structure on the left.

BENZENE is a special six carbon ring compound with three alternating double bonds. This structure imparts unique properties to benzene which are different from other ring compounds. Because many fragrant oils contain a benzene ring, these compounds became known as AROMATIC. It might be useful to compare the structures for the series of cycloalkane and cycloalkenes and benzene.

Although the double bonds may be at the position shown, other evidence indicates that they are not confined to specific positions. The actual structure must have characteristics somewhere in between, hence the use of the circle in the center structure. The bonds between the carbons in benzene are neither pure single bonds nor pure double bonds, but rather a some hybrid of the two. The bond lengths are identical but with an intermediate value between the lengths of carbon-carbon single bonds and double bonds.

Properties
Structure	Physical Properties	Chemical Reactivity
C6H6 Only one H or other group may be bonded to the carbon in a benzene ring.	Non polar- good industrial solvents for other nonpolar compounds Insoluble in water liquid at room temperature	Relatively unreactive. Even though double bonds are present, aromatics do not undergo addition type reactions. Reactions occur by substitution of the hydrogen for another group. All compounds: Combustion Reaction

BENZENE NAMES The root name is simply benzene. If other groups are attached to the benzene ring, they are named according to group names followed by the word benzene. Example on the left: A one carbon branch = methane - drop "ane" and add "yl to get methylbenzene. An older common name is toluene.
For the Quiz questions below, click on Quiz to get a graphic, then write the name of the structure, finally check the first answer pull down box for the correct name, and the second answer for an explanation of how it was named.
Graphic	Name	Name explanation
Quiz	Answer ethylbenzene	Answer 2 C branch of ethane drop "ane" add "yl" = ethylbenzene
Example	1,3-dimethyl- benzene	There are two methyl groups attached to benzene it is necessary to number the positions. Arbitrarily one methyl group is defined as number 1. For this compound the second methyl groups is on the third carbon, hence 1,3. Use "di" to indicate two methyl groups - 1,3-dimethylbenzene.
Quiz	Answer propylbenzene	Answer 3 C branch of propane drop "ane" add "yl" = propylbenzene
Example	isopropyl- benzene	3 carbon branch of propane - drop "ane", add "yl". But now notice that the center of the three carbon propyl branch is attached to the benzene, so use "iso" (stands for isomer) = isopropylbenzene