chemistry 22.4

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Chemistry 22.4

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22.4 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.

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Hydrocarbon Rings >

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22.4 Cyclic Hydrocarbons

Cyclic Hydrocarbons

What is the general structure of cyclic hydrocarbons?

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22.4 Hydrocarbon Rings > 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.

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22.4 Hydrocarbon Rings > Cyclic Hydrocarbons

Three Ways to Represent Cyclic Hydrocarbons

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Hydrocarbon Rings >

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22.4 Aromatic Hydrocarbons

Aromatic Hydrocarbons

What is the most accurate description of the bonding in a benzene ring?

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22.4 Hydrocarbon Rings > 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.

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22.4 Hydrocarbon Rings > Aromatic Hydrocarbons

The Structure of Benzene

Benzene can be shown as switching, or resonating, between two arrangements of alternating double and single bonds.

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22.4 Hydrocarbon Rings > 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.

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22.4 Hydrocarbon Rings > Aromatic Hydrocarbons

Space-filling Model of Benzene

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22.4 Hydrocarbon Rings > 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.

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22.4 Hydrocarbon Rings > Aromatic Hydrocarbons

A benzene ring can have two or more substituents.

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22.4 Hydrocarbon Rings > Aromatic Hydrocarbons

The molecules of many dyes include benzene rings.

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Section Quiz

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Assess students’ understanding of the concepts in Section

22.4 Section Quiz.

22.4.

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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.

a. aliphatic, aromatic

b. aromatic, aliphatic

c. aliphatic, cyclic

d. aromatic, cyclic

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22.4 Section Quiz.

2. The carbon-carbon bonds in a benzene molecule are

a. alternating double and single bonds.

b. identical hybrid bonds.

c. all double bonds.

d. all single bonds.

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22.4 Section Quiz.

3. When an alkane has a benzene ring as a substituent, the ring is called _______ group.

a. a benzene

b. a toluene

c. a phenyl

d. an arene

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