Alkenes

• Alkenes can't rotate around the double bond
• Electrophiles are electron loving , they undergo addition reactions when attacked by electrophiles called electrophilic addition
• Alkenes can be named differently due to stereoisomerism ( E or Z )
• To determine if alkenes are E or Z ,you first find the Mr of each group and those with the highest Mr is the priority group. If the priority groups are on opposite sides then it's a E isomer and if the priority groups are on the same sides they are a Z isomer.

  
• Reaction with hydrogen halides

  The mechanism of alkenes that form Halogenalkanes is electrophilic addition

  • The double bond would break and it's electrons would transferred to the slightly positive hydrogen on the hydrogen halides.
  • So the bond between the hydrogen and halide would transfer to halide
  • Then a carbocation would form.
  • There can be 1° , 2° and 3° but the carbocation that is most likely to form in the most stable one which is the 3° and the least is 1°. This product is the major product
  • The halide would then be attracted to the carbon that's missing a bond

  
• Reaction with bromine water

  The mechanism for the alkene to react with halide compounds to form dihaloalkanes is electrophilic addition

  
• Reaction between alkenes and sulfuric acid

  The mechanism for alkenes to react with sulfuric acid to form alkyl Hydrogensulphate is electrophilic addition

  • The sulphuric acid needs to be concentrated

  
• Polymers are long chains molecules called monomers joined together by covalent bonds. The monomers in addition polymers is usually alkenes
• Repeating units always focused on the two carbons around the double bond e.g. propene would be poly(propene)

  
• Why are polymers/plastics solid in room temperature?

  Polymer chains are held together by Van Der Waais forces which are weak but due to the chains being longer they are stronger and more energy is required to break them so they have a higher boiling point
• Reactivity of polymers

  They are unreactive due to non-polar C-C bond is the repeating unit so there's nowhere for a species to attack at