1. Alkanes and Aromatic Hydrocarbons
Cycloalkanes
Aromatic Hydrocarbons

2. Cycloalkanes Cyclopropane CH2 CH2 CH2 Cyclobutane CH2 CH2
The is a group of alkanes that have a cyclic structure. These cycloalkanes contain a carbon chain that is in a ring. Each cycloalkane has a formula that is 2C less than the corresponding alkane. For example, propane is C3H8 whereas cyclopropane ic C3H6. Butane is C4H10 and cyclobutane is C4H10. The names of the cyclic structures use the prefix cyclo in from of the alkane name for the carbon chain.

3. More Cycloalkanes
Cyclopentane CH2
CH CH2
CH CH2
Cyclohexane
CH2

4. Naming Cycloalkanes with Side Groups
Number of Naming
side groups
One Side group name goes in front of the cycloalkane name.
Two Number the ring in the direction that gives the lowest numbers to the side groups.

5. Cycloalkanes with Side Groups

6. Learning Check

7. Solution

8. Aromatic Compounds and Benzene
Aromatic compounds contain benzene.
Benzene, C6H6 , is represented as a six carbon ring with 3 double bonds.
Two possible can be drawn to show benzene in this form.

9. Benzene Structure
The structures for benzene can also be written as a single structure where the alternating double bonds are written as a circle within the ring.
Benzene
structure

10. Aromatic Compounds in Nature and Health
Many aromatic compounds are common in nature and in medicine.

11. Naming Aromatic Compounds
Aromatic compounds are named with benzene as the parent chain. One side group is named in front of the name benzene.
methylbenzene chlorobenzene
(toluene)

12. Naming Aromatic Compounds
When two groups are attached to benzene, the ring is numbered to give the lower numbers to the side groups. The prefixes ortho (1,2), meta (1,3-) and para (1,4-) are also used.

13. Some Common Names
Some substituted benzene rings also use a common name. Then naming with additional more side groups uses the ortho-, meta-, para- system.

14. Learning Check Select the names for each structure:
1. Chlorocyclohexane
2. Chlorobenzene
3. 1-chlorobenzene
1. Meta-methyltoluene
2. Meta-dimethylbenzene
3. 1,3-dimethylbenzene

15. Solution Select the names for each structure: 2. Chlorobenzene
1. Meta-methyltoluene
2. Meta-dimethylbenzene
3. 1,3-dimethylbenzene

16. Learning Check
Write the structural formulas for each of the following:
A. 1,3-dichlorobenzene
B. Ortho-chlorotoluene

17. Solution Write the structural formulas for each of the following:
A. 1,3-dichlorobenzene
B. Ortho-chlorotoluene