Reactions Of Alkenes Flashcards
Why are alkenes more reactive than alkanes?
Because alkenes have a pi bond
What is a C=C double bond made up of?
A pi bond and a sigma bond
The electron density is concentrated above and below the plane of the sigma bond
What electrons are more exposed?
The pi electrons are more exposed than the electrons in the sigma bond as the pi electrons are on the outside of the double bond
Which bond is weaker- the pi bond or sigma bond?
The pi bond is weaker- therefore broken more readily
What are the 4 addition reactions alkenes can undergo?
Hydrogen in the presence of a nickel catalyst
Halogens
Hydrogen halides
Steam in the presence of an acid catalyst
What do each addition reactions involve?
The addition of a small molecule across the double bond- causing the pi bond to break and for new bonds to form
What is formed during an addition reaction?
An alkane
What is hydrogenation?
An addition reaction in which hydrogen is added across a double bond
What is the test for unsaturation?
Reaction of alkenes with bromine
Used to identify if there is a C=C bond present
What colour is bromine water?
Orange solution
What happens when bromine water is added to an alkene?
Bromine adds across the double bond
The orange colour disappears- showing the presence of a C=C bond
What do alkenes form when they react with gaseous hydrogen halides at room temperature?
Haloalkanes
When are alcohols formed?
When alkenes react with steam in the presence of a phosphoric acid catalyst
How many products are formed when there is an unsymmetrical alkene being formed with an unsymmetrical molecule?
2 possible products
What is hydrogenation?
Alkene -> alkane
In the presence of Ni catalyst
150 degrees Celsius temperature
