Reactions involving alkenes

What are three important reactions involving alkenes?

1. Catalytic addition (hydrogenation)
   • Converts alkenes to alkanes.
   • Reactions require a metal catalyst (e.g. platinum) and high pressures.
2. Electrophilic addition
   • Halogenation
     • Elementary bromine or chlorine can be added to alkenes to create vicinal di-halogen alkenes:
       
       $CH_{2}=CH_{2} + Br_{2} \Longrightarrow BrCH_{2}-CH_{2}Br$
       
       
       
   • Hydrohalogenation
     • Addition of HCl or HBr in a Markovnikov^44.1 fashion:
       
       $CH_{3}-CH=CH_{2} + HCl \Longrightarrow CH_{3}-CHCl-CH_{3}$

3. Combustion
   • Chemical combination with oxygen to yield carbon dioxide and water.
4. Elimination reaction
   • Method to synthesize alkenes.
   • Elimination of H$_{2}$O from alcohol will yield alkenes.
5. Cracking
   • Method to synthesize alkenes by breaking larger hydrocarbons into smaller ones. This method is used in the petroleum industry where heat, pressure and catalysts yield a variety of products including alkenes.