Chapter 13 Unsaturated Hydrocarbons

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Chapter 13Unsaturated Hydrocarbons

• Hydrocarbon containing at least 1 carbon-carbon
  multiple bond
• Double C-C bond ALKENE
• Triple C-C bond ALKYNE

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Unsaturated Hydrocarbons contd

• Fig. 13.1
• In ethene, the atoms are in a flat rather than a
  tetrahedral arrangement.

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Alkene/alkyne Nomenclature

• Identify longest chain CONTAINING DOUBLE (TRIPLE)
  BOND
• Number from end closest to double (triple) bond
• Name and number of substituents BEFORE alkene
  (alkyne) name
• Name cyclic alkenes as cyclo(alkene)
• Two double bonds are called diene 3. triene

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Nomenclature Examples
1 ? 8
3,5,7-trimethyl-3-octene
5 ? 1
2,3-dimethyl-1,3-pentadiene
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Nomenclature ExamplesCycloalkenes
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Isomerism in Alkenes
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Cis-Trans Isomerism

• Fig. 13.3
• Cis-trans isomers Different representatives of
  the cis and trans isomers of 2-butene.

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Cis-Trans Isomerism and Vision
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Physical Properties of Alkenes

• Similar to those of alkanes
• Low density
• Insoluble in water
• Soluble in non-polar solvents
• Alkenes generally have lower BP and MP than
  corresponding alkanes

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Chemistry of Alkenes

• Addition reactions atoms or groups are added to
  both carbons of a double bond
• Symmetrical addition
• Same atoms or groups are added to each carbon
• Asymmetrical addition
• Different atoms or groups are added to each
  carbon

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Symmetrical Additions

• Hydrogenation H2 is added to double bond
• Halogenation X2 is added to double bond (where X
  halogen)

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Unsaturated Hydrocarbons contd

• Fig. 13.9
• A bromine in water solution is reddish brown.
  When a small amount of such a solution is added
  to an unsaturated hydrocarbon, the added solution
  is decolorized.

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Asymmetrical Additions

• Hydrohalogenation Hydrogen is added to one
  carbon halogen to the other
• Hydration Hydrogen is added to one carbon
• -OH is added to the other

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Asymmetrical Additions, continued

• Markovnikovs rule The rich get richer (in
  terms of hydrogen)

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Alkene Reactions
Markovnikov The rich get richer
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Polymerization

• Repetitive bonding of monomers to form long,
  repeating molecule

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Unsaturated Hydrocarbons contd
CAG 13.1
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Alkynes

• Chemical and physical properties are similar to
  alkenes
• Nomenclature Replace ane with yne
• Follow rules for naming alkenes

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Aromatic Hydrocarbons
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Benzene
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Nomenclature of Aromatic Hydrocarbons
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Nomenclature of Aromatic HydrocarbonsDi-substitut
ed Benzene Derivatives
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Nomenclature of Aromatic HydrocarbonsTri-substitu
ted Benzene Derivatives
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Nomenclature of Aromatic HydrocarbonsBenzene as
a substituent (Phenyl group)
2-phenyl-2-benzene
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Chemical Reactions of Aromatic Hydrocarbons

• Alkylation
• Halogenation