Chapter 11 Unsaturated Hydrocarbons

1
Chapter 11 Unsaturated Hydrocarbons

• 11.1
• Alkenes and Alkynes

2
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.
• CH3CH2CH3

3
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.

4
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.

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Naming Alkenes

• The names of alkenes
• use the corresponding alkane name.
• change the ending to ene.
• Alkene IUPAC Common
• H2CCH2 ethene ethylene
• H2CCH-CH3 propene propylene
• cyclohexene

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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.

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Naming Alkynes

• The names of alkynes
• use the corresponding alkane name.
• change the ending to yne.
• Alkyne IUPAC Common
• HCCH ethyne acetylene
• HCC-CH3 propyne

8
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.
• CH2CH-CH2-CH3 1-butene
• 1 2 3 4
• CH3-CHCH-CH3 2-butene
• 1 2 3 4
• CH3-CH2-C?C-CH3 2-pentyne
• 5 4 3 2 1

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Learning Check

• Write the IUPAC name for each of the following
• 1. CH2CH-CH2-CH3
• 2. CH3-CHCH-CH3
• CH3
• 3. CH3-CHC-CH3
• 4. CH3-C?C-CH3

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Solution

• Write the IUPAC name for each of the following
• 1. CH2CH-CH2-CH3 1-butene
• 2. CH3-CHCH-CH3 2-butene
• CH3
• 3. CH3-CHC-CH3 2-methyl-2-butene
• 4. CH3-C?C-CH3 2-butyne

11
Learning Check

• Write the IUPAC name for each of the following
• A. CH3-CH2-CC-CH3
• CH3
• ?
• B. CH3-CH2-CCH-CH3

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Solution

• Write the IUPAC name for each of the following
• A. CH3-CH2-CC-CH3 2-pentyne
• CH3
• ?
• B. CH3-CH2-CCH-CH3 3-methyl-2-pentene