Reaction of Alkenes

• The C=C bond is the functional group in alkenes
• The fact that alkenes have a double bound allows them to undergo addition reactions. This means the double bond can open up and join to atoms of another molecule.
• There are 3 types of addition reactions, ones with hydrogen, ones with water and ones with halogens.
• If we add hydrogen to an alkene and supply a catalyst the double bond will break apart and the hydrogen atoms will bond to the carbons. This forms an alkane (it is now saturated). For example, propene + hydrogen ---> propane.
• Addition reactions with water are done by adding an alkene and water. using a catalyst and high temperatures the alkenes double bond will open and the water will split into a hydrogen molecule and an OH group. These will bond to the carbon atoms. The product is an alcohol as it has an OH group. For example with a catalyst and high temperatures Ethene + Water ---> Ethanol
• Ethanol is used for alcoholic drinks and industrial processes
• In addition reactions with water, after the reaction you have to find a way to separate the alcohol, unreacted water, and unreacted alkene. The alkene is easy to separate as it has a low boiling point. If we cool the mixture the alkene will remain as a gas and the alcohol and water will stay together. Separating the water is harder and must be done with fractional distillation.
• fraction distillation works by taking a mixture and putting it in a round bottom heating flask. For example the mixture of ethanol and water. When we begin heating ethanol will boil first and condense in the test tube. Water will remain in the heating flask as it didn't evaporate.

  
• addiction reaction with halogens is very similar to an addition reaction with hydrogen, but it DOES NOT need any catalyst. For example if we add ethene and bromine, and then shake, we will get dibromoethane.

  
• Reacting an alkene with a halogen will produce a halogenoalkane.