20.8 Aromatic Hydrocarbons
- 6 carbon ring w/double bonds
-”benzene ring”
- smell nice (cinnamon and vanilla)
-different than cyclo- hydrocarbons
Cyclohexane
Puckered
109.5
o <‘s
More H
Saturated
Benzene
Flat
120 o <‘s
Fewer H
Unsaturated

Figure 20.8: Two Lewis structures for the benzene ring .

Figure 20.8: Shorthand notation for benzene rings.

Figure 20.9: The bonding in the benzene ring is a combination of different Lewis structures.

Figure 20.10:
Names of some common monosubstituted benzenes.

20.10 Functional Groups

Hydrocarbon derivatives = primarily
HC’s but have additional atoms or groups of atoms called functional groups. A functional group is a reactive portion of a molecule that undergoes predictable reactions.

Common functional groups
 alcohols
 ethers
 aldehydes
 ketones
 carboxylic acids
 esters

alcohol
 hydroxyl group (-OH)
Some examples are
OH
CH
3
CH CH
3
2-propanol
CH
3
OH methanol
CH
3
CH
2
OH ethanol
Methanol = gasoline
Ethanol = alcohol beverage
Isopropyl = rubbing alcohol

ether
 oxygen “bridge”
An example is
CH
3
CH
2
O CH
2 diethyl ether
CH
3
(This is the most common ether, often called simply ether, used as an anesthetic.)

carboxylic acid
 carboxyl group, -COOH
An example is O
CH
3
C OH ethanoic acid

ester
 compound formed from a carboxylic acid, RCOOH, and an alcohol, R’OH.
The general structure is
O
R C O R'

aldehyde
 carbonyl group (C=O) with at least one H atom.
An example is O
CH
3
CH ethanal

ketone
 carbonyl group with two hydrocarbon
An example is
O
CH
3
CH
2
C
2-butanone
CH
3