Transcript Chapter 11 Unsaturated Hydrocarbons 11.1 Alkenes and Alkynes

Chapter 11 Unsaturated
Hydrocarbons
11.1
Alkenes and Alkynes
1
Saturated Hydrocarbons
Saturated hydrocarbons
• have the maximum number of hydrogen atoms
attached to each carbon atom.
• are alkanes and cycloalkanes with single C-C
bonds.
CH3—CH2—CH3
2
Unsaturated Hydrocarbons
Unsaturated hydrocarbons
• have fewer hydrogen
atoms attached to the
carbon chain than alkanes.
• are alkenes with double
bonds.
• are alkynes with triple
bonds.
3
Bond Angles in Alkenes and
Alkynes
According to VSEPR theory:
• the three groups bonded to
carbon atoms in a double bond
are at 120° angles.
• alkenes are flat because the
atoms in a double bond all lie
in the same plane.
• the two groups bonded to each
carbon in a triple bond are at
180° angles.
4
Naming Alkenes
The names of alkenes
• use the corresponding alkane name.
• change the ending to –ene.
Alkene
IUPAC
Common
H2C=CH2
ethene
ethylene
H2C=CH─CH3
propene
propylene
cyclohexene
5
Ethene (Ethylene)
Ethene or ethylene
• is an alkene with the formula
C2H4.
• has two carbon atoms connected
by a double bond.
• has two H atoms bonded to each
C atom.
• is flat with all the C and H atoms
in the same plane.
• is used to accelerate the ripening
of fruits.
6
Naming Alkynes
The names of alkynes
• use the corresponding alkane name.
• change the ending to –yne.
Alkyne
IUPAC
Common
HC≡CH
ethyne
acetylene
HC≡C─CH3
propyne
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Naming Alkenes and Alkynes
When the carbon chain of an alkene or alkyne has four
or more C atoms, number the chain to give the lowest
number to the first carbon in the double or triple bond.
CH2=CH─CH2─CH3
1
2
3
4
CH3─CH=CH─CH3
1
2
3
4
3
2-butene
4
CH3─CH2─CC─CH3
5
1-butene
2
2-pentyne
1
8
Learning Check
Write the IUPAC name for each of the following:
1. CH2=CH─CH2─CH3
2. CH3─CH=CH─CH3
CH3
|
3. CH3─CH=C─CH3
4. CH3─CC─CH3
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Solution
Write the IUPAC name for each of the following:
1. CH2=CH─CH2─CH3 1-butene
2. CH3─CH=CH─CH3 2-butene
CH3
|
3. CH3─CH=C─CH3
2-methyl-2-butene
4. CH3─CC─CH3
2-butyne
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Learning Check
Write the IUPAC name for each of the following:
A. CH3─CH2─C≡C─CH3
CH3

B. CH3─CH2─C=CH─CH3
11
Solution
Write the IUPAC name for each of the following:
A. CH3─CH2─C≡C─CH3
2-pentyne
CH3

B. CH3─CH2─C=CH─CH3
3-methyl-2-pentene
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