Chapter 8

• Organic chemistry


  The study of carbon-based compounds
• Learning outcomes


  • Recognize the properties of alkenes and alkynes relative to alkanes
  • Name alkenes and alkynes given their structures
  • Write formulas for alkenes and alkynes given their names
  • Classify structure as cis and trans isomers
  • Draw structures for cis-trans isomers given their names

  
• Alkene


  A hydrocarbon with one or more carbon-carbon double covalent bonds

  
• Bonding of alkenes


  • Carbon-carbon double covalent bonds

  
• Alkenes


  • Prop-1-ene or 1-propene

  
• Physical properties of alkenes


  • Colorless, nonpolar, combustible, almost odorless
  • Insoluble in water but soluble in organic solvents
  • Simplest alkenes (ethene, propene, butane) are gases at room temperature
  • Boiling points depend on molecular structure - higher molecular chain = higher boiling point
• Chemical properties of alkenes


  • More reactive than alkanes due to instability of double bond
  • Participate in combustion, addition, hydrogenation, halogenation reactions
  • Can be reacted to form polymers

  
• Applications of alkenes


  • Ethylene produced from natural gas via thermal cracking, used as raw material for plastics
• Geometric (cis/trans) isomers


  Alkenes have rigid structure, no rotation about double bond, atoms lie in single plane

  
• Naming of alkenes and cycloalkenes


  1. Identify longest carbon chain

  2. Identify position of double bond

  3. Identify substituents and their positions

  4. Apply IUPAC rules

  
• Multiple double bonds


  • Alkenes can have more than one double bond

  
• Alkyne


  A hydrocarbon with one or more carbon-carbon triple covalent bonds

  
• Physical properties of alkynes


  • Similar to alkenes and alkanes

  
• Chemical properties and uses of alkynes


  • Participate in addition, substitution, and polymerization reactions
  • Used in welding, as fuel, and in organic synthesis
• Cycloalkyne


  Cyclic alkyne

  
• Naming of alkynes


  1. Identify longest carbon chain

  2. Identify position of triple bond

  3. Identify substituents and their positions

  4. Apply IUPAC rules

  
• The International Union of Pure and Applied Chemistry (IUPAC) names for alkynes parallel those of alkenes, except that the family ending is -yne rather than -ene