reactions of alkenes

electrophilic addition

• alkene double bond opens up an atoms are added to the carbon atoms

• Electrophilic addition reactions happen because the double bond has got plenty of electrons and is easily attacked by eletrophiles

electrophiles

• electron pair acceptors

• usually positively charged ions

• polar molecules where the partially positive area is attracted to the electrons

Producing ethane from ethene

Reacts with hydrogen gas in an addition reaction to produce ethane

It will need a nickel catalyst and a temperature of 150

mechanism for halogens reacting with alkenes

making alcohols from alkenes

• made by steam hydration

• 300 degrees and a pressure of 60-70atm

• phosphoric (V) acid catalyst is needed

• Reaction is reversable

• only produces a low yield of about 5% but you can recycle the unreacted alkene gas making the overall yield much better

alkene reaction with hydrogen halides

• undergo addition reactions to form haloalkenes

two products formed by adding halides to unsymmetrical alkenes

• carbocations with more alkyl groups are more stable because the aklyl groups feed electrons towards the positive charge

• The more stable cation is more likely to form

  least stable → most stable

  primary → secondary → tertiary

Markownikoff’s rule

The major product from addition of a hydrogen halide to an unsymmetrical alkene is the one where hydrogen adds to the carbon with the most hydrogens already attached.