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 betacarotene contains hydrocarbon
rings. You will learn about
hydrocarbon rings and the
properties of compounds formed
from these rings.
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22.4
Hydrocarbon Rings
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Cyclic Hydrocarbons
Cyclic Hydrocarbons
What is the general structure of cyclic
hydrocarbons?
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22.4
Hydrocarbon Rings
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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
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Cyclic Hydrocarbons
Three Ways to Represent Cyclic Hydrocarbons
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22.4
Hydrocarbon Rings
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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
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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
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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
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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
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Aromatic Hydrocarbons
Space-filling Model of Benzene
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Hydrocarbon Rings
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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
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Aromatic Hydrocarbons
A benzene ring can have two or more
substituents.
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22.4
Hydrocarbon Rings
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Aromatic Hydrocarbons
The molecules of many dyes include
benzene rings.
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22.4 Section Quiz.
Assess students’ understanding
of the concepts in Section 22.4.
Continue to:
-or-
Launch:
Section Quiz
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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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END OF SHOW