Halogenoalkanes

• Who is the presenter of the ecology no alkanes video?

  Chris Harris
• What is the purpose of the video on ecology no alkanes?

  To provide an overview for AQA exams
• Where can viewers purchase the PowerPoint used in the video?

  Link in the description box
• What do halogen alkanes contain?


  One or more halogens attached to alkanes
• How do you name halogen alkanes?

  Identify longest carbon chain and halogen positions
• Why must halogen positions be in alphabetical order when naming?

  To ensure correct nomenclature of compounds
• What prefixes are used for halogens in naming?

  Fluoro, chloro, bromo, iodo
• What happens to boiling points of halogen alkanes down the group?

  Boiling points increase down the group
• What causes the increase in boiling points of halogen alkanes?

  Stronger intermolecular forces with more electrons
• What type of bond do halogen alkanes have?

  A polar bond
• What is a nucleophile?

  A substance that donates electron pairs
• What is the mechanism for halogen alkanes reacting with hydroxide ions?

  Nucleophilic substitution
• What conditions are needed for halogen alkanes to react with hydroxide ions?

  Warm aqueous sodium hydroxide
• What is the role of the Liebig condenser in the reaction?

  To prevent volatile substances from escaping
• What happens to the carbon during nucleophilic substitution?

  It forms a new bond with the nucleophile
• What is formed when halogen alkanes react with hydroxide ions?

  An alcohol and sodium halide
• What is the product called when halogen alkanes react with cyanide ions?

  A nitrile
• What conditions are required for halogen alkanes to react with cyanide ions?

  Warm ethanolic potassium cyanide
• Why is excess ammonia needed in the reaction with ammonia?

  To stabilize the intermediate product formed
• What is produced when ammonia reacts with halogen alkanes?

  An amine and ammonium ion
• What are the key steps in the nucleophilic substitution mechanism with hydroxide ions?

  1. Nucleophile attacks the Delta positive carbon
  2. Carbon forms a bond with the nucleophile
  3. Weakest bond (carbon-halogen) breaks
  4. Halogen is replaced by hydroxide
• What are the key steps in the nucleophilic substitution mechanism with cyanide ions?

  1. Nucleophile attacks the Delta positive carbon
  2. Carbon forms a bond with cyanide
  3. Halogen is replaced by cyanide
  4. Nitrile product is formed
• What are the key steps in the nucleophilic substitution mechanism with ammonia?

  1. Nucleophile attacks the Delta positive carbon
  2. Carbon forms a bond with ammonia
  3. Intermediate product is formed
  4. Excess ammonia stabilizes the product
• What are the properties and trends of halogen alkanes?

  • Polar bonds due to electronegativity
  • Boiling points increase down the group
  • React with nucleophiles via substitution
• What are the prefixes used for multiple halogens in naming halogen alkanes?

  • Di- for two
  • Tri- for three
  • Tetra- for four
• What role does ammonia play in the reaction described?

  Ammonia acts as a base and nucleophile
• What is produced when ammonia reacts in the described mechanism?

  An amine and ammonium ion
• How can amines be identified based on their smell?

  They have a distinguishable fishy smell
• What determines the reactivity of halogenated alkanes?

  Bond strength and bond enthalpy
• Which carbon-halogen bond has the lowest bond enthalpy?

  C-I bond
• Why are reactions with the C-I bond more reactive?

  It has the weakest bond and easiest to break
• What happens when halogenated alkanes react with hydroxide ions in ethanol?

  They undergo elimination to form alkenes
• What role does the solvent play in the reaction of halogenated alkanes?

  The solvent determines if elimination or substitution occurs
• What is produced when hydroxide ions act as a base in ethanol?

  Water and an alkene
• How does the solvent affect the behavior of hydroxide ions?

  It changes them from nucleophiles to bases
• What are CFCs and their primary use?

  Chlorofluorocarbons used in refrigerants
• Why are CFCs harmful to the ozone layer?

  They break down ozone when exposed to UV light
• What happens to CFCs when they are exposed to UV radiation?

  The carbon-chlorine bond breaks, forming radicals
• What is the initiation step in the breakdown of ozone by CFCs?

  UV breaks C-Cl bonds, forming radicals
• How do chlorine radicals propagate the breakdown of ozone?

  They react with ozone to form oxygen and more radicals