Reaction of alkenes

• Why are alkenes more reactive than alkanes?

  Have a C=C double bond which is very reactive.
• What is a functional group?

  A functional group is a group of atoms in a molecule that determine how the molecule reacts.
• What chemical test can we use to distinguish alkenes and alkanes?

  1. Add orange bromine water and shake.
  2. If it is an alkane it will remain orange (saturated)
  3. But if it is an alkene it will turn colourless (unsatured)
• What type of reactions can alkene be part of, because of C=C double bond?

  Addition reactions
• How do addition reactions work?

  Two molecules combine to form one single molecule. The C=C double carbon bond breaks and opens up for new atoms to be added to each carbon.
• What is hydrogenation?

  Addition of hydrogen to an alkene in the presence of a catalyst.

  Forms an alkane.
• How does hydrogenation work?

  1. An alkene reacts with hydrogen in the presence of a catalyst.
  2. This breaks double bond and adds a hydrogen to each carbon.
• How do alkenes form alcohols?

  1. React with steam ( gaseous water at a high temperature) in the presence of a catalyst.
  2. This breaks the double bond hydrogen is added to one bond and OH goes to another
  3. Then need to separate out the alcohol.
• What happens when alkenes react with halogens?

  Halogenation, double bond breaks and each carbon will bond to a halogen atom.
• Do alkanes tend to undergo complete or incomplete combustion?

  Usually Complete
• Do alkenes tend to undergo complete or incomplete combustion?

  Often Incomplete
• What is incomplete combustion?

  Combustion without sufficient oxygen to react completely.
• What are the drawbacks of incomplete combustion?

  1. Smoky yellow flame
  2. Less energy released than from complete combustion
  3. Produces pollutants.
• What harmful products can be produced by the incomplete combustion of hydrocarbons?

  1. Carbon
  2. Carbon monoxide
  3. Unburnt hydrocarbons