alkanes and haloalkanes

• Thermal cracking produces a high number of alkanes and alkenes

  
  

  Conditions: High temperature (around 1200K) and high pressure (around 7000 kPa)
• Catalytic cracking produces a large number of aromatic compounds and alkenes. A zeolite catalyst is used

  Conditions: Slight pressure (100 kPa) and high temperature (around 720 K)
• The initiation step in free radical substitution occurs when the halogen atom turns into a free radical under the prescence of UV light in a process called homolytic fission

  A)

  
• Propogation is the second step in free radical substitution. it is when the free chlorine radicals displace a hydrogen atom on an alkane to form a haloalkane. This process produces another chlorine radical, which can lead to a chain reaction

  
• Termination is the final step in free radical substitution, where 2 radicals combine to form a neutral molecule

  
• CFCs (chlorofluorocarbons) are banned as they can decompose ozone. The chlorine atom becomes a free radical (due to the UV light breaking the C-Cl bonds) as the CFCs enter the upper atmosphere. The chlorine is considered to be a catalyst

  
• Haloalkanes are susceptible to attack by nucleophiles (lone pair donors) due to the halogen atom being electronegative, meaning the carbon is more positive. The weaker the bond (the lower the bond enthalpy), the faster the rate of reaction.

  
• Nucleophilic substitution with AQUEOUS hydroxide ions:

  
  

  Functional group change: Haloalkane -> alcohol

  Reagent: potassium/sodium hydroxide

  Conditions: AQUEOUS and done under reflux

  
• Nucleophilic substitution with cyanide ions:

  
  

  Functional group change: Haloalkane -> nitrile

  Reagent: Potassium cyanide dissolved in ethanol

  Conditions: Heated and done under reflux

  
• Nucleophilic substitution with ammonia ions:

  Functional group change: Haloalkane -> primary amine

  Reagent: EXCESS CONCENTRATED ammonia (excess increases the amine yield) dissolved in ethanol

  Conditions: Heating under pressure in a sealed container (so the ammonia doesn't dissociate)

  
• An elimination reaction is when a halogen is removed from a haloalkane to form an alkene. OH- ions are used.

  Reagent: Sodium/potassium hydroxide

  Conditions: ETHANOLIC and heated under reflux

  
• Elimination reactions are when the halogen in haloalkanes are removed to produce an alkene. They use OH- ions to remove the haloalkane

  Reagent: Sodium/potassium hydroxide

  Conditions: ETHANOLIC and heated under reflux

  
• An elimination reaction is when a halogen is removed from a haloalkane to form an alkene. OH- ions are required for the reaction to occur

  Reagent: Potassium/sodium hydroxide

  Conditions: ETHANOLIC and heated under reflux