4.2.2 haloalkanes

• Haloalkanes are alkanes with 1 or more halogens attached to them
• Steps for naming halogenalkanes:

  1. Find the longest carbon chain, which forms the last part of the name

  2. The names and positions of the halogen on the molecules come first (prefix)

  3. Use prefixes like fluoro-, chloro-, bromo-, iodo- and numbers to state their position on carbon chains in alphabetical order if there's more than 1 halogen present

  4. If there are multiple halogens of the same type, prefix with "di", "tri", "tetra"
• Haloalkanes have a polar bond due to the halogen attached to them and can be attacked by nucleophiles
• Haloalkanes can be attacked by nucleophiles like ammonia, hydroxide ions, cyanide ions, and water (a weak nucleophile)
• Reaction with hydroxide ions:

  • Haloalkanes react via nucleophilic substitution with warm aqueous sodium hydroxide under reflux
  • The nucleophile attacks the delta positive carbon, replacing the halogen on the haloalkane, leading to substitution
  • The C-X bond breaks heterolytically, forming a new bond
  • Overall reaction: R-X + NaOH -> ROH + NaX (R= alkyl group, X= halogen)
• Haloalkanes also react with water via nucleophilic substitution by heating with water, producing alcohols
• Haloalkanes become more reactive going down the group and are hydrolyzed the fastest
• CFCs (chlorofluorocarbons) break down ozone in the atmosphere and are stable molecules broken down by UV radiation
• CFCs destroy ozone by breaking down to form chlorine radicals that catalyze the breakdown of ozone
• Alternatives to CFCs include HFCs (hydrofluorocarbons) and hydrocarbons, as well as pump sprays, inert gases, and ammonia in industrial fridges and freezers
• The hydroxyl group (OH) can be added to a molecule by reacting it with water, which is called hydration or hydroxylation.