Reactions Of Alkenes Flashcards
Which are more reactive: alkenes or alkanes?
Alkenes
Why are alkenes more reactive than alkanes?
This is because they contain a Pi bond and therefore the electrons in the Pi bond are more exposed. The Pi bond therefore breaks easily.
Which is weaker the sigma bond or the Pi bond?
The Pi bond.
What type of reactions do alkenes undergo?
Addition reactions
Name four addition reactions of alkenes?
Hydrogen in the presence of a nickel catalyst
Halogens
Hydrogen halides
Steam in the presence of an acid catalyst
What is formed from a hydrogenation reaction?
An alkane
What is the alkene mixed with in a hydrogenation reaction?
Hydrogen
Where is the hydrogen atom added in hydrogenation?
Across a double bond.
At what temperature does hydrogenation occur?
432K
In what type of reaction are the reactants passed over a nickel catalyst?
Hydrogenation
How many bonds are hydrogenated in a hydrogenation reaction.
All of them so long as there is enough hydrogen molecules.
How many hydrogen atoms are added to the double bond during hydrogenation?
2 atoms are added (so 1 molecule)
What is the product of the halogenation of alkenes?
Haloalkane
At what temperature does halogenation take place?
Room temperature
What does bromine water test for?
Unsaturation
What will happen to the bromine water if added to an alkene?
It will become colourless.
Why does the bromine water turn colourless if added to an alkene?
Bromine is added across the double bond.
What colour is unreacted bromine water?
Orange
What happens if bromine water is added to an alkane?
Nothing- no bromine is added to the compound and so the bromine water stays orange.
How should bromine water be added to a solution?
Dropwise
What is the product of a reaction involving an alkene and a gaseous hydrogen halide?
A haloalkane
What happens in the reaction of alkenes and halogen halides if the alkene is a liquid?
The hydrogen halide is bubbled through it.
What does two liquid hydrogen halides can be reacted with an alkene to form a haloalkane?
Concentrated hydrochloric acid
Concentrated hydrobromic acid
These are essentially solutions of the hydrogen halides in water.
In the reaction of alkenes and hydrogen halides, what state is the hydrogen halide usually in?
Gaseous unless it is concentrated HCl or concentrated HBr.
