Haloalkanes

• What is a Haloalkane?

  A compound containing the elements carbon, hydrogen and a halogen, when naming the haloalkane the halogen is the prefix i.e chlorobutane
• Which bond in the haloalkane is polar?

  The carbon-halogen bond is polar, with the halogen having a delta negative and the carbon having a delta positive
• What does it mean if you have partial charges on the haloalkane?


  It means that the haloalkane is succeptible to attack by nucleophiles
• What is a nucleophile?

  It is an atom or group of atoms that is attracted to an electron deficient carbon atom, where it donates a pair of electrons to form a new covalent bond, some nucleophiles include: OH-, water and ammonia
• What mechanism does a haloalkane undergo with a nucleophile?

  Nucleophilic substitution
• What is hydrolysis?

  Chemical reaction, involving water or an aqueous solution of a hydroxide which causes the breaking of a bond or in a molecule, resulting in two products being formed
• Mechanism for hydrolysis

  1. the nucleophile approaches the carbon atom attached to the halogen on the opposite side of the halogen
  2. The lone pair of electrons on the nucleophile is attracted and donated to the delta positive carbon atom
  3. A new bond is then formed between the oh and the carbon
  4. The new product is then the alcohol and the halide ion which is formed
• What does the rate of hydrolysis of a haloalkane depend on?

  It depends upon the strength of the carbon-halogen bond
• What is the ranking in terms of strength of the carbon-halogen bonds?


  C-F is the highest and C-I is the lowest
• Will Fluroalkanes by hydrolysised?

  No, this is due to them needing a large quantity of energy to break the C-F bond
• What are the observations of haloalkanes when they react with silver nitrate?

  They will form precipitates, Chlorobutane produces a white precipitate, Bromobutane forms a cream precipitate and iodobutane produces a yellow precipitate
• What are uses of haloalkanes?

  Pesticides, refridgerants, Solvents, making polymers, flame retardants
• What happens in the ozone layer and how is ozone formed?

  Ozone is formed by oxygen undergoing homolytic fission to form 2O,

  The O then reacts with O2 to form ozone O3

  This is a steady reaction and is balanced

  However it became unbalanced when CFCs have been released this then causes the delicate equilibrium to be drastically effected
• What is a CFC?

  Chlorofluorocarbons they are used in refridgerator as refridgerants, they are stable, however they break down ozone and the atmosphere as well
• How do CFCs deplete the ozone?

  1. They undergo homolytic fission to form radicals this happens in the ozone because of the higher conc of UV light
  2. The C-Cl bond breaks because it has the lowest enthalpy (photodissociation)
  3. This forms two radicals
  4. These radicals then react with ozone to form ClO radicals and oxygen
  5. These radicals react with O and form Cl radical and oxygen
  6. This process is repeated many times and one CFC can result in the breakdown of 100,000 ozone molecules
• How can ozone also be broken down?

  Free radical substitution using NO radicals, this converts ozone into oxygen over time
• What was the montreal protocol?

  A treaty that bans the production of CFCs and this meant many companies had to look for alternatives