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 do nucleophiles contain that allows them to react?


  A lone electron pair
• Which of the following is NOT a common nucleophile?

  CN​:-
• How must nucleophiles be represented in chemical equations?


  With a lone electron pair and often a negative sign
• 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 is the mechanism for nucleophilic substitution to form amines?


  • An intermediate with an N​+​ atom is formed
  • Electrons are transferred to the N​+​ causing a hydrogen to be lost
• How does the molecular weight (Mr) 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​o​ (primary) and 2​o​ (secondary) halogenoalkanes
• What occurs during elimination reactions of halogenoalkanes?


  • Halogenoalkane is heated to high temperatures 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​o​ and 3​o​ (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
  • Helps minimize ozone depletion and global warming