Reactions of Alkenes

A series of free IGCSE Chemistry Activities and Experiments (Cambridge IGCSE Chemistry).

Reactions of Alkenes

1. Combustion
   Alkene + O₂ → CO₂ + H₂O
   
2. Addition Reaction
   a) Addition of steam - Hydration
   Example:
   Ethene + water → ethanol
   b) Addition of halogens to the double bonds - Bromination
   

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Addition reaction of alkenes - hydrogenation
Hydrogenation - alkenes react with hydrogen in the presence of a nickel catalyst at a temperature of 150°C to form alkanes.
Understand the mechanism of ‘heterogeneous catalysis’ in the hydrogenation of unsaturated hydrocarbons.
During this process the reactants get adsorbed onto the surface of the catalyst increasing the rate of reaction.

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Reaction of Alkenes with Bromine Water

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Substitution and Addition Reactions
Substitution reaction for saturated hydrocarbons - Alkane
In a substitution reaction, one of the hydrocarbon’s hydrogens are removed (usually on the end) and replaced with an atom of halogen.
C₅H₁₂ + Cl₂ → C₅H₁₁Cl + HCl
C₅H₁₂ + HCl → C₅H₁₁Cl + H₂

Addition reaction for unsaturated hydrocarbons - Alkene
The double bond is broken to a single bond. This allows the carbons on either side of the broken bond to have an extra bond available, so the halogen atoms add to either side of where the double bond broke.
C₅H₁₀ + Cl₂ → C₅H₁₀Cl₂
C₅H₁₀ + HCl → C₅H₁₁Cl

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