Alkenes Flashcards
What is an alkene?
A hydrocarbon with a carbon-carbon double bond
Why are alkenes described as unsaturated?
They have a carbon-carbon double bond
Describe the electron density of the double bond
It is a region of high electron density
What type of isomerism can alkenes exhibit?
Stereoisomerism (E-Z or cis-trans)
What physical feature of alkenes causes their stereoisomerism?
That the double bond cannot rotate
What two type of reactions do alkenes typically undergo?
Electrophilic addition or polymerisation
Which three reagents do alkenes typically react with?
HBr, H₂SO₄ and Br₂
What type of reagents do alkenes react with?
Electrophiles
What are the products of an electrophilic addition reaction with Br₂?
A dibromoalkane
Why is bromine water used as a test for alkenes?
The Br₂ reacts with the alkene so its reddish-brown colour is decolourised
What are the products of an addition reaction with HBr?
A bromoalkane
What is a carbocation intermediate?
An intermediate molecule in a reaction which has a positive charge on a carbon atom
Describe the variation in stabilities of the different orders of carbocation
Tertiary > secondary > primary
How does stability of carbocations effect the products of an addition reaction with HBr?
More stable carbocation is formed resulting in a major and minor product
What is the product of a reaction with an alkene and concentrated H₂SO₄?
An alcohol
