Unsaturated Hydrocarbons

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• Unsaturated Hydrocarbons
• Contain carbon-carbon multiple bonds.
• Alkenes CC double bonds
• Alkynes CC triple bonds
• Aromatics benzene rings

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• Naming Alkenes
• Step 1 Name the longest chain that contains the
  CC bond. Use the IUPAC root and the ene
  ending.
• Step 2 Number the longest chain so the CC bond
  gets the lowest number possible.
• Step 3 Designate the CC bond in the name with
  the lowest-numbered carbon.

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• Examples
• 1 2 3 4
• CH3-CHCH-CH3
• 2-butene
• 6 5 4 3 2 1
• CH3-CH2-CH2-CHCH-CH3
• 2-hexene

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• Naming Alkenes, cont.
• Step 4 Locate and name attached groups.
• Step 5 Combine all the names as you did with
  alkanes.

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• Because there is no free rotation about the CC
  bond, geometric isomerism is possible.

TRANS
CIS
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• Alkynes
• Ethyne (commonly called acetylene) is the
  simplest alkyne and is used as a fuel for torches
  and in making plastics.

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• Alkynes are named in exactly the same ways as
  alkenes, except the ending yne is used.
• Examples

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• Alkene Reactions
• Alkenes are quite chemically reactive
• Many reactions are addition reactions

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• Alkene Reactions, cont.
• Hydrogenation (addition) reactions can occur in
  the presence of a catalyst (Pt, Pd, or Ni).
• The hydrogenation of vegetable oils is an
  important commercial process.

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• Alkene Reactions, cont.
• Unsymmetrical alkene addition reactions follow
  Markovnikovs rule which states that when a
  molecule of H-X adds to an alkene, the H
  predominantly attaches to the carbon already
  bonded to the most hydrogens. The rich get
  richer.

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• Alkene Reactions, cont.
• Hydration (addition of water) reactions follow
  Markovnikovs rule
• This reaction requires an acid catalyst.

H2SO4
CH3 CH CH2 H20 gtCH3 CH CH3

OH
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• Alkene Reactions, cont.
• Addition polymerization addition reaction
  between double bonded compounds.

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• Polymerization
• Polymers long chain products made up of
  repeating units.
• Monomer the starting material that becomes the
  repeating units of a polymer.

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• Benzene
• Aromatic compounds contain the benzene ring.

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• This gives rise to two possible benzene
  structures
• Which are better represented by
• Note that there is only 1 available bonding site
  on each carbon atom!

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• In benzene, the six p orbital bonding electrons
  of the sp2 hybridized carbon atoms can move
  freely around the ring.
• A hybrid orbital view of the benzene structure