Halogenoalkanes

• What type of bonds do halogenoalkanes contain?

  Polar bonds
• Why do halogenoalkanes have polar bonds?

  Because halogens are more electronegative than carbon atoms
• What regions are formed in halogenoalkanes due to polar bonds?

  ∂+ and ∂- regions
• What are nucleophiles attracted to in molecules?

  ∂+ regions
• What is the charge of a nucleophile?

  They often have a negative sign
• Name three common nucleophiles.

  CN$^-$, :NH$3$, -:OH
• What is nucleophilic substitution?

  • A reaction mechanism where nucleophiles attack halogenoalkanes
  • Produces alcohols or amines from halogenoalkanes
• What happens during the nucleophilic substitution mechanism for alcohols?

  The nucleophile attacks the ∂+ carbon and electrons are transferred to the chlorine

  
• What occurs in the nucleophilic substitution mechanism for amines?

  An intermediate with an N$^+$ atom is formed, causing a hydrogen to be lost
• How does the molecular weight of the halogen affect the bond enthalpy?

  The greater the Mr of the halogen, the lower the bond enthalpy
• For which types of halogenoalkanes can nucleophilic substitution reactions occur?

  1° (primary) and 2° (secondary) halogenoalkanes
• What occurs during elimination reactions of halogenoalkanes?

  • Halogenoalkane is heated under alcoholic conditions
  • Nucleophile acts as a base and removes a hydrogen atom
  • Results in the elimination of the halide and formation of a carbon-carbon double bond (alkene)
• From which types of halogenoalkanes can elimination reactions occur?

  2° and 3° (tertiary) halogenoalkanes
• What is the role of ozone in the atmosphere?

  It absorbs UV radiation
• How do CFCs contribute to ozone depletion?

  CFCs absorb UV radiation, breaking down carbon-halogen bonds to form free radicals

  
• What measures are being taken to prevent ozone depletion?

  • Production of CFC-free solvents
  • Minimizing entry of harmful substances into the atmosphere
  • Helping to reduce ozone depletion and global warming