Halagenoalkanes

• Nucleophile is an electron pair donor
• Base is a proton acceptor
• Nucleophilic substitution is a reaction where an atom or group of atoms is replaced with a new atom or group of atoms via attack by a nucleophile
• Elimination is a reaction in which an atom or group of atoms is removed from a reactant
• Halogenoalkanes are more reactive than alkanes due to a polar bond
• • Halogen is more electronegative than the carbon atom
  • Halogen has a greater tendency to attract the shared pair of electrons in the covalent bond
  • Making it a partially negative and partially positive end
• Haogenoalkanes are used as propellants, aerosols and pharmaceuticals
• OH- nucleophilic substitution:

  • Dilute + aqueous KOH, warm with reflux
  • produces an alcohol
• CN- Nucleophilic substituition:

  • KCN, dissolved in water and ethanol, warm with reflux
  • Produces a nitrile
• NH3 nucleophilic substitution:

  • Excess NH3
  • heat, pressure, sealed container
  • Produces an amine
• Excess ammonia is used so no further reactions occur and so a salt isn't produced
• To determine the relative rates of hydrolysis:

  1. Warm 5 drops of each halogenoalkane to 60 degrees with 1 cm3 of 0.1 M aqueous silver nitrate, using ethanol as a metal solvent
  2. Time how long it takes for a precipitate to form
• Elimination:

  • Concentrated alcoholic KOH dissolved in ethanol
  • hot, reflux, alcoholic
• Elimination:

  • Halogen is always removed
  • Hydrogen adjacent to the halogen is removed
  • The C=C bond is formed between the 2 carbons between the hydrogen chosen and the halogen
  • 2 possible isomers