Electrophilic addition in alkenes

  • Alkenes are more reactive than alkanes. 
  • This is due to the C=C double bond. 
  • Mean bond enthalpy is +347 kj mol 
  • The double bond is an area of high electrin density so electrophiles such as Br2 and Hbr are attracted to it. 
  • In alkenes, the bond breaks and a small molecule is added across the two carbon atoms. 
  • Halogenation is an addition reaction in which a halogen is added across the C=C bond.
  • Adding bromine water to an alkene will form a haloalkene and the bromine water will decolourise. 
  • The test for identifying an alkene is ; 
  • CH2CH2 =Br2 -> BrCH2Br
  • Haloalkanes can be formed by an addition reaction between a hydrogen halide such as HBr and an alkene. 
  • Hydrogen halides like HCL, HBr and Hl are gases at room temperature so they are bubbled trough the alkene to cause a reaction. 
  • CH2CH2 + HBr -> CH3CH2Br
  • Hydration is an addition reaction between an alkene and steam
  • The alkene must be in gaseous form for the reaction to occur. 
  • The temperature must be high, around 300 degree celcius, as must be the pressure about 65 atm. 
  • Phosphoric acid acts as the catalyst 
  • CH2CH2 + H20 -> CH3CH3OH
  • Alkenes react with concentrated sulfruic acid under cold conditions to…


No comments have yet been made