haloalkanes

• nucleophiles:

  • hydroxide ions, OH-
  • water molecules
  • ammonia molecules
• nucleophilic substitution in haloalkanes

  • nucleophile replaces halogen
• an example of nucleophilic substitution is hydrolysis
• hydrolysis involves water or an aqueous solution of a hydroxide that causes the breaking of a bond in a molecule
• hydrolysis of haloalkane

  • the nucleophile, OH- approaches partially positive carbon atom attached to halogen from behind
  • carbon-halogen bond breaks by heterolytic fission
  • OH replaces halogen
  • products: alcohol + halide ion
• haloalkanes to alcohols

  • can use aqueous sodium hydroxide
  • heated under reflux to obtain good yield
• fluoroalkanes are unreactive
• C-I is the weakest carbon-halogen bond
• rate of hydrolysis increases as strength of carbon-halogen bond decreases
• Tertiary haloalkanes are hydrolysed the fastest, whilst primary haloalkanes are hydrolysed the slowest
• To Produce Alcohols

  Haloalkanes can react with an aqueous alkali, such as aqueous sodium or potassium hydroxide, to produce alcohols in a nucleophilic substitution reaction. The hydroxide ion acts as a nucleophile.
• To Produce Alkenes

  Haloalkanes can react with ethanolic potassium hydroxide (KOH) to produce alkenes in an elimination reaction. The hydroxide ion acts as a base.
• Hydrolysis with Silver Nitrate

  Haloalkanes can be broken down in their reaction with aqueous silver nitrate and ethanol.

  The water in the solution acts as a nucleophile which leads to formation of the alcohol and releases the halide ions into the solution. The halide ions then react with the silver ions from silver nitrate to form silver.