Haloalkanes

• What are halogen alkanes?


  Alkanes that have one or more halogens attached to them
• How do you name halogen alkanes?

  By finding the longest carbon chain and using prefixes for halogens in alphabetical order
• What prefixes are used for halogens in naming halogen alkanes?

  Fluoro, chloro, bromo, iodo
• What is the significance of the order of halogen prefixes in naming?

  They must be in alphabetical order
• What do the prefixes di-, tri-, and tetra- indicate in the context of halogen alkanes?

  They indicate the number of halogen atoms present
• How do the boiling points of halogen alkanes change down the group?

  The boiling points increase as you go down the group
• What governs the boiling points of halogen alkanes?

  The strength of the intermolecular forces
• Why do halogen alkanes have increased van der Waals forces as you go down the group?

  Because the number of electrons in the halogen atoms increases
• What type of bond do halogen alkanes have that allows them to be attacked by nucleophiles?

  A polar bond
• What is a nucleophile?


  A substance that donates an electron pair
• Name three examples of nucleophiles.

  Cyanide, ammonia, hydroxide
• What is the mechanism called when halogen alkanes react with hydroxide ions?

  Nucleophilic substitution
• What conditions are required for the reaction of halogen alkanes with hydroxide ions?

  Warm aqueous sodium hydroxide under reflux
• What happens to the carbon atom during nucleophilic substitution with hydroxide ions?

  The carbon atom forms a new bond with the hydroxide ion and breaks the carbon-halogen bond
• What is the overall reaction when a halogen alkane reacts with sodium hydroxide?

  It forms an alcohol and sodium halide
• What is the product formed when halogen alkanes react with cyanide ions?

  A nitrile
• What conditions are required for the reaction of halogen alkanes with cyanide ions?

  Warm ethanol with potassium cyanide under reflux
• What is the role of ammonia in the reaction with halogen alkanes?

  Ammonia acts as a nucleophile and a base
• Why is it important to have an excess of ammonia in the reaction with halogen alkanes?

  To stabilize the intermediate product formed during the reaction
• What is formed after the nucleophilic substitution reaction with ammonia?


  An amine and ammonium ion
• What is the characteristic smell of amines?

  A fishy smell
• What are the key reactions of halogen alkanes?

  1. Reaction with hydroxide ions (nucleophilic substitution)

  2. Reaction with cyanide ions (nucleophilic substitution)

  3. Reaction with ammonia (nucleophilic substitution)
• What role does ammonia play in the reaction described?

  Ammonia acts as a base by accepting a proton.
• What is produced when ammonia reacts in the described mechanism?


  An amine and ammonium ion (NH$_4^+$) are produced.
• How can amines be identified based on their smell?

  Amines can be identified by their distinct fishy smell.
• What type of reaction occurs when ammonia acts as a nucleophile?

  Ammonia acts as a nucleophile by donating a lone pair of electrons.
• What determines the reactivity of halogenated alkenes?

  The bond strength or bond enthalpy determines the reactivity of halogenated alkenes.
• Which carbon-halogen bond has the lowest bond enthalpy?

  The C-I bond has the lowest bond enthalpy.
• Why is the C-I bond more reactive than the C-F bond?

  Because the C-I bond is weaker and easier to break than the C-F bond.
• What is the difference between elimination and substitution reactions in halogenated alkenes?

  • Elimination: Forms an alkene by removing a halogen and a hydrogen.
  • Substitution: Replaces a halogen with a hydroxyl group to form an alcohol.
• What solvent is used in the elimination reaction of halogenated alkenes?

  Ethanol is used as the solvent in the elimination reaction.
• What happens to the hydroxide ion in the elimination reaction?

  The hydroxide ion acts as a base and accepts a proton, forming water.
• What is the product of the elimination reaction involving a halogenated alkane and hydroxide ions?


  The product is an alkene.
• How do solvents affect the behavior of hydroxide ions in reactions?

  The solvent determines whether hydroxide ions act as a base or a nucleophile.
• What are CFCs and their common uses?

  CFCs are chlorofluorocarbons used in refrigerants and propellants.
• Why are CFCs harmful to the ozone layer?

  CFCs break down ozone in the atmosphere when exposed to UV radiation.
• What happens to CFCs when they are exposed to UV radiation?

  The carbon-chlorine bond breaks, forming radicals.
• How do chlorine radicals contribute to ozone depletion?

  Chlorine radicals catalyze the breakdown of ozone into oxygen molecules.
• What is the termination step in the radical reaction involving CFCs?

  The termination step occurs when two radicals react to form a stable molecule.
• What are the alternatives to CFCs that are now used?

  Hydrofluorocarbons (HFCs) and hydrocarbons are used as alternatives to CFCs.