Alkanes

• Tetrahedral arrangement around each carbon

  bond angle is 109.4°
• Homolytic bond fission = breaking of a covalent bond with one of the bonded electrons going to each atom, forming two radicals
• Heterolytic bond fission = breaking of a covalent bond forming a cation and anion
• Radical = very reactive species with an unpaired electron
• Addition reactions = reactions in which a reactant is added to an unsaturated molecule to make a saturated molecule
• Substitution reaction = reaction in which an atom of group of atoms is replaced with a different atom or group of atoms
• Elimination reaction = removal of a molecule from a saturated molecule to make an unsaturated molecule
• Curly arrows = used to show the movement of electron pairs when bonds are being broken or made
• Complete combustion: e.g. heptane

  C7H16 +11O2 -> 7CO2 + 8H2O
• Incomplete combustion: e.g heptane

  C7H16 + 7.5O2 -> 7CO + 8H2O

  C7H16 + 4O2 -> 7C + 8H2O
• Radical substitution = reaction which occurs by a free radical mechanism and results in substitution of one or more of the atoms
• Radical Substitution: e.g methane + Br

  • Initiation: Br2 -> Br. + Br. With UV
  • Propagation 1: CH4 + Br. -> .CH3 + HBr
  • Propagation 2: .CH3 + Br2 -> CH3Br + Br.
  • Termination: Br. + Br. -> Br2

  .CH3 + .CH3 -> C2H6

  .CH3 + Br. -> CH3Br