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• Unsaturated hydrocarbon


  A hydrocarbon in which one or more carbon–carbon multiple bonds (double bonds, triple bonds, or both) are present

  
• Unsaturated hydrocarbons


  • They are chemically more reactive than their saturated counterparts
  • Their multiple bonds serve as locations where chemical reactions can occur

  
• Functional group


  The part of an organic molecule where most of its chemical reactions occur
• Subdivisions of unsaturated hydrocarbons according to the type of multiple bonds

  • Alkenes
  • Alkynes
  • Aromatic Hydrocarbons

  
• Alkenes


  An acyclic unsaturated hydrocarbon that contains one or more carbon–carbon double bonds

  
• Alkene functional group


  The -ene ending means a double bond is present

  
• Simplest alkenes

  • Ethene (C2H4)
  • Propene (C3H6)

  
• Cycloalkenes


  A cyclic unsaturated hydrocarbon that contains one or more carbon–carbon double bonds within the ring system

  
• Alkynes


  An acyclic unsaturated hydrocarbon that contains one or more carbon–carbon triple bonds

  
• Alkyne functional group

  The -yne ending means a triple bond is present

  
• The simplest member of alkynes has the formula C2H2, Ethyne

  
• CH2=CH-CH2-C≡CH

  • pent-1-ene-4-yne
• CH2=CH-CH2-C≡C-CH3

  • hex-1-ene-4-yne
• Cumulated

  When two multiple bonds are connected to a similar atom
• Conjugated

  When two multiple bonds are separated by a single bond
• Nonconjugated (Isolated)

  When two multiple bonds are separated by more than one single bond
• Constitutional isomerism is possible for alkenes, just as it was for alkanes

  
• Skeletal isomers

  Constitutional isomers that have different carbon-chain arrangements as well as different hydrogen atom arrangements

  
• Cis-trans (geometric) isomerism

  Possible for some alkenes due to the structural rigidity associated with carbon–carbon double bonds

  
• Combustion of alkenes

  Alkenes, like alkanes, are very flammable. The combustion products, as with any hydrocarbon, are carbon dioxide and water
• Addition reaction

  A reaction in which atoms or groups of atoms are added to each carbon atom of a carbon–carbon multiple bond in a hydrocarbon or hydrocarbon derivative

  
• Symmetrical addition reaction

  An addition reaction in which identical atoms (or groups of atoms) are added to each carbon of a carbon–carbon multiple bond

  
• Hydrogenation reaction

  An addition reaction in which H2 is incorporated into molecules of an organic compound
• Halogenation reaction

  An addition reaction in which a halogen is incorporated into molecules of an organic compound
• Hydrohalogenation reaction

  An addition reaction in which a hydrogen halide (HCl, HBr, or HI) is incorporated into molecules of an organic compound
• Hydration reaction

  An addition reaction in which H2O is incorporated into molecules of an organic compound
• Markovnikov's rule

  When an unsymmetrical molecule of the form HQ adds to an unsymmetrical alkene, the hydrogen atom from the HQ becomes attached to the unsaturated carbon atom that already has the most hydrogen atoms

  
• The physical properties of alkynes are similar to those of alkenes and alkanes

  
• The same substances that add to double bonds (H2, HCl, Cl2, and so on) also add to triple bonds