alkanes

• In alkanes as the carbon chain length increases the boiling point increases.
• In an alkane, as the carbon chain length increases the:

  Molecules have a greater surface area of contact

  London forces are stronger as more electrons

  More energy is needed to overcome the London forces
• The boiling point of alkanes decreases with increased branching
• In alkanes, increased branching has:

  Less surface points of contact between the molecules

  Weaker London forces

  Less energy is needed to overcome the London forces
• Alkanes have a low reactivity
• Alkanes have low reactivity because:

  High bond enthalpy - lots of energy to break

  Low polarity

  Strong carbon-carbon and carbon-hydrogen bonds in the molecules
• Alkanes are useful as fuels when burnt
• Complete combustion of alkanes:

  Excess of oxygen

  Produces Carbon dioxide and water
• Incomplete combustion of alkane:

  Limited oxygen

  Produces CO - toxic
• Carbon monoxide:

  Highly toxic

  Hard to detect due to colourless and odourless.
• Reaction of alkane and halogen:

  Reaction type - substitution

  Mechanism - radical substitution
• General reaction of alkane and halogen produces:

  Haloalkane + hydrogen halide

  With uv light
• 3 steps of radical substitution mechanism

  1. Initiation
  2. Propagation
  3. Tetrmination