1. Chemistry 22.4

2. Hydrocarbon Rings
Beta-carotene is an important nutrient in carrots that also gives carrots their orange color. The hydrocarbon skeleton of beta-carotene contains hydrocarbon rings. You will learn about hydrocarbon rings and the properties of compounds formed from these rings.

3. Cyclic Hydrocarbons
Cyclic Hydrocarbons
What is the general structure of cyclic hydrocarbons?

4. Cyclic Hydrocarbons
In some hydrocarbon compounds, the carbon chain is in the form of a ring.
Compounds that contain a hydrocarbon ring are called cyclic hydrocarbons.

5. Three Ways to Represent Cyclic Hydrocarbons
The simplest cyclic hydrocarbon has a 3-carbon ring. Rings containing up to 20 carbon atoms are found in nature. Rings with 5 or 6 carbons are the most abundant.

6. Aromatic Hydrocarbons
What is the most accurate description of the bonding in a benzene ring?

7. Aromatic Hydrocarbons
In a benzene molecule, the bonding electrons between carbon atoms are shared evenly around the ring.
An aromatic compound is an organic compound that contains a benzene ring or other ring in which the bonding is like that of benzene.

8. Aromatic Hydrocarbons
The Structure of Benzene
Benzene can be shown as switching, or resonating, between two arrangements of alternating double and single bonds.

9. Aromatic Hydrocarbons
The three symbols below can be used to represent the benzene ring. If the bonds are shown as alternating single and double bonds (on right), it is important to remember that bonds don’t actually alternate and that all six bonds are identical.

10. Aromatic Hydrocarbons
Space-filling Model of Benzene
This is a space-filling model of benzene. Applying Concepts What is the molecular formula of benzene?

11. Aromatic Hydrocarbons
Substituted Aromatic Compounds
Compounds with a substituent on a benzene ring are named as a derivative of benzene. When benzene is a substituent, it is called a phenyl group.

12. Aromatic Hydrocarbons
A benzene ring can have two or more substituents.

13. Aromatic Hydrocarbons
The molecules of many dyes include benzene rings.
The molecules of many dyes include benzene rings. Dyes that contain aromatic compounds are called aniline dyes.

14. 22.4 Section Quiz.
22.4.

15. 22.4 Section Quiz.
1. Choose the correct words for the spaces. Alkanes that do not contain a ring structure are _______ hydrocarbons. Alkanes that do contain ring structures are called _________ hydrocarbons.
aliphatic, aromatic
aromatic, aliphatic
aliphatic, cyclic
aromatic, cyclic

16. 22.4 Section Quiz.
2. The carbon-carbon bonds in a benzene molecule are
alternating double and single bonds.
identical hybrid bonds.
all double bonds.
all single bonds.

17. 22.4 Section Quiz.
3. When an alkane has a benzene ring as a substituent, the ring is called _______ group.
a benzene
a toluene
a phenyl
an arene

18. END OF SHOW