Reaction of alkenes

Alkenes all react in a similar way as they all have the same functional group (a carbon carbon double bond.)

Molecules with the same functional group are called a homologous series.

Combustion of alkenes

When we combust alkenes we produce carbon dioxide and water. We also produce unburnt carbon particles because of incomplete combustion and because alkenes burn in air with a smokey flame.

Hydrogenation

Reacting with hydrogen

This requires a temperature of 150 degrees and a nickel catalyst.

The two hydrogen atoms will add across the double bond of the alkene, which will make it an alkane.

Therefore, reacting alkene with hydrogen turns it into an alkane.

Hydration

Reacting with water

The water must be in the form of steam and the temperature must be around 300 degrees. The pressure must be around 70 atmospheres. We use phosphoric acid as a catalyst to speed up the reaction.

When we add water to an alkene, we make an alcohol.

This reaction is reversible, so to increase the yield of our product, any unreacted alkene and steam are passed back through the catalyst.

Reacting with the halogens

Alkenes react rapidly with halogens.

The two atoms of the halogen are added across the double bond, turning the carbon double bond back to a single one.