3.3.3 - Halogenalkenes

• What are the reagents and conditions for an elimination reaction with OH- ions?

  
  

  • Reagents: Potassium / Sodium Hydroxide
  • Conditions: in ethanol; Heat
• In an elimination reaction, OH- acts as a base
• Changes in functional groups:

  • Hydroxide ions: Halogenoalkanes to Alcohol
  • Cyanide Ions: Halogenoalkane to Nitrile
  • Ammonia: Halogenoalkane to Amine
• What are the products in an elimination reaction? alkene + water + nucleophile
• What is the equation for ozone depletion? 2O3 -> 3O2
• Fuels: Substances that release heat energy when they undergo combustion
• Reagents and conditions for catalytic hydrogenation:

  • Hydrogen
  • Ni catalyst
  • High pressure
• Halogenoalkanes are insoluble as C-H bonds are non-polar, not compensated for enough by C-X bond polarity
• Halogenoalkanes have a polar bond as halogen has a higher electronegativity than C ( halogen is δ-, carbon is δ+)
• What is the most important factor in determining their halogenalkenes reactivity?

  
  

  Carbon-halogen bond enthalpy
• Nucleophile: A negatively charged ion/δ− atom with a lone pair of electrons which can be donated to an electron deficient atom
• What are CFCs?

  • Chlorine-fluoro-carbons - haloalkanes containing C, F and Cl only (no H)
• Are halogenoalkanes soluble in water? Insoluble as C-H bonds are non-polar, not
• Do halogenoalkanes have a polar bond? why? Yes polar, as halogen has a higher electronegativity than C ( halogen is δ-, carbon is δ+)
• Which intermolecular forces do they have? why? Permanent dipole-dipole and van der Waals forces of attraction
• When would they have higher boiling points?

  • Increase Carbon chain length
  • Halogen further down group 7
• What is the most important factor in determining their reactivity? Carbon-halogen bond enthalpy
• What is a nucleophile? A negatively charged ion/δ− atom with a lone pair of electrons which can be donated to an electron deficient atom
• Give 3 examples of nucleophiles :OH- :CN- :NH3
• What is formed in the elimination reaction of haloalkanes?

  • An alkene,
  • water
  • and halogen ion