Basic Chemistry Copyright © 2011 Pearson Education, Inc. 1 Chapter 17 Organic Chemistry 17.2 Alkenes, Alkynes, and Polymers
Basic Chemistry Copyright © 2011 Pearson Education, Inc.1
Chapter 17 Organic Chemistry
17.2 Alkenes, Alkynes, and Polymers
Basic Chemistry Copyright © 2011 Pearson Education, Inc.2
Unsaturated Compounds: Alkenes and AlkynesUnsaturated compounds • have fewer hydrogen
atoms attached to the carbon chain than alkanes
• are alkenes with C=C double bonds
• are alkynes with triple C≡C bonds
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Naming Alkenes and Alkynes
The names of alkenes and alkynes• use the corresponding alkane names • change the end to ene for alkenes
• change the end to yne for alkynes
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Example of Writing an Alkene Name Write the IUPAC name for the following:
CH3
| CH3─CH=C─CH3
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Example of Writing an Alkene Name (continued)STEP 1 Name the longest carbon chain that
contains a double or triple bond.
butene
STEP 2 Number the carbon chain starting from the end nearer the double or triple bond.
CH3
| CH3─CH=C─CH3
4 3 2 1
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Example of Writing an Alkene Name (continued)STEP 3 Give the location and name of each
substituent (alphabetical order) as a prefix to the alkene or alkyne name.
CH3
|CH3─CH=C─CH3 2-methyl-2-butene
4 3 2 1
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Learning Check
Write the IUPAC name for the following: Br
CH3─CH─CC─CH3
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Solution
STEP 1 Name the longest carbon chain that contains a double or triple bond.
pentyne
STEP 2 Number the carbon chain starting from the end nearer the double or triple bond.
Br
CH3─CH─C≡C─CH3 5 4 3 2 1
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Solution (continued)
STEP 3 Give the location and name of each substituent (alphabetical order) as a prefix to the alkene or alkyne name.
Br
CH3─CH─C≡C─CH3 5 4 3 2 1
4-bromo-2-pentyne
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Learning Check
Draw the condensed structural formula for
2-methyl-3-hexyne.
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Solution
STEP 1 Draw the main chain of carbon atoms. For 3-hexyne, there are six carbon atoms in the chain, with
a triple bond between carbons 3 and 4,C─C─C≡C─C─C
STEP 2 Number the chain and place the substituents on the carbons indicated by the numbers.
CH3 C─C─C≡C─C─C
1 2 3 4 5 6
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Solution (continued)
STEP 3 Add the correct number of hydrogen atoms to give four bonds to each C atom.
CH3
CH3─CH─C≡C─CH2─CH3
1 2 3 4 5 6
2-methyl-3-hexyne
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Polymers
Polymers are • large, long-chain molecules• found in nature, including cellulose in plants,
starches in food, and proteins and DNA in the body
• also made synthetically, for example, polyethylene and polystyrene, Teflon, and nylon
• made up of small repeating units called monomers
• made by reaction of small alkenes
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PolymerizationIn polymerization, small repeating units called
monomers join to form a long-chain polymer.
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Learning Check
What is the name and condensed structural formula of the starting monomer for polyethylene?
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Learning Check
Name the monomer used to make Teflon, and use four monomers to draw the condensed structural formula of a portion of a Teflon polymer.
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Solution
F F │ │ F─C═C─F tetrafluoroethene (monomer)
F F F F F F F F │ │ │ │ │ │ │ │ ─C─C─C─C─C─C─C─C─ portion of Teflon │ │ │ │ │ │ │ │ F F F F F F F F
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Recycling Plastics
Recycling is simplified by using codes found on plastic items.
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Learning Check
What type of plastic is indicated by each of the following codes?
A.
B.
C.
3 PVC
5PP
6PS